The PCA9956B is an I2C-bus controlled 24-channel constant current LED driveroptimized for dimming and blinking 57 mA Red/Green/Blue/Amber (RGBA) LEDs in amusementproducts. Each LED output has its own 8-bit resolution (256 steps) fixed frequencyindividual PWM controller that operates at 31.25 kHz with a duty cycle that isadjustable 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 fixedfrequency of 122 Hz and an adjustable frequency between 15 Hz to once every 16.8 secondswith a duty cycle that is adjustable from 0 % to 99.6 % that is used to either dim orblink all LEDs with the same value.

Each LED output can be off, on (no PWM control), set at its individual PWM controllervalue or at both individual and group PWM controller values. The PCA9956B operates witha supply voltage range of 3 V to 5.5 V and the constant current sink LED outputs allowup to 20 V for the LED supply. The output peak current is adjustable with an 8-bitlinear DAC from 225 μA to 57 mA.

This device has built-in open, short load and overtemperature detection circuitry. Theerror information from the corresponding register can be read via theI2C-bus. Additionally, a thermal shutdown feature protects the device wheninternal junction temperature exceeds the limit allowed for the process.

The PCA9956B device has a Fast-mode Plus (Fm+) I2C-bus interface. Fm+ devicesoffer higher frequency (up to 1 MHz) or more densely populated bus operation (up to 4000pF).

The active LOW output enable input pin (OE) blinks all theLED outputs and can be used to externally PWM the outputs, which is useful when multipledevices 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 PCA9956B 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, PCA9956B willhave a unique Sub Call address to identify it as a 24-channel LED driver. This allowsmixing of devices with different channel widths. Three hardware address pins on PCA9956Ballow up to 125 devices on the same bus.

The Software Reset (SWRST) function allows the master to perform a reset of the PCA9956Bthrough the I2C-bus, identical to the Power-On Reset (POR) that initializes theregisters to their default state causing the output current switches to be OFF (LEDoff). This allows an easy and quick way to reconfigure all device registers to the samecondition.

• 24 LED drivers. Each output programmable at:
  • Off
  • On
  • Programmable LED brightness
  • Programmable group dimming/blinking mixed with individual LEDbrightness
  • Programmable LED output delay to reduce EMI and surge currents
• 24 constant current output channels can sink up to 57 mA, tolerate up to 20 Vwhen OFF
• Output current adjusted through an external resistor (REXT input)
• Output current accuracy
  • ±4 % between output channels
  • ±6 % between PCA9956B devices
• Open/short load/overtemperature detection mode to detect individual LEDerrors
• 1 MHz Fast-mode Plus compatible I2C-bus interface with 30 mA highdrive capability on SDA output for driving high capacitive buses
• 256-step (8-bit) linear programmable brightness per LED output varying from fullyoff (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 to updateoutputs byte-by-byte or all at the same time (default to ‘Change on STOP’).
• Active LOW Output Enable (OE) input pin allows forhardware blinking and dimming of the LEDs
• Three quinary hardware address pins allow 125 PCA9956B devices to be connected tothe same I2C-bus and to be individually programmed
• Four software programmable I2C-bus addresses (one LED Group Calladdress and three LED Sub Call addresses) allow groups of devices to beaddressed at the same time in any combination (for example, one register usedfor ‘All Call’ so that all the PCA9956Bs on the I2C-bus can beaddressed at the same time and the second register used for three differentaddresses so that 1?3 of all devices on the bus can be addressed at the sametime in a group). Software enable and disable for each programmableI2C-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 theI2C-bus
• 8 MHz internal oscillator requires no external components
• Internal power-on reset
• Noise filter on SDA/SCL inputs
• No glitch on LEDn outputs 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
• -40 °C to +85 °C operation
• ESD protection exceeds 3000 V HBM per JESD22-A114
• Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
• Packages offered: HTSSOP38

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