General Description
The MAX7325 2-wire serial-interfaced peripheral features
16 I/O ports. Ports are divided into eight push-pull out-
puts and eight I/Os with selectable internal pullups and
transition detection. Eight ports are push-pull outputs
and eight I/Os may be used as a logic input or an open-
drain output. Ports are overvoltage protected to +6V.
All I/O ports configured as inputs are continuously mon-
itored for state changes (transition detection). State
changes are indicated by the INT output. The interrupt
is latched, allowing detection of transient changes.
When the MAX7325 is subsequently accessed through
the serial interface, any pending interrupt is cleared.
The open-drain outputs are rated to sink 20mA, and are
capable of driving LEDs. The RST input clears the serial
interface, terminating any I2C communication to or from
the MAX7325.
The MAX7325 uses two address inputs with four-level
logic to allow 16 I2C slave addresses. The slave
address also determines the power-up logic state for
the I/O ports, and enables or disables internal 40kΩ
pullups in groups of four ports.
The MAX7325 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 MAX7325 is available in 24-pin QSOP and TQFN
packages and is specified over the -40°C to +125°C
automotive temperature range.
Applications
Cell Phones Notebooks
SAN/NAS Satellite Radio
Servers Automotive
Features
♦400kHz I2C Serial Interface
♦+1.71V to +5.5V Operation
♦8 Push-Pull Outputs
♦8 Open-Drain I/O Ports, Rated to 20mA Sink
Current
♦I/O Ports are Overvoltage Protected to +6V
♦Selectable I/O Port Power-Up Default Logic States
♦Transient Changes are Latched, Allowing
Detection Between Read Operations
♦INT Output Alerts Change on Inputs
♦AD0 and AD2 Inputs Select from 16 Slave
Addresses
♦Low 0.6µA (typ) Standby Current
♦-40°C to +125°C Temperature Range
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
________________________________________________________________ Maxim Integrated Products 1
19-3807; Rev 0; 9/06
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLE
Ordering Information
PART TEMP RANGE PIN-PACKAGE PKG
CODE
MAX7325AEG+ -40°C to +125°C 24 QSOP E24-1
MAX7325ATG+ -40°C to +125°C 24 TQFN-EP*
(4mm x 4mm) T2444-3
Typical Application Circuit and Functional Diagram appear
at end of data sheet.
Selector Guide
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
+Denotes lead-free package.
*EP = Exposed paddle.
TQFN (4mm x 4mm)
+
TOP VIEW
MAX7325
19
20
21
22
12 3456
18 17 16 15 14 13
23
24
12
11
10
9
8
7
SCL
V+
SDA
INT
AD2
P0
P1
P2
P3
P4
P5
AD0
O15
O13
O12
O11
RST
O10
O8
O9
GND
P6
P7
O14
EXPOSED PADDLE
Pin Configurations
Pin Configurations continued at end of data sheet.
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
(All voltages referenced to GND.)
Supply Voltage V+....................................................-0.3V to +6V
SCL, SDA, AD0, AD2, RST, INT, P0–P7 ...................-0.3V to +6V
O8–O15 ........................................................-0.3V to (V+ + 0.3V)
O8–O15 Output Current ...................................................±25mA
P0–P7 Sink 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
DC ELECTRICAL CHARACTERISTICS
(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+
TA = -40°C to
+125°C 0.6 1.9 µA
Supply Current
(Interface Running) I+ fSCL = 400kHz; other
digital inputs at V+
TA = -40°C to
+125°C 23 55 µA
V+ < 1.8V
0.8 x V+
Input High-Voltage
VIH V+ ≥ 1.8V
0.7 x V+
V
V+ < 1.8V
0.2 x V+
Input Low-Voltage
VIL V+ ≥ 1.8V
0.3 x V+
V
Input Leakage Current
IIH, IIL SDA, SCL, AD0, AD2, RST, P0–P7 at V+ or
GND, internal pullup disabled
-0.2
+0.2 µA
Input Capacitance
10 pF
V+ = +1.71V, ISINK = 5mA (QSOP) 90 180
V+ = +1.71V, ISINK = 5mA (TQFN) 90 230
V+ = +2.5V, ISINK = 10mA (QSOP)
110
210
V+ = +2.5V, ISINK = 10mA (TQFN)
110
260
V+ = +3.3V, ISINK = 15mA (QSOP)
130
230
V+ = +3.3V, ISINK = 15mA (TQFN)
130
280
V+ = +5V, ISINK = 20mA (QSOP)
140
250
Output Low Voltage
O8–O15, P0–P7 VOL
V+ = +5V, ISINK = 20mA (TQFN)
140
300
mV
V+ = +1.71V, ISOURCE = 2mA
V + - 250 V + - 30
V+ = +2.5V, ISOURCE = 5mA
V + - 360 V + - 70
V+ = +3.3V, ISOURCE = 5mA
V + - 260 V + - 100
Output High Voltage
O8–O15 VOH
V+ = +5V, ISOURCE = 10mA
V + - 360 V + - 120
mV
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
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
_______________________________________________________________________________________ 3
PORT AND INTERRUPT INT TIMING CHARACTERISTICS
(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
TIMING CHARACTERISTICS
(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
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 1µs
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) in order 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. tRand tFmeasured 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.
