The MAX1608’s outputs reset to a low state, while the

MAX1609’s outputs reset to a high-impedance state.

Below V+ = 0.8V (typical), the POR states cannot be

enforced, and the I/O pins of both devices exhibit

increasingly weak pulldown current capability, eventu-

ally becoming high impedance.

The MAX1608 is designed for applications that control

n-channel MOSFETs, while the MAX1609 is designed to

control p-channel MOSFETs. The power-on state keeps

the external MOSFETs off at power-up. Both devices

are suited for applications that use the parallel input for

serial functionality, although IO_s serving as inputs

must first be programmed to high impedance when

using the MAX1608.

Thermal Shutdown

These devices have internal thermal-shutdown circuitry

that sets all outputs to a high-impedance state (IO_

pins) when the junction temperature exceeds +140°C

typical. Thermal shutdown only occurs during an over-

load condition on the IO_ pins. The device cycles

between thermal shutdown and the overcurrent condi-

tion (with 10°C hysteresis) until the overload condition

is removed. The device asserts ALERT low while it is in

thermal shutdown, indicating this fault status. ALERT

will be reasserted immediately after it is cleared if the

device is still hot. ALERT can only be completely

cleared once the fault condition is removed and the

device has cooled. Alternatively, forcing the IO_ to high

impedance will allow the junction to cool down.

Octal SMBus-to-Parallel I/O Expanders

12

______________________________________________________________________________________

POR STATE

7

MASKL7

1

6

MASKL6

1

5

MASKL5

1

4

MASKL4

1

1

MASKL1

1

NAME

BIT

2

MASKL2

1

3

MASKL3

1

MASKL0

1

0

Masks IO1 high-to-low interrupt. 0 = interrupts, 1 = masked.

Masks IO7 high-to-low interrupt. 0 = interrupts, 1 = masked.

Masks IO6 high-to-low interrupt. 0 = interrupts, 1 = masked.

Masks IO5 high-to-low interrupt. 0 = interrupts, 1 = masked.

Masks IO4 high-to-low interrupt. 0 = interrupts, 1 = masked.

Masks IO2 high-to-low interrupt. 0 = interrupts, 1 = masked.

Masks IO3 high-to-low interrupt. 0 = interrupts, 1 = masked.

FUNCTION

Masks IO0 high-to-low interrupt. 0 = interrupts, 1 = masked.

Table 5. Data Register 3 (NDR3 and SDR3) Bit Assignments (Read or Write)

Table 6. IO_ Status Data Register (RSB) Bit Assignments (Read Only)

7

DATA7

6

DATA6

5

DATA5

4

DATA4

1

DATA1

NAME

BIT

2

DATA2

3

DATA3

DATA0

0

Indicates the current state of IO1. 1 = high, 0 = low.

Indicates the current state of IO7. 1 = high, 0 = low.

Indicates the current state of IO6. 1 = high, 0 = low.

Indicates the current state of IO5. 1 = high, 0 = low.

Indicates the current state of IO4. 1 = high, 0 = low.

Indicates the current state of IO2. 1 = high, 0 = low.

Indicates the current state of IO3. 1 = high, 0 = low.

FUNCTION

Indicates the current state of IO0. 1 = high, 0 = low.