PCA9673_1

© NXP B.V. 2007. All rights reserved.

Product data sheet

Rev. 01 — 1 February 2007

18 of 33

NXP Semiconductors

PCA9673

10.3 Differences between the PCA9673 and the PCF8575

The PCA9673 is a drop in replacement for the PCF8575 and can used without electrical

or software modifications, but there is a difference in interrupt output release timing during

the read operation.

Write operations are identical. At the completion of each 8-bit write sequence the data is

stored in its associated 8-bit write register at ACK or NACK. The first byte goes to P0n

while the second goes to P1n. Subsequent writes without a STOP wrap around to P0n

then P1n again. Any write will update both read registers and clear interrupts.

Read operations are identical. Both devices update the byte register with the pin data as

each 8-bit read is initiated, the very first read after an address cycle corresponds to ports

P0n while the second (even byte) corresponds to P1n and subsequent reads without a

STOP wrap around to P0n then P1n again.

During read operations, the PCA9673 interrupt output will be cleared in a byte-wise

fashion as each byte is read. Reading the first byte will clear any interrupts associated

with the P0n pins. This first byte read operation will have no effect on interrupts associated

with changes of state on the P1n pins. Interrupts associated with the P1n pins will be

cleared when the second byte is read. Reading the second byte has no effect on

interrupts associated with the changes of state on the P0x pins. The PCF8575 interrupt

output will clear after reading both bytes of data regardless of whether data was changed

in the first byte or the second byte or both bytes.

11. Limiting values

[1]

Total package (maximum) output current is 600 mA.

Table 4.

Limiting values

In accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol

Parameter

Conditions

Min

Max

Unit

supply voltage

−0.5

+6

V

supply current

-

±100

mA

ground supply current

-

±600

mA

input voltage

5.5

V

input current

-

±20

mA

output current

-

±50[1]

mA

total power dissipation

-

600

mW

P/out

power dissipation per output

-

200

mW

storage temperature

−65

+150

°C

ambient temperature

operating

−40

+85

°C