MAX6730-MAX6735 General Description Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output The MAX6730-MAX6735 single/dual/triple-voltage microprocessor (P) supervisors feature a watchdog timer and manual reset capability. The MAX6730-MAX6735 offer factory-set reset thresholds for monitoring voltages from +0.9V to +5V and an adjustable reset input for monitoring voltages down to +0.63V. The combination of these features significantly improves system reliability and accuracy when compared to separate ICs or discrete components. The active-low reset output asserts and remains asserted for the reset timeout period after all the monitored voltages exceed their respective thresholds. Multiple factory-set reset threshold combinations reduce the number of external components required. The MAX6730/MAX6731 monitor a single fixed voltage, the MAX6732/MAX6733 monitor two fixed voltages, and the MAX6734/MAX6735 monitor two fixed voltages and one adjustable voltage. All devices are offered with six minimum reset timeout periods ranging from 1.1ms to 1120ms. The MAX6730-MAX6735 feature a watchdog timer with an independent watchdog output. The watchdog timer prevents system lockup during code execution errors. A watchdog startup delay of 54s after reset asserts allows system initialization during power-up. The watchdog operates in normal mode with a 1.68s delay after initialization. The MAX6730/MAX6732/MAX6734 provide an active-low, open-drain watchdog output. The MAX6731/MAX6733/ MAX6735 provide an active-low, push-pull watchdog output. Other features include a manual reset input (MAX6730/ MAX6731/MAX6734/MAX6735) and push-pull reset output (MAX6731/MAX6733/MAX6735) or open-drain reset output (MAX6730/MAX6732/MAX6734). The MAX6730- MAX6733 are offered in a tiny SOT23-6 package. The MAX6734/MAX6735 are offered in a space-saving SOT23-8 package. All devices are fully specified over the extended -40C to +85C temperature range. Benefits and Features VCC1 (Primary Supply) Reset Threshold Voltages from +1.575V to +4.63V VCC2 (Secondary Supply) Reset Threshold Voltages from +0.79V to +3.08V Adjustable RSTIN Threshold for Monitoring Voltages Down to +0.63V (MAX6734/MAX6735 Only) Six Reset Timeout Options Watchdog Timer with Independent Watchdog Output * 35s (min) Initial Watchdog Startup Period * 1.12s (min) Normal Watchdog Timeout Period Manual Reset Input (MAX6730/MAX6731/MAX6734/MAX6735) Guaranteed Reset Valid down to VCC1 or VCC2 = +0.8V Push-Pull RESET or Open-Drain RESET Output Immune to Short VCC Transients Low Supply Current: 14A (typ) at +3.6V Small 6-Pin and 8-Pin SOT23 Packages Pin Configurations appear at end of data sheet. Typical Operating Circuit Multivoltage Systems Telecom/Networking Equipment Computers/Servers Portable/Battery-Operated Equipment Industrial Equipment Printer/Fax Set-Top Boxes 19-2629; Rev 8; 12/15 +3.3V VCC1 VCC2 RSTIN RST MAX6734 MAX6735 WDI Applications +1.8V +0.9V VCORE PUSHBUTTON SWITCH WDO VCC (I/O) VDD (MEMORY) RESET I/O P NMI MR GND GND MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Absolute Maximum Ratings VCC1, VCC2, RSTIN, MR, WDI to GND...................-0.3V to +6V RST, WDO to GND (open drain)..............................-0.3V to +6V RST, WDO to GND (push-pull)............... -0.3V to (VCC1 + 0.3V) Input Current/Output Current (all pins)................................20mA Continuous Power Dissipation (TA = +70C) 6-Pin SOT23-6 (derate 4.3mW/C above +70C).....347.8mW 8-Pin SOT23-8 (derate 5.6mW/C above +70C).....444.4mW Operating Temperature Range............................ -40C to +85C Storage Temperature Range............................. -65C to +150C Junction Temperature.......................................................