Typical Application Circuit and Functional Diagram appear
at end of data sheet.
Pin Configurations continued at end of data sheet.
●Cell Phones
●SAN/NAS
●Servers
●Notebooks
●Satellite Radio
General Description
The MAX7326 2-wire serial-interfaced peripheral features
16 I/O ports. The ports are divided into 12 push-pull out-
puts and four input ports with selectable internal pullups.
Input ports are overvoltage protected to +6V and feature
transition detection with interrupt output.
The four input ports are continuously monitored for state
changes (transition detection). The interrupt is latched,
allowing detection of transient changes. Any combina-
tion of inputs can be selected using the interrupt mask
to assert the open-drain, +6V-tolerant INT output. When
the MAX7326 is subsequently accessed through the
serial interface, any pending interrupt is cleared. The 12
push-pull outputs are rated to sink 20mA and are capable
of driving LEDs. The RST input clears the serial inter-
ace, terminating any I2C communication to or from the
MAX7326.
The MAX7326 uses two address inputs with four-level
logic to allow 16 I2C slave addresses. The slave address
also sets the power-up default state for the 12 output
ports and enables or disables internal 40kΩ pullups in
groups of two input ports.
The MAX7326 is one device in a family of pin-compatible
port expanders with a choice of input ports, open-drain
I/O ports, and push-pull output ports (see Table 1).
The MAX7326 is available in 24-pin QSOP and TQFN
packages and is specified over the -40°C to +125°C
automotive temperature range.
Applications
Features
●400kHz I2C Serial Interface
●+1.71V to +5.5V Operating Voltage
●12 Push-Pull Outputs Rated at 20mA Sink Current
●4 Input Ports with Matchable Latching Transition
Detection
●Input Ports are Overvoltage Protected to +6V
●Transient Changes are Latched, Allowing Detection
Between Read Operations
●INT Output Alerts Change on Any Selection of Inputs
●AD0 and AD2 Inputs Select from 16 Slave Addresses
●Low 0.6µA Standby Current
●-40°C to +125°C Temperature Range
19-3804; Rev 1; 5/14
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
PART INPUTS INTERRUPT
MASK
OPEN-
DRAIN
OUTPUTS
PUSH-PULL
OUTPUTS
MAX7324 8 Yes — 8
MAX7325 Up to 8 — Up to 8 8
MAX7326 4 Yes — 12
MAX7327 Up to 4 — Up to 4 12
PART TEMP RANGE PIN-PACKAGE
MAX7326AEG+ -40°C to +125°C 24 QSOP
MAX7326ATG+ -40°C to +125°C 24 TQFN-EP*
(4mm x 4mm)
TQFN (4mm x 4mm)
TOP VIEW
+
MAX7326
19
20
21
22
1 2 3 4 5 6
18 17 16 15 14 13
23
24
12
11
10
9
8
7
SCL
V+
SDA
INT
AD2
O0 O1 I2 I3 I4 I5
AD0
O15
O13
O12
O11
RST
O10
O8
O9
GND
O6
O7
O14
EXPOSED PAD
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Selector Guide
Ordering Information
Pin Congurations
EVALUATION KIT AVAILABLE
(All voltages referenced to GND.)
Supply Voltage V+ ...................................................-0.3V to +6V
SCL, SDA, AD0, AD2, RST, INT, I2–I5 ...................-0.3V to +6V
O0, O1, O6–O15 ....................................... -0.3V to V+ + 0.3V
O0, O1, O6–O15 Output Current .................................?25mA
SDA Sink Current .............................................................. 10mA
INT Sink Current.................................................................10mA
Total V+ Current .................................................................50mA
Total GND Current ...........................................................100mA
Continuous Power Dissipation (TA = +70°C)
24-Pin QSOP (derate 9.5mW/°C over +70°C) .........761.9mW
24-Pin TQFN (derate 20.8mW/°C over +70°C) ......1666.7mW
Operating Temperature Range ......................... -40°C to +125°C
Junction Temperature ...................................................... +150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
(V+ = +1.71V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at V+ = +3.3V, TA = +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Operating Supply Voltage V+TA = -40°C to +125°C 1.71 5.50 V
Power-On-Reset Voltage VPOR V+ falling 1.6 V
Standby Current (Interface Idle) ISTB SCL and SDA and other digital inputs at V+ 0.6 1.9 µA
Supply Current (Interface Running) I+fSCL = 400kHz, other digital inputs at V+ 23 55 µA
Input High-Voltage SDA, SCL,
AD0, AD2, RST, I2–I5 VIH
V+ < 1.8V 0.8 x V+ V
V+ ≥ 1.8V 0.7 x V+
Input Low-Voltage SDA, SCL, AD0,
AD2, RST, I2–I5 VIL
V+ < 1.8V 0.2 x V+ V
V+ ≥ 1.8V 0.3 x V+
Input Leakage Current SDA, SCL,
AD0, AD2, RST, I2–I5 IIH, IIL
SDA, SCL, AD0, AD2, RST, I2–I5 at V+ or
GND -0.2 +0.2 µA
Input Capacitance SDA, SCL, AD0,
AD2, RST, I2–I5 10 pF
Output Low-Voltage O0, O1,
O6–O15 VOL
V+ = +1.71V, ISINK = 5mA QSOP 90 180
mV
TQFN 90 230
V+ = +2.5V, ISINK = 10mA QSOP 110 210
TQFN 110 260
V+ = +3.3V, ISINK = 15mA QSOP 130 230
TQFN 130 280
V+ = +5V, ISINK = 20mA QSOP 140 250
TQFN 140 300
Output High-Voltage O0, O1,
O6–O15 VOH
V+ = +1.71V, ISOURCE = 2mA V+ - 250 V+ - 30
mV
V+ = +2.5V, ISOURCE = 5mA V+ - 360 V+ - 30
V+ = +3.3V, ISOURCE = 5mA V+ - 260 V+ - 30
V+ = +5V, ISOURCE = 10mA V+ - 360 V+ - 30
Output Low-Voltage SDA VOLSDA ISINK = 6mA 250 mV
Output Low-Voltage INT VOLINT ISINK = 5mA 130 250 mV
Port Input Pullup Resistor RPU 25 40 55 kΩ
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2
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Electrical Characteristics
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.
