PCAL6408A Datasheet, PDF (1/48 Pages) NXP Semiconductors – Low-voltage translating, 8-bit I2C-bus/SMBus I/O expander with interrupt output, reset, and configuration registers

PCAL6408A
Low-voltage translating, 8-bit I²C-bus/SMBus I/O expander
with interrupt output, reset, and configuration registers
Rev. 2 — 6 December 2012
Product data sheet
1. General description
The PCAL6408A is an 8-bit general-purpose I/O expander that provides remote I/O
expansion for most microcontroller families via the I²C-bus interface.
NXP I/O expanders provide a simple solution when additional I/Os are needed while
keeping interconnections to a minimum, for example, in battery-powered mobile
applications for interfacing to sensors, push buttons, keypad, etc. In addition to providing
a flexible set of GPIOs, it simplifies interconnection of a processor running at one voltage
level to I/O devices operating at a different (usually higher) voltage level. The PCAL6408A
has built-in level shifting feature that makes these devices extremely flexible in mixed
signal environments where communication between incompatible I/O voltages is required.
Its wide V_DD range of 1.65 V to 5.5 V on the dual power rail allows seamless
communications with next-generation low voltage microprocessors and microcontrollers
on the interface side (SDA/SCL) and peripherals at a higher voltage on the port side.
There are two supply voltages for PCAL6408A: V_DD(I2C-bus) and V_DD(P). V_DD(I2C-bus)
provides the supply voltage for the interface at the master side (for example, a
microcontroller) and the V_DD(P) provides the supply for core circuits and Port P. The
bidirectional voltage level translation in the PCAL6408A is provided through V_DD(I2C-bus).
V_DD(I2C-bus) should be connected to the V_DD of the external SCL/SDA lines. This indicates
the V_DD level of the I²C-bus to the PCAL6408A, while the voltage level on Port P of the
PCAL6408A is determined by the V_DD(P).
The PCAL6408A contains the PCA6408A register set of 8-bit Configuration, Input, Output,
and Polarity Inversion registers and additionally, the PCAL6408A has Agile I/O, which are
additional features specifically designed to enhance the I/O. These additional features
are: programmable output drive strength, latchable inputs, programmable
pull-up/pull-down resistors, maskable interrupt, interrupt status register, programmable
open-drain or push-pull outputs. The PCAL6408A is a pin-to-pin replacement to the
PCA6408A, however, the PCAL6408A powers up with all I/O interrupts masked. This
mask default allows for a board bring-up free of spurious interrupts at power-up.
At power-on, the I/Os are configured as inputs. However, the system master can enable
the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for
each input or output is kept in the corresponding input or output register. The polarity of
the Input Port register can be inverted with the Polarity Inversion register, saving external
logic gates. Programmable pull-up and pull-down resistors eliminate the need for discrete
components.