+150C Lead Temperature (soldering, 10s).................................. +300C Soldering Temperature (reflow) Lead (Pb)-free packages.............................................+260C Package containing lead (Pb) .....................................+240C 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. Package Thermal Characteristics (Note 1) 6 SOT23 Junction-to-Ambient Thermal Resistance (JA).........230C/W Junction-to-Case Thermal Resistance (JC)................76C/W 8 SOT23 Junction-to-Ambient Thermal Resistance (JA).........180C/W Junction-to-Case Thermal Resistance (JC)................60C/W Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. Electrical Characteristics (VCC1 = VCC2 = +0.8V to +5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2) PARAMETER Supply Voltage SYMBOL VCC1, VCC2 ICC1 Supply Current ICC2 VCC1 Reset Threshold www.maximintegrated.com CONDITIONS VTH1 MIN TYP 0.8 MAX UNITS 5.5 V VCC1 < +5.5V, all I/O connections open, outputs not asserted 15 39 VCC1 < +3.6V, all I/O connections open, outputs not asserted 10 28 VCC2 < +3.6V, all I/O connections open, outputs not asserted 4 11 VCC2 < +2.75V, all I/O connections open, outputs not asserted 3 9 A L (falling) 4.500 4.625 4.750 M (falling) 4.250 4.375 4.500 T (falling) 3.000 3.075 3.150 S (falling) 2.850 2.925 3.000 R (falling) 2.550 2.625 2.700 Z (falling) 2.250 2.313 2.375 Y (falling) 2.125 2.188 2.250 W (falling) 1.620 1.665 1.710 V (falling) 1.530 1.575 1.620 V Maxim Integrated 2 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Electrical Characteristics (continued) (VCC1 = VCC2 = +0.8V to +5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2) PARAMETER VCC2 Reset Threshold SYMBOL VTH2 CONDITIONS MIN TYP MAX T (falling) 3.000 3.075 3.150 S (falling) 2.850 2.925 3.000 R (falling) 2.550 2.625 2.700 Z (falling) 2.250 2.313 2.375 Y (falling) 2.125 2.188 2.250 W (falling) 1.620 1.665 1.710 V (falling) 1.530 1.575 1.620 I (falling) 1.350 1.388 1.425 H (falling) 1.275 1.313 1.350 G (falling) 1.080 1.110 1.140 F (falling) 1.020 1.050 1.080 E (falling) 0.810 0.833 0.855 D (falling) 0.765 0.788 0.810 Reset Threshold Tempco Reset Threshold Hysteresis VHYST VCC_ to RST Output Delay tRD Reset Timeout Period tRP UNITS V 20 ppm/C Referenced to VTH typical 0.5 % VCC1 = (VTH1 + 100mV) to (VTH1 - 100mV) or VCC2 = (VTH2 + 75mV) to (VTH2 - 75mV) 45 s D1 1.1 1.65 2.2 D2 8.8 13.2 17.6 D3 140 210 280 D5 280 420 560 D6 560 840 1120 D4 1120 1680 2240 626.5 ms ADJUSTABLE RESET COMPARATOR INPUT (MAX6734/MAX6735) RSTIN Input Threshold VRSTIN 611 RSTIN Input Current IRSTIN -25 RSTIN Hysteresis RSTIN to Reset Output Delay tRSTIND VRSTIN to (VRSTIN - 30mV) 642 mV +25 nA 3 mV 22 s MANUAL RESET INPUT (MAX6730/MAX6731/MAX6734/MAX6735) MR Input Threshold VIL VIH MR Minimum Pulse Width 0.3 x VCC1 0.7 x VCC1 1 MR Glitch Rejection MR to Reset Output Delay MR Pullup Resistance www.maximintegrated.com tMR 25 V s 100 ns 200 ns 50 80 k Maxim Integrated 3 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Electrical Characteristics (continued) (VCC1 = VCC2 = +0.8V to +5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 35 54 72 1.12 1.68 2.24 UNITS WATCHDOG INPUT Watchdog Timeout Period WDI Pulse Width WDI Input Voltage WDI Input Current tWD-L First watchdog period after reset timeout period tWD-S Normal mode tWDI (Note 3) 50 VIL IWDI ns 0.3 x VCC1 VIH 0.7 x VCC1 WDI = 0 or VCC1 -1 s +1 V A RESET/WATCHDOG OUTPUT RST/WDO Output Low Voltage (Push-Pull or Open Drain) RST/WDO Output High Voltage (Push-Pull Only) RST/WDO Output Open-Drain Leakage Current VOL VOH VCC1 or VCC2 +0.8V, ISINK = 1A, output asserted 0.3 VCC1 or VCC2 +1.0V, ISINK = 50A, output asserted 0.3 VCC1 or VCC2 +1.2V, ISINK = 100A, output asserted 0.3 VCC1 or VCC2 +2.7V, ISINK = 1.2mA, output asserted 0.3 VCC1 or VCC2 +4.5V, ISINK = 3.2mA, output asserted 0.4 VCC1 +1.8V, ISOURCE = 200A, output not asserted 0.8 x VCC1 VCC1 +2.7V, ISOURCE = 500A, output not asserted 0.8 x VCC1 VCC1 +4.5V, ISOURCE = 800A, output not asserted 0.8 x VCC1 Output not asserted V V 0.5 A Note 2: Devices tested at TA = +25C. Overtemperature limits are guaranteed by design and not production tested. Note 3: Parameter guaranteed by design. www.maximintegrated.com Maxim Integrated 4 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Typical Operating Characteristics (VCC1 = +5V, VCC2 = +3.3V, TA = +25C, unless otherwise noted.) 10 8 6 ICC2 4 2 TOTAL 12 10 8 ICC1 6 4 16 ICC2 2 -15 10 35 60 0 85 -40 TEMPERATURE (C) SUPPLY CURRENT (A) 16 14 12 TOTAL 8 6 ICC1 4 2 0 -15 10 35 60 ICC2 -40 -15 10 35 TEMPERATURE (C) www.maximintegrated.com 8 ICC1 6 4 ICC2 0 85 -40 60 85 -15 10 35 60 85 TEMPERATURE (C) SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +1.8V, VCC2 = +1.2V) 10 TOTAL 10 TEMPERATURE (C) MAX6730-35 toc04 18 12 1.010 NORMALIZED THRESHOLD VOLTAGE vs. TEMPERATURE MAX6730-35 toc05 -40 14 2 NORMALIZED THRESHOLD VOLTAGE 0 14 SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +2.5V, VCC2 = +1.8V) MAX6730-35 toc03 16 18 SUPPLY CURRENT (A) ICC1 12 SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +3.3V, VCC2 = +2.5V) MAX6730-35 toc02 TOTAL 14 18 SUPPLY CURRENT (A) SUPPLY CURRENT (A) 16 MAX6730-35 toc01 18 SUPPLY CURRENT vs. TEMPERATURE (VCC1 = +5V, VCC2 = +3.3V) 1.008 1.006 1.004 1.002 1.000 0.998 0.996 0.994 0.992 0.990 -40 -15 10 35 60 85 TEMPERATURE (C) Maxim Integrated 5 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Typical Operating Characteristics (continued) (VCC1 = +5V, VCC2 = +3.3V, TA = +25C, unless otherwise noted.) 1.0035 1.0030 1.0025 1.0020 1.0015 1.0010 1.0005 1.0000 0.9995 10 35 60 85 RST 2V/div 10 1 MAX6730-35 toc09 VCC_ TO RESET OUTPUT DELAY (s) 10 100 1000 VCC_ TO RESET OUTPUT DELAY vs. TEMPERATURE (100mV OVERDRIVE) 70 65 60 55 50 45 -45 -15 10 35 TEMPERATURE (C) www.maximintegrated.com MR 2V/div RESET THRESHOLD OVERDRIVE (mV) 75 40 MAX6730-35 toc08 100 TEMPERATURE (C) 80 MR TO RESET OUTPUT DELAY 60 85 40ns/div RSTIN TO RESET OUTPUT DELAY vs. TEMPERATURE 30 MAX6730-35 toc10 -15 -40 RST ASSERTS ABOVE THIS LINE 1000 RSTIN TO RESET OUTPUT DELAY (s) 0.9990 10,000 MAXIMUM VCC_ TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE MAX6730-35 toc07 MAX6730-35 toc06 NORMALIZED TIMEOUT PERIOD 1.0040 MAXIMUM VCC_ TRANSIENT DURATION (ms) NORMALIZED TIMEOUT PERIOD vs. TEMPERATURE 28 26 24 22 20 18 16 14 12 10 -45 -15 10 35 60 85 TEMPERATURE (C) Maxim Integrated 6 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Pin Configurations TOP VIEW RST 1 GND 2 + MAX6730 MAX6731 WDO 3 SOT23-6 6 VCC1 RST 1 5 WDI GND 2 4 MR WDO 3 + MAX6732 MAX6733 6 VCC1 5 WDI 4 VCC2 RST 1 GND 2 WDI 3 + MAX6734 MAX6735 WDO 4 SOT23-6 8 VCC1 7 RSTIN 6 VCC2 5 MR SOT23-8 Pin Description MAX6730 MAX6731 PIN MAX6732 MAX6733 MAX6734 MAX6735 NAME 1 1 1 RST 2 2 2 GND FUNCTION Active-Low Reset Output. The MAX6730/MAX6732/MAX6734 provide an open-drain output. The MAX6731/MAX6733/MAX6735 provide a push-pull output. RST asserts low when any of the following conditions occur: VCC1 or VCC2 drops below its preset threshold, RSTIN drops below its reset threshold, or MR is driven low. Opendrain versions require an external pullup resistor. Ground Active-Low Watchdog Output. The MAX6730/MAX6732/MAX6734 provide an open-drain WDO output. The MAX6731/MAX6733/MAX6735 provide a push-pull WDO output. WDO asserts low when no low-to-high or high-to-low transition occurs on WDI within the watchdog timeout period (tWD) or if an undervoltage lockout condition exists for VCC1, VCC2, or RSTIN. WDO deasserts without a timeout period when VCC1, VCC2, and RSTIN exceed their reset thresholds, or when the manual reset input is asserted. Open-drain versions require an external pullup resistor. 