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
4 _______________________________________________________________________________________
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
STANDBY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
STANDBY CURRENT (µA)
MAX7325 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
SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
MAX7325 toc02
-40-25-105 203550658095110125
0
10
20
30
40
50
60
V+ = +3.3V
V+ = +5.0V
V+ = +2.5V
V+ = +1.71V
fSCL = 400kHz
OUTPUT VOLTAGE LOW
vs. TEMPERATURE
TEMPERATURE (°C)
OUTPUT VOLTAGE LOW (V)
MAX7325 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
OUTPUT VOLTAGE HIGH
vs. TEMPERATURE
TEMPERATURE (°C)
OUTPUT VOLTAGE HIGH (V)
MAX7325 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
Pin Description
PIN
QSOP
TQFN NAME FUNCTION
122 INT Interrupt Output, Active Low. INT is an open-drain output.
223 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).
4–11 1–8 P0–P7 Open-Drain I/O Ports
12 9 GND Ground
13–20 10–17 O8–O15 Output Ports. O8–O15 are push-pull outputs rated at 20mA.
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 ceramic capacitor of at least 0.047µF.
— EP EP Exposed Paddle. Connect exposed pad to GND.
Detailed Description
MAX7319–MAX7329 Family Comparison
The MAX7324–MAX7327 family consists of four pin-
compatible, 16-port expanders that integrate the func-
tions of the MAX7320 and one of either MAX7319,
MAX7321, MAX7322, or MAX7323.
Functional Overview
The MAX7325 is a general-purpose port expander oper-
ating from a +1.71V to +5.5V supply with eight push-pull
outputs and eight open-drain I/O ports. Each open-drain
output is rated to sink 20mA, and the entire device is
rated to sink 100mA into all ports combined. The outputs
drive loads connected to supplies up to +5.5V.
The MAX7325 is set to two of 32 I2C slave addresses
(see Tables 2 and 3) using the address select inputs
AD0 and AD2, and is accessed over an I2C serial inter-
face up to 400kHz. The eight outputs and eight I/Os
have different slave addresses. The eight push-pull out-
puts have the 101xxxx addresses and the eight inputs
have addresses with 110xxxx. The RST input clears the
serial interface in case of a bus lockup, terminating any
serial transaction to or from the MAX7325.
Configure any port as a logic input by setting the port
output logic-high (logic-high for an open-drain output is
high impedance). When the MAX7325 is read through
the serial interface, the actual logic levels at the ports
are read back.
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
_______________________________________________________________________________________ 5
PART
I2C
SLAVE
ADDRESS
INPUTS
INPUT
INTERRUPT
MASK
OPEN-
DRAIN
OUTPUTS
PUSH-
PULL
OUTPUTS
CONFIGURATION
16-PORT EXPANDERS
MAX7324
8 Yes — 8
8 input and 8 push-pull output versions:
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
101xxxx
and
110xxxx
Up to 8
— Up to 8 8
8 I/O and 8 push-pull output versions:
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.
Table 1. MAX7319–MAX7329 Family Comparison
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
6 _______________________________________________________________________________________
PART
I2C
SLAVE
ADDRESS
INPUTS
INPUT
INTERRUPT
MASK
OPEN-
DRAIN
OUTPUTS
PUSH-
PULL
OUTPUTS
CONFIGURATION
MAX7326
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
101xxxx
and
110xxxx
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.