Absolute Maximum Ratings
Note 1: All parameters are tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 2: A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL of the SCL signal) to bridge
the undefined region of SCL’s falling edge.
Note 3: Guaranteed by design.
Note 4: Cb = total capacitance of one bus line in pF. ISINK ≤ 6mA. tR and tF measured between 0.3 x V+ and 0.7 x V+.
Note 5: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns.
(V+ = +1.71V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at V+ = +3.3V, TA = +25°C.) (Note 1)
(V+ = +1.71V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at V+ = +3.3V, TA = +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Port Output Data Valid tPPV CL ≤ 100pF 4 µs
Port Input Setup Time tPSU CL ≤ 100pF 0 µs
Port Input Hold Time tPH CL ≤ 100pF 4 µs
INT Input Data Valid Time tIV CL ≤ 100pF 4 µs
INT Reset Delay Time from STOP tIP CL ≤ 100pF 4 µs
INT Reset Delay Time from
Acknowledge tIR CL ≤ 100pF 4 µs
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Serial Clock Frequency fSCL 400 kHz
Bus Free Time Between a STOP
and a START Condition tBUF 1.3 µs
Hold Time (Repeated) START
Condition tHD,STA 0.6 µs
Repeated START Condition
Setup Time tSU,STA 0.6 µs
STOP Condition Setup Time tSU,STO 0.6 µs
Data Hold Time tHD,DAT (Note 2) 0.9 µs
Data Setup Time tSU,DAT 100 ns
SCL Clock Low Period tLOW 1.3 µs
SCL Clock High Period tHIGH 0.7 µs
Rise Time of Both SDA and SCL
Signals, Receiving tR(Notes 3, 4) 20 +
0.1Cb
300 ns
Fall Time of Both SDA and SCL
Signals, Receiving tF(Notes 3, 4) 20 +
0.1Cb
300 ns
Fall Time of SDA Transmitting tF,TX (Notes 3, 4) 20 +
0.1Cb
250 ns
Pulse Width of Spike Suppressed tSP (Note 5) 50 ns
Capacitive Load for Each
Bus Line Cb(Note 3) 400 pF
RST Pulse Width tW500 ns
RST Rising to START Condition
Setup Time tRST 1 µs
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3
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Timing Characteristics
Port and Interrupt INT Timing Characteristics
(TA = +25°C, unless otherwise noted.)
PIN NAME FUNCTION
QSOP TQFN
1 22 INT Interrupt Output, Active Low. INT is an open-drain output.
2 23 RST Reset Input, Active Low. Drive RST low to clear the 2-wire interface.
3, 21 24, 18 AD2, AD0 Address Inputs. Select device slave address with AD0 and AD2. Connect AD0 and AD2
To either GND, V+, SCL, or SDA to give four logic combinations (see Tables 2 and 3).
4, 5, 10,
11, 13–20
1, 2, 7, 8,
10–17
O0, O1,
O6–O15 Output Ports. These push-pull outputs are rated at 20mA.
6–9 3–6 I2–I5 Input Ports. I2 and I5 are CMOS-logic inputs protected to +6V.
12 9 GND Ground
22 19 SCL I2C-Compatible Serial-Clock Input
23 20 SDA I2C-Compatible Serial-Data I/O
24 21 V+ Positive Supply Voltage. Bypass V+ to GND with a 0.047µF ceramic capacitor.
— EP EP Exposed Pad. Connect EP to GND.
OUTPUT-VOLTAGE HIGH
vs. TEMPERATURE
TEMPERATURE (°C)
OUTPUT-VOLTAGE HIGH (V)
MAX7326 toc04
-40 -25 -10 5 20 35 50 65 80 95 110 125
0
1
2
3
4
5
6
V+ = +3.3V
ISOURCE = 5mA
V+ = +5.0V
ISOURCE = 10mA
V+ = +2.5V, ISOURCE = 5mA
V+ = +1.71V, ISOURCE = 2mA
OUTPUT-VOLTAGE LOW
vs. TEMPERATURE
TEMPERATURE (°C)
OUTPUT-VOLTAGE LOW (V)
MAX7326 toc03
-40 -25 -10 5 20 35 50 65 80 95 110 125
0
0.05
0.10
0.15
0.20
0.25
V+ = +3.3V
ISINK = 15mA
V+ = +5.0V
ISINK = 20mA
V+ = +2.5V
ISINK = 10mA
V+ = +1.71V
ISINK = 5mA
V+ = +1.62V
ISINK = 4mA
SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
SUPPLY CURRENT (A)
MAX7326 toc02
-40 -25 -10 5 20 35 50 65 80 95 110 125
0
10
20
30
40
50
60
V+ = +3.3V
V+ = +5.0V
V+ = +2.5V
V+ = +1.71V
fSCL = 400kHz
STANDBY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
STANDBY CURRENT (A)
MAX7326 toc01
-40 -25 -10 5 20 35 50 65 80 95 110 125
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
V+ = +3.3V
V+ = +5.0V
V+ = +2.5V
V+ = +1.71V
fSCL = 0kHz
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MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Pin Description
Typical Operating Characteristics
Detailed Description
MAX7319–MAX7329 Family Comparison
The MAX7324–MAX7327 family consists of four pin-
compatible, 16-port expanders that integrate the
functions of the MAX7320 and one of either the MAX7319,
MAX7321, MAX7322, or MAX7323.