3 3 4 WDO 4 -- 5 MR 5 5 3 WDI 6 6 8 VCC1 Primary Supply-Voltage Input. VCC1 provides power to the device when it is greater than VCC2. VCC1 is the input to the primary reset threshold monitor. -- 4 6 VCC2 Secondary Supply-Voltage Input. VCC2 provides power to the device when it is greater than VCC1. VCC2 is the input to the secondary reset threshold monitor. 7 Undervoltage Reset Comparator Input. RSTIN provides a high-impedance comparator input for the adjustable reset monitor. RST asserts low if the voltage RSTIN at RSTIN drops below the 626mV internal reference voltage. Connect a resistive voltage-divider to RSTIN to monitor voltages higher than 626mV. Connect RSTIN to VCC1 or VCC2 if unused. -- -- www.maximintegrated.com Active-Low Manual Reset Input. Drive MR low to force a reset. RST remains asserted as long as MR is low and for the reset timeout period after MR releases high. MR has a 50k pullup resistor to VCC1; leave MR open or connect to VCC1 if unused. Watchdog Input. If WDI remains high or low for longer than the watchdog timeout period, the internal watchdog timer expires and the watchdog output asserts low. The internal watchdog timer clears whenever RST asserts or a rising or falling edge on WDI is detected. The watchdog has an initial watchdog timeout period (35s min) after each reset event and a short timeout period (1.12s min) after the first valid WDI transition. Leaving WDI unconnected does not disable the watchdog timer function. Maxim Integrated 7 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Table 1. Reset Voltage Threshold Suffix Guide** VCC1 NOMINAL VOLTAGE THRESHOLD(V) VCC2 NOMINAL VOLTAGE THRESHOLD (V) LT 4.625 3.075 MS 4.375 2.925 MR 4.375 2.625 TZ 3.075 2.313 SY 2.925 2.188 PART NO. SUFFIX RY 2.625 2.188 TW 3.075 1.665 SV 2.925 1.575 RV 2.625 1.575 TI 3.075 1.388 SH 2.925 1.313 RH 2.625 1.313 TG 3.075 1.110 SF 2.925 1.050 RF 2.625 1.050 TE 3.075 0.833 SD 2.925 0.788 RD 2.625 0.788 ZW 2.313 1.665 YV 2.188 1.575 ZI 2.313 1.388 YH 2.188 1.313 ZG 2.313 1.110 YF 2.188 1.050 ZE 2.313 0.833 YD 2.188 0.788 WI 1.665 1.388 VH 1.575 1.313 WG 1.665 1.110 VF 1.575 1.050 WE 1.665 0.833 VD 1.575 0.788 Table 2. Reset Timeout Period Suffix Guide ACTIVE TIMEOUT PERIOD TIMEOUT PERIOD SUFFIX MIN (ms) MAX (ms) D1 1.1 2.2 D2 8.8 17.6 D3 140 280 D5 280 560 D6 560 1120 D4 1120 2240 Detailed Description Supply Voltages The MAX6730-MAX6735 microprocessor (P) supervisors maintain system integrity by alerting the P to fault conditions. The MAX6730-MAX6735 monitor one to three supply voltages in P-based systems and assert an active-low reset output when any monitored supply voltage drops below its preset threshold. The output state remains valid for VCC1 or VCC2 greater than +0.8V. Threshold Levels The two-letter code in the Reset Voltage Threshold Suffix Guide (Table 1) indicates the threshold level combinations for VCC1 and VCC2. Reset Output The MAX6730-MAX6735 feature an active-low reset output (RST). RST asserts when the voltage at either VCC1 or VCC2 falls below the voltage threshold level, VRSTIN drops below its threshold, or MR is driven low (Figure 1). RST remains low for the reset timeout period (Table 2) after VCC1, VCC2, and RSTIN increase above their respective thresholds