PCF8574; PCF8574A
Remote 8-bit I/O expander for I2C-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 I2C-bus (serial clock (SCL), serial data (SDA)).
The devices consist of eight quasi-bidirectional ports, 100 kHz I2C-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 I2C-bus, so there can be up to 16 of these I/O expanders PCF8574/74A together on
the same I2C-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 I2C-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
I2C-bus to parallel port expander
100 kHz I2C-bus interface (Standard-mode I2C-bus)
Operating supply voltage 2.5 V to 6 V with non-overvoltage tolerant I/O held to VDD
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
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-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
Type number
Topside mark
PCF8574P
PCF8574P
PCF8574AP
PCF8574AP
PCF8574T/3
PCF8574T
PCF8574AT/3
PCF8574AT
PCF8574TS/3
8574TS
PCF8574ATS/3
8574A
Package
Name
Description
Version
DIP16
plastic dual in-line package; 16 leads (300 mil)
SOT38-4
SO16
plastic small outline package; 16 leads; body width 7.5 mm
SOT162-1
SSOP20
plastic shrink small outline package; 20 leads;
body width 4.4 mm
SOT266-1
4.1 Ordering options
Table 2.
Ordering options
Type number
Orderable
part number
Package Packing method
Minimum
order
quantity
Temperature range
PCF8574P
PCF8574P,112
DIP16
Standard marking
* IC’s tube - DSC bulk pack
1000
Tamb = 40 C to +85 C
PCF8574AP
PCF8574AP,112
DIP16
Standard marking
* IC’s tube - DSC bulk pack
1000
Tamb = 40 C to +85 C
PCF8574T/3
PCF8574T/3,512
SO16
Standard marking
* tube dry pack
1920
Tamb = 40 C to +85 C
PCF8574T/3,518
SO16
Reel 13” Q1/T1
*standard mark SMD dry pack
1000
Tamb = 40 C to +85 C
PCF8574AT/3,512
SO16
Standard marking
* tube dry pack
1920
Tamb = 40 C to +85 C
PCF8574AT/3,518
SO16
Reel 13” Q1/T1
*standard mark SMD dry pack
1000
Tamb = 40 C to +85 C
PCF8574AT/3
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
2 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
Table 2.
Ordering options …continued
Type number
Orderable
part number
Package Packing method
Minimum
order
quantity
Temperature range
PCF8574TS/3
PCF8574TS/3,112
SSOP20
Standard marking
* IC’s tube - DSC bulk pack
1350
Tamb = 40 C to +85 C
PCF8574TS/3,118
SSOP20
Reel 13” Q1/T1
*standard mark SMD
2500
Tamb = 40 C to +85 C
PCF8574ATS/3 PCF8574ATS/3,118 SSOP20
Reel 13” Q1/T1
*standard mark SMD
2500
Tamb = 40 C to +85 C
5. Block diagram
PCF8574
PCF8574A
INTERRUPT
LOGIC
LP FILTER
INT
A0
A1
A2
SCL
SDA
I2C-BUS
CONTROL
INPUT
FILTER
SHIFT
REGISTER
8 bits
P0
P1
P2
P3
P4
P5
P6
P7
I/O
PORT
write pulse
read pulse
POWER-ON
RESET
VDD
VSS
002aad624
Fig 1.
Block diagram
write pulse
100 μA
VDD
IOH
Itrt(pu)
data from Shift Register
D
Q
FF
P0 to P7
IOL
CI
S
power-on reset
VSS
D
Q
FF
read pulse
CI
S
to interrupt logic
data to Shift Register
002aac109
Fig 2.
PCF8574_PCF8574A
Product data sheet
Simplified schematic diagram of P0 to P7
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
3 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
6. Pinning information
6.1 Pinning
A0
1
16 VDD
A1
2
15 SDA
A2
3
P0
4
14 SCL
13 INT
PCF8574P
PCF8574AP 12
P1 5
P7
11 P6
6
P2
10 P5
7
P3
9
8
VSS
P4
1
20 P7
2
19 P6
18 n.c.
A0
1
16 VDD
n.c.
3
A1
2
15 SDA
SDA
4
A2
3
14 SCL
VDD
5
P0
4
13 INT
A0
6
P1
5
12 P7
A1
7
14 P3
P2
6
11 P6
n.c.
8
13 n.c.
P3
7
10 P5
A2
9
12 P2
VSS
8
9
P0 10
11 P1
PCF8574T/3
PCF8574AT/3
P4
17 P5
PCF8574TS/3
PCF8574ATS/3
002aad626
002aad625
Fig 3.
INT
SCL
Pin configuration for DIP16
Fig 4.
Pin configuration for SO16
16 P4
15 VSS
002aad627
Fig 5.
Pin configuration for
SSOP20
6.2 Pin description
Table 3.
PCF8574_PCF8574A
Product data sheet
Pin description
Symbol
Pin
Description
DIP16, SO16
SSOP20
A0
1
6
address input 0
A1
2
7
address input 1
A2
3
9
address input 2
P0
4
10
quasi-bidirectional I/O 0
P1
5
11
quasi-bidirectional I/O 1
P2
6
12
quasi-bidirectional I/O 2
P3
7
14
quasi-bidirectional I/O 3
VSS
8
15
supply ground
P4
9
16
quasi-bidirectional I/O 4
P5
10
17
quasi-bidirectional I/O 5
P6
11
19
quasi-bidirectional I/O 6
P7
12
20
quasi-bidirectional I/O 7
INT
13
1
interrupt output (active LOW)
SCL
14
2
serial clock line
SDA
15
4
serial data line
VDD
16
5
supply voltage
n.c.
-
3, 8, 13, 18
not connected
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
4 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-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 VDD or VSS directly or through resistors.
R/W
slave address
0
1
0
0
fixed
A2
A1
A0
R/W
slave address
0
0
hardware
selectable
1
1
fixed
1
A2
A1
0
hardware
selectable
002aad628
002aad629
a. PCF8574
Fig 6.
A0
b. PCF8574A
PCF8574 and PCF8574A slave addresses
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 I2C-bus without address conflict.
Table 4.