Table 1. MAX7319–MAX7329 Family Comparison (continued)
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
_______________________________________________________________________________________ 7
The open-drain ports offer latching transition detection
when used as inputs. All input ports are continuously
monitored for changes. An input change sets one of 8
flag bits that identify changed input(s). All flags are
cleared upon a subsequent read or write transaction to
the MAX7325.
A latching interrupt output, INT, is programmed to flag
logic changes on ports used as inputs. Data changes
on any input port forces INT to a logic-low. Changing
the I/O port level through the serial interface does not
cause an interrupt. The interrupt output INT is deassert-
ed when the MAX7325 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 four (see Table 2).
Use the slave address selection to ensure that I/O ports
used as inputs are logic-high on power-up. I/O ports
with internal pullups enabled default to a logic-high out-
put state. I/O ports with internal pullups disabled
default to a logic-low output state.
Output port power-up logic levels are selected by the
address select inputs, AD0 and AD2. Ports default to
logic-high or logic-low on power-up in groups of four
(see Tables 2 and 3).
Initial Power-Up
On power-up, the transition detection logic is reset, and
INT is deasserted. The transition flags are cleared to indi-
cate no data changes. The power-up default states of the
16 I/O ports are set according to the I2C slave address
selection inputs, AD0 and AD2 (Tables 2 and 3). For I/O
ports used as inputs, ensure that the default states are
logic-high so that the I/O ports power up in the high-
impedance state. All I/O ports configured with pullups
enabled also have a logic-high power-up state.
Power-On Reset
The MAX7325 contains an integral power-on-reset
(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 to
less than VPOR, the MAX7325 resets all register con-
tents to the POR defaults (Tables 2 and 3).
RST
Input
The active-low RST input voids any I2C transaction
involving the MAX7325, forcing the MAX7325 into the
I2C STOP condition. A reset does not affect the inter-
rupt output (INT).
Standby Mode
When the serial interface is idle, the MAX7325 automatical-
ly 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 MAX7325
slave address, set the power-up I/O state for the ports,
and select which inputs have pullup resistors. Internal
pullups and power-up default states are set in groups
of four (see Table 2).
The MAX7325 slave address is determined on each I2C
transmission, regardless of whether the transmission is
actually addressing the MAX7325. The MAX7325 distin-
guishes whether address inputs AD0 and AD2 are con-
nected to SDA or SCL instead of fixed logic levels V+
or GND during this transmission. The MAX7325 slave
address can be configured dynamically in the applica-
tion without cycling the device supply.
On initial power-up, the MAX7325 cannot decode the
address inputs AD0 and AD2 fully until the first I2C
transmission. AD0 and AD2 initially appear to be
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.
Table 1. MAX7319–MAX7329 Family Comparison (continued)
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
8 _______________________________________________________________________________________
connected to V+ or GND. This is important because the
address selection is used to determine the power-up
logic state and whether pullups are enabled. At power-
up, the I2C SDA and SCL bus interface lines are high
impedance at the inputs of every device (master or
slave) connected to the bus, including the MAX7325.
This is guaranteed as part of the I2C specification.
Therefore, when address inputs AD0 and AD2 are con-
nected to SDA or SCL during power-up, they appear to
be connected to V+.
The power-up logic uses AD0 to select the power-up
state and whether pullups are enabled for ports P0–P3,
and AD2 for ports P4–P7. 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 deselects the
pullups and sets the default logic state to low (Table 2).
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.
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. If SDA and SCL are terminated with
pullup resistors to a different supply voltage than the
MAX7325’s supply voltage, and if that pullup supply
rises later than the MAX7325’s supply, then SDA or
SCL may appear at power-up to be connected to GND.
In such applications, use the four address combina-
tions that are selected by connecting address inputs
AD0 and AD2 to V+ or GND (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 neces-
sarily the MAX7325) is put on the bus, and an unex-
pected combination of ports can initialize as logic-low
outputs instead of inputs or logic-high outputs.