Functional Overview
The MAX7326 is a general-purpose port expander
operating from a +1.71V to +5.5V supply that provides
12 push-pull output ports with 20mA sink, 10mA source
drive capability, and four CMOS input ports that are
overvoltage protected to +6V. The MAX7326 is rated to
sink a total of 100mA and source a total of 50mA from all
12 combined outputs.
The MAX7326 is set to two of 32 I2C slave addresses
(see Tables 2 and 3) using address inputs AD0 and AD2,
and is accessed over an I2C serial interface up to 400kHz.
Eight outputs use a different slave address from the other
four outputs and four inputs. Eight push-pull outputs (O8–
O15) use the 101xxxx addresses while the four outputs
(O0, O1, O6, and O7) and inputs (I2–I5) use addresses
with 110xxxx. The RST input clears the serial interface in
case of a bus lockup, terminating any serial transaction to
or from the MAX7326.
Table 1. MAX7319–MAX7329 Family Comparison
PART
I2C
SLAVE
ADDRESS
INPUTS
INPUT
INTERRUPT
MASK
OPEN-
DRAIN
OUTPUTS
PUSH-
PULL
OUTPUTS
CONFIGURATION
16-PORT EXPANDERS
MAX7324
101xxxx
And
110xxxx
8 Yes — 8
8 inputs and 8 push-pull outputs version:
8 input ports with programmable latching transition
detection interrupt and selectable pullups.
8 push-pull outputs with selectable default logic
levels.
Offers maximum versatility for automatic input
monitoring. An interrupt mask selects which inputs
cause an interrupt on transitions, and transition flags
identify which inputs have changed (even if only for a
transient) since the ports were last read.
MAX7325 Up to 8 — Up to 8 8
8 I/O and 8 push-pull outputs version:
8 open-drain I/O ports with latching transition
detection interrupt and selectable pullups.
8 push-pull outputs with selectable default logic
levels.
Open-drain outputs can level shift the logic-high state
to a higher or lower voltage than V+ using external
pullup resistors, but pullups draw current when output
is low. Any open-drain port can be used as an input
by setting the open-drain output to logic-high.
Transition flags identify which open-drain port inputs
have changed (even if only for a transient) since the
ports were last read.
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5
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Table 1. MAX7319–MAX7329 Family Comparison (continued)
PART
I2C
SLAVE
ADDRESS
INPUTS
INPUT
INTERRUPT
MASK
OPEN-
DRAIN
OUTPUTS
PUSH-
PULL
OUTPUTS
CONFIGURATION
MAX7326
101xxxx
and
110xxxx
4 Yes — 12
4 input-only, 12 push-pull output versions:
4 input ports with programmable latching transition
detection interrupt and selectable pullups.
12 push-pull outputs with selectable default logic
levels.
Offers maximum versatility for automatic input
monitoring. An interrupt mask selects which inputs
cause an interrupt on transitions, and transition flags
identify which inputs have changed (even if only for a
transient) since the ports were last read.
MAX7327 Up to 4 — Up to 4 12
4 I/O, 12 push-pull output versions:
4 open-drain I/O ports with latching transition
detection interrupt and selectable pullups.
12 push-pull outputs with selectable default logic
levels.
Open-drain outputs can level shift the logic-high
state to a higher or lower voltage than V+ using
external pullup resistors, but pullups draw current
when output is low. Any open-drain port can be used
as an input by setting the open-drain output to logic-
high. Transition flags identify which open-drain port
inputs have changed (even if only for a transient)
since the ports were last read.
8-PORT EXPANDERS
MAX7319 110xxxx 8 Yes — —
Input-only versions:
8 input ports with programmable latching transition
detection interrupt and selectable pullups.
MAX7320 101xxxx — — — 8
Output-only versions:
8 push-pull outputs with selectable power-up default
levels.
MAX7321 110xxxx Up to 8 — Up to 8 —
I/O versions:
8 open-drain I/O ports with latching transition
detection interrupt and selectable pullups.
MAX7322 110xxxx 4 Yes — 4
4 input-only, 4 output-only versions:
4 input ports with programmable latching transition
detection interrupt and selectable pullups.
4 push-pull outputs with selectable power-up default
levels.
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MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
When the MAX7326 is read through the serial interface,
the actual logic levels at the ports are read back.
The four input ports offer latching transition detection
functionality. All input ports are continuously monitored
for changes. An input change sets 1 of 4 flag bits that
identify the changed input(s). All flags are cleared upon a
subsequent read or write transaction to the MAX7326.
A latching interrupt output (INT) is programmed to flag
input data changes on the four input ports through an
interrupt mask register. By default, data changes on any
input port force INT to a logic-low. Interrupt output INT and
all transition flags are deasserted when the MAX7326 is
next accessed through the serial interface.
Internal pullup resistors to V+ are selected by the address
select inputs (AD0 and AD2). Pullups are enabled on the
input ports in groups of two (see Table 2).
Initial Power-Up
On power-up, the transition detection logic is reset, and
INT is deasserted. The interrupt mask register is set to
0x3C, enabling the interrupt output for transitions on
all four input ports. The transition flags are cleared to
indicate no data changes. The power-up default states
of the 12 push-pull outputs are set according to the I2C
slave address selection inputs, AD0 and AD2 (see Tables
2 and 3). Pullups are enabled on the input port in groups
of two (see Table 2).
