EVALUATION KIT AVAILABLE 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 General Description Benefits and Features The MAX6955 is a compact display driver that interfaces microprocessors to a mix of 7-segment, 14-segment, and 16-segment LED displays through an I2C-compatible 2-wire serial interface. The MAX6955 drives up to 16 digits 7-segment, 8 digits 14-segment, 8 digits 16-segment, or 128 discrete LEDs, while functioning from a supply voltage as low as 2.7V. The driver includes five I/O expander or general-purpose I/O (GPIO) lines, some or all of which can be configured as a key-switch reader. The key-switch reader automatically scans and debounces a matrix of up to 32 switches. * Simplifies Driving 5 x 7 Matrix LED Displays Included on chip are full 14- and 16-segment ASCII 104-character fonts, a hexadecimal font for 7-segment displays, multiplex scan circuitry, anode and cathode drivers, and static RAM that stores each digit. The maximum segment current for the display digits is set using a single external resistor. Digit intensity can be independently adjusted using the 16-step internal digital brightness control. The MAX6955 includes a low-power shutdown mode, a scan-limit register that allows the user to display from 1 to 16 digits, segment blinking (synchronized across multiple drivers, if desired), and a test mode, which forces all LEDs on. The LED drivers are slew-rate limited to reduce EMI. For an SPI-compatible version, refer to the MAX6954 data sheet. An evaluation kit (EV kit) for the MAX6955 is available. * Applications Set-Top Boxes Bar Graph Displays Panel Meters Audio/Video Equipment * Drives Common-Cathode Monocolor and Bicolor LED Displays * Drives Up to 16 Digits 7-Segment, 8 Digits 14-Segment, * * * * * 8 Digits 16-Segment, 128 Discrete LEDs, or a Combination of Digit Types * 2.7V to 5.5V Operation Standard 2-Wire Interface Supports a Variety of Microprocessor Architectures * 400kbps 2-Wire I2C-Compatible Interface Integrated Flexibility Supports Different Application Requirements * Built-In ASCII 104-Character Font for 14-Segment and 16-Segment Digits and Hexadecimal Font for 7-Segment Digits * 16-Step Digit-by-Digit Digital Brightness Control * Display Blanked on Power-Up * Automatic Blinking Control for Each Segment * 10A (typ) Low-Power Shutdown (Data Retained) Five GPIO Port Pins Can Be Configured as Key-Switch Reader to Scan and Debounce Up to 32 Switches with n-Key Rollover * IRQ Output when a Key Input Is Debounced Slew-Rate-Limited Segment Drivers for Lower EMI 36-Pin SSOP and 40-Pin DIP and TQFN Packages Automotive Temperature Range Standard Covers Usage in Harsh Environments Functional Diagram ISET PWM BRIGHTNESS CONTROL CURRENT SOURCE Ordering Information OSC PART TEMP RANGE PIN-PACKAGE OSC_OUT MAX6955AAX+ -40C to +125C 36 SSOP MAX6955ATL+ -40C to +125C 40 TQFN-EP* *EP = Exposed pad. BLINK SCL AD0 AD1 SDA CHARACTER GENERATOR ROM BLINK CONTROL RAM Pin Configurations and Typical Operating Circuits appear at end of data sheet. LED DRIVERS DIGIT MULTIPLEXER DIVIDER/ COUNTER NETWORK MAX6955 +Denotes a lead(Pb)-free/RoHS-compliant package. 19-2548; Rev 4; 7/15 P0 TO P4/IRQ GPIO AND KEY-SCAN CONTROL White Goods CONFIGURATION REGISTER 2-WIRE SERIAL INTERFACE O0 TO O18 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Absolute Maximum Ratings Voltage (with Respect to GND) V+ .........................................................................-0.3V to +6V SCL, SDA, AD0, AD1 ...........................................-0.3V to +6V All Other Pins............................................-0.3V to (V+ + 0.3V) Current O0-O7 Sink Current ......................................................935mA O0-O18 Source Current .................................................55mA SCL, SDA, AD0, AD1, BLINK, OSC, OSC_OUT, ISET ....20mA P0, P1, P2, P3, P4/IRQ ....................................................40mA GND .....................................................................................1A Continuous Power Dissipation (TA = +70C) 36-Pin SSOP (derate at 11.8mW/C above +70C) .....941mW 40-Pin TQFN (derate at 25.6mW/C above +70C)....2051.3mW Operating Temperature Range (TMIN to TMAX) ...............................................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. DC Electrical Characteristics (Typical Operating Circuit, V+ = 2.7V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER SYMBOL Operating Supply Voltage V+ Shutdown Supply Current ISHDN Operating Supply Current I+ CONDITIONS MIN TYP 2.7 Shutdown mode, all digital inputs at V+ or GND TA = +25C 10 MAX UNITS 5.5 V 35 A TA = TMIN to TMAX 40 All segments on, all TA = +25C digits scanned, intensity set to full, internal oscillator, no display or OSC_OUT TA = TMIN to TMAX load connected 22 30 mA 35 OSC = RC oscillator, RSET = 56k, CSET = 22pF, V+ = 3.3V 4 MHz Master Clock Frequency fOSC Dead Clock Protection Frequency fOSC 95 kHz OSC Internal/External Detection Threshold VOSC 1.7 V OSC driven externally 1 8 OSC High Time tCH 50 ns OSC Low Time tCL 50 ns Slow Segment Blink Period OSC = RC oscillator, RSET = 56k, fSLOWBLINK C SET = 22pF, V+ = 3.3V Fast Segment Blink Period fFASTBLINK Fast or Slow Segment Blink Duty Cycle www.maximintegrated.com OSC = RC oscillator, RSET = 56k, CSET = 22pF, V+ = 3.3V 49.5 1 s 0.5 s 50.5 % Maxim Integrated | 2 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 DC Electrical Characteristics (continued) (Typical Operating Circuit, V+ = 2.7V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS -32 -40 -48 mA VLED = 2.2V, V+ = 3.3V Segment Drive Source Current Segment Current Slew Rate Segment Drive Current Matching ISEG VLED = 2.2V, V+ = 2.7V TA = +25C ISEG/t TA = +25C, V+ = 3.3V 11 mA/s ISEG TA = +25C, V+ = 3.3V 5 % LOGIC INPUTS AND OUTPUTS Input High Voltage SDA, SCL, AD0, AD1 VIH Input Low Voltage SDA, SCL, AD0, AD1 VIL Input Leakage Current SDA, SCL, AD0, AD1, OSC, P0, P1, P2, P3, P4/IRQ SDA Output Low Voltage 0.7 x V+ IIH, IIL VOLSDA Port Logic-High Input Voltage P0, P1, P2, P3, P4/IRQ VIHP Port Logic-Low Input Voltage P0, P1, P2, P3, P4/IRQ VILP Port Hysteresis Voltage P0, P1, P2, P3, P4/IRQ VIP Port Input Pullup Current from V+ IIPU Port Output Low Voltage VOLP Blink Output Low Voltage VOLBK -1 ISINK = 6mA 0.3 x V+ V +1 A 0.4 V 0.7 x V+ V 0.3 x V+ V 0.03 x V+ V P0 to P3 configured as key-scan inputs, V+ = 3.3V 75 A ISINK = 8mA 0.3 0.5 V ISINK = 0.6mA 0.1 0.3 V OSC_OUT Output High Voltage VOHOSC ISOURCE = 1.6mA OSC_OUT Output Low Voltage VOLOSC ISINK = 1.6mA www.maximintegrated.com V V+ 0.4 V 0.4 V Maxim Integrated | 3 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Timing Characteristics (Typical Operating Circuit, V+ = 2.7V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 400 kHz TIMING CHARACTERISTICS Serial Clock Frequency fSCL Bus Free Time Between a STOP and a START Condition tBUF 1.3 s Hold Time (Repeated) START Condition tHD, tSTA 0.6 s Repeated START Condition Setup Time tSU, tSTA 0.6 s STOP Condition Setup Time tSU:STO 0.6 s Data Hold Time tHD, tDAT (Note 3) 0.9 Data Setup Time tSU, tDAT 100 s ns SCL Clock Low Period tLOW 1.3 s SCL Clock High Period tHIGH 0.6 s Rise Time of Both SDA and SCL Signals, Receiving tR (Notes 2, 4) 20 + 0.1CB 300 ns Fall Time of Both SDA and SCL Signals, Receiving tF (Notes 2, 4) 20 + 0.1CB 300 ns tF, tX (Notes 2, 5) 20 + 0.1CB 300 ns Pulse Width of Spike Suppressed tSP (Notes 2, 6) 50 ns Capacitive Load for Each Bus Line CB (Note 2) Fall Time of SDA Transmitting 0 400 pF Note 1: All parameters tested at TA = +25C. Specifications over temperature are guaranteed by design. Note 2: Guaranteed by design. Note 3: A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL- of the SCL signal) in order to bridge the undefined region of SCL's falling edge. Note 4: CB = total capacitance of one bus line in pF. tR and tF measured between 0.3V+ and 0.7V+. Note 5: ISINK 6mA. CB = total capacitance of one bus line in pF. tR and tF measured between 0.3V+ and 0.7V+. Note 6: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns. www.maximintegrated.com Maxim Integrated | 4 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Typical Operating Characteristics (V+ = 3.3V, LED forward voltage = 2.4V, Typical Application Circuit, TA = +25C, unless otherwise noted.) INTERNAL OSCILLATOR FREQUENCY vs. TEMPERATURE 4.2 4.0 3.8 RSET = 56k CSET = 22pF MAX6954 toc03 RSET = 56k CSET = 22pF MAX6955 toc02 RSET = 56k CSET = 22pF 4.4 OSCILLATOR FREQUENCY (MHz) MAX6955 toc01 4.4 OSCILLATOR FREQUENCY (MHz) INTERNAL OSCILLATOR WAVEFORM AT OSC AND OSC_OUT PINS INTERNAL OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE 4.2 OSC 4.0 0V 3.8 OSC_OUT 0V 3.6 3.6 TEMPERATURE (C) SUPPLY VOLTAGE (V) 100ns/div OSC: 500mV/div OSC_OUT: 2V/div DEAD CLOCK OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE SEGMENT SOURCE CURRENT vs. SUPPLY VOLTAGE WAVEFORM AT PINS O0 AND O18, MAXIMUM INTENSITY 50 80 110 OSCILLATOR FREQUENCY (MHz) 110 RSET = 56k CSET = GND 105 2.5 100 95 90 85 3.0 3.5 4.0 4.5 5.0 5.5 MAX6954 toc06 1.02 MAX6955 toc05 20 CURRENT NORMALIZED TO 40mA -10 MAX6955 toc04 -40 1.00 O0 0.98 0V 0.96 0.94 O18 VLED = 1.8V 80 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) 1V/div 200s/div GPIO SINK CURRENT vs. TEMPERATURE PORT INPUT PULLUP CURRENT vs. TEMPERATURE KEY-SCAN OPERATION (KEY_A AND IRQ) 4.5 5.0 40 OUTPUT = LOW VPORT = 0.6V VCC = 5.5V 35 30 25 20 VCC = 3.3V 15 VCC = 2.5V 10 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 MAX6954 toc09 0.5 OUTPUT = HIGH VPORT = 1.4V 0.4 VCC = 5.5V MAX6955 toc08 4.0 KEY-SCAN SOURCE CURRENT (mA) 3.5 MAX 6955 toc07 3.0 45 GPIO SINK CURRENT (mA) 0V 0.92 2.5 KEY_A 0.3 0.2 0V VCC = 3.3V IRQ VCC = 2.5V 0.1 0V 5 0 0 -40 -10 20 50 80 TEMPERATURE (C) www.maximintegrated.com 110 -40 -10 20 50 TEMPERATURE (C) 80 110 400s/div KEY_A: 1V/div IRQ: 2V/div Maxim Integrated | 5 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Pin Description PIN NAME FUNCTION SSOP TQFN-EP 1, 2, 34, 35 36, 37, 33, 34 P0-P3 3 38 AD0 Address Input 0. Sets device slave address. Connect to GND, V+, SCL, or SDA to give four logic combinations. See Table 5. 