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