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 PCA9955B devices
• Open/short load/overtemperature detection mode to detect individual LED errors (Rext < 3 kΩ)
• 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-bybyte
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
• Three quinary hardware address pins allow 125 PCA9955B devices to be connected to the same I2C-bus and
to be individually programmed
• 4 software programmable I2C-bus addresses (one LED Group Call address and three LED Sub Call
addresses) allow groups of devices to be addressed at the same time in any combination (for example, one
register used for ‘All Call’ so that all the PCA9955Bs on the I2C-bus can be addressed at the same time and
the second register used for three different addresses so that 1⁄3 of all devices on the bus can be addressed at
the same time in a group). Software enable and disable for each programmable I2C-bus address.
• Unique power-up default Sub Call address allows mixing of devices with different channel 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 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 +105 °C operation
• ESD protection exceeds 4000 V HBM per JESD22-A114
• Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
• Packages offered: HTSSOP28
– PCA9955BTW/Q900 for automotive
Applications
• Amusement products
• RGB or RGBA LED drivers
• LED status information
• LED displays
• LCD backlights
• Keypad backlights for cellular phones or handheld devices
• Fade-in and fade-out for breathlight control
• Automotive lighting (PCA9955BTW/Q900)