4 39 SDA I2C-Compatible Serial Data I/O 5 40 SCL I2C-Compatible Serial Clock Input 6 1 AD1 Address Input 1. Sets device slave address. Connect to GND, V+, SCL, or SDA to give four logic combinations. See Table 5. 7-15, 22-31 2-10, 21-30 O0-O18 16, 18 12, 13, 15 GND Ground 17 14 ISET Segment Current Setting. Connect ISET to GND through series resistor RSET to set the peak current. 19, 21 16, 18, 19 V+ Positive Supply Voltage. Bypass V+ to GND with a 47F bulk capacitor and a 0.1F ceramic capacitor. 20 17 OSC Multiplex Clock Input. To use internal oscillator, connect capacitor CSET from OSC to GND. To use external clock, drive OSC with a 1MHz to 8MHz CMOS clock. 32 31 BLINK 33 32 OSC_OUT 36 35 P4/IRQ -- 11, 20 N.C. -- -- EP General-Purpose I/O Ports (GPIOs). GPIO can be configured as logic inputs or open-drain outputs. Enabling key scanning configures some or all ports P0-P3 as key-switch matrix inputs with internal pullup (Key_A through Key_D). Digit/Segment Drivers. When acting as digit drivers, outputs O0 to O7 sink current from the display common cathodes. When acting as segment drivers, O0 to O18 source current to the display anodes. O0 to O18 are high impedance when not being used as digit or segment drivers. Blink Clock Output. Output is open drain. Clock Output. OSC_OUT is a buffered clock output to allow easy blink synchronization of multiple MAX6955s. Output is push-pull. General-Purpose I/O Port. Also functions as IRQ output when key scanning is enabled. Not Internally Connected Exposed Paddle. Internally connected to GND. Connect to a large ground plane to improve thermal performance. Detailed Description The MAX6955 is a serially interfaced display driver that can drive up to 16 digits 7-segment, 8 digits 14-segment, 8 digits 16-segment, 128 discrete LEDs, or a combination of these display types. Table 1 shows the drive capability of the MAX6955 for monocolor and bicolor displays. The MAX6955 includes 104-character ASCII font maps for 14-segment and 16-segment displays, as well as the hexadecimal font map for 7-segment displays. The characters follow the standard ASCII font, with the addition of the following common symbols: , , , , , , , and . Seven bits represent the 104-character font map; an 8th bit is used to select whether the deci- www.maximintegrated.com mal point (DP) is lit. Seven-segment LED digits can be controlled directly or use the hexadecimal font. Direct segment control allows the MAX6955 to be used to drive bar graphs and discrete LED indicators. Tables 2, 3, and 4 list the connection schemes for 16-, 14-, and 7-segment digits, respectively. The letters in Tables 2, 3, and 4 correspond to the segment labels shown in Figure 1. (For applications that require mixed display types, see Tables 38-41.) Serial Interface Serial Addressing The MAX6955 operates as a slave that sends and receives data through an I2C-compatible 2-wire interface. The interface uses a serial data line (SDA) and a Maxim Integrated | 6 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 1a 1b 1f 2f 2b 1g 1e a 2a f 2g 2e 1c h i j g1 e 2c 1dp m f b l k h i g1 g2 c 2dp 2d 1d a2 a1 e m j b g2 l k c dp d dp d2 d1 Figure 1. Segment Labeling for 7-Segment Display, 14-Segment Display, and 16-Segment Display Table 1. MAX6955 Drive Capability DISPLAY TYPE 7 SEGMENT (16-CHARACTER HEXADECIMAL FONT) 14 SEGMENT/ 16 SEGMENT (104-CHARACTER ASCII FONT MAP) DISCRETE LEDs (DIRECT CONTROL) Monocolor 16 8 128 Bicolor 8 4 64 serial clock line (SCL) to achieve bidirectional communication between master(s) and slave(s). A master (typically a microcontroller) initiates all data transfers to and from the MAX6955, and generates the SCL clock that synchronizes the data transfer (Figure 2). The MAX6955 SDA line operates as both an input and an open-drain output. A pullup resistor, typically 4.7k, is required on the SDA. The MAX6955 SCL line operates only as an input. A pullup resistor, typically 4.7k, is required on SCL if there are multiple masters on the 2-wire interface, or if the master in a single-master system has an open-drain SCL output. Each transmission consists of a START condition (Figure 3) sent by a master, followed by the MAX6955 7-bit slave address plus R/W bit (Figure 4), a register address byte, 1 or more data bytes, and finally a STOP condition (Figure 3). Bit Transfer Start and Stop Conditions Slave Address Both SCL and SDA remain high when the interface is not busy. A master signals the beginning of a transmission with a START (S) condition by transitioning SDA from high to low while SCL is high. When the master has finished communicating with the slave, it issues a STOP (P) condition by transitioning the SDA from low to high while SCL is high. The bus is then free for another transmission (Figure 3). www.maximintegrated.com One data bit is transferred during each clock pulse. The data on the SDA line must remain stable while SCL is high (Figure 5). Acknowledge The acknowledge bit is a clocked 9th bit that the recipient uses to handshake receipt of each byte of data (Figure 6). Thus, each byte transferred effectively requires 9 bits. The master generates the 9th clock pulse, and the recipient pulls down SDA during the acknowledge clock pulse, such that the SDA line is stable low during the high period of the clock pulse. When the master is transmitting to the MAX6955, the MAX6955 generates the acknowledge bit because the MAX6955 is the recipient. When the MAX6955 is transmitting to the master, the master generates the acknowledge bit because the master is the recipient. The MAX6955 has a 7-bit-long slave address (Figure 4). The eighth bit following the 7-bit slave address is the R/W bit. It is low for a write command, high for a read command. The first 3 bits (MSBs) of the MAX6955 slave address are always 110. Slave address bits A3, A2, A1, and A0 are selected by the address input pins AD1 and AD0. These two input pins can be connected to GND, V+, SDA, or SCL. The MAX6955 has 16 possible slave addresses (Table 5) and therefore a maximum of 16 MAX6955 devices can share the same interface. Maxim Integrated | 7 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 2. Connection Scheme for Eight 16-Segment Digits DIGIT O0 O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 0 CCO -- a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp 1 -- CC1 a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp 2 a1 a2 CC2 -- b c d1 d2 e f g1 g2 h i j k l m dp 3 a1 a2 -- CC3 b c d1 d2 e f g1 g2 h i j k l m dp 4 a1 a2 b c CC4 -- d1 d2 e f g1 g2 h i j k l m dp 5 a1 a2 b c -- CC5 d1 d2 e f g1 g2 h i j k l m dp 6 a1 a2 b c d1 d2 CC6 -- e f g1 g2 h i j k l m dp 7 a1 a2 b c d1 d2 -- CC7 e f g1 g2 h i j k l m dp Table 3. Connection Scheme for Eight 14-Segment Digits DIGIT O0 O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 0 CCO -- a -- b c d -- e f g1 g2 h i j k l m dp 1 -- CC1 a -- b c d -- e f g1 g2 h i j k l m dp 2 a -- CC2 -- b c d -- e f g1 g2 h i j k l m dp 3 a -- -- CC3 b c d -- e f g1 g2 h i j k l m dp 4 a -- b c CC4 -- d -- e f g1 g2 h i j k l m dp 5 a -- b c -- CC5 d -- e f g1 g2 h i j k l m dp 6 a -- b c d -- CC6 -- e f g1 g2 h i j k l m dp 7 a -- b c d -- -- CC7 e f g1 g2 h i j k l m dp Table 4. Connection Scheme for Sixteen 7-Segment Digits DIGIT O0 O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 0, 0a CC0 -- 1a -- 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2dp 2dp 1, 1a -- CC1 1a -- 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2, 2a 1a -- CC2 -- 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2dp 3, 3a 1a -- -- CC3 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2dp 4, 4a 1a -- 1b 1c CC4 -- 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2dp 5, 5a 1a -- 1b 1c -- CC5 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2dp 6, 6a 1a -- 1b 1c 1d 1dp CC6 -- 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2dp 7, 7a 1a -- 1b 1c 1d 1dp -- CC7 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g 2dp Message Format for Writing A write to the MAX6955 comprises the transmission of the MAX6955's slave address with the R/W bit set to zero, followed by at least 1 byte of information. The first byte of information is the command byte, which determines which register of the MAX6955 is to be written by the next byte, if received. If a STOP condition is detected after the command byte is received, then the MAX6955 takes no further action (Figure 7) beyond storing the command byte. www.maximintegrated.com Any bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MAX6955 selected by the command byte (Figure 8). If multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequent MAX6955 internal registers because the command byte address generally autoincrements (Table 6) (Figure 9). Maxim Integrated | 8 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 SDA tSU, STA tSU, DAT tLOW tBUF tHD, STA tHD, DAT tSU, STO SCL tHIGH tHD, STA tR tF START CONDITION REPEATED START CONDITION STOP CONDITION START CONDITION Figure 2. 