PIN
CONNECTION
DEVICE ADDRESS PORT POWER-UP DEFAULT
40kΩ INPUT PULLUPS ENABLED
AD2
AD0 A6A5A4A3A2A1A0P7P6P5P4P3P2P1P0P7P6P5P4P3P2P1
P0
SCL
GND110000011110000YYYY———
—
SCL
V+
110000111111111YYYYYYY
Y
SCL
SCL110001011111111YYYYYYY
Y
SCL
SDA110001111111111YYYYYYY
Y
SDA
GND110010011110000YYYY———
—
SDA
V+
110010111111111YYYYYYY
Y
SDA
SCL110011011111111YYYYYYY
Y
SDA
SDA110011111111111YYYYYYY
Y
GND
GND110100000000000———————
—
GND
V+
110100100001111———— YYY
Y
GND
SCL110101000001111———— Y Y Y
Y
GND
SDA110101100001111———— Y Y Y
Y
V+
GND110110011110000YYYY———
—
V+ V+
110110111111111YYYYYYY
Y
V+
SCL110111011111111YYYYYYY
Y
V+
SDA110111111111111YYYYYYY
Y
Table 2. MAX7325 Address Map for Ports P0–P7
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
_______________________________________________________________________________________ 9
PIN
C O NN EC TIO N
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
101000011110000
SCL
V+
101000111111111
SCL
SCL
101001011111111
SCL
SDA
101001111111111
SDA
GND
101010011110000
SDA
V+
101010111111111
SDA
SCL
101011011111111
SDA
SDA
101011111111111
GND
GND
101100000000000
GND
V+
101100100001111
GND
SCL
101101000001111
GND
SDA
101101100001111
V+
GND
101110011110000
V+
V+
101110111111111
V+
SCL
101111011111111
V+
SDA
101111111111111
Table 3. MAX7325 Address Map for Outputs O8–O15
Port Inputs
I/O port inputs switch at the CMOS-logic levels as
determined by the expander’s supply voltage, and are
overvoltage tolerant to +6V, independent of the
expander’s supply voltage.
I/O Port Input Transition Detection
All I/O ports configured as inputs are monitored for
changes since the expander was last accessed through
the serial interface. The state of the ports is stored in an
internal “snapshot” register for transition monitoring. The
snapshot is continuously compared with the actual input
conditions, and if a change is detected for any port input,
INT is asserted to signal a state change. The input ports
are sampled (internally latched into the snapshot register)
and the old transition flags cleared during the I2C acknowl-
edge of every MAX7325 read and write access. The previ-
ous port transition flags are read through the serial
interface as the second byte of a 2-byte read sequence.
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
10 ______________________________________________________________________________________
Serial Interface
Serial Addressing
The MAX7325 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 mas-
ter(s) and slave(s). The master initiates all data transfers
to and from the MAX7325 and generates the SCL clock
that synchronizes the data transfer (Figure 1).
SDA operates as both an input and an open-drain out-
put. 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 sin-
gle-master system has an open-drain SCL output.
Each transmission consists of a START condition sent
by a master, followed by the MAX7325’s 7-bit slave
addresses plus R/Wbits, 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 transmis-
sion 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).
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
Figure 1. 2-Wire Serial Interface Timing Details
SDA
SCL
START
CONDITION
STOP
CONDITION
SP
Figure 2. START and STOP Conditions
SDA
SCL
DATA LINE STABLE;
DATA VALID
CHANGE OF DATA
ALLOWED
Figure 3. Bit Transfer
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, such that the SDA line is stable low during
the high period of the clock pulse. When the master is
transmitting to the MAX7325, the device generates the
acknowledge bit because the MAX7325 is the recipi-
ent. When the MAX7325 is transmitting to the master,
the master generates the acknowledge bit because the
master is the recipient.
Slave Address
Each MAX7325 has two different 7-bit slave addresses
(Tables 2 and 3). The addresses are different to communi-
cate to either the eight push-pull outputs or the eight I/Os.
The 8th bit of the slave address following the 7-bit slave
address is the R/Wbit. It is low for a write command, and
high for a read command (Figure 5). The first (A6), sec-
ond (A5), and third (A4) bits of the MAX7325 slave
address are always 1, 1, and 0 (P0–P7) or 1, 0, and 1
(O8 to O15). Connect AD0 and AD2 to GND, V+, SDA,
or SCL to select the slave address bits A3, A2, A1, and
A0. The MAX7325 has 16 possible pairs of slave
addresses (Tables 2 and 3), allowing up to 16
MAX7325 devices on an I2C bus.
