OM13330,598

OM13330,598 1 General description

The PCA9952 and PCA9955 are I2C-bus controlled 16-channel constant current LEDdriver optimized for dimming and blinking 57 mA Red/Green/Blue/Amber (RGBA) LEDsin amusement products. Each LEDn output has its own 8-bit resolution (256 steps)fixed frequency individual PWM controller that operates at 31.25 kHz with a duty cyclethat is adjustable from 0 % to 99.6 % to allow the LED to be set to a specific brightnessvalue. An additional 8-bit resolution (256 steps) group PWM controller has both a fixedfrequency of 122 Hz and an adjustable frequency between 15 Hz to once every 16.8seconds with a duty cycle that is adjustable from 0 % to 99.6 % that is used to either dimor blink all LEDs with the same value.Each LEDn output can be off, on (no PWM control), set at its individual PWM controllervalue or at both individual and group PWM controller values. The PCA9952 andPCA9955 operate with a supply voltage range of 3 V to 5.5 V and the constant currentsink LEDn outputs allow up to 40 V for the LED supply. The output peak current isadjustable with an 8-bit linear DAC from 225 μA to 57 mA.These devices have 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 junctiontemperature exceeds the limit allowed for the process.The PCA9952 and PCA9955 devices have 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 PCA9952 is identical to PCA9955 except for the following differences:
• The PCA9952 has only three hardware address pins compared to four on PCA9955.
• The PCA9952 has an output enable pin (OE) and the PCA9955 does not.The active LOW output enable input pin (OE), available only on PCA9952, blinks all theLEDn outputs and can be used to externally PWM the outputs, which is useful whenmultiple devices need to be dimmed or blinked together without using software control.Software programmable LED Group and three Sub Call I2C-bus addresses allow allor defined groups of PCA9952/55 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 marqueechasing effect, thus minimizing I2C-bus commands. On power-up, PCA9952/55 will havea unique Sub Call address to identify it as a 16-channel LED driver. This allows mixingof devices with different channel widths. Four hardware address pins on PCA9955 allowup to 16 devices on the same bus. In the case of PCA9952, three hardware address pinsallow up to 8 devices on the same bus.The Software Reset (SWRST) function allows the master to perform a reset of thePCA9952/55 through the I2C-bus, identical to the Power-On Reset (POR) that initializesthe registers to their default state causing the output current switches to be OFF (LED

OM13330,598 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 LEDn output enable delay to reduce EMI and surge currents
• 16 constant current output channels can sink up to 57 mA, tolerate up to 40 V whenOFF
• Output current adjusted through an external resistor
• Output current accuracy– ±6 % between output channels– ±8 % between PCA9952/55 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 capabilityon SDA output for driving high capacitive buses
• 256-step (8-bit) linear programmable brightness per LEDn output varying from fully off(default) to maximum brightness using a 31.25 kHz PWM signal
• 256-step group brightness control allows general dimming (using a 122 Hz PWMsignal) from fully off to maximum brightness (default)
• 256-step group blinking with frequency programmable from 15 Hz to 16.8 s and dutycycle from 0 % to 99.6 %
• Output state change programmable on the Acknowledge or the STOP Command toupdate outputs byte-by-byte or all at the same time (default to ‘Change on STOP’).
• Active LOW Output Enable (OE) input pin (only on PCA9952) allows for hardwareblinking and dimming of the LEDs
• Four hardware address pins allow 16 PCA9955 devices to be connected to the sameI2C-bus and to be individually programmed
• Four software programmable I2C-bus addresses (one LED Group Call address andthree LED Sub Call addresses) allow groups of devices to be addressed at the sametime in any combination (for example, one register used for ‘All Call’ so that all thePCA9952/55s on the I2C-bus can be addressed at the same time and the secondregister used for three different addresses so that 1⁄3 of all devices on the bus canbe addressed at the same time in a group). Software enable and disable for eachprogrammable I2C-bus address.
• Unique power-up default Sub Call address allows mixing of devices with differentchannel widths
• Software Reset feature (SWRST Call) allows the device to be reset through the I2C-bus
• 8 MHz internal oscillator requires no external components
• Internal power-on reset
• Noise filter on SDA/SCL inputs
• No glitch on LED on power-up
• Low standby current
• Operating power supply voltage (VDD) range of 3 V to 5.5 V
• 5.5 V tolerant inputs on non-LED pins

OM13330,598 3 Applications

• Amusement products
• RGB or RGBA LED drivers
• LED status information
• LED displays
• LCD backlights
• Keypad backlights for cellular phones or handheld devices
• Automotive lighting