PCF8574 address map
Pin connectivity
PCF8574_PCF8574A
Product data sheet
Address of PCF8574
Address byte value
Write
Read
7-bit
hexadecimal
address
without R/W
-
40h
41h
20h
1
-
42h
43h
21h
0
-
44h
45h
22h
1
1
-
46h
47h
23h
1
0
0
-
48h
49h
24h
0
1
0
1
-
4Ah
4Bh
25h
0
1
1
0
-
4Ch
4Dh
26h
0
1
1
1
-
4Eh
4Fh
27h
A2
A1
A0
A6
A5
A4
A3
A2
A1
A0 R/W
VSS
VSS
VSS
0
1
0
0
0
0
0
VSS
VSS
VDD
0
1
0
0
0
0
VSS
VDD
VSS
0
1
0
0
0
1
VSS
VDD
VDD
0
1
0
0
0
VDD
VSS
VSS
0
1
0
0
VDD
VSS
VDD
0
1
0
VDD
VDD
VSS
0
1
0
VDD
VDD
VDD
0
1
0
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
5 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
Table 5.
PCF8574A address map
Pin connectivity
Address of PCF8574A
Address byte value
Write
Read
7-bit
hexadecimal
address
without R/W
-
70h
71h
38h
1
-
72h
73h
39h
1
0
-
74h
75h
3Ah
1
1
-
76h
77h
3Bh
1
0
0
-
78h
79h
3Ch
1
1
0
1
-
7Ah
7Bh
3Dh
1
1
1
1
0
-
7Ch
7Dh
3Eh
1
1
1
1
1
-
7Eh
7Fh
3Fh
A2
A1
A0
A6
A5
A4
A3
A2
A1
A0 R/W
VSS
VSS
VSS
0
1
1
1
0
0
0
VSS
VSS
VDD
0
1
1
1
0
0
VSS
VDD
VSS
0
1
1
1
0
VSS
VDD
VDD
0
1
1
1
0
VDD
VSS
VSS
0
1
1
1
VDD
VSS
VDD
0
1
1
VDD
VDD
VSS
0
1
VDD
VDD
VDD
0
1
8. I/O programming
8.1 Quasi-bidirectional I/Os
A quasi-bidirectional I/O is an input or output port without using a direction control register.
Whenever the master reads the register, the value returned to master depends on the
actual voltage or status of the pin. At power on, all the ports are HIGH with a weak 100 A
internal pull-up to VDD, but can be driven LOW by an internal transistor, or an external
signal. The I/O ports are entirely independent of each other, but each I/O octal is
controlled by the same read or write data byte.
Advantages of the quasi-bidirectional I/O over totem pole I/O include:
• Better for driving LEDs since the p-channel (transistor to VDD) is small, which saves
die size and therefore cost. LED drive only requires an internal transistor to ground,
while the LED is connected to VDD through a current-limiting resistor. Totem pole I/O
have both n-channel and p-channel transistors, which allow solid HIGH and LOW
output levels without a pull-up resistor — good for logic levels.
• Simpler architecture — only a single register and the I/O can be both input and output
at the same time. Totem pole I/O have a direction register that specifies the port pin
direction and it is always in that configuration unless the direction is explicitly
changed.
• Does not require a command byte. The simplicity of one register (no need for the
pointer register or, technically, the command byte) is an advantage in some
embedded systems where every byte counts because of memory or bandwidth
limitations.
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
6 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
There is only one register to control four possibilities of the port pin: Input HIGH, input
LOW, output HIGH, or output LOW.
Input HIGH: The master needs to write 1 to the register to set the port as an input mode
if the device is not in the default power-on condition. The master reads the register to
check the input status. If the external source pulls the port pin up to VDD or drives
logic 1, then the master will read the value of 1.
Input LOW: The master needs to write 1 to the register to set the port to input mode if
the device is not in the default power-on condition. The master reads the register to
check the input status. If the external source pulls the port pin down to VSS or drives
logic 0, which sinks the weak 100 A current source, then the master will read the value
of 0.
Output HIGH: The master writes 1 to the register. There is an additional ‘accelerator’ or
strong pull-up current when the master sets the port HIGH. The additional strong pull-up
is only active during the HIGH time of the acknowledge clock cycle. This accelerator
current helps the port’s 100 A current source make a faster rising edge into a heavily
loaded output, but only at the start of the acknowledge clock cycle to avoid bus
contention if an external signal is pulling the port LOW to VSS/driving the port with
logic 0 at the same time. After the half clock cycle there is only the 100 A current
source to hold the port HIGH.
Output LOW: The master writes 0 to the register. There is a strong current sink
transistor that holds the port pin LOW. A large current may flow into the port, which
could potentially damage the part if the master writes a 0 to the register and an external
source is pulling the port HIGH at the same time.
VDD
input HIGH
pull-up with
resistor to VDD or
external drive HIGH
P port
P7 - P0
weak 100 µA
current source
(inactive when
output LOW)
output HIGH
accelerator
pull-up
pull-down with
resistor to VSS or
external drive LOW
output LOW
input LOW
VSS
002aah683
Fig 7.
PCF8574_PCF8574A
Product data sheet
Simple quasi-bidirectional I/O
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
7 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
8.2 Writing to the port (Output mode)
The master (microcontroller) sends the START condition and slave address setting the
last bit of the address byte to logic 0 for the write mode. The PCF8574/74A acknowledges
and the master then sends the data byte for P7 to P0 to the port register. As the clock line
goes HIGH, the 8-bit data is presented on the port lines after it has been acknowledged by
the PCF8574/74A. If a LOW is written, the strong pull-down turns on and stays on. If a
HIGH is written, the strong pull-up turns on for 1⁄2 of the clock cycle, then the line is held
HIGH by the weak current source. The master can then send a STOP or ReSTART
condition or continue sending data. The number of data bytes that can be sent
successively is not limited and the previous data is overwritten every time a data byte has
been sent and acknowledged.
Ensure a logic 1 is written for any port that is being used as an input to ensure the strong
external pull-down is turned off.
SCL
1
2
3
4
5
6
7
8
9
slave address
data 1
SDA S A6 A5 A4 A3 A2 A1 A0 0
START condition
R/W
data 2
A P7 P6 1 P4 P3 P2 P1 P0 A P7 P6 0 P4 P3 P2 P1 P0 A
P5
acknowledge
from slave
P5
acknowledge
from slave
acknowledge
from slave
write to port
tv(Q)
data output from port
tv(Q)
DATA 1 VALID
DATA 2 VALID
P5 output voltage
Itrt(pu)
P5 pull-up output current
IOH
INT
td(rst)
Fig 8.
002aah349
Write mode (output)
Simple code WRITE mode:
<S> <slave address + write> <ACK> <data out> <ACK> <data out> <ACK> ...
<data out> <ACK> <P>
Remark: Bold type = generated by slave device.