and after MR releases high. Whenever VCC1, VCC2, or RSTIN go below the reset threshold before the end of the reset timeout period, the internal timer restarts. The MAX6730/MAX6732/ MAX6734 provide an opendrain RST output, and the MAX6731/MAX6733/MAX6735 provide a push-pull RST output. **Standard versions are shown in bold and are available in a D3 timeout option only. Standard versions require 2500-piece order increments and are typically held in sample stock. There is a 10,000-piece order increment on nonstandard versions. Other threshold voltages may be available; contact factory for availability. www.maximintegrated.com Maxim Integrated 8 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Manual Reset Input Many P-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. A logic low on MR asserts the reset output, clears the watchdog timer, and deasserts the watchdog output. Reset remains asserted while MR is low and for the reset timeout period (tRP) after MR returns high. An internal 50k pullup resistor allows MR to be left open if unused. Drive MR with TTL or CMOS-logic levels or with open-drain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manual reset function; external debounce circuitry is not required. Connect a 0.1F capacitor from MR to GND to provide additional noise immunity when driving MR over long cables or if the device is used in a noisy environment. Adjustable Input Voltage (RSTIN) The MAX6734/MAX6735 provide an additional highimpedance comparator input with a 626mV threshold to monitor a third supply voltage. To monitor a voltage higher than 626mV, connect a resistive-divider to the circuit as shown in Figure 2 to establish an externally controlled threshold voltage, VEXT_TH. VEXT_TH = 626mV x VCC1, VCC2 RSTIN VCC (MIN) RST VEXT_TH R1 MAX6734 MAX6735 RSTIN R2 GND Figure 2. Monitoring a Third Voltage (R1+ R2) R2 VTH tRP tRP WDO MR Figure 1. RST, WDO, and MR Timing Diagram www.maximintegrated.com Maxim Integrated 9 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output The RSTIN comparator derives power from VCC1, and the input voltage must remain less than or equal to VCC1. Low leakage current at RSTIN allows the use of largevalued resistors, resulting in reduced power consumption of the system. Watchdog The watchdog feature monitors P activity through the watchdog input (WDI). A rising or falling edge on WDI within the watchdog timeout period (tWD) indicates normal P operation. WDO asserts low if WDI remains high or low for longer than the watchdog timeout period. Leaving WDI unconnected does not disable the watchdog timer. The devices include a dual-mode watchdog timer to monitor P activity. The flexible timeout architecture provides a long-period initial watchdog mode, allowing complicated systems to complete lengthy boots, and a short-period normal watchdog mode, allowing the supervisor to provide quick alerts when processor activity fails. After each reset event (VCC power-up, brownout, or manual reset), there is a long initial watchdog period of 35s (min). The long watchdog period mode provides an extended time for the system to power up and fully initialize all P and system components before assuming responsibility for routine watchdog updates. VCC1, VCC2 RSTIN VCC (MIN) The usual watchdog timeout period (1.12s min) begins after the initial watchdog timeout period (tWD-L) expires or after the first transition on WDI (Figure 3). During normal operating mode, the supervisor asserts the WDO output if the P does not update the WDI with a valid transition (high to low or low to high) within the standard timeout period (tWD-S) (1.12s min). Connect MR to WDO to force