2-Wire Serial Interface Timing Details SDA SCL S P START CONDITION STOP CONDITION Figure 3. Start and Stop Conditions SDA 1 START MSB SCL 1 0 A3 A2 A1 A0 R/W ACK LSB Figure 4. Slave Address www.maximintegrated.com Maxim Integrated | 9 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 5. MAX6955 Address Map Operation with Multiple Masters Message Format for Reading PIN CONNECTION DEVICE ADDRESS The MAX6955 is read using the MAX6955's internally AD1 AD0 A6 A5 A4 A3 A2 A1 A0 stored command byte as address pointer, the same GND GND 1 1 0 0 0 0 0 way the stored command byte is used as address GND for a write. V+ 1 pointer 1 0 0 autoincrements 0 0 1 pointer The generally after each data byte is read using the same rules as for GND SDA 1 1 0 0 0 1 0 a write (TableSCL 6). Thus, a read is0 initiated by first1configGND 1 1 0 0 1 uring the MAX6955's command byte by performing a 1 can 0 now0 read1 n consecu0 0 writeV+(FigureGND 7). The 1master V+ the MAX6955, 1 1 0with the 0 1 data 0 byte 1 tive V+ bytes from first being addressed by V+ read from SDA the 1register 1 0 0 1 the1 initial0 izedV+ command byte 1(Figure 9). 0When0 performing readSCL 1 1 1 1 after-write verification, reset the command byte's SDA because GND the1 stored 1 byte 0 address 1 0 generally 0 0is address SDA V+ after 1 the write 1 0 1 6). 0 0 1 autoincremented (Table SDA SDA 1 1 0 1 0 1 0 SDA SCL 1 1 0 1 0 1 1 SCL GND 1 1 0 1 1 0 0 SCL V+ 1 1 0 1 1 0 1 SCL SDA 1 1 0 1 1 1 0 SCL SCL 1 1 0 1 1 1 1 If the MAX6955 is operated on a 2-wire interface with multiple masters, a master reading the MAX6955 should use a repeated start between the write, which sets the MAX6955's address pointer, and the read(s) that takes the data from the location(s). This is because it is possible for master 2 to take over the bus after master 1 has set up the MAX6955's address pointer but before master 1 has read the data. If master 2 subsequently changes the MAX6955's address pointer, then master 1's delayed read may be from an unexpected location. Command Address Autoincrementing Address autoincrementing allows the MAX6955 to be configured with the shortest number of transmissions by minimizing the number of times the command byte needs to be sent. The command address or the font pointer address stored in the MAX6955 generally increments after each data byte is written or read (Table 6). To utilize the autoincrement read cycle feature, the master clocks SCL after the first data byte is read, and the MAX6955 continues sending data, incrementing the pointer after each byte is sent. A not-acknowledge or stop condition halts autoincrement. Digit Type Registers The MAX6955 uses 32 digit registers to store the characters that the user wishes to display. These digit registers are implemented with two planes, P0 and P1. Each digit is represented by 2 bytes of memory, 1 byte in plane P0 and the other in plane P1. The digit registers are mapped so that a digit's data can be updated in plane P0, plane P1, or both planes at the same time (Table 7). If the blink function is disabled through the Blink Enable Bit E (Table 20) in the configuration register, then the digit register data in plane P0 is used to multiplex the display. The digit register data in P1 is not used. If the blink function is enabled, then the digit register data in both plane P0 and plane P1 are alternately used to multiplex the display. Blinking is achieved by multiplexing the LED display using data plane P0 and plane P1 on alternate phases of the blink clock (Table 21). Table 6. Command Address Autoincrement Rules COMMAND BYTE ADDRESS RANGE x0000000 to x0001100 x0001101 x0001111 to x1111110 x1111111 www.maximintegrated.com AUTOINCREMENT BEHAVIOR Command byte address autoincrements after byte read or written. Factory reserved; do not write this register. Command byte address autoincrements after byte read or written. Command byte address remains at x1111111 after byte read or written. Maxim Integrated | 10 MAX6955 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan The data in the digit registers does not control the digit segments directly for 14- and 16-segment displays. Instead, the register data is used to address a character generator that stores the data for the 14- and 16segment fonts (Tables 8 and 9). The lower 7 bits of the digit data (D6 to D0) select the character from the font. The most significant bit of the register data (D7) controls the DP segment of the digits; it is set to 1 to light DP, and to zero to leave DP unlit (Table 10). For 7-segment displays, the digit plane data register can be used to address a character generator, which contains the data of a 16-character font containing the hexadecimal font. The decode mode register can be used to disable the character generator and allow the segments to be controlled directly. Table 11 shows the one-to-one pairing of each data bit to the appropriate segment line in the digit plane data registers. The hexadecimal font is decoded according to Table 12. Display Blink Mode The digit-type register configures the display driver for various combinations of 14-segment digits, 16-segment digits, and/or pairs, or 7-segment digits. The function of this register is to select the appropriate font for each digit and route the output of the font to the appropriate MAX6955 driver output pins. The MAX6955 has four digit drive slots. A slot can be filled with various combinations of monocolor and bicolor 16-segment displays, 14-segment displays, or two 7-segment displays. Each pair of bits in the register corresponds to one of the four digit drive slots, as shown in Table 13. Each bit also corresponds to one of the eight common-cathode digit drive outputs, CC0 to CC7. When using bicolor digits, the anode connections for the two digits within a slot are always the same. This means that a slot correctly drives two monocolor or one bicolor 14- or 16-segment digit. The digit type register can be written, but cannot be read. Examples of configuration settings required for some display digit combinations are shown in Table 14. On initial power-up, all control registers are reset, the display is blanked, intensities are set to minimum, and shutdown is enabled (Table 16). 7-Segment Decode-Mode Register In 7-segment mode, the hexadecimal font can be disabled (Table 15). The decode-mode register selects between hexadecimal code or direct control for each of eight possible pairs of 7-segment digits. Each bit in the register corresponds to one pair of digits. The digit pairs are {digit 0, digit 0a} through {digit 7, digit 7a}. Disabling decode mode allows direct control of the 16 LEDs of a dual 7-segment display. Direct control mode can also be used to drive a matrix of 128 discrete LEDs. A logic high selects hexadecimal decoding, while a logic low bypasses the decoder. When direct control is selected, the data bits D7 to D0 correspond to the segment lines of the MAX6955. Write x0010000 to blank all segments in hexadecimal decode mode. www.maximintegrated.com The display blinking facility, when enabled, makes the driver flip automatically between displaying the digit register data in planes P0 and P1. If the digit register data for any digit is different in the two planes, then that digit appears to flip between two characters. To make a character appear to blink on or off, write the character to one plane, and use the blank character (0x20) for the other plane. Once blinking has been configured, it continues automatically without further intervention. Blink Speed The blink speed is determined by the frequency of the multiplex clock, OSC, and by the setting of the Blink Rate Selection Bit B (Table 19) in the configuration register. The Blink Rate Selection Bit B sets either fast or slow blink speed for the whole display. Initial Power-Up Configuration Register The configuration register is used to enter and exit shutdown, select the blink rate, globally enable and disable the blink function, globally clear the digit data, select between global or digit-by-digit control of intensity, and reset the blink timing (Tables 17-20 and 22-25). The configuration register contains 7 bits: * S bit selects shutdown or normal operation (read/write). * B bit selects the blink rate (read/write). * E bit globally enables or disables the blink function (read/write). * T bit resets the blink timing (data is not stored--transient bit). * R bit globally clears the digit data for both planes P0 and P1 for ALL digits (data is not stored--transient bit). * I bit selects between global or digit-by-digit control of intensity (read/write). * P bit returns the current phase of the blink timing (read only--a write to this bit is ignored). Character Generator Font Mapping The font is composed of 104 characters in ROM. The lower 7 bits of the 8-bit digit register represent the character selection. The most significant bit, shown as x in the ROM map of Tables 8 and 9, is 1 to light the DP segment and zero to leave the DP segment unlit. The character map follows the standard ASCII font for 96 characters in the x0101000 through x1111111 Maxim Integrated | 11 MAX6955 range. The first 16 characters of the 16-segment ROM map cover 7-segment displays. These 16 characters are numeric 0 to 9 and characters A to F (i.e., the hexadecimal set). Multiplex Clock and Blink Timing The OSC pin can be fitted with capacitor CSET to GND to use the internal RC multiplex oscillator, or driven by an external clock to set the multiplex clock frequency and blink rate. The multiplex clock frequency determines the frequency that the complete display is updated. With OSC at 4MHz, each display digit is enabled for 200s. The internal RC oscillator uses an external resistor, RSET, and an external capacitor, CSET, to set the oscillator frequency. The suggested values of RSET (56k) and C SET (22pF) set the oscillator at 4MHz, which makes the blink frequency 0.5Hz or 1Hz. The external clock is not required to have a 50:50 duty cycle, but the minimum time between transitions must be 50ns or greater and the maximum time between transitions must be 750ns. The on-chip oscillator may be accurate enough for applications using a single device. If an exact blink rate is required, use an external clock ranging between 1MHz and 8MHz to drive OSC. The OSC inputs of multiple MAX6955s can be connected to a common external clock to make the devices blink at the same rate. The relative blink phasing of multiple MAX6955s can be synchronized by setting the T bit in the control register for all the devices in quick succession. If the serial interfaces of multiple MAX6955s are daisy-chained by connecting the DOUT of one device to the DIN of the next, then synchronization is achieved automatically by updating the configuration register for all devices simultaneously. Figure 10 is the multiplex timing diagram. OSC_OUT Output The OSC_OUT output is a buffered copy of either the internal oscillator clock or the clock driven into the OSC pin if the external clock has been selected. The feature is useful if the internal oscillator is used, and the user wishes to synchronize other MAX6955s to the same blink frequency. The oscillator is disabled while the MAX6955 is in shutdown. Scan-Limit Register The scan-limit register sets how many 14-segment digits or 16-segment digits or pairs of 7-segment digits are displayed, from 1 to 8. A bicolor digit is connected as two monocolor digits. The scan register also limits the number of keys that can be scanned. Since the number of scanned digits affects the display brightness, the scan-limit register should not be used to www.maximintegrated.com 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan blank portions of the display (such as leading-zero suppression). Table 26 shows the scan-limit register format. Intensity Registers Digital control of display brightness is provided and can be managed in one of two ways: globally or individually. Global control adjusts all digits together. Individual control adjusts the digits separately. The default method is global brightness control, which is selected by clearing the global intensity bit (I data bit D6) in the configuration register. This brightness setting applies to all display digits. The pulse-width modulator is then set by the lower nibble of the global intensity register, address 0x02. The modulator scales the average segment current in 16 steps from a maximum of 15/16 down to 1/16 of the peak current. The minimum interdigit blanking time is set to 1/16 of a cycle. When using bicolor digits, 256 color/brightness combinations are available. Individual brightness control is selected by setting the global intensity bit (I data bit D6) in the configuration register. The pulse-width modulator is now no longer set by the lower nibble of the global intensity register, address 0x02, and the data is ignored. Individual digital control of display brightness is now provided by a separate pulse-width modulator setting for each digit. Each digit is controlled by a nibble of one of the four intensity registers: intensity10, intensity32, intensity54, and intensity76 for all display types, plus intensity10a, intensity32a, intensity54a, and intensity76a for the extra eight digits possible when 7-segment displays are used. The data from the relevant register is used for each digit as it is multiplexed. The modulator scales the average segment current in 16 steps in exactly the same way as global intensity adjustment. Table 27 shows the global intensity register format. Table 28 shows individual segment intensity registers. Table 29 shows the even individual segment intensity format. Table 30 shows the odd individual segment intensity format. GPIO and Key Scanning The MAX6955 features five general-purpose input/output (GPIO) ports: P0 to P4. These ports can be individually enabled as logic inputs or open-drain logic outputs. The GPIO ports are not debounced when configured as inputs. The ports can be read and the outputs set using the 2-wire interface. Some or all of the five ports can be configured to perform key scanning of up to 32 keys. Ports P0 to P4 are renamed Key_A, Key_B, Key_C, Key_D, and IRQ, respectively, when used for key scanning. The full keyscanning configuration is shown in Figure 11. Table 31 is the GPIO data register. Maxim Integrated | 12 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 7. Register Address Map REGISTER ADDRESS (COMMAND BYTE) D15 D14 D13 D12 D11 D10 D9 D8 HEX CODE No-Op X 0 0 0 0 0 0 0 Decode Mode X 0 0 0 0 0 0 1 0x00 0x01 Global Intensity X 0 0 0 0 0 1 0 0x02 Scan Limit X 0 0 0 0 0 1 1 0x03 Configuration X 0 0 0 0 1 0 0 0x04 GPIO Data X 0 0 0 0 1 0 1 0x05 Port Configuration X 0 0 0 0 1 1 0 0x06 Display Test X 0 0 0 0 1 1 1 0x07 Write KEY_A Mask Read KEY_A Debounce X 0 0 0 1 0 0 0 0x08 Write KEY_B Mask Read KEY_B Debounce X 0 0 0 1 0 0 1 0x09 Write KEY_C Mask Read KEY_C Debounce X 0 0 0 1 0 1 0 0x0A Write KEY_D Mask Read KEY_D Debounce X 0 0 0 1 0 1 1 0x0B Write Digit Type Read KEY_A Pressed X 0 0 0 1 1 0 0 0x0C Read KEY_B Pressed* Read KEY_C Pressed* Read KEY_D Pressed* Intensity 10 Intensity 32 Intensity 54 Intensity 76 Intensity 10a (7 Segment Only) Intensity 32a (7 Segment Only) Intensity 54a (7 Segment Only) Intensity 76a (7 Segment Only) Digit 0 Plane P0 Digit 1 Plane P0 Digit 2 Plane P0 Digit 3 Plane P0 Digit 4 Plane P0 Digit 5 Plane P0 Digit 6 Plane P0 Digit 7 Plane P0 Digit 0a Plane P0 (7 Segment Only) Digit 1a Plane P0 (7 Segment Only) Digit 2a Plane P0 (7 Segment Only) Digit 3a Plane P0 (7 Segment Only) X X X X X X X X X X X X X X X X X X X X X X X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B *Do NOT write to register. www.maximintegrated.com Maxim Integrated | 13 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 7. Register Address Map (continued) REGISTER ADDRESS (COMMAND BYTE) D13 D12 D11 D10 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D15 X X X X X X X X X X X X X X X X X X X X D14 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Write Digit 0 Planes P0 and P1 with Same Data, Reads as 0x00 X 1 1 0 0 Write Digit 1 Planes P0 and P1 with Same Data, Reads as 0x00 X 1 1 0 Write Digit 2 Planes P0 and P1 with Same Data, Reads as 0x00 X 1 1 Write Digit 3 Planes P0 and P1 with Same Data, Reads as 0x00 X 1 Write Digit 4 Planes P0 and P1 with Same Data, Reads as 0x00 X Write Digit 5 Planes P0 and P1 with Same Data, Reads as 0x00 HEX CODE D9 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D8 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 0 0 0x60 0 0 0 1 0x61 0 0 0 1 0 0x62 1 0 0 0 1 1 0x63 1 1 0 0 1 0 0 0x64 X 1 1 0 0 1 0 1 0x65 Write Digit 6 Planes P0 and P1 with Same Data, Reads as 0x00 X 1 1 0 0 1 1 0 0x66 Write Digit 7 Planes P0 and P1 with Same Data, Reads as 0x00 X 1 1 0 0 1 1 1 0x67 Write Digit 0a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 0 0 0 0x68 Write Digit 1a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 0 0 1 0x69 Digit 4a Plane P0 (7 Segment Only) Digit 5a Plane P0 (7 Segment Only) Digit 6a Plane P0 (7 Segment Only) Digit 7a Plane P0 (7 Segment Only) Digit 0 Plane P1 Digit 1 Plane P1 Digit 2 Plane P1 Digit 3 Plane P1 Digit 4 Plane P1 Digit 5 Plane P1 Digit 6 Plane P1 Digit 7 Plane P1 Digit 0a Plane P1 (7 Segment Only) Digit 1a Plane P1 (7 Segment Only) Digit 2a Plane P1 (7 Segment Only) Digit 3a Plane P1 (7 Segment Only) Digit 4a Plane P1 (7 Segment Only) Digit 5a Plane P1 (7 Segment Only) Digit 6a Plane P1 (7 Segment Only) Digit 7a Plane P1 (7 Segment Only) www.maximintegrated.com 0x2C 0x2D 0x2E 0x2F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F Maxim Integrated | 14 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 7. Register Address Map (continued) REGISTER ADDRESS (COMMAND BYTE) HEX CODE D15 D14 D13 D12 D11 D10 D9 D8 Write Digit 2a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 0 1 0 0x6A Write Digit 3a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 0 1 1 0x6B Write Digit 4a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 1 0 0 0x6C Write Digit 5a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 1 0 1 0x6D Write Digit 6a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 1 1 0 0x6E Write Digit 7a Planes P0 and P1 with Same Data (7 Segment Only), Reads as 0x00 X 1 1 0 1 1 1 1 0x6F Note: Unused register bits read as zero. START CONDITION SCL CLOCK PULSE FOR ACKNOWLEDGMENT 1 2 8 9 SDA SDA BY TRANSMITTER SCL DATA LINE STABLE, CHANGE OF DATA DATA VALID ALLOWED SDA BY RECEIVER S Figure 5. Bit Transfer Figure 6. Acknowledge One diode is required per key switch. Note that the forward voltages of the diode and LED must exceed VIH of P0-P3. If this condition is not met, the voltage input to the port might be lower than the logic threshold and keys will not be detected properly. The MAX6955 can only scan the maximum 32 keys if the scan-limit register is set to scan the maximum eight digits. If the MAX6955 is driving fewer digits, then a maximum of (4 x n) switches can be scanned, where n is the number of digits set in the scan-limit register. For example, if the MAX6955 is driving four 14-segment digits, cathode drivers O0 to O3 are used. Only 16 keys can be scanned in this configuration; the switches shown connected to O4 through O7 are not read. If the user wishes to scan fewer than 32 keys, then fewer scan lines can be configured for key scanning. The unused Key_x ports are released back to their orig- inal GPIO functionality. If key scanning is