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
8 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
8.3 Reading from a port (Input mode)
The port must have been previously written to logic 1, which is the condition after
power-on reset. To enter the Read mode the master (microcontroller) addresses the slave
device and sets the last bit of the address byte to logic 1 (address byte read). The slave
will acknowledge and then send the data byte to the master. The master will NACK and
then send the STOP condition or ACK and read the input register again.
The read of any pin being used as an output will indicate HIGH or LOW depending on the
actual state of the pin.
If the data on the input port changes faster than the master can read, this data may be
lost. The DATA 2 and DATA3 are lost because these data did not meet the setup time and
hold time (see Figure 9).
slave address
data from port
SDA S A6 A5 A4 A3 A2 A1 A0 1
START condition
R/W
DATA 1
A
data from port
A
acknowledge
from slave
DATA 4
no acknowledge
from master
1
P
STOP
condition
acknowledge
from master
read from
port
DATA 2
data at
port
DATA 1
DATA 3
th(D)
DATA 4
tsu(D)
INT
tv(INT)
trst(INT)
trst(INT)
002aah383
A LOW-to-HIGH transition of SDA while SCL is HIGH is defined as the STOP condition (P). Transfer of data can be stopped at
any moment by a STOP condition. When this occurs, data present at the last acknowledge phase is valid (output mode). Input
data is lost.
Fig 9.
Read mode (input)
Simple code for Read mode:
<S> <slave address + read> <ACK> <data in> <ACK> ... <data in> <ACK> <data in>
<NACK> <P>
Remark: Bold type = generated by slave device.
8.4 Power-on reset
When power is applied to VDD, an internal Power-On Reset (POR) holds the
PCF8574/74A in a reset condition until VDD has reached VPOR. At that point, the reset
condition is released and the PCF8574/74A registers and I2C-bus/SMBus state machine
will initialize to their default states of all I/Os to inputs with weak current source to VDD.
Thereafter VDD must be lowered below VPOR and back up to the operation voltage for
power-on reset cycle.
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
9 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
8.5 Interrupt output (INT)
The PCF8574/74A provides an open-drain output (INT) which can be fed to a
corresponding input of the microcontroller (see Figure 10). As soon as a port input is
changed, the INT will be active (LOW) and notify the microcontroller.
An interrupt is generated at any rising or falling edge of the port inputs. After time tv(Q), the
signal INT is valid.
The interrupt will reset to HIGH when data on the port is changed to the original setting or
data is read or written by the master.
In the Write mode, the interrupt may be reset (HIGH) on the rising edge of the
acknowledge bit of the address byte and also on the rising edge of the write to port pulse.
The interrupt will always be reset (HIGH) on the falling edge of the write to port pulse (see
Figure 8).
The interrupt is reset (HIGH) in the Read mode on the rising edge of the read from port
pulse (see Figure 9).
During the interrupt reset, any I/O change close to the read or write pulse may not
generate an interrupt, or the interrupt will have a very short pulse. After the interrupt is
reset, any change in I/Os will be detected and transmitted as an INT.
At power-on reset all ports are in Input mode and the initial state of the ports is HIGH,
therefore, for any port pin that is pulled LOW or driven LOW by external source, the
interrupt output will be active (output LOW).
VDD
device 1
device 2
device 16
PCF8574
PCF8574
PCF8574A
INT
INT
INT
MICROCONTROLLER
INT
002aad634
Fig 10. Application of multiple PCF8574/74As with interrupt
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
10 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
9. Characteristics of the I2C-bus
The I2C-bus is for 2-way, 2-wire communication between different ICs or modules. The
two wires are a serial data line (SDA) and a serial clock line (SCL). Both lines must be
connected to a positive supply via a pull-up resistor when connected to the output stages
of a device. Data transfer may be initiated only when the bus is not busy.
9.1 Bit transfer
One data bit is transferred during each clock pulse. The data on the SDA line must remain
stable during the HIGH period of the clock pulse as changes in the data line at this time
will be interpreted as control signals (see Figure 11).
SDA
SCL
data line
stable;
data valid
change
of data
allowed
mba607
Fig 11. Bit transfer
9.1.1 START and STOP conditions
Both data and clock lines remain HIGH when the bus is not busy. A HIGH-to-LOW
transition of the data line while the clock is HIGH is defined as the START condition (S). A
LOW-to-HIGH transition of the data line while the clock is HIGH is defined as the STOP
condition (P) (see Figure 12).
SDA
SCL
S
P
START condition
STOP condition
mba608
Fig 12. Definition of START and STOP conditions
9.2 System configuration
A device generating a message is a ‘transmitter’; a device receiving is the ‘receiver’. The
device that controls the message is the ‘master’ and the devices which are controlled by
the master are the ‘slaves’ (see Figure 13).
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
11 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
SDA
SCL
MASTER
TRANSMITTER/
RECEIVER
SLAVE
RECEIVER
SLAVE
TRANSMITTER/
RECEIVER
MASTER
TRANSMITTER
MASTER
TRANSMITTER/
RECEIVER
I2C-BUS
MULTIPLEXER
SLAVE
002aaa966
Fig 13. System configuration
9.3 Acknowledge
The number of data bytes transferred between the START and the STOP conditions from
transmitter to receiver is not limited. Each byte of eight bits is followed by one
acknowledge bit (see Figure 14). The acknowledge bit is an active LOW level (generated
by the receiving device) that indicates to the transmitter that the data transfer was
successful.
A slave receiver which is addressed must generate an acknowledge after the reception of
each byte. Also a master must generate an acknowledge after the reception of each byte
that has been clocked out of the slave transmitter. The device that wants to issue an
acknowledge bit has to pull down the SDA line during the acknowledge clock pulse, so
that the SDA line is stable LOW during the HIGH period of the acknowledge bit related
clock pulse; set-up and hold times must be taken into account.
A master receiver must signal an end of data to the transmitter by not generating an
acknowledge on the last byte that has been clocked out of the slave. In this event, the
transmitter must leave the data line HIGH to enable the master to generate a STOP
condition.
data output
by transmitter
not acknowledge
data output
by receiver
acknowledge
SCL from master
1
2
S
START
condition
8
9
clock pulse for
acknowledgement
002aaa987
Fig 14. Acknowledgement on the I2C-bus
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
12 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
10. Application design-in information
10.1 Bidirectional I/O expander applications
In the 8-bit I/O expander application shown in Figure 15, P0 and P1 are inputs, and
P2 to P7 are outputs. When used in this configuration, during a write, the input (P0 and
P1) must be written as HIGH so the external devices fully control the input ports.
