Datasheet

PCF8574_PCF8574A All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 5 — 27 May 2013 14 of 33
NXP Semiconductors
PCF8574; PCF8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
while (INT == 1); //Monitor the interrupt pin. If INT = 1 do nothing
//When INT = 0 then read input ports
<S> <slave address read> <ACK> <1010 0010> <NACK> <P> //Read PCF8574 data
If (P0 == 0) //Temperature sensor activated
{
// write to PCF8574 with data 0010 1011b to turn on LED (P7), on Switch (P3)
and keep P[1:0] as input ports.
<S> <0100 0000> <ACK> <0010 1011> <ACK> <P> // Write to PCF8574
}
10.3 High current-drive load applications
The GPIO has a minimum guaranteed sinking current of 10 mA per bit at 5 V. In
applications requiring additional drive, two port pins may be connected together to sink up
to 20 mA current. Both bits must then always be turned on or off together. Up to five pins
can be connected together to drive 80 mA, which is the device recommended total limit.
Each pin needs its own limiting resistor as shown in Figure 16
to prevent damage to the
device should all ports not be turned on at the same time.
10.4 Migration path
NXP offers newer, more capable drop-in replacements for the PCF8574/74A in newer
space-saving packages.
PCA9670 replaces the interrupt output of the PCA9674 with hardware reset input to retain
the maximum number of addresses and the PCA9672 replaces address A2 of the
PCA9674 with hardware reset input to retain the interrupt but limit the number of
addresses.
Fig 16. High current-drive load application
002aah385
V
DD
P0
P1
P2
P3
P4
P5
P6
P7
V
DD
SDA
SCL
INT
A0
A1
A2
CORE
PROCESSOR
V
DD
LOAD
Table 6. Migration path
Type number I
2
C-bus
frequency
Voltage range Number of
addresses
per device
Interrupt Reset Total package
sink current
PCF8574/74A 100 kHz 2.5 V to 6 V 8 yes no 80 mA
PCA8574/74A 400 kHz 2.3 V to 5.5 V 8 yes no 200 mA
PCA9674/74A 1 MHz Fm+ 2.3 V to 5.5 V 64 yes no 200 mA
PCA9670 1 MHz Fm+ 2.3 V to 5.5 V 64 no yes 200 mA
PCA9672 1 MHz Fm+ 2.3 V to 5.5 V 16 yes yes 200 mA