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MAX7312

2-Wire-Interfaced 16-Bit I/O Port Expander with Interrupt and Hot-Insertion Protection

Maxim Integrated 

2-Wire-Interfaced 16-Bit I/O Port Expander

with Interrupt and Hot-Insertion Protection

Table 2. Registers 0x00, 0x01—Input Port Registers

I7

I6

I5

I4

I3

I2

I1

I0

BIT

I15

I14

I13

I12

I11

I10

I9

I8

Table 3. Registers 0x02, 0x03—Output Port Registers

O7

O6

O5

O4

O3

O2

O1

O0

BIT

O15

O14

O13

O12

O11

O10

O9

O8

Power-up default

1

1

1

1

1

1

1

1

Table 4. Registers 0x04, 0x05—Polarity Inversion Registers

I/O7

I/O6

I/O5

I/O4

I/O3

I/O2

I/O1

I/O0

BIT

I/O15

I/O14

I/O13

I/O12

I/O11

I/O10

I/O9

I/O8

Power-up default

0

0

0

0

0

0

0

0

Table 5. Registers 0x06, 0x07—Configuration Registers

I/O7

I/O6

I/O5

I/O4

I/O3

I/O2

I/O1

I/O0

BIT

I/O15

I/O14

I/O13

I/O12

I/O11

I/O10

I/O9

I/O8

Power-up default

1

1

1

1

1

1

1

1

Table 6. Register 0x08—Timeout Register

BIT

76543210

Power-up default 0 0 0 0 0 0 0 1

Output Port Registers

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.

Polarity Inversion Registers

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.

Configuration Registers

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.

Bus Timeout

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.

Standby

The MAX7312 goes into standby when the I2C bus is

idle. Standby supply current is typically 2.9µA.

Applications Information

Hot Insertion

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.

Power-Supply Consideration

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.

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