The desired HIGH or LOW logic levels may be written to the ports used as outputs (P2 to
P7). If 10 A internal output HIGH is not enough current source, the port needs external
pull-up resistor. During a read, the logic levels of the external devices driving the input
ports (P0 and P1) and the previous written logic level to the output ports (P2 to P7) will be
read.
The GPIO also has an interrupt line (INT) that can be connected to the interrupt logic of
the microcontroller. By sending an interrupt signal on this line, the remote I/O informs the
microprocessor that there has been a change of data on its ports without having to
communicate via the I2C-bus.
VDD
VDD
CORE
PROCESSOR
VDD
SDA
SCL
INT
A0
A1
A2
P0
P1
P2
P3
P4
P5
P6
P7
temperature sensor
battery status
control for latch
control for switch
control for audio
control for camera
control for MP3
002aah384
Fig 15. Bidirectional I/O expander application
10.2 How to read and write to I/O expander (example)
In the application example of PCF8574 shown in Figure 15, the microcontroller wants to
control the P3 switch ON and the P7 LED ON when the temperature sensor P0 changes.
1. When the system power on:
Core Processor needs to issue an initial command to set P0 and P1 as inputs and
P[7:2] as outputs with value 1010 00 (LED off, MP3 off, camera on, audio off,
switch off and latch off).
2. Operation:
When the temperature changes above the threshold, the temperature sensor signal
will toggle from HIGH to LOW. The INT will be activated and notifies the ‘core
processor’ that there have been changes on the input pins. Read the input register.
If P0 = 0 (temperature sensor has changed), then turn on LED and turn on switch.
3. Software code:
//System Power on
// write to PCF8574 with data 1010 0011b to set P[7:2] outputs and P[1:0] inputs
<S> <0100 0000> <ACK> <1010 0011> <ACK> <P>//Initial setting for PCF9574
PCF8574_PCF8574A
Product data sheet
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13 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-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.
VDD
VDD
P0
P1
P2
P3
P4
P5
P6
P7
SDA
SCL
INT
CORE
PROCESSOR
VDD
A0
A1
A2
LOAD
002aah385
Fig 16. High current-drive load application
10.4 Migration path
NXP offers newer, more capable drop-in replacements for the PCF8574/74A in newer
space-saving packages.
Table 6.
Migration path
Type number
I2C-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
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.
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
14 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
11. Limiting values
Table 7.
Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol
Parameter
Conditions
Min
Max
Unit
VDD
supply voltage
0.5
+7
V
IDD
ISS
supply current
-
100
mA
ground supply current
-
100
mA
VI
input voltage
VSS 0.5
VDD + 0.5 V
II
input current
-
20
mA
IO
output current
-
25
mA
Ptot
total power dissipation
-
400
mW
P/out
power dissipation per output
-
100
mW
Tj(max)
maximum junction temperature
-
125
C
Tstg
storage temperature
Tamb
ambient temperature
operating
65
+150
C
40
+85
C
12. Thermal characteristics
Table 8.
PCF8574_PCF8574A
Product data sheet
Thermal characteristics
Symbol
Parameter
Conditions
Typ
Unit
Rth(j-a)
thermal resistance from junction
to ambient
SO16 package
115
C/W
SSOP20 package
136
C/W
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Rev. 5 — 27 May 2013
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15 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
13. Static characteristics
Table 9.
Static characteristics
VDD = 2.5 V to 6 V; VSS = 0 V; Tamb = 40 C to +85 C; unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
Supply
VDD
supply voltage
2.5
-
6.0
V
IDD
supply current
operating mode; VDD = 6 V; no load;
VI = VDD or VSS; fSCL = 100 kHz
-
40
100
A
Istb
standby current
standby mode; VDD = 6 V; no load;
VI = VDD or VSS
-
2.5
10
A
VPOR
power-on reset voltage
VDD = 6 V; no load; VI = VDD or VSS
-
1.3
2.4
V
0.5
-
+0.3VDD
V
[1]
Input SCL; input/output SDA
VIL
LOW-level input voltage
VIH
HIGH-level input voltage
0.7VDD
-
VDD + 0.5
V
IOL
LOW-level output current
VOL = 0.4 V
3
-
-
mA
IL
leakage current
VI = VDD or VSS
1
-
+1
A
Ci
input capacitance
VI = VSS
-
-
7
pF
I/Os; P0 to P7
VIL
LOW-level input voltage
0.5
-
+0.3VDD
V
VIH
HIGH-level input voltage
0.7VDD
-
VDD + 0.5
V
IIHL(max)
maximum allowed input current
through protection diode
VI VDD or VI VSS
-
-
400
A
IOL
LOW-level output current
VOL = 1 V; VDD = 5 V
10
25
-
mA
IOH
HIGH-level output current
VOH = VSS
30
-
300
A
Itrt(pu)
transient boosted pull-up current HIGH during acknowledge (see
Figure 8); VOH = VSS; VDD = 2.5 V
-
1
-
mA
Ci
input capacitance
-
-
10
pF
Co
output capacitance
-
-
10
pF
Interrupt INT (see Figure 8)
IOL
LOW-level output current
VOL = 0.4 V
1.6
-
-
mA
IL
leakage current
VI = VDD or VSS
1
-
+1
A
0.5
-
+0.3VDD
V
Select inputs A0, A1, A2
VIL
LOW-level input voltage
VIH
HIGH-level input voltage
ILI
input leakage current
[1]
pin at VDD or VSS
0.7VDD
-
VDD + 0.5
V
250
-
+250
nA
The power-on reset circuit resets the I2C-bus logic at VDD < VPOR and sets all I/Os to logic 1 (with current source to VDD).
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
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PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
14. Dynamic characteristics
Table 10. Dynamic characteristics
VDD = 2.5 V to 6 V; VSS = 0 V; Tamb = 40 C to +85 C; unless otherwise specified.
