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PCA9955A Datasheet

16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver

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PCA9955A
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED
driver
Rev. 3 — 14 October 2014
Product data sheet
1. General description
The PCA9955A is an I2C-bus controlled 16-channel constant current LED driver optimized
for dimming and blinking 57 mA Red/Green/Blue/Amber (RGBA) LEDs in amusement
products. Each LED output has its own 8-bit resolution (256 steps) fixed frequency
individual PWM controller that operates at 31.25 kHz with a duty cycle that is adjustable
from 0 % to 100 % 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 122 Hz
and an adjustable frequency between 15 Hz to once every 16.8 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 PCA9955A operates
with a supply voltage range of 3 V to 5.5 V and the constant current sink LED outputs
allow up to 20 V for the LED supply. The output peak current is adjustable with an 8-bit
linear DAC from 225 A to 57 mA.
Gradation control for all current sources is achieved via the I2C-bus serial interface and
allows user to ramp current automatically without MCU intervention. 8-bit DACs are
available to adjust brightness levels for each LED current source. There are four
selectable gradation control groups and each group has independently four registers to
control ramp-up and ramp-down rate, step time, hold ON/OFF time and final hold ON
output current. Two gradation operation modes are available for each group, one is single
shot mode (output pattern once) and the other is continuous mode (output pattern repeat).
Each channel can be set to either gradation mode or normal mode and assigned to any
one of these four gradation control groups.
This device has built-in open, short load and overtemperature detection circuitry. The error
information from the corresponding register can be read via the I2C-bus. Additionally, a
thermal shutdown feature protects the device when internal junction temperature exceeds
the limit allowed for the process.
The PCA9955A device has a Fast-mode Plus (Fm+) I2C-bus interface. Fm+ devices offer
higher frequency (up to 1 MHz) or more densely populated bus operation (up to 4000 pF).
The active LOW output enable input pin (OE) blinks all the LED outputs and can be used
to externally PWM the outputs, which is useful when multiple devices need to be dimmed
or blinked together without using software control.
Software programmable LED Group and three Sub Call I2C-bus addresses allow all or
defined groups of PCA9955A 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. On power-up, PCA9955A has a unique


NXP Semiconductors Electronic Components Datasheet

PCA9955A Datasheet

16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver

No Preview Available !

NXP Semiconductors
PCA9955A
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Sub Call address to identify it as a 16-channel LED driver. This unique address allows
mixing of devices with different channel widths. Three hardware address pins on
PCA9955A allow up to 125 devices on the same bus.
The Software Reset (SWRST) function allows the master to perform a reset of the
PCA9955A through the I2C-bus, identical to the Power-On Reset (POR) that initializes the
registers to their default state causing the output current switches to be OFF (LED off).
This allows an easy and quick way to reconfigure all device registers to the same
condition.
2. Features and benefits
16 LED drivers. Each output programmable at:
Off
On
Programmable LED brightness
Programmable group dimming/blinking mixed with individual LED brightness
Programmable LED output delay to reduce EMI and surge currents
Gradation control for all channels
Each channel can assign to one of four gradation control groups
Programmable gradation time and rate for ramp-up and/or ramp-down operations
Programmable step time (6-bit) from 0.5 ms (minimum) to 512 ms (maximum)
Programmable hold-on time after ramp-up and hold-off time after ramp-down (3-bit)
from 0 s to 6 s
Programmable final ramp-up and hold-on current
Programmable brightness current output adjustment, either linear or exponential
curve
16 constant current output channels can sink up to 57 mA, tolerate up to 20 V when
OFF
Output current adjusted through an external resistor (REXT input)
Output current accuracy
4 % between output channels
6 % between PCA9955A devices
Open/short load/overtemperature detection mode to detect individual LED errors
1 MHz Fast-mode Plus compatible I2C-bus interface with 30 mA high drive capability
on SDA output for driving high capacitive buses
256-step (8-bit) linear programmable brightness per LED output varying from fully off
(default) to maximum brightness fully ON using a 31.25 kHz PWM signal
256-step group brightness control allows general dimming (using a 122 Hz PWM
signal) from fully off to maximum brightness (default)
256-step group blinking with frequency programmable from 15 Hz to 16.8 s and duty
cycle from 0 % to 99.6 %
Output state change programmable on the Acknowledge or the STOP condition to
update outputs byte-by-byte or all at the same time (default to ‘Change on STOP’).
Active LOW Output Enable (OE) input pin allows for hardware blinking and dimming of
the LEDs
PCA9955A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 14 October 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
2 of 62


Part Number PCA9955A
Description 16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Maker NXP
Total Page 30 Pages
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