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