Symbol
I2C-bus
Parameter
timing[1]
Conditions
Min
Typ
Max
Unit
(see Figure 17)
fSCL
SCL clock frequency
-
-
100
kHz
tBUF
bus free time between a STOP and
START condition
4.7
-
-
s
tHD;STA
hold time (repeated) START condition
4
-
-
s
tSU;STA
set-up time for a repeated START condition
4.7
-
-
s
tSU;STO
set-up time for STOP condition
4
-
-
s
tHD;DAT
data hold time
0
-
-
ns
tVD;DAT
data valid time
-
-
3.4
s
tSU;DAT
data set-up time
250
-
-
ns
tLOW
LOW period of the SCL clock
4.7
-
-
s
tHIGH
HIGH period of the SCL clock
4
-
-
s
tr
rise time of both SDA and SCL signals
-
-
1
s
tf
fall time of both SDA and SCL signals
-
-
0.3
s
Port timing (see Figure 8 and Figure 9)
tv(Q)
data output valid time
CL 100 pF
-
-
4
s
tsu(D)
data input set-up time
CL 100 pF
0
-
-
s
th(D)
data input hold time
CL 100 pF
4
-
-
s
Interrupt INT timing (see Figure 9)
tv(INT)
valid time on pin INT
from port to INT;
CL 100 pF
-
-
4
s
trst(INT)
reset time on pin INT
from SCL to INT;
CL 100 pF
-
-
4
s
[1]
All the timing values are valid within the operating supply voltage and ambient temperature range and refer to VIL and VIH with an input
voltage swing of VSS to VDD.
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
17 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
protocol
START
condition
(S)
tSU;STA
bit 7
MSB
(A7)
tLOW
bit 6
(A6)
tHIGH
bit 0
(R/W)
acknowledge
(A)
STOP
condition
(P)
1 / fSCL
0.7 × VDD
SCL
0.3 × VDD
tBUF
tf
tr
0.7 × VDD
SDA
0.3 × VDD
tSU;DAT
tHD;STA
tHD;DAT
tVD;DAT
tVD;ACK
tSU;STO
002aab175
Rise and fall times refer to VIL and VIH.
Fig 17. I2C-bus timing diagram
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
18 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
15. Package outline
DIP16: plastic dual in-line package; 16 leads (300 mil)
SOT38-4
ME
seating plane
D
A2
A
A1
L
c
e
Z
w M
b1
(e 1)
b
b2
MH
9
16
pin 1 index
E
1
8
0
5
10 mm
scale
DIMENSIONS (inch dimensions are derived from the original mm dimensions)
UNIT
A
max.
A1
min.
A2
max.
b
b1
b2
c
D (1)
E (1)
e
e1
L
ME
MH
w
Z (1)
max.
mm
4.2
0.51
3.2
1.73
1.30
0.53
0.38
1.25
0.85
0.36
0.23
19.50
18.55
6.48
6.20
2.54
7.62
3.60
3.05
8.25
7.80
10.0
8.3
0.254
0.76
inches
0.17
0.02
0.13
0.068
0.051
0.021
0.015
0.049
0.033
0.014
0.009
0.77
0.73
0.26
0.24
0.1
0.3
0.14
0.12
0.32
0.31
0.39
0.33
0.01
0.03
Note
1. Plastic or metal protrusions of 0.25 mm (0.01 inch) maximum per side are not included.
OUTLINE
VERSION
REFERENCES
IEC
JEDEC
JEITA
EUROPEAN
PROJECTION
ISSUE DATE
95-01-14
03-02-13
SOT38-4
Fig 18. Package outline SOT38-4 (DIP16)
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
19 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
SO16: plastic small outline package; 16 leads; body width 7.5 mm
SOT162-1
D
E
A
X
c
HE
y
v M A
Z
9
16
Q
A2
A
(A 3)
A1
pin 1 index
θ
Lp
L
1
8
e
detail X
w M
bp
0
5
10 mm
scale
DIMENSIONS (inch dimensions are derived from the original mm dimensions)
UNIT
A
max.
A1
A2
A3
bp
c
D (1)
E (1)
e
HE
L
Lp
Q
v
w
y
mm
2.65
0.3
0.1
2.45
2.25
0.25
0.49
0.36
0.32
0.23
10.5
10.1
7.6
7.4
1.27
10.65
10.00
1.4
1.1
0.4
1.1
1.0
0.25
0.25
0.1
0.01
0.019 0.013
0.014 0.009
0.41
0.40
0.30
0.29
0.05
0.419
0.043
0.055
0.394
0.016
inches
0.1
0.012 0.096
0.004 0.089
0.043
0.039
0.01
0.01
Z
(1)
0.9
0.4
0.035
0.004
0.016
θ
8o
o
0
Note
1. Plastic or metal protrusions of 0.15 mm (0.006 inch) maximum per side are not included.
REFERENCES
OUTLINE
VERSION
IEC
JEDEC
SOT162-1
075E03
MS-013
JEITA
EUROPEAN
PROJECTION
ISSUE DATE
99-12-27
03-02-19
Fig 19. Package outline SOT162-1 (SO16)
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
20 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
SSOP20: plastic shrink small outline package; 20 leads; body width 4.4 mm
D
SOT266-1
E
A
X
c
y
HE
v M A
Z
11
20
Q
A2
A
(A 3)
A1
pin 1 index
θ
Lp
L
1
10
detail X
w M
bp
e
0
2.5
5 mm
scale
DIMENSIONS (mm are the original dimensions)
UNIT
A
max.
A1
A2
A3
bp
c
D (1)
E (1)
e
HE
L
Lp
Q
v
w
y
Z (1)
θ
mm
1.5
0.15
0
1.4
1.2
0.25
0.32
0.20
0.20
0.13
6.6
6.4
4.5
4.3
0.65
6.6
6.2
1
0.75
0.45
0.65
0.45
0.2
0.13
0.1
0.48
0.18
10 o
o
0
Note
1. Plastic or metal protrusions of 0.20 mm maximum per side are not included.
OUTLINE
VERSION
SOT266-1
REFERENCES
IEC
JEDEC
JEITA
EUROPEAN
PROJECTION
ISSUE DATE
99-12-27
03-02-19
MO-152
Fig 20. Package outline SOT266-1 (SSOP20)
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
21 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
16. Handling information
All input and output pins are protected against ElectroStatic Discharge (ESD) under
normal handling. When handling ensure that the appropriate precautions are taken as
described in JESD625-A or equivalent standards.
17. Soldering of SMD packages
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering ICs can be found in Application Note AN10365 “Surface mount reflow
soldering description”.
17.1 Introduction to soldering
Soldering is one of the most common methods through which packages are attached to
Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both
the mechanical and the electrical connection. There is no single soldering method that is
ideal for all IC packages. Wave soldering is often preferred when through-hole and
Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not
suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high
densities that come with increased miniaturization.
17.2 Wave and reflow soldering
Wave soldering is a joining technology in which the joints are made by solder coming from
a standing wave of liquid solder. The wave soldering process is suitable for the following:
• Through-hole components
• Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless
packages which have solder lands underneath the body, cannot be wave soldered. Also,
leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,
due to an increased probability of bridging.
