PCA8574; PCA8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
Rev. 3 — 3 June 2013
Product data sheet
1. General description
The PCA8574/74A provides general-purpose remote I/O expansion via the two-wire
bidirectional I
2
C-bus (serial clock (SCL), serial data (SDA)).
The devices consist of eight quasi-bidirectional ports, 400 kHz I
2
C-bus interface, three
hardware address inputs and interrupt output operating between 2.3 V and 5.5 V. The
quasi-bidirectional port can be independently assigned as an input to monitor interrupt
status or keypads, or as an output to activate indicator devices such as LEDs. The system
master can read from the input port or write to the output port through a single register.
The low current consumption of 4.5
A
(typical, static) is great for mobile applications and
the latched output ports have 25 mA high current sink drive capability for directly driving
LEDs.
The PCA8574 and PCA8574A are identical, except for the different fixed portion of the
slave address. The three hardware address pins allow eight of each device to be on the
same I
2
C-bus, so there can be up to 16 of these I/O expanders PCA8574/74A together on
the same I
2
C-bus, supporting up to 128 I/Os (for example, 128 LEDs).
The active LOW open-drain interrupt output (INT) can be connected to the interrupt logic
of the microcontroller and is activated when any input state differs from its corresponding
input port register state. It is used to indicate to the microcontroller that an input state has
changed and the device needs to be interrogated without the microcontroller continuously
polling the input register via the I
2
C-bus.
The internal Power-On Reset (POR) initializes the I/Os as inputs with a weak internal
pull-up 100
A
current source.
2. Features and benefits
I
2
C-bus to parallel port expander
400 kHz I
2
C-bus interface (Fast-mode I
2
C-bus)
Operating supply voltage 2.3 V to 5.5 V with 5.5 V tolerant I/Os held to V
DD
with
100
A
current source
8-bit remote I/O pins that default to inputs at power-up
Latched outputs with 25 mA sink capability for directly driving LEDs
Total package sink capability of 200 mA
Active LOW open-drain interrupt output
Eight programmable slave addresses using three address pins
Low standby current (4.5
A
typical)
40 C
to +85
C
operation
NXP Semiconductors
PCA8574; PCA8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
ESD protection exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM per
JESD22-C101
Latch-up testing is done to JEDEC standard JESD78 which exceeds 100 mA
Packages offered: SO16, TSSOP16, SSOP20
3. Applications
LED signs and displays
Servers
Key pads
Industrial control
Medical equipment
PLCs
Cellular telephones
Mobile devices
Gaming machines
Instrumentation and test measurement
4. Ordering information
Table 1.
Ordering information
Topside mark Package
Name
PCA8574D
[1]
PCA8574AD
[2]
PCA8574PW
PCA8574APW
PCA8574TS
[3]
PCA8574ATS
[4]
[1]
[2]
[3]
[4]
Type number
Description
plastic small outline package; 16 leads; body width 7.5 mm
plastic thin shrink small outline package; 16 leads;
body width 4.4 mm
plastic shrink small outline package; 20 leads;
body width 4.4 mm
Version
SOT162-1
SOT403-1
SOT266-1
PCA8574D
PCA8574AD
PCA8574
PA8574A
PCA8574
PA8574A
SO16
TSSOP16
SSOP20
PCA8574D drop-in replacement for PCF8574T/3.
PCA8574AD drop-in replacement for PCF8574AT/3.
PCA8574TS drop-in replacement for PCF8574TS/3.
PCA8574ATS drop-in replacement for PCF8574ATS/3.
PCA8574_PCA8574A
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2013. All rights reserved.
Product data sheet
Rev. 3 — 3 June 2013
2 of 32
NXP Semiconductors
PCA8574; PCA8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
4.1 Ordering options
Table 2.