Accessing the MAX7325
The MAX7325 is accessed though an I2C interface. The
MAX7325 has two different 7-bit slave addresses for
either the eight open-drain I/O ports (P0–P7) or the
eight push-pull ports (O8–O15). See Tables 2 and 3.
Asingle-byte read from the I/O ports (P0–P7) of the
MAX7325 returns the status of the eight I/O ports and
clears both the internal transition flags and the INT out-
put when the master acknowledges the slave address
byte. A single-byte read from the eight push-pull ports
(O8–O15) returns the status of the eight output ports,
read back as inputs.
A 2-byte read from the I/O ports (P0–P7) of the
MAX7325 returns the status of the eight I/O ports (as for
a single-byte read), followed by the transition flags.
Again, the internal transition flags and the INT output
are cleared when the master acknowledges the slave
address byte, yet the previous transition flag data is
sent as the second byte. A 2-byte read from the push-
pull ports of the MAX7325 repeatedly returns the status
of the eight output ports, read back as inputs.
Amultibyte read (more than 2 bytes before the I2C
STOP bit) from the I/O ports (P0–P7) of the MAX7325
repeatedly returns the port data, followed by the transi-
tion flags. As the port data is resampled for each trans-
mission, and the transition flags are reset each time, a
multibyte read continuously returns the current data
and identifies any changing input ports.
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
______________________________________________________________________________________ 11
SCL
SDA BY
TRANSMITTER
CLOCK PULSE
FOR ACKNOWLEDGEMENT
START
CONDITION
SDA BY
RECEIVER
12 89
S
Figure 4. Acknowledge
SDA
SCL
A5
MSB LSB
ACKA4 A1A3 A0A2 R/W
Figure 5. Slave Address
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
12 ______________________________________________________________________________________
If a port input data change occurs during the read
sequence, then INT is reasserted during the I2C STOP
bit. The MAX7325 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 two-byte read).
A multibyte read from the push-pull ports of the
MAX7325 repeatedly returns the status of the eight out-
put ports, read back as inputs.
A single-byte write to either port groups of the
MAX7325 sets the logic state of all eight ports.
A multibyte write to either port group of the MAX7325
repeatedly sets the logic state of all eight ports.
Reading the MAX7325
A read from the open-drain I/O ports of the MAX7325
starts with the master transmitting the port group’s
slave address with the R/Wbit set to high. The
MAX7325 acknowledges the slave address, and sam-
ples the ports during the acknowledge bit. INT
deasserts during the slave address acknowledge.
Typically, the master reads 1 or 2 bytes from the
MAX7325, each byte being acknowledged by the mas-
ter upon reception with the exception of the last byte.
When the master reads one byte from the open-drain
ports of the MAX7325 and subsequently issues a STOP
condition (Figure 6), the MAX7325 transmits the current
port data, clears the change flags, and resets the tran-
sition detection. INT deasserts during the slave
SCL
MAX7325 SLAVE ADDRESS
S1 1 0 A P
1
PORT
tIV
N
P0 ACKNOWLEDGE
FROM MASTER
ACKNOWLEDGE
FROM MAX7325 P1
P2P3P4P5
P6
P7
D0D1D2D3D4D5D6D7
PORT I/O
INT OUTPUT
R/W PORT SNAPSHOT
tPH
tIR
PORT SNAPSHOT
S = START CONDITION SHADED = SLAVE TRANSMISSION
P = STOP CONDITION N = NOT ACKNOWLEDGE
tPSU tIP
INT REMAINS HIGH UNTIL STOP CONDITION
Figure 6. Reading Open-Drain Ports of the MAX7325 (1 Data Byte)
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
______________________________________________________________________________________ 13
SCL
MAX7325 SLAVE ADDRESSS110 A
P
1
PORTS
INT OUTPUT
R/W PORT SNAPSHOT
tIV
tPH
tIR
AD0D1D2D3D4D5D6D7
PORT SNAPSHOT
