I2C general purpose I/O expanders

General purpose I/O expanders provide GPIO expansion for most microprocessor families allowing designers to save the GPIOs on microprocessors for other important functions.

As more features and processing requirements, such as LED control, hardware control monitors, and humidity sensors in the computing space are added to applications, the limited numbers of GPIOs on microprocessors are becoming more valuable. By implementing our I/O expanders, designers can utilize the microprocessor GPIOs for important functions and use the I/O expander for other duties including system monitoring, ACPI power switches, sensors, push buttons, LEDs, fans, etc.

GPIO are ideal for adding fan and LED control to systems. They are also ideal for monitoring system functions and accepting push-button inputs.

All our I2C general purpose I/O expanders offer similar functionality and most have an INT output but several newer devices also have a RESET input or RESET and OE input. The INT output is used to signal the microcontroller when any of the inputs change state (1 to 0, or 0 to 1). The RESET input can be used to initialize the device to its default state without de-powering it. This is useful in situations where the I2C bus has a glitch that prevents proper transmission of data between the microprocessor and I/O expander. Incorrect data in the I/O expander is eliminated through resetting it. Other slave devices without a RESET input require their power supply to be lowered to 0V and then powered back up to V_CC for the slave device to return to its default state which can be inefficient and time consuming in the application. The OE is used to "Hi-Z" the outputs without having to use I2C commands. This is useful in applications such as LED control where the OE pin can be connected to the microcontroller and all LEDs blinked or dimmed at the same time while the individually LEDs are controlled via the I2C bus.

The PCF8574(A) and PCF8575(C) devices have an interrupt output, and the 8 or 16 I/O pins are used as inputs or outputs. An open-drain interrupt is activated when any input state differs from its corresponding input port register state and is used to indicate to the system master that an input state has changed. The outputs provide active sink current but are a current source to provide the source current. The PCF8574, PCF8575, and PCF8575C have the same I2C address while the PCF8574A has a slightly different fixed address allowing 16 devices (eight PCF8574A and eight PCF8574/PCF8575(C) in any combination) to be on the same I2C bus. The PCF8575C has open drain outputs and is optimized for automotive applications.

These are updated versions of the PCF8574(A) and PCF8575 that offer 400KHz operation over a V_CC range of 2.3 to 5.5V with 5V-tolerance and the ability to sink 25mA per bit with all bits on (i.e., a total of 200mA for 8-bit products and 400mA for 16-bit products) over the -40 to +85°C temperature range.

The PCA9500 is a is a replacement for the PCF8574 8-bit I/O expander and for the 24C02 2kbit serial EEPROM in one 16-pin package. The PCA9500 has the same footprint as the PCF8574 except the interrupt output has been replace by the EEPROM write protect. The PCA9500 has the same I2C addresses as the PCF8574 and 24C02 and is seen as two different slave devices by the bus master.

The PCA9501 is a combination of the PCF8574 8-bit I/O expander and of the 24C02 2kbit serial EEPROM in one 20-pin TSSOP package. The four extra pins allow the interrupt output to be included in addition to the write protect and the three other pins are used to offer a total of six address pins allowing up to 64 of these devices to share the same I2C bus. It is seen as two different slave devices by the bus master with the I/O expander address starting with 1 and the EEPROM starting with 0. The PCA9500/PCA9501 devices are designed for telecom maintenance and control applications.

The PCA9502 is an 8-bit I/O expander with configurable I2C or SPI host interface. The I/O pins offer standard CMOS input or output, and the input states are latchable.

The PCA9505 and PCA9506 are 40-bit wide GPIOs electrically identical to the PCA9539 including the interrupt output and reset input but include an Output Enable. The PCA9505 and PCA9506 are identical except that the PCA9505 has internal pull-up resistors on each pin while the PCA9506 doesn't.

The PCA9534/PCA9535 are identical to the PCA9554/PCA9555 except that there is no internal pullup resistor. They are useful in battery-powered applications to minimize current drain and in applications where the outputs need to be tri-stated at power up or where external pulldown resistors are used.

The PCA9536 is identical to the PCA9554 except that it is a 4-bit instead of 8-bit GPIO in an 8-pin package, the I2C address is different/fixed, and there is no Interrupt Output.