enabled, regardless of the number of keys being scanned, P4/IRQ is always configured as IRQ (Table 32). The key-scanning circuit utilizes the LEDs' commoncathode driver outputs as the key-scan drivers. O0 to O7 go low for nominally 200s (with OSC = 4MHz) in turn as the displays are multiplexed. By varying the oscillator frequency, the debounce time changes, though key scanning still functions. Key_x inputs have internal pullup resistors that allow the key condition to be tested. The Key_x input is low during the appropriate digit multiplex period when the key is pressed. The timing diagram of Figure 12 shows the normal situation where all eight LED cathode drivers are used. www.maximintegrated.com Maxim Integrated | 15 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 D15 COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION D14 D13 D12 D11 D10 D9 D8 ACKNOWLEDGE FROM MAX6955 SLAVE ADDRESS S 0 A COMMAND BYTE A R/W P ACKNOWLEDGE FROM MAX6955 Figure 7. Command Byte Received ACKNOWLEDGE FROM MAX6955 HOW CONTROL BYTE AND DATA BYTE MAP INTO MAX6955's REGISTERS D15 D14 D13 D12 D11 D10 D9 ACKNOWLEDGE FROM MAX6955 D8 D7 D6 D5 D4 D3 D2 D1 D0 ACKNOWLEDGE FROM MAX6955 S SLAVE ADDRESS 0 A COMMAND BYTE A DATA BYTE A P A P 1 BYTE R/W AUTOINCREMENT MEMORY WORD ADDRESS Figure 8. Command and Single Data Byte Received ACKNOWLEDGE FROM MAX6955 HOW CONTROL BYTE AND DATA BYTE MAP INTO MAX6955's REGISTERS D15 D14 D13 D12 D11 D10 D9 ACKNOWLEDGE FROM MAX6955 D8 D7 D6 D5 D4 D3 D2 D1 D0 ACKNOWLEDGE FROM MAX6955 S SLAVE ADDRESS 0 A COMMAND BYTE A DATA BYTE n BYTE R/W AUTOINCREMENT MEMORY WORD ADDRESS Figure 9. n Data Bytes Received Each key press is scanned twice in a 25.6ms time period with a nominal oscillator frequency of 4MHz, as shown in Figure 12. In the first key test period of 1.6ms, input level at ports P0-P3 (Key_A, Key_B, Key_C, and Key_D) are examined in conjunction with the signal-low period of ports O0-O7 to see if any key is pressed. If pressed, the corresponding key pressed register bit is set. In the second key test period of 1.6ms, input level at ports P0-P3 are examined again (debounce) to see if the key is still pressed. If still pressed, the corresponding debounce register bit is set. The debounce time between key tests is 12.8ms. www.maximintegrated.com Port Configuration Register The port configuration register selects how the five port pins are used. The port configuration register format is described in Table 33. Key Mask Registers The Key_A Mask, Key_B Mask, Key_C Mask, and Key_D Mask write-only registers (Table 34) configure the key-scanning circuit to cause an interrupt only when selected (masked) keys have been debounced. Each bit in the register corresponds to one key switch. The bit is clear to disable interrupt for the switch, and set to enable interrupt. Keys are always scanned (if enabled through the port configuration register), regardless of the setting of these interrupt bits, and the key status is stored in the appropriate Key_x pressed register. Maxim Integrated | 16 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 START OF NEXT CYCLE ONE COMPLETE 1.6ms MULTIPLEX CYCLE AROUND 8 DIGITS 200s DIGIT 0 DIGIT 1 DIGIT 2 DIGIT 3 DIGIT 4 DIGIT 5 DIGIT 6 DIGIT 7 DIGIT 0 CATHODE DRIVER INTENSITY SETTINGS DIGIT 0's 200s MULTIPLEX TIMESLOT 1/16TH HIGH-Z (MIN ON) HIGH-Z 2/16TH LOW HIGH-Z 3/16TH LOW HIGH-Z 4/16TH LOW HIGH-Z 5/16TH LOW HIGH-Z 6/16TH LOW HIGH-Z 7/16TH LOW HIGH-Z 8/16TH LOW HIGH-Z 9/16TH LOW HIGH-Z 10/16TH LOW HIGH-Z 11/16TH LOW HIGH-Z 12/16TH LOW HIGH-Z 13/16TH LOW HIGH-Z 14/16TH LOW HIGH-Z 15/16TH LOW 15/16TH (MAX ON) ANODE (LIT) HIGH-Z LOW CURRENT SOURCE ENABLED HIGH-Z MINIMUM 12.5s INTERDIGIT BLANKING INTERVAL HIGH-Z ANODE (UNLIT) HIGH-Z Figure 10. Multiplex Timing Diagram (OSC = 4MHz) www.maximintegrated.com Maxim Integrated | 17 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 LED OUTPUT O0 SW A0 SW C0 SW B0 SW D0 LED0 LED OUTPUT O1 SW A1 SW B1 SW C1 SW D1 SW A2 SW B2 SW C2 SW D2 LED OUTPUT O2 LED1 LED OUTPUT O3 SW A3 SW B3 SW C3 SW D3 LED2 LED OUTPUT O4 SW A4 SW B4 SW D4 SW C4 LED3 LED OUTPUT O5 SW A5 SW C5 SW B5 SW D5 LED4 LED OUTPUT O6 SW A6 SW C6 SW B6 SW D6 LED5 LED OUTPUT O7 SW A7 VCC SW B7 SW C7 SW D7 LED SEGMENT IS OPTIONAL AND BASED ON APPLICATION. KEY_A (P0) KEY_B (P1) KEY_C (P2) KEY_D (P3) IRQ (P4) MICROCONTROLLER INTERRUPT Figure 11. Key-Scanning Configuration A 25.6MS KEY-SCAN CYCLE 12.8MS FIRST HALF KEY-SCAN CYCLE 1.6ms MULTIPLEX CYCLE 1 1.6ms MULTIPLEX CYCLE 2 12.8MS SECOND HALF KEY-SCAN CYCLE 1.6ms MULTIPLEX CYCLE 8 1.6ms MULTIPLEX CYCLE 1 1.6ms MULTIPLEX CYCLE 6 12.5s TO 187.5s DIGIT PERIOD LED OUTPUT 00 LED OUTPUT 01 LED OUTPUT 02 LED OUTPUT 03 LED OUTPUT 04 LED OUTPUT 05 LED OUTPUT 06 LED OUTPUT 07 FIRST KEY TEST PERIOD START END START SECOND KEY TEST PERIOD (DEBOUNCE) END START OF NEXT KEY-SCAN CYCLE INTERRUPT ASSERTED IF PERIOD DEBOUNCE REGISTER UPDATED Figure 12. Key-Scan Timing Diagram www.maximintegrated.com Maxim Integrated | 18 MAX6955 Key Debounced Registers The Key_A debounced, Key_B debounced, Key_C debounced, and Key_D debounced read-only registers (Table 35) show which keys have been detected as debounced by the key-scanning circuit. Each bit in the register corresponds to one key switch. The bit is set if the switch has been correctly debounced since the register was read last. Reading a debounced register clears that register (after the data has been read) so that future keys pressed can be identified. If the debounced registers are not read, the key-scan data accumulates. However, as there is no FIFO in the MAX6955, the user is not able to determine key order, or whether a key has been pressed more than once, unless the debounced key status registers are read after each interrupt, and before the next keyscan cycle. Reading any of the four debounced registers clears the P4/IRQ output. If a key is pressed and held down, the key is reported as debounced (and IRQ issued) only once. The key must be detected as released by the keyscanning circuit, before it debounces again. If the debounced registers are being read in response to the P4/IRQ being asserted, then the user should generally read all four registers to ensure that all the keys that were detected by the key-scanning circuit are discovered. Key Pressed Registers The Key_A pressed, Key_B pressed, Key_C pressed, and Key_D pressed read-only registers (Table 36) show which keys have been detected as pressed by the key-scanning circuit during the last test. Each bit in the register corresponds to one key switch. The bit is set if the switch has been detected as pressed by the key-scanning circuit during the last test. The bit is cleared if the switch has not been detected as pressed by the key-scanning circuit during the last test. Reading a pressed register does not clear that register or clear the P4/IRQ output. Display Test Register The display test register (Table 37) operates in two modes: normal and display test. Display test mode turns all LEDs on (including DPs) by overriding, but not altering, all controls and digit registers (including the shutdown register), except for the digit-type register and the GPIO configuration register. The duty cycle, while in display test mode, is 7/16 (see the Choosing Supply Voltage to Minimize Power Dissipation section). www.maximintegrated.com 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan External Components RSET and CSET to Set Oscillator Frequency and Peak Segment Current The RC oscillator uses an external resistor, RSET, and an external capacitor, CSET, to set the frequency, fOSC. The allowed range of fOSC is 1MHz to 8MHz. RSET also sets the peak segment current. The recommended values of RSET and CSET set the oscillator to 4MHz, which makes the blink frequencies selectable between 0.5Hz and 1Hz. The recommended value of RSET also sets the peak current to 40mA, which makes the segment current adjustable from 2.5mA to 37.5mA in 2.5mA steps. ISEG = KL/RSET mA fOSC = KF/(RSET x CSET) MHz where: KL = 2240 KF = 10K (typ) RSET = external resistor in k CSET = external capacitor in pF CSTRAY = stray capacitance from OSC pin to GND in pF The recommended value of RSET is 56k and the recommended value of CSET is 22pF. The recommended value of R SET is the minimum allowed value, since it sets the display driver to the maximum allowed peak segment current. RSET can be set to a higher value to set the segment current to a lower peak value where desired. The user must also ensure that the peak current specifications of the LEDs connected to the driver are not exceeded. The effective value of CSET includes not only the actual external capacitor used, but also the stray capacitance from OSC to GND. This capacitance is usually in the 1pF to 30pF range, depending on the layout used. Applications Information Driving Bicolor LEDs Bicolor digits group a red and a green die together for each display element, so that the element can be lit red or green (or orange), depending on which die (or both) is lit. The MAX6955 allows each segment's current to be set individually from the 1/16th (minimum current and LED intensity) to 15/16th (maximum current and LED intensity), as well as off (zero current). Thus, a bicolor (red-green) segment pair can be set to 256 color/intensity combinations. Maxim Integrated | 19 MAX6955 Choosing Supply Voltage to Minimize Power Dissipation The MAX6955 drives a peak current of 40mA into LEDs with a 2.2V forward-voltage drop when operated from a supply voltage of at least 3.0V. The minimum voltage drop across the internal LED drivers is therefore (3.0V 2.2V) = 0.8V. If a higher supply voltage is