Power-On Reset (POR)
The MAX7326 contains an integral POR circuit that
ensures all registers are reset to a known state on
power-up. When V+ rises above VPOR (1.6V max), the
POR circuit releases the registers and 2-wire interface
for normal operation. When V+ drops below VPOR, the
MAX7326 resets all output register contents to the POR
defaults (Tables 2 and 3).
RST Input
The active-low RST input operates as a reset that voids
any I2C transaction involving the MAX7326 and forcing
the MAX7326 into the I2C STOP condition. The reset
action does not clear the interrupt output (INT).
Standby Mode
When the serial interface is idle, the MAX7326 auto-
matically enters standby mode, drawing minimal supply
current.
Slave Address, Power-Up Default
Logic Levels, and Input Pullup Selection
Address inputs AD0 and AD2 determine the MAX7326
slave address and select which inputs have pullup
resistors. Pullups are enabled on the input ports in
groups of two (see Table 2).
The MAX7326 slave address is determined on each I2C
transmission, regardless of whether the transmission
is actually addressing the MAX7326. The MAX7326
distinguishes whether address inputs AD0 and AD2 are
connected to SDA or SCL instead of fixed logic levels
V+ or GND during this transmission. This means that the
MAX7326 slave address can be configured dynamically in
the application without cycling the device supply.
On initial power-up, the MAX7326 cannot decode address
inputs AD0 and AD2 fully until the first I2C transmission.
This is important because the address selection is used to
determine the power-up logic state (output low or I/O high),
and whether pullups are enabled. However, at power-up,
the I2C SDA and SCL bus interface lines are high imped-
ance at the pins of every device (master or slave) connect-
ed to the bus, including the MAX7326. This is guaranteed
as part of the I2C specification. Therefore, when address
inputs AD0 and AD2 are connected to SDA or SCL during
power-up, they appear to be connected to V+. The port
Table 1. MAX7319–MAX7329 Family Comparison (continued)
PART
I2C
SLAVE
ADDRESS
INPUTS
INPUT
INTERRUPT
MASK
OPEN-
DRAIN
OUTPUTS
PUSH-
PULL
OUTPUTS
CONFIGURATION
MAX7323 110xxxx Up to 4 — Up to 4 4
4 I/O, 4 output-only versions:
4 open-drain I/O ports with latching transition
detection interrupt and selectable pullups.
4 push-pull outputs with selectable power-up default
levels.
MAX7328
MAX7329
0100xxx
0111xxx Up to 8 — Up to 8 — 8 open-drain I/O ports with nonlatching transition
detection interrupt and pullups on all ports.
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MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
selection logic uses AD0 to select whether pullups are
enabled for ports I2 and I3, and to set the initial logic
level for those ports, and AD2 for ports I4 and I5. The
rule is that a logic-high, SDA, or SCL connection selects
the pullups and sets the default logic state to high. A
logic-low sets the default to low (Tables 2 and 3). This means
that the port configuration is correct on power-up for a
standard I2C configuration, where SDA or SCL are pulled
up to V+ by the external I2C pullup resistors.
The power-up default states of the 12 push-pull outputs
are set according to the I2C slave address selection
inputs, AD0 and AD2 (Tables 2 and 3).
There are circumstances where the assumption that
SDA = SCL = V+ on power-up is not true—for example,
in applications in which there is legitimate bus activity
during power-up. Also, if SDA and SCL are terminated
with pullup resistors to a different supply voltage than the
MAX7326’s supply voltage, and if that pullup supply rises
later than the MAX7326’s supply, then SDA or SCL may
appear at power-up to be connected to GND. In appli-
cations like this, use the four address combinations that
are selected by strapping address inputs AD0 and AD2 to
V+ or ground (shown in bold in Tables 2 and 3). These
selections are guaranteed to be correct at power-up,
independent of SDA and SCL behavior. If one of the
other 12 address combinations is used, an unexpected
combination of pullups might be asserted until the first
I2C transmission (to any device, not necessarily
the MAX7326) is put on the bus, and an unexpected
combination of ports may initialize as logic-low outputs
instead of inputs or logic-high outputs.
Port Inputs
Port inputs switch at CMOS-logic levels as determined by
the expander’s supply voltage, and are overvoltage toler-
ant to +6V, independent of the expander’s supply voltage.
Port-Input Transition Detection
All four input ports are monitored for changes since the
expander was last accessed through the serial inter-
face. The state of the input ports is stored in an internal
“snapshot” register for transition monitoring. The snap-
shot is continuously compared with the actual input
conditions, and if a change is detected for any port input,
then an internal transition flag is set for that port. The
four port inputs are sampled (internally latched into the
snapshot register) and the old transition flags are cleared
during the I2C acknowledge of every MAX7326 read and
write access. The previous port transition flags are read
through the serial interface as the second byte of a 2-byte
read sequence.
Table 2. MAX7326 Address Map for Ports O0, O1, I2–I5, O6, and O7
PIN
CONNECTION DEVICE ADDRESS PORT POWER-UP DEFAULT 40kΩ INPUT PULLUPS ENABLED
AD2 AD0 A6 A5 A4 A3 A2 A1 A0 O7 O6 I5 I4 I3 I2 O1 O0 O7 O6 I5 I4 I3 I2 O1 O0
SCL GND 1 1 0 0 0 0 0 1 1
Inputs
0 0
Pullups are not enabled for push-pull outputs.
Y Y — —
Pullups are not enabled for push-pull outputs.