The PCA9537 is identical to the PCA9534 except that it is a 4-bit instead of 8-bit GPIO in a 10-pin package, the I2C address is different/fixed, and there is a Hardware Reset input in addition to the Interrupt Output.

The PCA9538/PCA9539 are identical to the PCA9534/PCA9535 except that the I2C address range is different, and the A2 address pin input has been replaced by a Hardware Reset input. The Hardware Reset input allows the device to be reset remotely if the I2C bus hangs up.

The PCA9554(A) and PCA9555 are footprint and I2C address-identical to the PCF8574(A) and PCF8575 but provide push-pull outputs with active source and sink current sources. Internal pull up resistors provide the source current to imitate the PCF8574(A)/PCF8575. Additionally, there are four sets of registers that are programmable and provide for configuration (I or O) control, input (value), output (value), or polarity (active high or low). Although pinout and I2C addresses are the same as the PCF857X series, software changes are required due to the command byte. The application note AN469 discusses these software changes.

The PCA9557 features a hardware reset pin instead of the interrupt output that allows the device to be reset remotely should the I2C bus become hung up. The PCA9557 is an improved version of the PCA9556 and has the electrical characteristics of the PCA9554/PCA9554A.

The PCA9558 is a highly integrated, multi-function device composed of a 5-bit multiplexed/1-bit latched 6-bit I2C EEPROM, an 8-bit I/O expander (open drain), and a 2kbit serial EEPROM with write protect. The multiplexer can be used to select digital information between a set of 5-bits of default hardware inputs and an alternative set of inputs provided by the I2C interface and stored in the EEPROM. Examples of this type of selection include processor voltage configuration or processor Vendor IDentification (VID) and DIP switch or jumper replacement since the settings can be easily changed via the I2C without having to open the cabinet and the non-volatile memory retains the settings when the power is turned off. The I/O expander function is used to control, monitor, or collect remote information or power LEDs. Monitored or collected information can be read through the I2C or can be stored in the internal 2kbit serial EEPROM. Control information can be programmed through the I2C or can be programmed through the EEPROM. Information such as card identification or revision/maintenance history can be stored in the EEPROM on every card and can be read or written via the I2C when required.

These are Fast-mode Plus (Fm+) versions of the PCA8574(A) and PCA8575 that offer 1MHz operation up to 540pF bus loading and, at lower speeds, up to 4000pF. Three address pins allow for 64 different addresses by using inputs of GND, V_CC, SCL, and SDA. The PCA9674(A) and PCA9675 are drop-in upgrades to the PCA8574(A) and PCA8575. The PCA9670 and PCA9675 are drop-in upgrades to the PCA8574(A) and PCA8575. The PCA9670 and PCA9671 are identical to the PCA9674 and PCA9675 except that the interrupt pin has been replaced with a hardware reset pin. The PCA9672 and PCA9673 are identical to the PCA9674 and PCA9675 except that the A2 address pin has been replaced by a hardwre reset pin which limits them to only 16 different addresses.

The PCA9698 is a 40-bit wide Advanced GPIO. Maximum frequency is 1000kHz. SDA output current is ten times stronger than normal to allow use in large area networks without the need for bus buffers. Each byte will change on acknowledge or wait for a stop condition, allowing you to update the output registers on multiple devices and then change all the outputs at once—which is great for large sign applications. Each pin can sink 25mA and all pins can be on (40 x 25mA = 1 amp) when using the HVQFN package. When used for sensing input, the inputs can be masked so you don't generate an interrupt. Three address pins allow for 64 different addresses by using inputs of GND, V_CC, SCL, or SDA so you can control up to 2560 LEDs on one I2C bus. Additionally there is a GPIO All Call fixed address that allows you to turn on or off LEDs on all the GPIOs in the circuit with a single command sequence—which is great for lamp test or darking the array between displays. A hardware reset input will reset the device to its power up state. There is even an Output Enable pin that will tri-state the outputs which are selectable between push pull and open drain. There is no internal pull up resistor on the I/O pins.