used, the driver absorbs a higher voltage, and the driver's power dissipation increases accordingly. However, if the LEDs used have a higher forward-voltage drop than 2.2V, the supply voltage must be raised accordingly to ensure that the driver always has at least 0.6V of headroom. The voltage drop across the drivers with a nominal 5V supply (5.0V - 2.2V) = 2.8V is nearly 3 times the drop across the drivers with a nominal 3.3V supply (3.3V 2.2V) = 1.1V. In most systems, consumption is an important design criterion, and the MAX6955 should be operated from the system's 3.3V nominal supply. In other designs, the lowest supply voltage may be 5V. The issue now is to ensure the dissipation limit for the MAX6955 is not exceeded. This can be achieved by inserting a series resistor in the supply to the MAX6955, ensuring that the supply decoupling capacitors are still on the MAX6955 side of the resistor. For example, consider the requirement that the minimum supply voltage to a MAX6955 must be 3.0V, and the input supply range is 5V 5%. Maximum supply current is 35mA + (40mA x 17) = 715mA. Minimum input supply voltage is 4.75V. Maximum series resistor value is (4.75V 3.0V)/0.715A = 2.44. We choose 2.2 5%. Worstcase resistor dissipation is at maximum toleranced resistance, i.e., (0.715A) 2 x (2.2 x 1.05) = 1.18W. The maximum MAX6955 supply voltage is at maximum input supply voltage and minimum toleranced resistance, i.e., 5.25V - (0.715A x 2.2 x 0.95) = 3.76V. Low-Voltage Operation The MAX6955 works over the 2.7V to 5.5V supply range. The minimum useful supply voltage is determined by the forward-voltage drop of the LEDs at the peak current ISEG, plus the 0.8V headroom required by the driver output stages. The MAX6955 correctly regulates ISEG with a supply voltage above this minimum voltage. If the supply drops below this minimum volt- www.maximintegrated.com 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan age, the driver output stages can brown out, and be unable to regulate the current correctly. As the supply voltage drops further, the LED segment drive current becomes effectively limited by the output driver's onresistance, and the LED drive current drops. The characteristics of each individual LED in a display digit are well matched, so the result is that the display intensity dims uniformly as supply voltage drops out of regulation and beyond. Computing Power Dissipation The upper limit for power dissipation (P D ) for the MAX6955 is determined from the following equation: PD = (V+ x 35mA) + (V+ - VLED) (DUTY x ISEG x N) where: V+ = supply voltage DUTY = duty cycle set by intensity register N = number of segments driven (worst case is 17) VLED = LED forward voltage at ISEG ISEG = segment current set by RSET PD = Power dissipation, in mW if currents are in mA Dissipation example: ISEG = 30mA, N = 17, DUTY = 15/16, VLED = 2.4V at 30mA, V+ = 3.6V PD = 3.6V (35mA) + (3.6V - 2.4V)(15/16 x 30mA x 17) = 0.700W Thus, for a 36-pin SSOP package (TJA = 1/0.0118 = +85C/W from Operating Ratings), the maximum allowed ambient temperature TA is given by: TJ(MAX) = TA + (PD x TJA) = +150C = TA + (0.700 x +85C/W) So TA = +90.5C. Thus, the part can be operated safely at a maximum package temperature of +85C. Power Supplies The MAX6955 operates from a single 2.7V to 5.5V power supply. Bypass the power supply to GND with a 0.1F capacitor as close to the device as possible. Add a 47F capacitor if the MAX6955 is not close to the board's input bulk decoupling capacitor. Maxim Integrated | 20 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 8. 16-Segment Display Font Map MSB LSB x000 x001 x010 x011 x100 x101 x110 x111 Table 9. 14-Segment Display Font Map MSB LSB 0000 0000 0001 0001 0010 0010 0011 0011 0100 0100 0101 0101 0110 0110 0111 0111 1000 1000 1001 1001 1010 1010 1011 1011 1100 1100 1101 1101 1110 1110 1111 1111 www.maximintegrated.com x000 x001 x010 x011 x100 x101 x110 x111 Maxim Integrated | 21 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 10. Digit Plane Data Register Format ADDRESS CODE (HEX) MODE REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 14-segment or 16-segment mode, writing digit data to use font map data with decimal place unlit 0x20 to 0x2F 0x40 to 0x4F 0x60 to 0x6F 0 Bits D6 to D0 select font characters 0 to 127 14-segment or 16-segment mode, writing digit data to use font map data with decimal place lit 0x20 to 0x2F 0x40 to 0x4F 0x60 to 0x6F 1 Bits D6 to D0 select font characters 0 to 127 7-segment decode mode, DP unlit 0x20 to 0x2F 0x40 to 0x4F 0x60 to 0x6F 0 0 0 0 D3 to D0 7-segment decode mode, DP lit 0x20 to 0x2F 0x40 to 0x4F 0x60 to 0x6F 1 0 0 0 D3 to D0 7-segment no-decode mode 0x20 to 0x2F 0x40 to 0x4F 0x60 to 0x6F Direct control of 8 segments Table 11. Segment Decoding for 7-Segment Displays MODE ADDRESS CODE (HEX) Segment Line www.maximintegrated.com 0x20 to 0x2F 0x40 to 0x4F 0x60 to 0x6F REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 dp a b c d e f g Maxim Integrated | 22 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 12. 7-Segment Segment Mapping Decoder for Hexadecimal Font REGISTER DATA 7-SEGMENT CHARACTER D6, D5, D4 0 -- X 1 -- X 2 -- X 3 -- X 4 -- X 5 -- X 6 -- X 7 -- X 8 -- X 9 -- X A -- X B -- X C -- X D -- X E -- X F -- X *The decimal point is set by bit D7 = 1. D7* ON SEGMENTS = 1 D3 D2 D1 D0 DP* A B C D E F G 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1 0 1 1 0 1 1 1 1 1 1 0 1 0 1 1 1 1 1 1 1 0 0 1 1 1 1 0 0 1 0 0 1 1 0 1 1 1 1 1 1 1 1 1 0 1 0 0 1 0 1 1 0 1 1 0 1 1 0 1 1 1 1 0 1 0 1 0 0 0 1 0 1 0 1 1 1 1 1 1 1 0 0 0 1 1 1 0 1 1 1 1 1 0 1 1 0 0 1 1 1 1 1 0 1 1 1 1 0 1 1 1 Table 13. Digit-Type Register DIGIT-TYPE REGISTER Output Drive Line Slot Identification www.maximintegrated.com ADDRESS CODE (HEX) 0x0C REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 CC7 CC6 CC5 CC4 CC3 CC2 CC1 CC0 Slot 4 Slot 3 Slot 2 Slot 1 Maxim Integrated | 23 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 14. Example Configurations for Display Digit Combinations REGISTER DATA DIGIT-TYPE REGISTER SETTING ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 Digits 7 to 0 are 16-segment or 7segment digits. 0x0C 0 0 0 0 0 0 0 0 Digit 0 is a 14-segment digit, digits 7 to 1 are 16-segment or 7segment digits. 0x0C 0 0 0 0 0 0 0 1 Digits 2 to 0 are 14-segment digits, digits 7 to 3 are 16segment or 7-segment digits. 0x0C 0 0 0 0 0 1 1 1 Digits 7 to 0 are 14-segment digits. 0x0C 1 1 1 1 1 1 1 1 Table 15. Decode-Mode Register Examples DECODE MODE No decode for digit pairs 7 to 0. Hexadecimal decode for digit pair 0, no decode for digit pairs 7 to 1. Hexadecimal decode for digit pairs 2 to 0, no decode for digit pairs 7 to 3. Hexadecimal decode for digit pairs 7 to 0. www.maximintegrated.com ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 0x01 0 0 0 0 0 0 0 0 0x00 0x01 0 0 0 0 0 0 0 1 0x01 0x01 0 0 0 0 0 1 1 1 0x07 0x01 1 1 1 1 1 1 1 1 0xFF REGISTER DATA HEX CODE Maxim Integrated | 24 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 16. Initial Power-Up Register Status REGISTER Decode Mode Global Intensity Scan Limit Control Register GPIO Data Port Configuration Display Test Key_A Mask Key_B Mask Key_C Mask Key_D Mask Digit Type Intensity10 Intensity32 Intensity54 Intensity76 Intensity10a Intensity32a Intensity54a Intensity76a Digit 0 Digit 1 Digit 2 Digit 3 Digit 4 Digit 5 Digit 6 Digit 7 Digit 0a Digit 1a Digit 2a Digit 3a Digit 4a Digit 5a Digit 6a Digit 7a Key_A Debounced Key_B Debounced Key_C Debounced Key_D Debounced Key_A Pressed Key_B Pressed Key_C Pressed Key_D Pressed www.maximintegrated.com POWER-UP CONDITION Decode mode enabled 1/16 (min on) Display 8 digits: 0, 1, 2, 3, 4, 5, 6, 7 Shutdown enabled, blink speed is slow, blink disabled Outputs are low No key scanning, P0 to P4 are all inputs Normal operation None of the keys cause interrupt None of the keys cause interrupt None of the keys cause interrupt None of the keys cause interrupt All are 16 segment or 7 segment 1/16 (min on) 1/16 (min on) 1/16 (min on) 1/16 (min on) 1/16 (min on) 1/16 (min on) 1/16 (min on) 1/16 (min on) Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes Blank digit, both planes No key presses have been detected No key presses have been detected No key presses have been detected No key presses have been detected Keys are not pressed Keys are not pressed Keys are not pressed Keys are not pressed ADDRESS CODE (HEX) 0x01 0x02 0x03 REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 1 X X 1 X X 1 X X 1 X X 1 0 X 1 0 1 1 0 1 1 0 1 0x04 0 0 X X 0 0 0 0 0x05 X X X 0 0 0 0 0 0x06 0 0 0 1 1 1 1 1 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D 0x6E 0x6F 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Maxim Integrated | 25 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 17. Configuration Register Format MODE Configuration Register Table 18. Shutdown Control (S Data Bit DO) Format REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 P I R T E B X S REGISTER DATA MODE D7 D6 D5 D4 D3 D2 D1 D0 Shutdown P I R T E B X 0 Normal Operation P I R T E B X 1 Table 19. Blink Rate Selection (B Data Bit D2) Format REGISTER DATA MODE D7 D6 D5 D4 D3 D2 D1 D0 Slow blinking. Segments blink on for 1s, off for 1s with fOSC = 4MHz. P I R T E 0 X S Fast blinking. Segments blink on for 0.5s, off for 0.5s with fOSC = 4MHz. P I R T E 1 X S Table 20. Global Blink Enable/Disable (E Data Bit D3) Format MODE D7 P P Blink function is disabled. Blink function is enabled. D6 I I D5 R R REGISTER DATA D4 D3 T 0 T 1 D2 B B D1 X X D0 S S Table 21. Digit Register Mapping with Blink Globally Enabled SEGMENT'S BIT SETTING IN PLANE P1 SEGMENT'S BIT SETTING IN PLANE P0 SEGMENT BEHAVIOR 0 0 Segment off. 0 1 Segment on only during the 1st half of each blink period. 