PCA9673 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 2 — 29 September 2011 19 of 33
NXP Semiconductors
PCA9673
Remote 16-bit I/O expander for Fm+ I
2
C-bus with interrupt and reset
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
V
DD
supply voltage 0.5 +6 V
I
DD
supply current - 100 mA
I
SS
ground supply current - 600 mA
V
I
input voltage V
SS
0.5 5.5 V
I
I
input current - 20 mA
I
O
output current - 50
[1]
mA
P
tot
total power dissipation - 600 mW
P/out power dissipation per output - 200 mW
T
stg
storage temperature 65 +150 C
T
amb
ambient temperature operating 40 +85 C