Product
PCA8574(A)	8				2.3-5.5		400
PCA8575	16				2.3-5.5		400
PCA9500	8				2.5-3.6		400
PCA9501	8				2.5-3.6		400
PCA9502	8				2.3-3.6		400	15
PCA9505	40				2.3-5.5		400
PCA9506	40				2.3-5.5		400
PCA9534	8				2.3-5.5		400
PCA9535	16				2.3-5.5		400
PCA9535C	16	Open Drain			2.3-5.5		400
PCA9536	4				2.3-5.5		400
PCA9537	4				2.3-5.5		400
PCA9538	8				2.3-5.5		400
PCA9539	16				2.3-5.5		400
PCA9554(A)	8				2.3-5.5		400
PCA9555	16				2.3-5.5		400
PCA9557	8				2.3-5.5		400
PCA9558	8	Open Drain			2.3-5.5		400
PCA9670	8				2.3-5.5		1000
PCA9671	16				2.3-5.5		1000
PCA9672	8				2.3-5.5		1000
PCA9673	16				2.3-5.5		1000
PCA9674(A)	8				2.3-5.5		1000
PCA9675	16				2.3-5.5		1000
PCA9698	40	Open Drain			2.3-5.5		1000
PCF8574(A)	8				2.5-6.0		100
PCF8575	16				2.5-5.5		400
PCF8575C	16	Open Drain			4.5-5.5		400

Product	Address	Group	# of Bits	Type *
PCA9557	0 0 1 1 A2 A1 A0 R/W	Group 3	8	PP/I
PCA8575	0 1 0 0 A2 A1 A0 R/W	Group 4	16	Q
PCA9500	0 1 0 0 A2 A1 A0 R/W	Group 4	8	Q
PCA9500	1 0 1 0 A2 A1 A0 R/W	Group A	Internal 2K EEPROM
PCA9505	0 1 0 0 A2 A1 A0 R/W	Group 4	40	PP/Q
PCA9506	0 1 0 0 A2 A1 A0 R/W	Group 4	40	PP/I
PCA9534	0 1 0 0 A2 A1 A0 R/W	Group 4	8	PP/I
PCA9535	0 1 0 0 A2 A1 A0 R/W	Group 4	16	PP/I
PCA9535C	0 1 0 0 A2 A1 A0 R/W	Group 4	16	Open Drain
PCA9554	0 1 0 0 A2 A1 A0 R/W	Group 4	8	PP/Q
PCA9555	0 1 0 0 A2 A1 A0 R/W	Group 4	16	PP/Q
PCF8574	0 1 0 0 A2 A1 A0 R/W	Group 4	8	Q
PCF8575	0 1 0 0 A2 A1 A0 R/W	Group 4	16	Q
PCF8575C	0 1 0 0 A2 A1 A0 R/W	Group 4	16	Open Drain
PCA8574A	0 1 1 1 A2 A1 A0 R/W	Group 7	8	Q
PCA9554A	0 1 1 1 A2 A1 A0 R/W	Group 7	8	PP/Q
PCF8574A	0 1 1 1 A2 A1 A0 R/W	Group 7	8	Q
PCA9502	0 1 A1 A0 X X X R/W	16 Addresses	8	PP/I (4mA)
PCA9536	1 0 0 0 0 0 1 R/W	Group 8	4	PP/Q
PCA9537	1 0 0 1 0 0 1 R/W	Group 9	4	PP/I
PCA9558	1 0 0 1 1 1 A1 A0 R/W	Group 9	8	Open Drain
PCA9538	1 1 1 0 0 A1 A0 R/W	Group E	8	PP/I
PCA9539	1 1 1 0 1 A1 A0 R/W	Group E	16	PP/I
PCA9501	0 A5 A4 A3 A2 A1 A0 R/W	64 Addresses	8	Q
PCA9501	1 A5 A4 A3 A2 A1 A0 R/W	64 Addresses	Internal 2K EEPROM
PCA9670	Varies	64 Addresses	8	Q
PCA9671	Varies	64 Addresses	16	Q
PCA9672	Varies	16 Addresses	8	Q
PCA9673	Varies	16 Addresses	16	Q
PCA9674(A)	Varies	64 Addresses	8	Q
PCA9675	Varies	64 Addresses	16	Q
PCA9698	Varies	64 Addresses	40	PP/I or Open Drain

* Notes:

• PP/I = totem pole (push-pull) I/Os that are configurable as inputs or outputs with inversion, 25mA sink and 10mA source. No internal pull up resistor.
• PP/Q = totem pole (push-pull) I/Os that are configurable as inputs or outputs with inversion, 25mA sink and 10mA source. 100 Kohm internal pull up resistor.
• Q = quasi I/Os which are not configurable but minimize length of read and write communications and software complexity, 25mA sink and weak 100uA internal current source or 100Kohm internal pull up resistor.