1 0 Segment on only during the 2nd half of each blink period. 1 1 Segment on. Table 22. Global Blink Timing Synchronization (T Data Bit D4) Format REGISTER DATA MODE Blink timing counters are unaffected. 2 Blink timing counters are reset during the I C acknowledge. D7 D6 D5 D4 D3 D2 D1 D0 P I R 0 E B X S P I R 1 E B X S Table 23. Global Clear Digit Data (R Data Bit D5) Format MODE REGISTER DATA D7 D6 D5 D4 D3 D2 D1 Digit data for both planes P0 and P1 are unaffected. P I 0 T E B X S Digit data for both planes P0 and P1 are cleared during the I2C acknowledge. P I 1 T E B X S www.maximintegrated.com D0 Maxim Integrated | 26 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 24. Global Intensity (I Data Bit D6) Format REGISTER DATA MODE D7 D6 D5 D4 D3 D2 D1 D0 Intensity for all digits is controlled by one setting in the global intensity register. P 0 R T E B X S Intensity for digits is controlled by the individual settings in the intensity10 and intensity76 registers. P 1 R T E B X S Table 25. Blink Phase Readback (P Data Bit D7) Format MODE D7 0 1 P1 Blink Phase P0 Blink Phase D6 I I REGISTER DATA D4 D3 T E T E D5 R R D2 B B D1 X X D0 S S Table 26. Scan-Limit Register Format SCAN LIMIT REGISTER DATA ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 HEX CODE Display Digit 0 only 0x03 X X X X X 0 0 0 0x00 Display Digits 0 and 1 0x03 X X X X X 0 0 1 0x01 Display Digits 0 1 2 0x03 X X X X X 0 1 0 0x02 Display Digits 0 1 2 3 0x03 X X X X X 0 1 1 0x03 Display Digits 0 1 2 3 4 0x03 X X X X X 1 0 0 0x04 Display Digits 0 1 2 3 4 5 0x03 X X X X X 1 0 1 0x05 Display Digits 0 1 2 3 4 5 6 0x03 X X X X X 1 1 0 0x06 Display Digits 0 1 2 3 4 5 6 7 0x03 X X X X X 1 1 1 0x07 Table 27. Global Intensity Register Format DUTY CYCLE TYPICAL SEGMENT CURRENT (mA) ADDRESS CODE (HEX) 1/16 (min on) 2.5 2/16 5 3/16 4/16 5/16 REGISTER DATA HEX CODE D7 D6 D5 D4 D3 D2 D1 D0 0x02 X X X X 0 0 0 0 0xX0 0x02 X X X X 0 0 0 1 0xX1 7.5 0x02 X X X X 0 0 1 0 0xX2 10 0x02 X X X X 0 0 1 1 0xX3 12.5 0x02 X X X X 0 1 0 0 0xX4 6/16 15 0x02 X X X X 0 1 0 1 0xX5 7/16 17.5 0x02 X X X X 0 1 1 0 0xX6 8/16 20 0x02 X X X X 0 1 1 1 0xX7 0xX8 9/16 22.5 0x02 X X X X 1 0 0 0 10/16 25 0x02 X X X X 1 0 0 1 0xX9 11/16 27.5 0x02 X X X X 1 0 1 0 0xXA 12/16 30 0x02 X X X X 1 0 1 1 0xXB 13/16 32.5 0x02 X X X X 1 1 0 0 0xXC 14/16 35 0x02 X X X X 1 1 0 1 0xXD 15/16 37.5 0x02 X X X X 1 1 1 0 0xXE 15/16 (max on) 37.5 0x02 X X X X 1 1 1 1 0xXF www.maximintegrated.com Maxim Integrated | 27 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 28. Individual Segment Intensity Registers REGISTER FUNCTION ADDRESS CODE (HEX) REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 Intensity10 Register 0x10 Digit 1 Digit 0 Intensity32 Register 0x11 Digit 3 Digit 2 Intensity54 Register 0x12 Digit 5 Digit 4 Intensity76 Register 0x13 Digit 7 Digit 6 Intensity10a Register 0x14 Digit 1a (7 segment only) Digit 0a (7 segment only) Intensity32a Register 0x15 Digit 3a (7 segment only) Digit 2a (7 segment only) Intensity54a Register 0x16 Digit 5a (7 segment only) Digit 4a (7 segment only) Intensity76a Register 0x17 Digit 7a (7 segment only) Digit 6a (7 segment only) Table 29. Even Individual Segment Intensity Format DUTY CYCLE TYPICAL SEGMENT CURRENT (mA) ADDRESS CODE (HEX) 1/16 (min on) 2.5 2/16 5 3/16 REGISTER DATA D7 D6 D5 D3 D2 D1 D0 0x10 to 0x17 0 0 0 0 0xX0 0x10 to 0x17 0 0 0 1 0xX1 7.5 0x10 to 0x17 0 0 1 0 0xX2 4/16 10 0x10 to 0x17 0 0 1 1 0xX3 5/16 12.5 0x10 to 0x17 0 1 0 0 0xX4 6/16 15 0x10 to 0x17 0 1 0 1 0xX5 7/16 17.5 0x10 to 0x17 0 1 1 0 0xX6 8/16 20 0x10 to 0x17 0 1 1 1 0xX7 See Table 30. D4 HEX CODE 9/16 22.5 0x10 to 0x17 1 0 0 0 0xX8 10/16 25 0x10 to 0x17 1 0 0 1 0xX9 11/16 27.5 0x10 to 0x17 1 0 1 0 0xXA 12/16 30 0x10 to 0x17 1 0 1 1 0xXB 13/16 32.5 0x10 to 0x17 1 1 0 0 0xXC 14/16 35 0x10 to 0x17 1 1 0 1 0xXD 15/16 37.5 0x10 to 0x17 1 1 1 0 0xXE 15/16 (max on) 37.5 0x10 to 0x17 1 1 1 1 0xXF www.maximintegrated.com Maxim Integrated | 28 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 30. Odd Individual Segment Intensity Format DUTY CYCLE TYPICAL SEGMENT CURRENT (mA) ADDRESS CODE (HEX) D7 D6 D5 D4 1/16 (min on) 2.5 0x10 to 0x17 0 0 0 0 2/16 5 0x10 to 0x17 0 0 0 1 0x1X 3/16 7.5 0x10 to 0x17 0 0 1 0 0x2X 4/16 10 0x10 to 0x17 0 0 1 1 0x3X 5/16 12.5 0x10 to 0x17 0 1 0 0 0x4X 6/16 15 0x10 to 0x17 0 1 0 1 0x5X 7/16 17.5 0x10 to 0x17 0 1 1 0 0x6X 8/16 20 0x10 to 0x17 0 1 1 1 0x7X 9/16 22.5 0x10 to 0x17 1 0 0 0 10/16 25 0x10 to 0x17 1 0 0 1 0x9X 11/16 27.5 0x10 to 0x17 1 0 1 0 0xAX 12/16 30 0x10 to 0x17 1 0 1 1 0xBX 13/16 32.5 0x10 to 0x17 1 1 0 0 0xCX 14/16 35 0x10 to 0x17 1 1 0 1 0xDX 15/16 37.5 0x10 to 0x17 1 1 1 0 0xEX 15/16 (max on) 37.5 0x10 to 0x17 1 1 1 1 0xFX REGISTER DATA D3 D2 D1 D0 HEX CODE 0x0X See Table 29 0x8X Table 31. GPIO Data Register REGISTER DATA D4 D3 D2 D1 D0 X P4 P3 P2 P1 P0 0 P4 or IRQ status P3 P2 P1 P0 MODE ADDRESS CODE (HEX) D7 D6 D5 Write GPIO Data 0x05 X X Read GPIO Data 0x05 0 0 Table 32. Port Scanning Function Allocation KEYS SCANNED None PORTS AVAILABLE 5 pins GPIO GPIO 1 to 8 3 pins Key_A GPIO 9 to 16 2 pins Key_A Key_B GPIO 17 to 24 1 pin Key_A Key_B Key_C GPIO IRQ 25 to 36 None Key_A Key_B Key_C Key_D IRQ www.maximintegrated.com P0 P1 P2 P3 P4 GPIO GPIO GPIO GPIO GPIO IRQ GPIO IRQ Maxim Integrated | 29 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 33. Port Configuration Register Format ADDRESS CODE (HEX) MODE D7 D6 D5 GPIO 0x06 Set number of keys scanned Configuration Register PORT ALLOCATION OPTIONS 0 Keys Scanned 0x06 0 0 0 8 Keys Scanned 0x06 0 0 1 16 Keys Scanned 0x06 0 1 0 24 Keys Scanned 0x06 0 1 1 32 Keys Scanned 0x06 1 X X EXAMPLE PORT CONFIGURATION SETTINGS No Keys Scanned, P4 and 0x06 0 0 0 P2 Are Outputs, Others Are Inputs 8 Keys Scanned, P3 and P1 Are 0x06 0 1 0 Outputs, P2 Is an Input 32 Keys 0x06 1 X X Scanned, No GPIO Ports REGISTER DATA D4 D3 D2 D1 D0 Set port direction for ports P0 to P4: 0 = output, 1 = input P4 IRQ IRQ IRQ IRQ P3 P3 P3 P3 Key_D P2 P2 P2 Key_C Key_C P1 P1 Key_B Key_B Key_B P0 Key_A Key_A Key_A Key_A 0 1 0 1 1 X 0 1 0 X X X X X X Table 34. Key Mask Register Format (Write Only) REGISTER DATA WITH APPROPRIATE SWITCH NAMED BELOW KEY MASK REGISTER ADDRESS CODE (HEX D7 D6 D5 D4 D3 D2 D1 D0 Key_A Mask Register 0x08 SW_A7 SW_A6 SW_A5 SW_A4 SW_A3 SW_A2 SW_A1 SW_A0 Key_B Mask Register 0x09 SW_B7 SW_B6 SW_B5 SW_B4 SW_B3 SW_B2 SW_B1 SW_B0 Key_C Mask Register 0x0A SW_C7 SW_C6 SW_C5 SW_C4 SW_C3 SW_C2 SW_C1 SW_C0 Key_D Mask Register 0x0B SW_ D7 SW_D6 SW_D5 SW_D4 SW_D3 SW_D2 SW_D1 SW_D0 www.maximintegrated.com Maxim Integrated | 30 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Table 35. Key Debounced Register Format (Read Only) KEY DEBOUNCED REGISTER ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 Key_A Debounced Register 0x08 SW_A7 SW_A6 SW_A5 SW_A4 SW_A3 SW_A2 SW_A1 SW_A0 Key_B Debounced Register 0x09 SW_B7 SW_B6 SW_B5 SW_B4 SW_B3 SW_B2 SW_B1 SW_B0 Key_C Debounced Register 0x0A SW_C7 SW_C6 SW_C5 SW_C4 SW_C3 SW_C2 SW_C1 SW_C0 Key_D Debounced Register 0x0B SW_D7 SW_D6 SW_D5 SW_D4 SW_D3 SW_D2 SW_D1 SW_D0 REGISTER DATA Table 36. Key Pressed Register Format (Read Only) KEY PRESSED REGISTER ADDRESS CODE (HEX D7 D6 D5 D4 D3 D2 D1 D0 Key_A Pressed Register 0x0C SW_A7 SW_A6 SW_A5 SW_A4 SW_A3 SW_A2 SW_A1 SW_A0 Key_B Pressed Register 0x0D SW_B7 SW_B6 SW_B5 SW_B4 SW_B3 SW_B2 SW_B1 SW_B0 Key_C Pressed Register 0x0E SW_C7 SW_C6 SW_C5 SW_C4 SW_C3 SW_C2 SW_C1 SW_C0 Key_D Pressed Register 0x0F SW_D7 SW_D6 SW_D5 SW_D4 SW_D3 SW_D2 SW_D1 SW_D0 REGISTER DATA Table 37. Display Test Register MODE ADDRESS CODE (HEX) REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 Normal Operation 0x07 X X X X X X X 0 Display Test 0x07 X X X X X X X 1 www.maximintegrated.com Maxim Integrated | 31 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 CC0: (2) 7-seg monocolor* or 7-seg bicolor CC1: 14-seg monocolor CC0: 14-seg monocolor CC1: 16-seg monocolor CC1: (2) 7-seg monocolor* or 7-seg bicolor CC0 and CC1: (2) 14-seg monocolor or 14-seg bicolor CC0 CC0 -- CC0 -- -- CC0 -- -- CC1 -- CC1 CC1 CC1 a1 1a a a a1 1a a a2 -- -- -- a2 -- -- b b 1b b b b 1b b c c 1c c c c 1c c 1d d1 d1 1d d d d1 1d d d2 1dp d2 d2 1dp -- -- d2 1dp -- e 1e e e 1e e e e 1e e f f 1f f f 1f f f f 1f f 010 g1 g1 1g g1 g1 1g g1 g1 g1 1g g1 011 g2 g2 2a g2 g2 2a g2 g2 g2 2a g2 012 h h 2b h h 2b h h h 2b h 013 i i 2c i i 2c i i i 2c i 014 j j 2d j j 2d j j j 2d k 015 k k 2e k k 2e k k k 2e l 016 l l 2f l l 2f l l l 2f l 017 m m 2g m m 2g m m m 2g m 018 dp dp 2dp dp dp 2dp dp dp dp 2dp dp CONFIGURATION CHOICE Common-Cathode Drive: Digit Type CC0: 16-seg monocolor CC1: 16-seg monocolor CC0 and CC1: (1)16-seg bicolor CC0 and CC1: (2) 7-seg bicolor or (4) 7-seg monocolor or (1) 7-seg bicolor and (2) 7-seg monocolor* CC0: 16-seg monocolor Table 38. Slot 1 Configuration 00 CC0 -- CC0 CC0 01 -- CC1 CC1 CC1 02 a1 a1 1a a1 03 a2 a2 -- a2 04 b b 1b 05 c c 1c 06 d1 d1 07 d2 08 e 09 ADDRESS CODE (HEX) REGISTER DATA D7 D6 D5 D4 D3 D2 0x0C See Table 41. See Table 40. See Table 39. D1 0 1 0 1 D0 0 0 1 1 *7-segment digits can be replaced by directly controlled discrete LEDs according to settings in decode mode register (Table 11). **The highlighted row is used in Typical Operating Circuit 1 for display digits 0 and 1. www.maximintegrated.com Maxim Integrated | 32 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 CC3: (2) 7-seg monocolor* or 7-seg bicolor a1 a1 1a a a a1 1a a -- a2 a2 -- -- -- a2 -- -- 02 CC2 -- CC2 CC2 CC2 CC2 -- CC2 -- -- CC2 03 -- CC3 CC3 CC3 -- -- CC3 -- CC3 CC3 CC3 04 b b 1b b b 1b b b b 1b b 05 c c 1c