a system reset in the event that no rising or falling edge is detected at WDI within the watchdog timeout period. WDO asserts low when no edge is detected by WDI, the RST output asserts low, the watchdog counter immediately clears, and WDO returns high. The watchdog counter restarts, using the long watchdog period, when the reset timeout period ends (Figure 4). Ensuring a Valid RESET Output Down to VCC = 0V The MAX6730-MAX6735 guarantee proper operation down to VCC = +0.8V. In applications that require valid reset levels down to VCC = 0V, use a 100k pulldown resistor from RST to GND. The resistor value used is not critical, but it must be large enough not to load the reset output when VCC is above the reset threshold. For most applications, 100k is adequate. Note that this configuration does not work for the open-drain outputs of MAX6730/MAX6732/MAX6734. VTH RST tRP WDO WDI < tWD-L < tWD-S < tWD-S > tWD-S < tWD-S < tWD-S tWD-S Figure 3. Watchdog Input/Output Timing Diagram (MR and WDO Not Connected) www.maximintegrated.com Maxim Integrated 10 MAX6730-MAX6735 VCC1, VCC2 RSTIN VCC (MIN) RST Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output VTH tRP tRP WDO WDI < tWD-L < tWD-S > tWD-S < tWD-L MR tMR Figure 4. Watchdog Input/Output Timing Diagram (MR and WDO Connected) Applications Information Interfacing to Ps with Bidirectional Reset Pins Microprocessors with bidirectional reset pins can interface directly with the open-drain RST output options. However, conditions might occur in which the push-pull output versions experience logic contention with the bidirectional reset pin of the P. Connect a 10k resistor between RST and the P's reset I/O port to prevent logic contention (Figure 5). VCC2 VCC1 VCC1 MAX6731 MAX6733 MAX6735 RST RESET TO OTHER SYSTEM COMPONENTS 10k RESET P VCC2 Falling VCC Transients The devices P supervisors are relatively immune to short-duration falling VCC_ transients (glitches). Small glitches on VCC_ are ignored by the MAX6730-MAX6735, preventing undesirable reset pulses to the P. The Typical Operating Characteristics show Maximum Transient Duration vs. Reset Threshold Overdrive, for which reset www.maximintegrated.com GND GND Figure 5. Interfacing to Ps with Bidirectional Reset I/O Maxim Integrated 11 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output pulses are not generated. The graph was produced using falling VCC_ pulses, starting above VTH and ending below the reset threshold by the magnitude indicated (reset threshold overdrive). The graph shows the maximum pulse width that a falling VCC transient typically might have without causing a reset pulse to be issued. As the amplitude of the transient increases (i.e., goes further below the reset threshold), the maximum allowable pulse width decreases. A 0.1F bypass capacitor mounted close to VCC_ provides additional transient immunity. Watchdog Software Considerations Setting and resetting the watchdog input at different points in the program rather than "pulsing" the watchdog input high-low-high or low-high-low helps the watchdog timer closely monitor software execution. This technique avoids a "stuck" loop, in which the watchdog timer continues to be reset within the loop, preventing the watchdog from timing out. Figure 6 shows an example flow diagram in which the I/O driving the watchdog input is set high at the beginning of the program, set low at the beginning of every subroutine or loop, and then set high again when the program returns to the beginning. If the program "hangs" in any subroutine, the I/O continually asserts low (or high), and the watchdog timer expires, issuing a reset or interrupt. Functional