SCL V+ 1 1 0 0 0 0 1 1 1 1 1 Y Y Y Y
SCL SCL 1 1 0 0 0 1 0 1 1 1 1 Y Y Y Y
SCL SDA 1 1 0 0 0 1 1 1 1 1 1 Y Y Y Y
SDA GND 1 1 0 0 1 0 0 1 1 0 0 Y Y — —
SDA V+ 1 1 0 0 1 0 1 1 1 1 1 Y Y Y Y
SDA SCL 1 1 0 0 1 1 0 1 1 1 1 Y Y Y Y
SDA SDA 1 1 0 0 1 1 1 1 1 1 1 Y Y Y Y
GND GND 1 1 0 1 0 0 0 0 0 0 0 — — — —
GND V+ 1 1 0 1 0 0 1 0 0 1 1 — — Y Y
GND SCL 1 1 0 1 0 1 0 0 0 1 1 — — Y Y
GND SDA 1 1 0 1 0 1 1 0 0 1 1 — — Y Y
V+ GND 1 1 0 1 1 0 0 1 1 0 0 Y Y — —
V+ V+ 1 1 0 1 1 0 1 1 1 1 1 Y Y Y Y
V+ SCL 1 1 0 1 1 1 0 1 1 1 1 Y Y Y Y
V+ SDA 1 1 0 1 1 1 1 1 1 1 1 Y Y Y Y
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8
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
A long read sequence (more than 2 bytes) can be used
to poll the expander continuously without the overhead
of resending the slave address. If more than 2 bytes are
read from the expander, the expander repeatedly returns
the 2 bytes of input port data followed by the transition
flags. The inputs are repeatedly resampled and the tran-
sition flags repeatedly reset for each pair of bytes read.
All changes that occur during a long read sequence are
detected and reported.
The MAX7326 includes a 4-bit interrupt mask register that
selects which inputs generate an interrupt upon change.
Each input’s transition flag is set when its input chang-
es, independent of the interrupt mask register settings.
The interrupt mask register allows the processor to be
interrupted for critical events, while the inputs and the
transition flags can be polled periodically to detect
less-critical events.
The INT output is not reasserted during a read sequence
to avoid recursive reentry into an interrupt service
routine. Instead, if a data change occurs that would
normally cause the INT output to be set, the INT
assertion is delayed until the STOP condition. INT is not
reasserted upon a STOP condition if the changed input
data is read before the STOP occurs. The INT logic
ensures that unnecessary interrupts are not asserted, yet
data changes are detected and reported no matter when
the change occurs.
Transition-Detection Masks
The transition-detection logic incorporates a change flag
and an interrupt mask bit for each of the four input ports.
The four change flags can be read through the serial
interface, and the 4-bit interrupt mask is set through the
serial interface.
Each port’s change flag is set when that port’s input
changes, and the change flag remains set even if the
input returns to its original state. The port’s interrupt
mask determines whether a change on that input port
generates an interrupt. Enable interrupts for high-priority
inputs using the interrupt mask. The interrupt allows the
system to respond quickly to changes on these inputs.
Poll the MAX7326 periodically to monitor less-important
inputs. The change flags indicate whether a permanent
or transient change has occurred on any input since the
MAX7326 was last accessed.
Table 3. MAX7326 Address Map for Outputs O8–O15
PIN
CONNECTION DEVICE ADDRESS OUTPUTS POWER-UP DEFAULT
AD2 AD0 A6 A5 A4 A3 A2 A1 A0 O15 O14 O13 O12 O11 O10 O9 O8
SCL GND 1 0 1 0 0 0 0 1 1 1 1 0 0 0 0
SCL V+ 1 0 1 0 0 0 1 1 1 1 1 1 1 1 1
SCL SCL 1 0 1 0 0 1 0 1 1 1 1 1 1 1 1
SCL SDA 1 0 1 0 0 1 1 1 1 1 1 1 1 1 1
SDA GND 1 0 1 0 1 0 0 1 1 1 1 0 0 0 0
SDA V+ 1 0 1 0 1 0 1 1 1 1 1 1 1 1 1
SDA SCL 1 0 1 0 1 1 0 1 1 1 1 1 1 1 1
SDA SDA 1 0 1 0 1 1 1 1 1 1 1 1 1 1 1
GND GND 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0
GND V+ 1 0 1 1 0 0 1 0 0 0 0 1 1 1 1
GND SCL 1 0 1 1 0 1 0 0 0 0 0 1 1 1 1
GND SDA 1 0 1 1 0 1 1 0 0 0 0 1 1 1 1
V+ GND 1 0 1 1 1 0 0 1 1 1 1 0 0 0 0
V+ V+ 1 0 1 1 1 0 1 1 1 1 1 1 1 1 1
V+ SCL 1 0 1 1 1 1 0 1 1 1 1 1 1 1 1
V+ SDA 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1
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9
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Serial Interface
Serial Addressing
The MAX7326 operates as a slave that sends and
receives data through an I2C interface. The interface uses
a serial-data line (SDA) and a serial-clock line (SCL) to
achieve bidirectional communication between master(s)
and slave(s). The master initiates all data transfers to
and from the MAX7326 and generates the SCL clock that
synchronizes the data transfer (Figure 1).
SDA operates as both an input and an open-drain output.
A pullup resistor, typically 4.7kΩ, is required on SDA.
SCL operates only as an input. A pullup resistor, typically
4.7kΩ, 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 sent
by a master, followed by the MAX7326’s 7-bit slave
addresses plus R/W bits, 1 or more data bytes, and finally
a STOP condition (Figure 2).
Start and Stop Conditions
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, the master issues a STOP
(P) condition by transitioning SDA from low to high while
SCL is high. The bus is then free for another transmission
(Figure 2).
Bit Transfer
One data bit is transferred during each clock pulse.
The data on SDA must remain stable while SCL is high
(Figure 3).
