PCF8574; PCF8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
Rev. 5 — 27 May 2013
Product data sheet
1. General description
The PCF8574/74A 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, 100 kHz I
2
C-bus interface, three
hardware address inputs and interrupt output operating between 2.5 V and 6 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. System
master can read from the input port or write to the output port through a single register.
The low current consumption of 2.5
A
(typical, static) is great for mobile applications and
the latched output ports directly drive LEDs.
The PCF8574 and PCF8574A 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 PCF8574/74A 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
100 kHz I
2
C-bus interface (Standard-mode I
2
C-bus)
Operating supply voltage 2.5 V to 6 V with non-overvoltage tolerant I/O held to V
DD
with 100
A
current source
8-bit remote I/O pins that default to inputs at power-up
Latched outputs directly drive LEDs
Total package sink capability of 80 mA
Active LOW open-drain interrupt output
Eight programmable slave addresses using three address pins
Low standby current (2.5
A
typical)
40 C
to +85
C
operation
ESD protection exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM per
JESD22-C101
NXP Semiconductors
PCF8574; PCF8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
Latch-up testing is done to JEDEC standard JESD78 which exceeds 100 mA
Packages offered: DIP16, SO16, SSOP20
3. Applications
LED signs and displays
Servers
Key pads
Industrial control
Medical equipment
PLC
Cellular telephones
Mobile devices
Gaming machines
Instrumentation and test measurement
4. Ordering information
Table 1.
Ordering information
Topside mark
PCF8574P
PCF8574AP
PCF8574T
PCF8574AT
8574TS
8574A
SSOP20
plastic shrink small outline package; 20 leads;
body width 4.4 mm
SOT266-1
SO16
plastic small outline package; 16 leads; body width 7.5 mm
SOT162-1
Package
Name
PCF8574P
PCF8574AP
PCF8574T/3
PCF8574AT/3
PCF8574TS/3
PCF8574ATS/3
DIP16
Description
plastic dual in-line package; 16 leads (300 mil)
Version
SOT38-4
Type number
4.1 Ordering options
Table 2.
Ordering options
Orderable
part number
PCF8574P,112
PCF8574AP,112
PCF8574T/3,512
PCF8574T/3,518
PCF8574AT/3
PCF8574AT/3,512
PCF8574AT/3,518
Package Packing method
Minimum
order
quantity
1000
1000
1920
1000
1920
1000
Temperature range
Type number
PCF8574P
PCF8574AP
PCF8574T/3
DIP16
DIP16
SO16
SO16
SO16
SO16
Standard marking
* IC’s tube - DSC bulk pack
Standard marking
* IC’s tube - DSC bulk pack
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
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
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
2 of 33
NXP Semiconductors
PCF8574; PCF8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
Table 2.
Ordering options
…continued
Orderable
part number
PCF8574TS/3,112
PCF8574TS/3,118
Package Packing method
Minimum
order
quantity
1350
2500
2500
Temperature range
Type number
PCF8574TS/3
SSOP20
SSOP20
Standard marking
* IC’s tube - DSC bulk pack
Reel 13” Q1/T1
*standard mark SMD
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
PCF8574ATS/3 PCF8574ATS/3,118 SSOP20
5. Block diagram
PCF8574
PCF8574A
INT
A0
A1
A2
SCL
SDA
INPUT
FILTER
I
2
C-BUS
CONTROL
LP FILTER
INTERRUPT
LOGIC
P0
P1
P2
P3
P4
P5
P6
P7
SHIFT
REGISTER
8 bits
I/O
PORT
write pulse
read pulse
V
DD
V
SS
POWER-ON
RESET
002aad624
Fig 1.
Block diagram
write pulse
I
trt(pu)
data from Shift Register
D
FF
CI
S
power-on reset
D
FF
read pulse
CI
S
Q
Q
100
μA
I
OH
V
DD
I
OL
P0 to P7
V
SS
data to Shift Register
002aac109
to interrupt logic
Fig 2.
PCF8574_PCF8574A
Simplified schematic diagram of P0 to P7
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
3 of 33
NXP Semiconductors
PCF8574; PCF8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
6. Pinning information
6.1 Pinning
A0
A1
A2
P0
1
2
3
4
16 V
DD
15 SDA
14 SCL
13 INT
A0
A1
A2
P0
1
2
3
4
5
6
7
8
002aad626
INT
SCL
16 V
DD
15 SDA
14 SCL
13 INT
12 P7
11 P6
10 P5
9
P4
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
002aad627
n.c.
SDA
V
DD
A0
A1
n.c.
A2
PCF8574P
PCF8574AP
12
P1 5
P7
P2
P3
V
SS
6
7
8
002aad625
11 P6
10 P5
9
P4
P1
P2
P3
V
SS
PCF8574T/3
PCF8574AT/3
PCF8574TS/3
PCF8574ATS/3
P0 10
Fig 3.
Pin configuration for DIP16
Fig 4.
Pin configuration for SO16
Fig 5.
Pin configuration for
SSOP20
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
3, 8, 13, 18
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
not connected
Description
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
4 of 33
NXP Semiconductors
PCF8574; PCF8574A
Remote 8-bit I/O expander for I
2
C-bus with interrupt
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
PCF8574/74A 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 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
002aad628
fixed
hardware
selectable
002aad629
a. PCF8574
Fig 6.
PCF8574 and PCF8574A slave addresses
b. PCF8574A
The last bit of the first byte defines the operation to be performed. When set to logic 1 a
read is selected, while a logic 0 selects a write operation (write operation is shown in
Figure 6).
7.1.1 Address maps
The PCF8574 and PCF8574A are functionally the same, but have a different fixed portion
(A6 to A3) of the slave address. This allows eight of the PCF8574 and eight of the
PCF8574A to be on the same I
2
C-bus without address conflict.
Table 4.
A2
A1
PCF8574 address map
Address of PCF8574
A6
A5
A4
A3
A2
A1
A0 R/W
Address byte value
Write
Read
A0
7-bit
hexadecimal
address
without R/W
20h
21h
22h
23h
24h
25h
26h
27h
Pin connectivity
V
SS
V
SS
V
SS
V
SS
V
DD
V
DD
V
DD
V
DD
V
SS
V
SS
V
DD
V
DD
V
SS
V
SS
V
DD
V
DD
V
SS
V
DD
V
SS
V
DD
V
SS
V
DD
V
SS
V
DD
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
-
-
-
-
-
-
-
-
40h
42h
44h
46h
48h
4Ah
4Ch
4Eh
41h
43h
45h
47h
49h
4Bh
4Dh
4Fh
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
5 of 33
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