PCA9901 Datasheet, PDF (1/27 Pages) NXP Semiconductors – One wire single LED driver

PCA9901
One wire single LED driver
Rev. 01 — 3 December 2009
Product data sheet
1. General description
The PCA9901 is a 20 mA current source for a single LED that allows stand-alone blinking
of a predefined pattern to off-load the microcontroller and save battery power.
Programming of the device is done through a training sequence: the host controller sends
the LED lighting sequence and the PCA9901 memorizes it. Once the sequence has been
memorized, the PCA9901 can be programmed to send it once or in a loop until the host
controller requests the sequence to be stopped.
Commands and blinking sequence are sent through a uni-directional one-wire interface.
Commands include: Training Start, Training End, Execute Sequence (once or in loop until
a Stop Command is requested) and Reset. A blinking sequence includes up to 3 different
blinking patterns, each defined by its ON and OFF timings.
A bypass mode allows the training sequence to be ignored and the LED output to follow
the one-wire interface Logic state to directly control the LED from the microcontroller.
An external resistor sets the maximum current that flows in the LED, which can be set
between 1 mA and 20 mA.
The PCA9901 operates from a 2.7 V to 5.5 V power supply.
2. Features
„ 1 wire interface to control the device
„ Stand-alone blinking capability while training the sequence to blink
„ Sequence includes up to 3 blinking elements
„ 12-bit (4096 steps) LED ON and OFF timings for each blinking element:
‹ ON timing is captured between 1 ms and 255 ms
‹ OFF timing is captured between 20 ms and 5.1 s
„ 1.8 V compliant one-wire logic interface
„ Training Start, Training End, Run-Once, Run, Stop and Reset commands
„ High side current controlled LED driver with 1 mA to 20 mA max current in the LED set
by an external resistor. 5 mA drive capability when no external resistor is connected
„ 110 mV max dropout voltage driver at 20 mA
„ Fully internal oscillator for sequence training, LED timing, Command and Sequencing
Controls
„ Short circuit and thermal protection
„ 2.7 V to 5.5 V power supply
„ Very low quiescent current: < 0.75 μA