PCA9635
16-bit Fm+ I2C-bus LED driver
Rev. 07 — 16 July 2009
Product data sheet
1. General description
The PCA9635 is an I2C-bus controlled 16-bit LED driver optimized for
Red/Green/Blue/Amber (RGBA) color mixing applications. Each LED output has its own
8-bit resolution (256 steps) fixed frequency individual PWM controller that operates at
97 kHz with a duty cycle that is adjustable from 0 % to 99.6 % to allow the LED to be set
to a specific brightness value. An additional 8-bit resolution (256 steps) group PWM
controller has both a fixed frequency of 190 Hz and an adjustable frequency between
24 Hz to once every 10.73 seconds with a duty cycle that is adjustable from 0 % to 99.6 %
that is used to either dim or blink all LEDs with the same value.
Each LED output can be off, on (no PWM control), set at its individual PWM controller
value or at both individual and group PWM controller values. The LED output driver is
programmed to be either open-drain with a 25 mA current sink capability at 5 V or
totem-pole with a 25 mA sink, 10 mA source capability at 5 V. The PCA9635 operates with
a supply voltage range of 2.3 V to 5.5 V and the outputs are 5.5 V tolerant. LEDs can be
directly connected to the LED output (up to 25 mA, 5.5 V) or controlled with external
drivers and a minimum amount of discrete components for larger current or higher voltage
LEDs.
The PCA9635 is one of the first LED controller devices in a new Fast-mode Plus (Fm+)
family. Fm+ devices offer higher frequency (up to 1 MHz) and more densely populated bus
operation (up to 4000 pF).
The active LOW Output Enable input pin (OE) allows asynchronous control of the LED
outputs and can be used to set all the outputs to a defined I2C-bus programmable logic
state. The OE can also be used to externally PWM the outputs, which is useful when
multiple devices need to be dimmed or blinked together using software control.
Software programmable LED Group and three Sub Call I2C-bus addresses allow all or
defined groups of PCA9635 devices to respond to a common I2C-bus address, allowing
for example, all red LEDs to be turned on or off at the same time or marquee chasing
effect, thus minimizing I2C-bus commands. Seven hardware address pins allow up to
126 devices on the same bus.
The Software Reset (SWRST) Call allows the master to perform a reset of the PCA9635
through the I2C-bus, identical to the Power-On Reset (POR) that initializes the registers to
their default state causing the outputs to be set HIGH (LED off). This allows an easy and
quick way to reconfigure all device registers to the same condition.