The reflow soldering process involves applying solder paste to a board, followed by
component placement and exposure to a temperature profile. Leaded packages,
packages with solder balls, and leadless packages are all reflow solderable.
Key characteristics in both wave and reflow soldering are:
•
•
•
•
•
•
Board specifications, including the board finish, solder masks and vias
Package footprints, including solder thieves and orientation
The moisture sensitivity level of the packages
Package placement
Inspection and repair
Lead-free soldering versus SnPb soldering
17.3 Wave soldering
Key characteristics in wave soldering are:
PCF8574_PCF8574A
Product data sheet
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PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
• Process issues, such as application of adhesive and flux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
• Solder bath specifications, including temperature and impurities
17.4 Reflow soldering
Key characteristics in reflow soldering are:
• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see Figure 21) than a SnPb process, thus
reducing the process window
• Solder paste printing issues including smearing, release, and adjusting the process
window for a mix of large and small components on one board
• Reflow temperature profile; this profile includes preheat, reflow (in which the board is
heated to the peak temperature) and cooling down. It is imperative that the peak
temperature is high enough for the solder to make reliable solder joints (a solder paste
characteristic). In addition, the peak temperature must be low enough that the
packages and/or boards are not damaged. The peak temperature of the package
depends on package thickness and volume and is classified in accordance with
Table 11 and 12
Table 11.
SnPb eutectic process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
350
< 2.5
235
220
2.5
220
220
Table 12.
Lead-free process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
350 to 2000
> 2000
< 1.6
260
260
260
1.6 to 2.5
260
250
245
> 2.5
250
245
245
Moisture sensitivity precautions, as indicated on the packing, must be respected at all
times.
Studies have shown that small packages reach higher temperatures during reflow
soldering, see Figure 21.
PCF8574_PCF8574A
Product data sheet
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Rev. 5 — 27 May 2013
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23 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
temperature
maximum peak temperature
= MSL limit, damage level
minimum peak temperature
= minimum soldering temperature
peak
temperature
time
001aac844
MSL: Moisture Sensitivity Level
Fig 21. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description”.
18. Soldering of through-hole mount packages
18.1 Introduction to soldering through-hole mount packages
This text gives a very brief insight into wave, dip and manual soldering.
Wave soldering is the preferred method for mounting of through-hole mount IC packages
on a printed-circuit board.
18.2 Soldering by dipping or by solder wave
Driven by legislation and environmental forces the worldwide use of lead-free solder
pastes is increasing. Typical dwell time of the leads in the wave ranges from
3 seconds to 4 seconds at 250 C or 265 C, depending on solder material applied, SnPb
or Pb-free respectively.
The total contact time of successive solder waves must not exceed 5 seconds.
The device may be mounted up to the seating plane, but the temperature of the plastic
body must not exceed the specified maximum storage temperature (Tstg(max)). If the
printed-circuit board has been pre-heated, forced cooling may be necessary immediately
after soldering to keep the temperature within the permissible limit.
18.3 Manual soldering
Apply the soldering iron (24 V or less) to the lead(s) of the package, either below the
seating plane or not more than 2 mm above it. If the temperature of the soldering iron bit is
less than 300 C it may remain in contact for up to 10 seconds. If the bit temperature is
between 300 C and 400 C, contact may be up to 5 seconds.
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
24 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
18.4 Package related soldering information
Table 13.
Suitability of through-hole mount IC packages for dipping and wave soldering
Package
PCF8574_PCF8574A
Product data sheet
Soldering method
Dipping
Wave
CPGA, HCPGA
-
suitable
DBS, DIP, HDIP, RDBS, SDIP, SIL
suitable
suitable[1]
PMFP[2]
-
not suitable
[1]
For SDIP packages, the longitudinal axis must be parallel to the transport direction of the printed-circuit
board.
[2]
For PMFP packages hot bar soldering or manual soldering is suitable.
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
25 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
19. Soldering: PCB footprints
Footprint information for reflow soldering of SO16 package
SOT162-1
Hx
Gx
P2
(0.125)
Hy
Gy
(0.125)
By
Ay
C
D2 (4x)
D1
P1
Generic footprint pattern
Refer to the package outline drawing for actual layout
solder land
occupied area
DIMENSIONS in mm
P2
P1
1.270
Ay
1.320 11.200
By
C
D1
D2
6.400
2.400
0.700
Gx
0.800 10.040
Gy
Hx
Hy
8.600 11.900 11.450
sot162-1_fr
Fig 22. PCB footprint for SOT162-1 (SO16); reflow soldering
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
26 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
Footprint information for reflow soldering of SSOP20 package
SOT266-1
Hx
Gx
(0.125)
P2
Hy
(0.125)
By
Gy
Ay
C
D2 (4x)
D1
P1
solder land
occupied area
DIMENSIONS in mm
P1
P2
Ay
By
C
D1
D2
Gx
Gy
Hx
Hy
0.650
0.750
7.200
4.500
1.350
0.400
0.600
6.900
5.300
7.300
7.450
sot266-1_fr
Fig 23. PCB footprint for SOT266-1 (SSOP20); reflow soldering
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
27 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
20. Abbreviations
Table 14.
PCF8574_PCF8574A
Product data sheet
Abbreviations
Acronym
Description
CDM
Charged-Device Model
CMOS
Complementary Metal Oxide Semiconductor
I/O
Input/Output
I2C-bus
Inter IC bus
ESD
ElectroStatic Discharge
FF
Flip-Flop
GPIO
General Purpose Input/Output
HBM
Human Body Model
IC
Integrated Circuit
LED
Light Emitting Diode
LP
Low-Pass
PLC
Programmable Logic Controller
POR
Power-On Reset
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
28 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
21. Revision history
Table 15.
Revision history
Document ID
Release date
Data sheet status
Change notice
Supersedes
PCF8574_PCF8574A v.5
20130527
Product data sheet
-
PCF8574 v.4
Modifications:
•
The format of this data sheet has been redesigned to comply with the new identity
guidelines of NXP Semiconductors.
•
•
Legal texts have been adapted to the new company name where appropriate.
•
•
Section 1 “General description”: updated
Electrical parameter letter-symbols and their definitions are updated to conform to NXP
presentation standards.