Click for datasheet. Also, see datasheet disclaimer.
, , indicate product status. Click or for more or less detail.

	PCA8574		Remote 8-bit I/O expander for I2C-bus with interrupt
	PCA8574A		Remote 8-bit I/O expander for I2C-bus with interrupt
	PCA8575		Remote 16-bit I/O expander for I2C-bus with interrupt
	PCA9500		8-Bit I2C I/O Port with 2-Kbit EEPROM
	PCA9501		8-Bit I2C I/O Port with Interrupt, 2-Kbit EEPROM, and Six Address Pins
	PCA9502		8-bit I/O expander for I2C/SPI bus
	PCA9505		40-bit I2C I/O port with reset, output enable, interrupt, and 100kΩ pull-up resistors
	PCA9506		40-bit I2C I/O port with reset, output enable, and interrupt
	PCA9534		8-Bit I2C Low Power I/O Port with Interrupt
	PCA9535		16-Bit I2C Low Power I/O Port with Interrupt
	PCA9535C		16-Bit I2C Low Power I/O Port with Interrupt and Open Drain Outputs
	PCA9536		4-bit I2C I/O port
	PCA9537		4-bit I2C low power I/O port with interrupt and reset
	PCA9538		8-bit I2C low power I/O port with interrupt and reset
	PCA9539		16-bit I2C and SMBus low-power I/O port with interrupt and device/register reset
	PCA9539R		16-bit I2C and SMBus low-power I/O port with interrupt and device-only reset
	PCA9554		8-Bit I2C I/O Port with Interrupt
	PCA9554A		8-Bit I2C I/O Port with Interrupt
	Datasheet (Nov 13, 2006) PCA9554AN DIL-16 Production SOT38-1 Pb-Free MSL=1 PCA9554AD SO-16 Production SOT162-1 Pb-Free          PCA9554ADB SSOP-16 Production SOT338-1 Pb-Free          PCA9554ATS SSOP-20 Production SOT266-1 Pb-Free MSL=1 PCA9554APW TSSOP-16 Production SOT403-1 Pb-Free          PCA9554ABS HVQFN-16 Production SOT629-1 Pb-Free          PCA9554ABS3 HVQFN-16 Production SOT758-1                   Family Functions Literature Models Support Docs Price Samples More...
	PCA9555		16-Bit I2C I/O Port with Interrupt
	PCA9556		Not recommended for new designs; See PCA9557
	PCA9557		8-Bit I2C I/O Port with Reset
	PCA9558		5-Bit Multiplexed/1-Bit Latched 6-Bit I2C EEPROM and Octal SMBus Registered Interface with 256-Byte I2C EEPROM
	PCA9574		8-bit I2C-bus and SMBus, level translating, low voltage GPIO with reset and interrupt
	PCA9575		16-bit I2C-bus and SMBus, level-translating, low-voltage GPIO with reset and interrupt
	PCA9670		Remote 8-bit I/O expander for Fm+ I2C-bus with reset
	PCA9671		Remote 16-bit I/O expander for Fm+ I2C-bus with reset
	PCA9672		Remote 8-bit I/O expander for Fm+ I2C-bus with interrupt and reset
	PCA9673		Remote 16-bit I/O expander for Fm+ I2C-bus with interrupt and reset
	PCA9674		Remote 8-bit I/O expander for Fm+ I2C-bus with interrupt
	PCA9674A		Remote 8-bit I/O expander for Fm+ I2C-bus with interrupt
	PCA9675		Remote 16-bit I/O expander for Fm+ I2C-bus with interrupt
	PCA9698		40-bit Fm+ I2C advanced I/O port with reset, output enable, and interrupt
	PCF8574		Remote 8-Bit I/O Expander for I2C Bus
	PCF8574A		Remote 8-Bit I/O Expander for I2C Bus with Alternate Slave Address
	PCF8575		Remote 16-Bit I/O Expander for I2C Bus
	PCF8575C		Remote 16-Bit I/O Expander for I2C Bus

• AN469 I²C I/O Ports, V2 (Jan 20, 2005)

• PCA9500 and PCA9501 FAQ

• GPIO Expanders
• SPI General Purpose I/O Expanders

• Bridges with GPIO