Figure 3. Bit TransferFigure 2. Start and Stop Conditions
Figure 1. 2-Wire Serial-Interface Timing Details
SDA
SCL
DATA LINE STABLE;
DATA VALID
CHANGE OF DATA
ALLOWED
SDA
SCL
START
CONDITION
STOP
CONDITION
S P
SCL
SDA
tRtF
tBUF
START
CONDITION
STOP
CONDITION
REPEATED START CONDITION
START CONDITION
tSU,STO
tHD,STA
tSU,STA
tHD,DAT
tSU,DAT
tLOW
tHIGH
tHD,STA
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10
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Acknowledge
The acknowledge bit is a clocked 9th bit the recipient
uses to acknowledge receipt of each byte of data (Figure
4). 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,
so the SDA line is stable low during the high period of
the clock pulse. When the master is transmitting to the
MAX7326, the MAX7326 generates the acknowledge bit
because the device is the recipient. When the MAX7326
is transmitting to the master, the master generates the
acknowledge bit because the master is the recipient.
Slave Address
The MAX7326 has two different 7-bit slave addresses
(Figure 5). The addresses are different to communicate
to the eight push-pull outputs (O8–O15) or the other eight
I/Os. The 8th bit following the 7-bit slave address is the
R/W bit. It is low for a write command and high for a read
command.
The first (A6), second (A5), and third (A4) bits of the
MAX7326 slave address are always 1, 1, and 0 (O0, O1,
I2–I5, O6, and O7) or 1, 0, and 1 (O8–O15). Connect
AD0 and AD2 to GND, V+, SDA, or SCL to select slave
address bits A3, A2, A1, and A0. The MAX7326 has 16
possible slave addresses (Tables 2 and 3), allowing up to
16 MAX7326 devices on an I2C bus.
Accessing the MAX7326
The MAX7326 is accessed though an I2C interface. The
MAX7326 provides two different 7-bit slave addresses for
either the group A of eight ports (O0, O1, I2–I5, O6, O7) or
the group B of eight ports (O8–O15). See Tables 2 and 3.
A single-byte read from the group A ports of the MAX7326
returns the status of the four input ports and four output
ports (read back as inputs), and clears both the inter-
nal transition flags and the INT output when the master
acknowledges the salve address byte. A single-byte read
from the group B ports of the MAX7326 returns the status
of the eight output ports, read back as inputs.
A 2-byte read from the group A ports of the MAX7326
returns the status of the four input ports (as for a
single-byte read), followed by the four transition flags for
the four input ports and four output ports. The internal
transition flags and the INT output are cleared when the
master acknowledges the slave address byte, but the
previous transition flag data is sent as the second byte.
A 2-byte read from the group B ports of the MAX7326
repeatedly returns the status of the eight output ports,
read back as inputs.
A multibyte read (more than 2 bytes before the I2C
STOP bit) from the group A ports of the MAX7326 repeat-
edly returns the port data, followed by the transition
flags. As the data is resampled for each transmission,
and the transition flags are reset each time, a multibyte
read continuously returns the current data and identifies
any changing input ports.
Figure 5. Slave Address
Figure 4. Acknowledge
SDA
SCL
A5
MSB LSB
ACKA4 A11 A3 A0A2 R/W
SCL
SDA BY
TRANSMITTER
CLOCK PULSE
FOR ACKNOWLEDGMENT
START
CONDITION
SDA BY
RECEIVER
1 2 8 9
S
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11
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
If a port input data change occurs during the read
sequence, then INT is reasserted during the I2C STOP
bit. The MAX7326 does not generate another interrupt
during a single-byte or multibyte read.
Input port data is sampled during the preceding I2C
acknowledge bit (the acknowledge bit for the I2C slave
address in the case of a single-byte or 2-byte read).
A multibyte read (more than 2 bytes before the I2C STOP
bit) from the group B ports of the MAX7326 repeatedly
returns the status of the eight output ports, read back as
inputs.
A single-byte write to the group A ports of the MAX7326
sets the logic state of the four I/O ports and the 4-bit inter-
rupt mask register and clears both the internal transition
flags and INT output when the master acknowledges the
slave address byte.
A single-byte write to the output ports of the MAX7326
sets the logic state of all eight ports.
A multibyte write to the group A ports of the MAX7326
repeatedly sets the logic state of the four I/O ports and
interrupt mask register.
A multibyte write to the group B ports of the MAX7326
repeatedly sets the logic state of all eight ports.
Reading from the MAX7326
A read from the group A ports of the MAX7326 starts with
the master transmitting the port group’s slave address
with the R/W bit set to high. The MAX7326 acknowl-
edges the slave address and samples the ports (takes
a snapshot) during the acknowledge bit. INT goes high
(high impedance if an external pullup resistor is not
fitted) during the slave address acknowledge. The master
can then issue a STOP condition after the acknowledge
(Figure 6). The snapshot is not taken, and the INT status
remains unchanged if the master terminates the serial
transaction with no acknowledge.
Typically, the master reads 1 or 2 bytes from the MAX7326
with each byte being acknowledged by the master upon
reception.
The master can read one byte from the group A ports of
the MAX7326 and issue a STOP condition (Figure 6).
In this case, the MAX7326 transmits the current port
data, clears the transition flags, and resets the transition
detection. INT goes high (high impedance if an external
pullup resistor is not fitted) during the slave address
acknowledge. The new snapshot data is the current
port data transmitted to the master, and therefore, port
changes occuring during the transmission are detected.
INT remains high until the STOP condition.
Figure 6. Reading Group A Ports of the MAX7326 (1 Data Byte)
SCL
MAX7326 SLAVE ADDRESS
S A P
1
PORTS
INT OUTPUT
R/W
ACKNOWLEDGE
FROM MAX7326
ACKNOWLEDGE
FROM MASTER
PORT SNAPSHOT
tIV
tPH
tIR
A
O0
O1
I2I3I4I5
O6
O7
D0D1D2D3D4D5D6D7
PORT SNAPSHOT
tPS tIP
INT REMAINS HIGH UNTIL STOP CONDITION
S = START CONDITION
P = STOP CONDITION
A = ACKNOWLEDGE FROM MASTER
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12
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
The master can read 2 bytes from the group A ports of the
MAX7326 and then issue a STOP condition (Figure 7). In
this case, the MAX7326 transmits the current port data,
followed by the transition flags. The transition flags are
then cleared, and transition detection restarts. INT goes
high (high impedance if an external pullup resistor is not
fitted) during the slave acknowledge. The new snapshot
data is the current port data transmitted to the master,
and therefore, port transitions occuring during the trans-
mission are detected. INT remains high until the STOP
condition.
A read from the group B ports of the MAX7326 starts
with the master transmitting the group’s slave address
with the R/W bit set high. The MAX7326 acknowledges
the slave address and samples the logic state of the
output ports during the acknowledge bit. The master
can read one or more bytes from the output ports of the
MAX7326, and then issue a STOP condition (Figure 8).
The MAX7326 transmits the current port data, read back
from the actual port outputs (not the port output latches)
during the acknowledge bit. If a port is forced to a logic
state other than its programmed state, the readback
reflects this. If driving a capacitive load, the readback port
level verification algorithms may need to take the RC rise/
fall time into account.
Typically, the master reads one byte from the group B
ports of the MAX7326, then issues a STOP condition
(Figure 8). However, the master can read two or more
bytes from the output ports of the MAX7326, and then
issue a STOP condition. In this case, the MAX7326
resamples the port outputs during each acknowledge and
transmits the new data each time.
Figure 8. Reading Group B Ports of the MAX7326
Figure 7. Reading Group A Ports of the MAX7326 (2 Data Bytes)
SCL
MAX7326 SLAVE ADDRESS
S A P
1
ACKNOWLEDGE FROM MAX7326
PORT SNAPSHOT DATA
PORT SNAPSHOT TAKEN
A
P0P1P2P3
DATA 1
P4P5P6P7
D0D1D2D3D4D5D6D7
PORT SNAPSHOT TAKEN ACKNOWLEDGE
FROM MASTER
R/W
S = START CONDITION
P = STOP CONDITION
A = ACKNOWLEDGE
SCL
MAX7326 SLAVE ADDRESSS A P1
PORTS
INT OUTPUT
R/W
ACKNOWLEDGE
FROM MAX7326 ACKNOWLEDGE
FROM MASTER
PORT SNAPSHOT
tIV
tPH
tIR
A
O0
O1
I2I3I4I5
O6
O7
D0D1D2D3D4D5D6D7
PORT SNAPSHOT
tPS tIP
F0
F1
F2F3F4F5
F6
F7
D7 D6 D5 D4 D3 D2 D1 D0 A
PORT SNAPSHOT
FLAG
INT REMAINS HIGH UNTIL STOP CONDITION
S = START CONDITION
P = STOP CONDITION
A = ACKNOWLEDGE
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13
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Writing to the MAX7326
A write to the group A ports of the MAX7326 starts with
the master transmitting the group’s slave address with the
R/W bit set low. The MAX7326 acknowledges the slave
address and samples the ports during the acknowledge.
INT goes high (high impedance if an external pullup
resistor is not fitted) during the slave address acknowl-
edge. The master can then issue a STOP condition after
the acknowledge (Figure 6), but typically the master
proceeds to transmit one or more bytes of data. The
MAX7326 acknowledges these subsequent bytes of data
and updates the four output ports and the 4-bit interrupt
mask register with each new byte until the master issues
a STOP condition (Figure 9).
A write to the group B ports of the MAX7326 starts with
the master transmitting the group’s slave address with the
R/W bit set low. The MAX7326 acknowledges the slave
address and samples the ports during the acknowledge
bit. The master can now transmit one or more bytes of
data. The MAX7326 acknowledges these subsequent
bytes of data and updates the corresponding group’s
ports with each new byte until the master issues a STOP
condition (Figure 10).
Figure 10. Writing to the Group B Ports of the MAX7326
Figure 9. Writing to the Group A Ports of the MAX7326
SCL
SDA
START CONDITION ACKNOWLEDGE
FROM SLAVE
SLAVE ADDRESS
S 0
1 2 3 4 5 6 7 8
A A A
tPV
DATA 1 DATA 2
DATA 2 VALIDDATA 1 VALID
WRITE
TO PORT
DATA OUT
FROM PORT
ACKNOWLEDGE
FROM SLAVE
ACKNOWLEDGE
FROM SLAVE
tPV
DATA TO PORT DATA TO PORT
R/W
SCL
SDA
START CONDITION R/W
SLAVE ADDRESS
S 0
1 2 3 4 5 6 7 8
A A A
tPV
DATA 1 DATA 2
tPV
DATA TO INTERRUPT MASK DATA TO INTERRUPT MASK
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14
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Applications Information
Port Input and I2C Interface Level Translation
from Higher or Lower Logic Voltages
The MAX7326’s SDA, SCL, AD0, AD2, RST, INT, and
I2–I5 are overvoltage protected to +6V, independent of
V+. This allows the MAX7326 to operate from a lower
supply voltage, such as +3.3V, while the I2C interface
and/or any of the four input ports are driven from a higher
logic level, such as +5V.
The MAX7326 can operate from a higher supply volt-
age, such as +3V, while the I2C interface and/or some
of the four input ports (I2–I5) are driven from a lower
logic level, such as +2.5V. For V+ < 1.8V, apply a
minimum voltage of 0.8 x V+ to assert a logic-high on
any input. For V+ ≥ 1.8V, apply a voltage of 0.7 x V+ to
assert a logic-high. For example, a MAX7326 operating
from a +5V supply may not recognize a +3.3V nominal
logic-high. One solution for input-level translation is to
drive the MAX7326 inputs from open-drain outputs. Use
a pullup resistor to V+ or a higher supply to ensure a high
logic voltage of greater than 0.7 x V+.
Port Output Signal-Level Translation
Each of the push-pull output ports (O0, O1, and
O6–O15) has protection diodes to V+ and GND (Figure
11). When a port output is driven to a voltage higher
than V+ or below GND, the appropriate protection diode
clamps the output to a diode drop above V+ or below
GND. Do not overvolt output ports O0, O1, and O6–O15.
When the MAX7326 is powered down (V+ = 0), each
output port appears as a diode clamp to GND (Figure 11).
Each of the four input ports ((I2–I5) has a protection diode
to GND (Figure 12). When a port input is driven to a
voltage lower than GND, the protection diode clamps the
output to a diode drop below GND.
Each of the four input ports (I2–I5) also has a 40kΩ
(typ) pullup resistor that can be enabled or disabled.
When a port input is driven to a voltage higher than
V+, the body diode of the pullup enable switch con-
ducts and the 40kΩ pullup resistor is enabled. When
the MAX7326 is powered down (V+ = 0), each input
port appears as a 40kΩ resistor in series with a diode
connected to zero. Input ports are protected to +6V
under any of these circumstances (Figure 12).
Driving LED Loads
When driving LEDs from one of the 12 output ports (O0,
O1, or O6–O15), a resistor must be fitted in series with
the LED to limit the LED current to no more than 20mA.
Connect the LED cathode to the MAX7326 port, and
the LED anode to V+ through the series current-limiting
resistor (RLED). Set the port output low to light the LED.
Figure 12. MAX7326 Input Port StructureFigure 11. MAX7326 Push-Pull Output Port Structure
I2–I5
PULLUP
ENABLE
INPUT
40kΩ
V+ V+
MAX7326
OUTPUT
V+V+
O0, O1,
O6–O15
MAX7326
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15
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Choose the resistor value according to the following
formula:
RLED = (VSUPPLY - VLED - VOL)/ILED
where:
RLED is the resistance of the resistor in series with the
LED (Ω).
VSUPPLY is the supply voltage used to drive the LED (V).
VLED is the forward voltage of the LED (V).
VOL is the output low voltage of the MAX7326 when
sinking ILED (V).
ILED is the desired operating current of the LED (A).
For example, to operate a 2.2V red LED at 10mA from a
+5V supply:
RLED = (5 - 2.2 - 0.1)/0.01 = 270Ω
Driving Load Currents Higher than 20mA
The MAX7326 can be used to drive loads such as relays
that draw more than 20mA by paralleling outputs. Use at
least one output per 20mA of load current (for example,
a 5V, 330mW relay draws 66mA and therefore requires
four paralleled outputs). Any combination of outputs can
be used as part of a load-sharing design, because any
combination of ports can be set or cleared at the same
time by writing to the MAX7326. Do not exceed a total
sink current of 100mA for the device.
The MAX7326 must be protected from the
negative-voltage transient generated when switching off
inductive loads (such as relays) by connecting a reverse-
biased diode across the inductive load. Choose the peak
current for the diode to be greater than the inductive load’s
operating current.
Power-Supply Considerations
The MAX7326 operates with a supply voltage of
+1.71V to +5.5V over the -40°C to +125°C tempera-
ture range. Bypass the supply to GND with a ceramic
capacitor of at least 0.047µF as close as possible to
the device. For the TQFN version, additionally connect
the exposed pad to GND.
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16
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
PACKAGE
TYPE
PACKAGE
CODE OUTLINE NO. LAND PATTERN
NO.
24 QSOP E24+1 21-0055 90-0172
24 TQFN T2444+3 21-0139 90-0022
TOP VIEW
24
23
22
21
20
19
18
17
1
2
3
4
5
6
7
8
INT V+
SDA
SCL
AD0
O15
O14
O13
O12
MAX7326
QSOP
+
RST
AD2
I2
O0
O1
I3
I4
16
15
9
10
O11
O10
I5
O6
14
13
11
12
O9
O8
O7
GND
MAX7326
I2
O7
O6
I5
I4
O11
O10
O9
O8
O15
O14
O13
O12
V+
3.3V
µC
SCL SCL
SDA
AD0
O1
O0
SDA
I3
GND
INPUT
INPUT
AD2
INT
OUTPUT
OUTPUT
OUTPUT
OUTPUT
INPUT
INPUT
OUTPUT
OUTPUT
OUTPUT
OUTPUT
RST
INT
RST
I2C
CONTROL
O9
O8
O11
O10
O12
O13
O14
O15
O1
O0
I3
I2
I4
I5
O6
O7
INT
GND
I/O
PORTS
POWER-
ON RESET
INPUT
FILTER
RST
SDA
SCL
AD2
AD0
N
MAX7326
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17
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Chip Information
PROCESS: BiCMOS
Pin Congurations (continued)
Typical Application CircuitFunctional Diagram
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.
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 10/06 Initial release —
1 7/14 No /V OPNs; removed automotive reference from Applications section; updated
Package Information 1, 18–20
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 specications 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.
MAX7326 I2C Port Expander with
12 Push-Pull Outputs and 4 Inputs
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2014 Maxim Integrated Products, Inc.
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18
Revision History
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.