Diagram VCC1 MR MAX6730- MAX6735 VCC1 VCC2 VREF RESET TIMEOUT PERIOD VCC1 MR PULLUP VCC1 VCC2 RESET OUTPUT DRIVER RST VCC1 WATCHDOG TIMER RSTIN WDO WDI VCC1 REF VREF / 2 GND START SET WDI HIGH PROGRAM CODE SUBROUTINE OR PROGRAM LOOP SET WDI LOW HANG IN SUBROUTINE SUBROUTINE COMPLETED RETURN Figure 6. Watchdog Flow Diagram www.maximintegrated.com Maxim Integrated 12 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Selector Guide PART NUMBER VOLTAGE MONITORS RST OUTPUT MANUAL RESET WATCHDOG INPUT WATCHDOG OUTPUT MAX6730 1 Open Drain Open Drain MAX6731 1 Push-Pull Push-Pull MAX6732 2 Open Drain -- Open Drain MAX6733 2 Push-Pull -- Push-Pull MAX6734 3 Open Drain Open Drain MAX6735 3 Push-Pull Push-Pull Ordering Information PART* MAX6730UT_D_ +T MAX6731UT_D_ +T MAX6732UT_ _D_ +T MAX6733UT_ _D_ -T MAX6734KA_ _D_ -T MAX6734KA_ _ D_+T MAX6734KA_ _D_ /V+T MAX6735KA_ _D_ +T TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Information PIN-PACKAGE 6 SOT23 6 SOT23 6 SOT23 6 SOT23 8 SOT23 8 SOT23 8 SOT23 8 SOT23 *Insert the threshold level suffixes for VCC1 and VCC2 (Table 1) after "UT" or "KA." For the MAX6730/MAX6731, insert only the VCC1 threshold suffix after the "UT." Insert the reset timeout delay (Table 2) after "D" to complete the part number. For example, the MAX6732UTLTD3+T provides a VCC1 threshold of +4.625V, a VCC2 threshold of +3.075V, and a 210ms reset timeout period. Sample stock is generally held on standard versions only. Standard versions have an order increment requirement of 2500 pieces. Nonstandard versions have an order increment requirement of 10,000 pieces. Contact factory for availability. +Denotes Lead(Pb)-free packages and - denotes leaded packages. Not all MAX6734KA_ _D_ options are available with leaded (-T) packages. See https://www.maximintegrated.com for available leaded options. Some devices are available in both leaded and lead(Pb)-free/ RoHS compliant packaging. For top mark information, please go to https://www.maximintegrated.com/en/design/packaging/topmark/ /V denotes an automotive qualified part. www.maximintegrated.com 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. LAND OUTLINE NO. PATTERN NO. PACKAGE TYPE PACKAGE CODE 6 SOT23 U6+1, U6-1 (MAX6733 only) 21-0058 90-0175 8 SOT23 K8SN-1 (MAX6734 only), K8SN+1 21-0078 90-0176 Chip Information PROCESS: BiCMOS Maxim Integrated 13 MAX6730-MAX6735 Single/Dual/Triple-Voltage P Supervisory Circuits with Independent Watchdog Output Revision History REVISION NUMBER REVISION DATE 0 10/02 Initial release. -- 1 12/02 Released MAX6730/MAX6731. 1 2 1/03 Released MAX6733. 1 3 3/04 Updated Typical Operating Circuit. 14 4 12/05 Added lead-free notation to Ordering Information. 5 3/09 Updated Pin Description and added Package Table. 6 11/11 Added automotive-qualified part information 7 4/13 8 12/15 PAGES CHANGED DESCRIPTION 1 7, 14 1 Added Package Thermal Characteristics and corrected power dissipation errors and package code for 8 SOT23 Added lead-free part numbers to Ordering Information table, updated Package Information table, and removed Standard Versions table. 2-4, 14 1, 13, 14 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. 14 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX6730UTLD3+T MAX6730UTSD2+T MAX6730UTSD3+T MAX6730UTTD3+T MAX6731UTTD3+T MAX6734KALTD3+T MAX6734KASHD3+T MAX6734KASVD3+T MAX6734KASYD3+T MAX6734KAZGD3+T MAX6734KAZWD3+T MAX6735KALTD3+T MAX6735KARVD3+T MAX6735KASHD3+T MAX6735KASVD3+T MAX6735KASYD3+T MAX6735KATGD3+T MAX6732UTZWD3+T MAX6732UTTGD3+T MAX6734KATZD3+T MAX6730UTRD3+T MAX6731UTLD3+T MAX6732UTSVD3+T MAX6740XKTGD3+T MAX6734KASDD3+T MAX6734KATGD3+T MAX6734KASVD2-T MAX6734KALTD3/V+T