Section 2 “Features and benefits”:
– third bullet item: appended “with non-overvoltage tolerant I/O held to VDD with 100 A
current source”
– added (new) fourth and seventh bullet items
– added sixth bullet item: “Total package sink capability of 80 mA”
– ninth bullet changed from “(10 A maximum)” to “(2.5 A typical)”
– deleted (old) 11th, 12th and 13th bullet items
•
•
Added (new) eighth bullet item “Mobile devices”
Table 1 “Ordering information”:
– Type number corrected from “PCF8574T” to “PCF8574/3”
– Type number corrected from “PCF8574AT” to “PCF8574AT/3”
– Type number corrected from “PCF8574TS” to “PCF8574TS/3”
– Type number corrected from “PCF8574ATS” to “PCF8574ATS/3”
•
•
•
•
PCF8574_PCF8574A
Product data sheet
Added Section 4.1 “Ordering options”
Figure 4 “Pin configuration for SO16”: updated type numbers (appended “/3”)
Figure 5 “Pin configuration for SSOP20”: updated type numbers (appended “/3”)
Section 6.2 “Pin description”: combined DIP16, SO16 and SSOP20 pin descriptions into
one table (Table 3)
•
•
Section 7 “Functional description” reorganized
•
Table 4 “PCF8574 address map” updated: added column for 7-bit hexadecimal address
without R/W
•
Table 5 “PCF8574A address map” updated: added column for 7-bit hexadecimal address
without R/W
•
Section 8.1 “Quasi-bidirectional I/Os”: re-written and placed before Section 8.4 “Power-on
reset”
•
•
•
•
•
•
added Section 8.2 “Writing to the port (Output mode)”
•
•
Section 9.3 “Acknowledge”, first paragraph, third sentence re-written.
Section 7.1 “Device address”, first paragraph, fourth sentence: appended “so they must be
externally held HIGH or LOW”
added Section 8.3 “Reading from a port (Input mode)”
Figure 9 “Read mode (input)”: changed symbol “tps” to “tsu”
Section 8.4 “Power-on reset” re-written
Section 8.5 “Interrupt output (INT)” re-written
Figure 10 “Application of multiple PCF8574/74As with interrupt” updated: changed
device 16 from “PCF8574” to “PCF8574A”
Added Section 10 “Application design-in information”
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
29 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
Table 15.
Revision history …continued
Document ID
Modifications: (continued)
Release date
•
Data sheet status
Change notice
Supersedes
Table 7 “Limiting values”:
– changed parameter description for symbol II from “DC input current” to “input current”
– changed parameter description for symbol IO from “DC output current” to “output
current”
– changed parameter description for symbol ISS from “supply current” to “ground supply
current”
– changed symbol “PO” to “P/out”
– added Tj(max) limits
•
•
Added Section 12 “Thermal characteristics”
Table 9 “Static characteristics”:
– table title changed from “DC characteristics” to “Static characteristics”
– sub-section “I/Os; P0 to P7”: changed parameter description for symbol Itrt(pu)
from “transient pull-up current” to “transient boosted pull-up current”
– moved sub-section “Port timing” to Table 10 “Dynamic characteristics”
– sub-section “Interrupt INT”: moved sub-sub-section “Timing” to Table 10 “Dynamic
characteristics”
•
Table 10 “Dynamic characteristics”:
– sub-section “I2C-bus timing”: deleted symbol/parameter “tSW, tolerable spike width on
bus”
– sub-section “Port timing”: changed symbol/parameter from “tpv, output data valid time”
to “tv(Q), data output valid time”
– sub-section “Port timing”: changed symbol/parameter from “tsu, input data set-up time”
to “tsu(D), data input set-up time”
– sub-section “Port timing”: changed symbol/parameter from “th, input data hold time”
to “th(D), data input hold time”
– sub-section “Interrupt INT”: changed parameter description for symbol tv(INT)
from “INT output valid time” to “valid time on pin INT”
– sub-section “Interrupt INT”: changed parameter description for symbol trst(INT)
from “INT reset delay time” to “reset time on pin INT”
•
Added Section 19 “Soldering: PCB footprints”
PCF8574 v.4
(9397 750 10462)
20021122
Product specification
-
PCF8574 v.3
PCF8574 v.3
(9397 750 09911)
20020729
Product specification
-
PCF8574 v.2
PCF8574 v.2
(9397 750 01758)
19970402
Product specification
-
PCF8574_PCF8574A v.1
PCF8574_PCF8574A v.1
(9397 750 70011)
199409
Product specification
-
-
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
30 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
22. Legal information
22.1 Data sheet status
Document status[1][2]
Product status[3]
Definition
Objective [short] data sheet
Development
This document contains data from the objective specification for product development.
Preliminary [short] data sheet
Qualification
This document contains data from the preliminary specification.
Product [short] data sheet
Production
This document contains the product specification.
[1]
Please consult the most recently issued document before initiating or completing a design.
[2]
The term ‘short data sheet’ is explained in section “Definitions”.
[3]
The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
22.2 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
Product specification — The information and data provided in a Product
data sheet shall define the specification of the product as agreed between
NXP Semiconductors and its customer, unless NXP Semiconductors and
customer have explicitly agreed otherwise in writing. In no event however,
shall an agreement be valid in which the NXP Semiconductors product is
deemed to offer functions and qualities beyond those described in the
Product data sheet.
22.3 Disclaimers
Limited warranty and liability — Information in this document is believed to
be accurate and reliable. However, NXP Semiconductors does not give any
representations or warranties, expressed or implied, as to the accuracy or
completeness of such information and shall have no liability for the
consequences of use of such information. NXP Semiconductors takes no
responsibility for the content in this document if provided by an information
source outside of NXP Semiconductors.
In no event shall NXP Semiconductors be liable for any indirect, incidental,
punitive, special or consequential damages (including - without limitation - lost
profits, lost savings, business interruption, costs related to the removal or
replacement of any products or rework charges) whether or not such
damages are based on tort (including negligence), warranty, breach of
contract or any other legal theory.
Notwithstanding any damages that customer might incur for any reason
whatsoever, NXP Semiconductors’ aggregate and cumulative liability towards
customer for the products described herein shall be limited in accordance
with the Terms and conditions of commercial sale of NXP Semiconductors.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
PCF8574_PCF8574A
Product data sheet
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in life support, life-critical or
safety-critical systems or equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors and its suppliers accept no liability for
inclusion and/or use of NXP Semiconductors products in such equipment or
applications and therefore such inclusion and/or use is at the customer’s own
risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Customers are responsible for the design and operation of their applications
and products using NXP Semiconductors products, and NXP Semiconductors
accepts no liability for any assistance with applications or customer product
design. It is customer’s sole responsibility to determine whether the NXP
Semiconductors product is suitable and fit for the customer’s applications and
products planned, as well as for the planned application and use of
customer’s third party customer(s). Customers should provide appropriate
design and operating safeguards to minimize the risks associated with their
applications and products.
NXP Semiconductors does not accept any liability related to any default,
damage, costs or problem which is based on any weakness or default in the
customer’s applications or products, or the application or use by customer’s
third party customer(s). Customer is responsible for doing all necessary
testing for the customer’s applications and products using NXP
Semiconductors products in order to avoid a default of the applications and
the products or of the application or use by customer’s third party
customer(s). NXP does not accept any liability in this respect.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) will cause permanent
damage to the device. Limiting values are stress ratings only and (proper)
operation of the device at these or any other conditions above those given in
the Recommended operating conditions section (if present) or the
Characteristics sections of this document is not warranted. Constant or
repeated exposure to limiting values will permanently and irreversibly affect
the quality and reliability of the device.
Terms and conditions of commercial sale — NXP Semiconductors
products are sold subject to the general terms and conditions of commercial
sale, as published at http://www.nxp.com/profile/terms, unless otherwise
agreed in a valid written individual agreement. In case an individual
agreement is concluded only the terms and conditions of the respective
agreement shall apply. NXP Semiconductors hereby expressly objects to
applying the customer’s general terms and conditions with regard to the
purchase of NXP Semiconductors products by customer.
No offer to sell or license — Nothing in this document may be interpreted or
construed as an offer to sell products that is open for acceptance or the grant,
conveyance or implication of any license under any copyrights, patents or
other industrial or intellectual property rights.
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
31 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
Export control — This document as well as the item(s) described herein
may be subject to export control regulations. Export might require a prior
authorization from competent authorities.
Non-automotive qualified products — Unless this data sheet expressly
states that this specific NXP Semiconductors product is automotive qualified,
the product is not suitable for automotive use. It is neither qualified nor tested
in accordance with automotive testing or application requirements. NXP
Semiconductors accepts no liability for inclusion and/or use of
non-automotive qualified products in automotive equipment or applications.
In the event that customer uses the product for design-in and use in
automotive applications to automotive specifications and standards, customer
(a) shall use the product without NXP Semiconductors’ warranty of the
product for such automotive applications, use and specifications, and (b)
whenever customer uses the product for automotive applications beyond
NXP Semiconductors’ specifications such use shall be solely at customer’s
own risk, and (c) customer fully indemnifies NXP Semiconductors for any
liability, damages or failed product claims resulting from customer design and
use of the product for automotive applications beyond NXP Semiconductors’
standard warranty and NXP Semiconductors’ product specifications.
Translations — A non-English (translated) version of a document is for
reference only. The English version shall prevail in case of any discrepancy
between the translated and English versions.
22.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
I2C-bus — logo is a trademark of NXP B.V.
23. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
PCF8574_PCF8574A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 27 May 2013
© NXP B.V. 2013. All rights reserved.
32 of 33
PCF8574; PCF8574A
NXP Semiconductors
Remote 8-bit I/O expander for I2C-bus with interrupt
24. Contents
1
2
3
4
4.1
5
6
6.1
6.2
7
7.1
7.1.1
8
8.1
8.2
8.3
8.4
8.5
9
9.1
9.1.1
9.2
9.3
10
10.1
10.2
10.3
10.4
11
12
13
14
15
16
17
17.1
17.2
17.3
17.4
18
18.1
18.2
General description . . . . . . . . . . . . . . . . . . . . . . 1
Features and benefits . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Ordering information . . . . . . . . . . . . . . . . . . . . . 2
Ordering options . . . . . . . . . . . . . . . . . . . . . . . . 2
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pinning information . . . . . . . . . . . . . . . . . . . . . . 4
Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 4
Functional description . . . . . . . . . . . . . . . . . . . 5
Device address . . . . . . . . . . . . . . . . . . . . . . . . . 5
Address maps. . . . . . . . . . . . . . . . . . . . . . . . . . 5
I/O programming . . . . . . . . . . . . . . . . . . . . . . . . 6
Quasi-bidirectional I/Os . . . . . . . . . . . . . . . . . . 6
Writing to the port (Output mode) . . . . . . . . . . . 8
Reading from a port (Input mode) . . . . . . . . . . 9
Power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . 9
Interrupt output (INT) . . . . . . . . . . . . . . . . . . . 10
Characteristics of the I2C-bus . . . . . . . . . . . . 11
Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
START and STOP conditions . . . . . . . . . . . . . 11
System configuration . . . . . . . . . . . . . . . . . . . 11
Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . 12
Application design-in information . . . . . . . . . 13
Bidirectional I/O expander applications . . . . . 13
How to read and write to I/O expander
(example) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
High current-drive load applications . . . . . . . . 14
Migration path . . . . . . . . . . . . . . . . . . . . . . . . . 14
Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . 15
Thermal characteristics . . . . . . . . . . . . . . . . . 15
Static characteristics. . . . . . . . . . . . . . . . . . . . 16
Dynamic characteristics . . . . . . . . . . . . . . . . . 17
Package outline . . . . . . . . . . . . . . . . . . . . . . . . 19
Handling information. . . . . . . . . . . . . . . . . . . . 22
Soldering of SMD packages . . . . . . . . . . . . . . 22
Introduction to soldering . . . . . . . . . . . . . . . . . 22
Wave and reflow soldering . . . . . . . . . . . . . . . 22
Wave soldering . . . . . . . . . . . . . . . . . . . . . . . . 22
Reflow soldering . . . . . . . . . . . . . . . . . . . . . . . 23
Soldering of through-hole mount packages . 24
Introduction to soldering through-hole mount
packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Soldering by dipping or by solder wave . . . . . 24
18.3
18.4
19
20
21
22
22.1
22.2
22.3
22.4
23
24
Manual soldering . . . . . . . . . . . . . . . . . . . . . .
Package related soldering information. . . . . .
Soldering: PCB footprints . . . . . . . . . . . . . . .
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . .
Revision history . . . . . . . . . . . . . . . . . . . . . . .
Legal information . . . . . . . . . . . . . . . . . . . . . .
Data sheet status . . . . . . . . . . . . . . . . . . . . . .
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . .
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . .
Contact information . . . . . . . . . . . . . . . . . . . .
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24
25
26
28
29
31
31
31
31
32
32
33
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP B.V. 2013.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Date of release: 27 May 2013
Document identifier: PCF8574_PCF8574A