MAX7312 Maxim, MAX7312 Datasheet - Page 11
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MAX7312
Manufacturer Part Number
MAX7312
Description
The MAX7312 2-wire-interfaced expander provides 16-bit parallel input/output (I/O) port expansion in SMBus™ and I²C applications
Manufacturer
Maxim
Datasheet
1.MAX7312.pdf
(16 pages)
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The output port registers (Table 3) set the outgoing
logic levels of the I/Os defined as outputs by the
respective configuration register. Reads from the out-
put port registers reflect the value that is in the flip-flop
controlling the output selection, not the actual I/O value.
The polarity inversion registers (Table 4) enable polarity
inversion of pins defined as inputs by the respective
port configuration registers. Set the bit in the polarity
inversion register to invert the corresponding port pin’s
polarity. Clear the bit in the polarity inversion register to
retain the corresponding port pin’s original polarity.
The configuration registers (Table 5) configure the
directions of the I/O pins. Set the bit in the respective
configuration register to enable the corresponding port
as an input. Clear the bit in the configuration register to
enable the corresponding port as an output.
Table 2. Registers 0x00, 0x01—Input Port Registers
Table 3. Registers 0x02, 0x03—Output Port Registers
Table 4. Registers 0x04, 0x05—Polarity Inversion Registers
Table 5. Registers 0x06, 0x07—Configuration Registers
Table 6. Register 0x08—Timeout Register
Power-up default
Power-up default
Power-up default
Power-up default
BIT
BIT
BIT
BIT
BIT
with Interrupt and Hot-Insertion Protection
2-Wire-Interfaced 16-Bit I/O Port Expander
______________________________________________________________________________________
7
0
I/O15
I/O15
I15
O15
I/O7
I/O7
I7
O7
1
0
1
6
0
Polarity Inversion Registers
5
0
Configuration Registers
Output Port Registers
I/O14
I/O14
I14
O14
I/O6
I/O6
4
0
I6
O6
1
0
1
3
0
2
0
I/O13
I/O13
O13
I/O5
I13
I/O5
O5
I5
1
0
1
1
0
0
1
I/O12
I/O12
O12
I/O4
I12
I/O4
O4
I4
1
0
1
Set register 0x08 LSB (bit 0) to enable the bus timeout
function (Table 6) or clear it to disable the bus timeout
function. Enabling the timeout feature resets the
MAX7312 serial bus interface when SCL stops either high
or low during a read or write. If either SCL or SDA is low
for more than 29ms after the start of a valid serial transfer,
the interface resets itself and sets up SDA as an input.
The MAX7312 then waits for another START condition.
The MAX7312 goes into standby when the I
idle. Standby supply current is typically 2.9µA.
The I/O ports I/O0–I/O15 interrupt output INT, and serial
interfaces SDA, SCL, AD0-2 remain high impedance
with up to 6V asserted on them when the MAX7312 is
powered down (V+ = 0V). The MAX7312 can therefore
be used in hot-swap applications.
The MAX7312 operates from a supply voltage of 2V to
5.5V. Bypass the power supply to GND with a 0.047µF
capacitor as close to the device as possible. For the QFN
version, connect the underside exposed pad to GND.
I/O11
I/O11
O11
I/O3
I/O3
I11
O3
I3
1
0
1
Applications Information
Power-Supply Consideration
I/O10
I/O10
O10
I/O2
I/O2
I10
O2
I2
1
0
1
I/O1
I/O9
I/O1
I/O9
O1
O9
I1
I9
1
0
1
Hot Insertion
Bus Timeout
Standby
2
C bus is
I/O0
I/O8
I/O0
I/O8
O0
O8
I0
I8
1
0
1
11