描述 Description

The PCA9574 is a CMOS device that provides 8 bits of General Purpose parallelInput/Output (GPIO) expansion in low voltage processor and handheld battery poweredmobile applications and was developed to enhance the NXP family of I2C-bus I/Oexpanders. The improvements include lower supply current, lower operating voltage of1.1 V to 3.6 V, dual and separate supply rails to allow voltage level translation anywherebetween 1.1 V and 3.6 V, 400 kHz clock frequency, and smaller packaging. Any of theeight I/O ports can be configured as an input or output independent of each other anddefault on start-up to inputs. I/O expanders provide a simple solution when additional I/Osare needed while keeping interconnections to a minimum; for example in battery poweredmobile applications and clamshell devices for interfacing to sensors, push buttons,keypad, etc. In addition to providing a flexible set of GPIOs, it simplifies interconnection ofa processor running at one voltage level to I/O devices operating at a different (usuallyhigher) voltage level. PCA9574 has built-in level shifting feature that makes these devicesextremely flexible in mixed signal environments where communication betweenincompatible I/Os is required. The core of PCA9574 can operate at a voltage as low as1.1 V while the I/O bank can operate in the range 1.1 V to 3.6 V. Bus-hold withprogrammable on-chip pull-up or pull-down feature for I/Os is also provided.
The system master can enable the I/Os as either inputs or outputs by writing to the I/Oconfiguration register bits. The data for each input or output is kept in the correspondingInput or Output register. The polarity of the read register can be inverted with the Polarityinversion register (active HIGH or active LOW operation). Either a bus-hold function orpull-up/pull-down feature can be selected by programming corresponding registers. Thebus-hold provides a valid logic level when the I/O bus is not actively driven. Whenbus-hold feature is not selected, the I/O ports can be configured to have pull-up orpull-down by programming the pull-up/pull-down configuration register.
An open-drain interrupt output pin (INT) allows monitoring of the input pins and is assertedeach time a change occurs on an input port unless that port is masked(default = masked). A ‘GPIO All Call’ command allows programming multiple PCA9574sat the same time even if they have different individual I2C-bus addresses. This allowsoptimal code programming when more than one device needs to be programmed with thesame instruction or if all outputs need to be turned on or off at the same time. The internalPower-On Reset (POR) or hardware reset pin (RESET) initializes the eight I/Os as inputs,sets the registers to their default values and initializes the device state machine. The I/Obank is held in its default state when the logic supply (VDD) is off.
One address select pin allows up to two PCA9574 devices to be connected with twodifferent addresses on the same I2C-bus.
The PCA9574 is available in TSSOP16 and HVQFN16 packages and isspecified over the ?40 °C to +85 °C industrial temperature range.

特性 Features

400 kHz I2C-bus serial interface
Compliant with I2C-bus Standard-mode (100 kHz)
Separate supply rails for core logic and I/O bank provides voltage level shifting
1.1 V to 3.6 V operation with level shifting feature
Very low standby current: < 1 μA
8 configurable I/O pins that default to inputs at power-up
Outputs: Totem pole: 1 mA source and 3 mA sink
Independently programmable 100 kΩ pull-up or pull-down for each I/O pin
Open-drain active LOW interrupt (INT) output pin allows monitoring of logic level change of pins programmed as inputs
Inputs: Programmable bus hold provides valid logic level when inputs are not actively driven
Programmable Interrupt Mask Control for input pins that do not require an interrupt when their states change or to prevent spurious interrupts default to mask at power-up
Polarity inversion register allows inversion of the polarity of the I/O pins when read
Active LOW reset (RESET) input pin resets device to power-up default state
GPIO All Call address allows programming of more than one device at the same time with the same parameters
2 programmable slave addresses using 1 address pin
-40 °C to +85 °C operation
ESD protection exceeds 7000 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: TSSOP16 and HVQFN16

應(yīng)用 Application

Cell phones
Media players
Multi voltage environments
Battery operated mobile gadgets
Motherboards
Servers
RAID systems
Industrial control
Medical equipment
PLCs
Gaming machines
Instrumentation and test measurement