Ordering options
Orderable
part number
PCA8574D,512
PCA8574D,518
PCA8574AD
PCA8574AD,512
PCA8574AD,518
PCA8574PW
PCA8574PW,112
PCA8574PW,118
Package
Packing method
Minimum
order
quantity
1920
1000
1920
1000
2400
2500
2400
2500
1350
2500
1350
2500
Temperature range
Type number
PCA8574D
SO16
SO16
SO16
SO16
TSSOP16
TSSOP16
Standard marking * tube dry pack
Reel 13” Q1/T1
*standard mark SMD dry pack
Standard marking * tube dry pack
Reel 13” Q1/T1
*standard mark SMD dry pack
Standard marking
* IC’s tube - DSC bulk pack
Reel 13” Q1/T1
*standard mark SMD
Standard marking
* IC’s tube - DSC bulk pack
Reel 13” Q1/T1
*standard mark SMD
Standard marking
* IC’s tube - DSC bulk pack
Reel 13” Q1/T1
*standard mark SMD
Standard marking
* IC’s tube - DSC bulk pack
Reel 13” Q1/T1
*standard mark SMD
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
T
amb
=
40 C
to +85
C
PCA8574APW PCA8574APW,112 TSSOP16
PCA8574APW,118 TSSOP16
PCA8574TS
PCA8574TS,112
PCA8574TS,118
PCA8574ATS
PCA8574ATS,112
PCA8574ATS,118
SSOP20
SSOP20
SSOP20
SSOP20
5. Block diagram
PCA8574
PCA8574A
INT
A0
A1
A2
SCL
SDA
INPUT
FILTER
I
2
C-BUS
CONTROL
LP FILTER
INTERRUPT
LOGIC
SHIFT
REGISTER
8 BITS
I/O
PORT
P0 to P7
write pulse
read pulse
V
DD
V
SS
POWER-ON
RESET
002aac677
Fig 1.
PCA8574_PCA8574A
Block diagram
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2013. All rights reserved.
Product data sheet
Rev. 3 — 3 June 2013
3 of 32
NXP Semiconductors
PCA8574; PCA8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
write pulse
I
trt(pu)
data from Shift Register
D
FF
CI
S
power-on reset
D
FF
read pulse
CI
S
Q
Q
I
OH
100 µA
V
DD
I
OL
P0 to P7
V
SS
data to Shift Register
002aah521
to interrupt logic
Fig 2.
Simplified schematic diagram of P0 to P7
6. Pinning information
6.1 Pinning
INT
SCL
A0
A1
A2
P0
P1
P2
P3
V
SS
1
2
3
4
5
6
7
8
002aac678
1
2
3
4
5
6
7
8
9
20 P7
19 P6
18 n.c.
17 P5
16 P4
15 V
SS
14 P3
13 n.c.
12 P2
11 P1
002aac680
16 V
DD
15 SDA
14 SCL
13 INT
12 P7
11 P6
10 P5
9
P4
A0
A1
A2
P0
P1
P2
P3
V
SS
1
2
3
4
5
6
7
8
002aac941
16 V
DD
15 SDA
14 SCL
13 INT
12 P7
11 P6
10 P5
9
P4
n.c.
SDA
V
DD
A0
A1
n.c.
A2
PCA8574D
PCA8574AD
PCA8574PW
PCA8574APW
PCA8574TS
PCA8574ATS
P0 10
Fig 3. Pin configuration for SO16
Fig 4. Pin configuration for
TSSOP16
Fig 5. Pin configuration for
SSOP20
PCA8574_PCA8574A
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2013. All rights reserved.
Product data sheet
Rev. 3 — 3 June 2013
4 of 32
NXP Semiconductors
PCA8574; PCA8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
6.2 Pin description
Table 3.
Symbol
A0
A1
A2
P0
P1
P2
P3
V
SS
P4
P5
P6
P7
INT
SCL
SDA
V
DD
n.c.
Pin description
Pin
DIP16, SO16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
-
SSOP20
6
7
9
10
11
12
14
15
16
17
19
20
1
2
4
5
address input 0
address input 1
address input 2
quasi-bidirectional I/O 0
quasi-bidirectional I/O 1
quasi-bidirectional I/O 2
quasi-bidirectional I/O 3
supply ground
quasi-bidirectional I/O 4
quasi-bidirectional I/O 5
quasi-bidirectional I/O 6
quasi-bidirectional I/O 7
interrupt output (active LOW)
serial clock line
serial data line
supply voltage
Description
3, 8, 13, 18 not connected
7. Functional description
Refer to
Figure 1 “Block diagram”.
7.1 Device address
Following a START condition, the bus master must send the address of the slave it is
accessing and the operation it wants to perform (read or write). The address format of the
PCA8574/74A is shown in
Figure 6.
Slave address pins A2, A1 and A0 are held HIGH or
LOW to choose one of eight slave addresses. To conserve power, no internal pull-up
resistors are incorporated on pins A2, A1, or A0 so they must be externally held HIGH or
LOW. The address pins (A2, A1, A0) can connect to V
DD
or V
SS
directly or through
resistors.
slave address
0
1
0
0
A2
A1
A0
R/W
slave address
0
1
1
1
A2
A1
A0
R/W
0
0
fixed
hardware
selectable
002aah469
fixed
hardware
selectable
002aah470
a. PCA8574
Fig 6.
PCA8574 and PCA8574A slave addresses
b. PCA8574A
PCA8574_PCA8574A
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2013. All rights reserved.
Product data sheet
Rev. 3 — 3 June 2013
5 of 32
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