c c 1c c c c 1c c 06 d1 d1 1d d1 d1 1d d d d1 1d d 07 d2 d2 1dp d2 d2 1dp -- -- d2 1dp -- 08 e e 1e e e 1e e e e 1e e 09 f f 1f f f 1f f f f 1f f 010 g1 g1 1g g1 g1 1g g1 g1 g1 1g g1 011 g2 g2 2a g2 g2 2a g2 g2 g2 2a g2 012 h h 2b h h 2b h h h 2b h 013 i i 2c i i 2c i i i 2c i 014 j j 2d j j 2d j j j 2d k 015 k k 2e k k 2e k k k 2e l 016 l l 2f l l 2f l l l 2f l 017 m m 2g m m 2g m m m 2g m 018 dp dp 2dp dp dp 2dp dp dp dp 2dp dp ADDRESS CODE (HEX) 0x0C D7 REGISTER DATA CC2 and CC3: (2) 14-seg monocolor or 14-seg bicolor CC3: 16-seg monocolor 1a a2 CC2: 14-seg monocolor CC2: (2) 7-seg monocolor* or 7-seg bicolor a1 a2 CC3: 14-seg monocolor CC2: 16-seg monocolor a1 01 CC2 and CC3: (1)16-seg bicolor CC3: 16-seg monocolor 00 CC2 and CC3: (2) 7-seg bicolor or (4) 7-seg monocolor or (1) 7-seg bicolor and (2) 7-seg monocolor* CONFIGURATION CHOICE Common-Cathode Drive: Digit Type CC2: 16-seg monocolor Table 39. Slot 2 Configuration See Table 41. D6 D5 See Table 40. D4 D3 D2 D1 D0 0 0 1 0 0 1 1 1 See Table 38. *7-segment digits can be replaced by directly controlled discrete LEDs according to settings in decode mode register (Table 11). **The highlighted row is used in Typical Operating Circuit 1 for display digits 2 and 3. www.maximintegrated.com Maxim Integrated | 33 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 -- -- -- b 1b b b c c 1c c c CC4 CC4 CC4 CC4 -- CC4 CC5 CC5 -- -- CC5 -- d1 1d d1 d1 1d d d d2 d2 1dp d2 d2 1dp -- e e 1e e e 1e e 09 f f 1f f f 1f f 010 g1 g1 1g g1 g1 1g g1 011 g2 g2 2a g2 g2 2a g2 012 h h 2b h h 2b h 013 i i 2c i i 2c 014 j j 2d j j 2d 015 k k 2e k k 016 l l 2f l l 017 m m 2g m 018 dp dp 2dp dp a2 02 b 03 c 04 05 CC4 and CC5: (1)16-seg bicolor 01 1a a1 a2 -- a2 b 1b b c 1c CC4 -- -- CC5 06 d1 07 08 ADDRESS CODE (HEX) REGISTER DATA D3 D2 D1 D0 1a a a2 -- -- b 1b b c 1c c -- -- CC4 CC5 CC5 CC5 d1 1d d -- d2 1dp -- e e 1e e f f 1f f g1 g1 1g g1 g2 g2 2a g2 h h 2b h i i i 2c i j j j 2d k 2e k k k 2e l 2f l l l 2f l m 2g m m m 2g m dp 2dp dp dp dp 2dp dp See Table 41. D6 D4 a1 0x0C D7 D5 CC4 and CC5: (2) 14-seg monocolor or 14-seg bicolor CC4: 14-seg monocolor a2 a1 CC5: (2) 7-seg monocolor* or 7-seg bicolor CC5: 14-seg monocolor a a1 CC5: 16-seg monocolor CC4: (2) 7-seg monocolor* or 7-seg bicolor a 00 CC4 and CC5: (2) 7-seg bicolor or (4) 7-seg monocolor or (1) 7-seg bicolor and (2) 7-seg monocolor* 1a CC5: 16-seg monocolor a1 CONFIGURATION CHOICE Common-Cathode Drive: Digit Type CC4: 16-seg monocolor CC4: 16-seg monocolor Table 40. Slot 3 Configuration 0 0 1 0 0 1 1 1 See Table 39. See Table 38. *7-segment digits can be replaced by directly controlled discrete LEDs according to settings in decode mode register (Table 11). **The highlighted row is used in Typical Operating Circuit 1 for display digits 4 and 5. www.maximintegrated.com Maxim Integrated | 34 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 CC6: 16-seg monocolor CC6: (2) 7-seg monocolor* or 7-seg bicolor CC6: 14-seg monocolor CC7: 16-seg monocolor CC7: (2) 7-seg monocolor* or 7-seg bicolor a1 1a a1 a1 1a a a a1 1a a a2 a2 -- a2 a2 -- -- -- a2 -- -- 02 b b 1b b b 1b b b b 1b b 03 c c 1c c c 1c c c c 1c c 04 d1 d1 1d d1 d1 1d d d d1 1d d 05 d2 d2 1dp d2 d2 1dp -- -- d2 1dp -- 06 CC6 -- CC6 CC6 CC6 CC6 -- CC6 -- -- CC6 07 -- CC7 CC7 CC7 -- -- CC7 -- CC7 CC7 CC7 08 e e 1e e e 1e e e e 1e e 09 f f 1f f f 1f f f f 1f f 010 g1 g1 1g g1 g1 1g g1 g1 g1 1g g1 011 g2 g2 2a g2 g2 2a g2 g2 g2 2a g2 012 h h 2b h h 2b h h h 2b h 013 i i 2c i i 2c i i i 2c i 014 j j 2d j j 2d j j j 2d k 015 k k 2e k k 2e k k k 2e l 016 l l 2f l l 2f l l l 2f l 017 m m 2g m m 2g m m m 2g m 018 dp dp 2dp dp dp 2dp dp dp dp 2dp dp ADDRESS CODE (HEX) REGISTER DATA CC6 and CC7: (2) 14-seg monocolor or 14-seg bicolor CC6 and CC7: (1)16-seg bicolor a1 01 CC7: 14-seg monocolor CC7: 16-seg monocolor 00 CC6 and CC7: (2) 7-seg bicolor or (4) 7-seg monocolor or (1) 7-seg bicolor and (2) 7-seg monocolor* CONFIGURATION CHOICE Common-Cathode Drive: Digit Type CC6: 16-seg monocolor Table 41. Slot 4 Configuration 0x0C D7 0 1 0 1 D6 0 0 1 1 D5 D4 D3 D2 D1 D0 See Table 40. See Table 39. See Table 38. *7-segment digits can be replaced by directly controlled discrete LEDs according to settings in the decode mode register (Table 11). **The highlighted row is used in Typical Operating Circuit 1 for display digits 6 and 7. www.maximintegrated.com Maxim Integrated | 35 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Typical Operating Circuits 3.3V O0 V+ 47F V+ O1 V+ O2 GND GND O3 GND O5 100nF O4 MAX6955 O6 O11 O12 O13 O14 O15 O16 O17 O18 O0 O1 O7 a b c d e f g dp Rcc Gcc O2 O4 O5 O6 O8 O9 O10 O7 a b c d e f g dp O1 O0 CC1 CC0 DIGIT 0b (RED), DIGIT 1b (GREEN) 7-SEGMENT BICOLOR LED O8 O9 O10 SCL O11 AD0 O12 AD1 O13 SDA O14 O15 BLINK O16 O17 OSC_OUT O18 P0 OSC P1 P2 ISET CSET P3 O0 O4 O5 O6 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O2 O3 DIGITS 0a AND 1a 7-SEGMENT MONOCOLOR P4/IRQ RSET DIGITS 2 AND 3 14-SEGMENT BICOLOR O0 O2 O3 O4 O0 O2 O3 O4 O5 O8 O9 O10 O5 O8 O9 O10 O11 O12 O13 O14 O11 O12 O13 O14 O15 O16 O17 O18 O15 O16 O17 O18 O6 O7 DIGIT 6 4 x 4 MATRIX OF DISCRETE MONOCOLOR LEDs www.maximintegrated.com a b c d e f g1 g2 h i j k l m dp Rcc Ccc DIGIT 7 4 x 4 MATRIX OF DISCRETE MONOCOLOR LEDs O0 O1 O2 O3 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O5 a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 5 16-SEGMENT MONOCOLOR O0 O1 O2 O3 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O4 a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 4 16-SEGMENT MONOCOLOR Maxim Integrated | 36 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Typical Operating Circuits (continued) 3.3V O0 V+ V+ O1 V+ O2 GND GND O3 GND O5 100nF 47F O4 O6 MAX6955 O7 O8 O9 O10 SCL O11 AD0 O12 AD1 O13 SDA O14 O15 O16 BLINK O17 OSC_OUT O18 P0 P1 OSC P2 P3 ISET CSET P4/IRQ RSET O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O0 a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O1 a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 0 O0 O1 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O2 a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 1 O0 O1 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O3 a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 2 O0 O1 O2 O3 O6 O6 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O4 a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc O0 O1 O2 O3 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O5 DIGIT 4 www.maximintegrated.com a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc O0 O1 O2 O3 O4 O5 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O6 DIGIT 5 a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 3 O0 O1 O2 O3 O4 O5 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O7 DIGIT 6 a a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 7 Maxim Integrated | 37 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Typical Operating Circuits (continued) 3.3V O0 V+ 47F V+ O1 V+ O2 GND GND O3 GND O5 100nF O4 O6 O11 O12 O13 O14 O15 O16 O17 O18 O0 O1 O7 MAX6955 a b c d e f g dp Rcc Gcc O2 O4 O5 O6 O8 O9 O10 O7 a b c d e f g dp O1 O0 CC1 CC0 DIGIT 0b (RED), DIGIT 1b (GREEN) 7-SEGMENT BICOLOR LED O8 O9 O10 SCL O11 AD0 O12 AD1 O13 SDA O14 O15 O16 BLINK O17 OSC_OUT O18 P0 P1 OSC P2 P3 ISET CSET O0 O4 O5 O6 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O2 O3 DIGITS 0a AND 1a 7-SEGMENT MONOCOLOR P4/IRQ RSET DIGITS 2 AND 3 14-SEGMENT BICOLOR O0 O1 O2 O3 O4 O5 O6 O7 SW00 SW01 SW02 SW03 SW04 SW05 SW06 SW07 P0 O0 O1 O2 O3 O4 O5 O6 O7 O0 O1 O2 O3 O4 O5 O6 O7 SW20 SW21 SW22 SW23 SW24 SW25 SW26 SW27 P2 SW10 SW11 SW12 SW13 SW14 SW15 SW16 SW17 P1 DIGIT 6 4 x 4 MATRIX OF DISCRETE MONOCOLOR LEDs www.maximintegrated.com a b c d e f g1 g2 h i j k l m dp Rcc Ccc O0 O1 O2 O3 O4 O5 O6 O7 SW30 SW31 SW32 SW33 SW34 SW35 SW36 SW37 P3 DIGIT 7 4 x 4 MATRIX OF DISCRETE MONOCOLOR LEDs O0 O1 O2 O3 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O5 a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 5 16-SEGMENT MONOCOLOR O0 O1 O2 O3 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O4 a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp cc DIGIT 4 16-SEGMENT MONOCOLOR Maxim Integrated | 38 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Pin Configurations O4 11 26 O13 O5 O6 7 O5 12 25 O12 O7 9 O6 13 24 O11 O8 10 O7 14 23 O10 20 OSC BLINK 31 32 33 22 O10 21 O9 20 EP* 19 ISET 17 8 V+ N.C. 21 V+ 23 O14 O13 O12 O11 26 18 22 O9 34 24 27 MAX6955 5 27 O14 O8 15 P0 P4/IRQ P3 P2 OSC_OUT 25 28 O3 10 GND 16 35 6 3 17 28 O15 4 29 V+ MAX6955 O2 O3 O4 O18 O17 O16 O15 30 2 16 O2 9 P1 29 O16 36 O1 8 37 30 O17 1 15 O0 7 + AD1 O0 O1 14 31 O18 SDA AD0 AD1 6 38 32 BLINK 13 33 OSC_OUT SCL 5 SCL SDA 4 39 34 P2 12 35 P3 11 P1 2 AD0 3 N.C. 36 P4/IRQ GND GND ISET GND V+ OSC P0 1 40 TOP VIEW TQFN-EP *EP = EXPOSED PAD. CONNECT EP TO GND. GND 18 19 V+ SSOP Chip Information PROCESS: CMOS Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE www.maximintegrated.com PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 36 SSOP A36-2 21-0040 90-0098 40 TQFN-EP T4066+5 21-0141 90-0055 Maxim Integrated | 39 2-Wire Interfaced, 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan MAX6955 Revision History PAGES CHANGED REVISION NUMBER REVISION DATE 0 -- Initial release -- 1 -- -- -- 2 12/06 -- -- 3 3/08 Corrected data sheet errors. 4 7/15 Removed automotive reference from data sheet and updated Benefits and Features section DESCRIPTION 1, 2, 3, 6, 15, 16, 18, 19, 36, 37, 38 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2015 Maxim Integrated Products, Inc. | 40 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX6955AAX+ MAX6955AAX+T MAX6955ATL+ MAX6955ATL+T MAX6955APL+