tPSU tIP
D7 D6 D5 D4 D3 D2 D1 D0 N
PORT SNAPSHOT
INT REMAINS HIGH UNTIL STOP CONDITION
I0
I1
I2I3I4I5
I6
I7 F0
F1
F2F3F4F5
F6
F7
PORT INPUTS INTERRUPT FLAGS
S = START CONDITION SHADED = SLAVE TRANSMISSION
P = STOP CONDITION N = NOT ACKNOWLEDGE
ACKNOWLEDGE
FROM MASTER
ACKNOWLEDGE
FROM MAX7325
Figure 7. Reading Open-Drain Ports of the MAX7325 (2 Data Bytes)
SCL
MAX7325 SLAVE ADDRESS
SA P
1
ACKNOWLEDGE FROM MAX7325
PORT SNAPSHOT DATA
PORT SNAPSHOT TAKEN
A
P0P1P2P3
DATA 1
P4P5P6P7
D0D1D2D3D4D5D6D7
PORT SNAPSHOT TAKEN ACKNOWLEDGE
FROM MASTER
R/W
Figure 8. Reading Push-Pull Ports of MAX7325
acknowledge. The new snapshot data is the current
port data transmitted to the master, and therefore, port
changes occuring during the transmission are detect-
ed. INT remains high until the STOP condition.
The master can read 2 bytes from the open-drain ports
of the MAX7325 and subsequently issues a STOP con-
dition (Figure 7). In this case, the MAX7325 transmits
the current port data, followed by the change flags. The
change flags are then cleared, and transition detection
is reset. INT goes high (high impedance if an external
pullup resistor is not fitted) during the slave acknowl-
edge. 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.
A read from the push-pull ports of the MAX7325 starts
with the master transmitting the group’s slave address
with the R/Wbit set high. The MAX7325 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 push-pull ports of the
MAX7325 and then issues a STOP condition (Figure 8).
The MAX7325 transmits the current port data, read
back from the actual port outputs (not the port output
latches) during the acknowledge. If a port is forced to a
logic state other than its programmed state, the read-
back reflects this. If driving a capacitive load, the read-
back port level verification algorithms may need to take
the RC rise/fall time into account.
Typically, the master reads one byte from the push-pull
ports of the MAX7325, then issues a STOP condition
(Figure 8). However, the master can read two or more
bytes from the group B ports of the MAX7325, then
issues a STOP condition. In this case, the MAX7325
resamples the port outputs during each acknowledge
and transmits the new data each time.
Writing the MAX7325
A write to either output port groups of the MAX7325
starts with the master transmitting the group’s slave
address with the R/Wbit set low. The MAX7325
acknowledges the slave address and samples the
ports during the acknowledge bit. INT goes high (high
impedance if an external pullup resistor is not fitted)
during the slave acknowledge only when it writes to the
open-drain ports. The master can now transmit one or
more bytes of data. The MAX7325 acknowledges these
subsequent bytes of data and updates the correspond-
ing group’s ports with each new byte until the master
issues a STOP condition (Figure 9).
Applications Information
Port Input and I2C Interface Level
Translation from Higher or
Lower Logic Voltages
The MAX7325’s SDA, SCL, AD0, AD2, RST, INT, O8–O15,
and P0–P7 are overvoltage protected to +6V. This
allows the MAX7325 to operate from a lower supply
voltage, such as +3.3V, while the I2C interface and/or
any of the eight I/O ports are driven as inputs from a
higher logic level, such as +5V.
The MAX7325 can operate from a higher supply volt-
age, such as +3V, while the I2C interface and/or some
of the I/O ports P0–P7 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 a V+ ≥1.8V, apply a voltage of 0.7 x V+ to assert a
logic-high. For example, a MAX7325 operating from a
+5V supply may not recognize a +3.3V nominal logic-
high. One solution for input-level translation is to drive
MAX7325 I/Os from open-drain outputs. Use a pullup
resistor to V+ or a higher supply to ensure a high logic
voltage greater than 0.7 x V+.
Port Output Signal-Level Translation
The open-drain output architecture allows for level trans-
lation to higher or lower voltages than the MAX7325’s
supply. Use an external pullup resistor on any output to
convert the high-impedance logic-high condition to a
positive voltage level. The resistor can be connected to
any voltage up to +6V, and the resistor value chosen to
ensure no more than 20mA is sunk in the logic-low condi-
tion. For interfacing CMOS inputs, a pullup resistor value
of 220kΩis a good starting point. Use a lower resistance
to improve noise immunity, in applications where power
consumption is less critical, or where a faster rise time is
needed for a given capacitive load.
Each of the push-pull output ports has protection
diodes to V+ and GND. When a port output is driven to
a voltage higher than V+ or lower than GND, the appro-
priate protection diode clamps the output to a diode
drop above V+ or below GND. When the MAX7325 is
powered down (V+ = 0V), every output port’s protection
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
14 ______________________________________________________________________________________
SCL
SDA
SLAVE ADDRESS
S0
12345678
AAA
DATA 1 DATA 2
DATA TO INTERRUPT MASK DATA TO INTERRUPT MASK
START CONDITION R/W ACKNOWLEDGE
FROM SLAVE
tPV
DATA 2 VALIDDATA 1 VALID
INTERNAL WRITE
TO PORT
DATA OUT
FROM PORT
ACKNOWLEDGE
FROM SLAVE
ACKNOWLEDGE
FROM SLAVE
tPV
Figure 9. Writing to the MAX7325
diodes to V+ and GND continue to appear as a diode
clamp from each output to GND (Figure 10).
Each of the I/O ports P0–P7 has a protection diode to
GND (Figure 11). When a port is driven to a voltage
lower than GND, the protection diode clamps the port
to a diode drop below GND.
Each of the I/O ports P0–P7 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 conducts and
the 40kΩpullup resistor is enabled. When the
MAX7325 is powered down (V+ = 0V), each I/O port
appears as a 40kΩresistor in series with a diode con-
nected to 0V. Input ports are protected to +6V under
any of these circumstances (Figure 11).
Driving LED Loads
When driving LEDs from one of the outputs, a resistor
must be fitted in series with the LED to limit the LED
current to no more than 20mA. Connect the LED cath-
ode to the MAX7325 port, and the LED anode to V+
through the series current-limiting resistor, RLED. Set
the port output low to illuminate the LED. 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 MAX7325 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 MAX7325 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 MAX7325. Do not exceed a total
sink current of 100mA for the device.
The MAX7325 must be protected from the negative-
voltage transient generated when switching off induc-
tive 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 MAX7325 operates with a supply voltage of +1.71V
to +5.5V. 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.
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
______________________________________________________________________________________ 15
P0–P7
PULLUP
ENABLE
INPUT
OUTPUT
40kΩ
MAX7325
V+ V+
Figure 11. MAX7325 Open-Drain I/O Port Structure
OUTPUT
V+
GNDGND
V+
O8–O15
MAX7325
Figure 10. MAX7325 Push-Pull Output Port Structure
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
16 ______________________________________________________________________________________
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
MAX7325
QSOP
+
RST
AD2
P2
P0
P1
P3
P4
16
15
9
10
O11
O10
P5
P6
14
13
11
12
O9
O8
P7
GND
Pin Configurations (continued)
MAX7325
P2
P7
P6
P5
P4
O11
O10
O9
O8
O15
O14
O13
O12
V+
3.3V
µC
SCL SCL
SDA
AD0
P1
P0
SDA
P3
GND
AD2
INT
OUTPUT
OUTPUT
OUTPUT
OUTPUT
RST
INT
RST
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
INPUT/OUTPUT
Typical Application Circuit
I2C
CONTROL
O9
O8
O11
O10
O12
O13
O14
O15
P1
P0
P3
P2
P4
P5
P6
P7
INT
I/O
PORTS
POWER-
ON RESET
INPUT
FILTER
RST
SDA
SCL
AD2
AD0
MAX7325
Functional Diagram
Chip Information
PROCESS: BiCMOS
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
______________________________________________________________________________________ 17
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
24L QFN THIN.EPS
PACKAGE OUTLINE,
21-0139 2
1
E
12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
18 ______________________________________________________________________________________
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE,
21-0139
2
2
E
12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
MAX7325
I2C Port Expander with 8 Push-Pull
and 8 Open-Drain I/Os
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19
© 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Heaney
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
QSOP.EPS
F
11
21-0055
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH