Sub-1V 555-like timer includes LED driver and charger

Semtech has introduced an analogue timer chip that runs from 0.9V, but can drive LEDs at over 3V, writes Steve Bush.

Called SX8122, to the timer it adds: a simple battery charger, a boost converter, and a power-down controller.

“It is designed for on/off button debouncing, delayed start-up timing, programmable sequencing and timing-out in toys, remote control, electric toothbrushes, buzzers, and LED pointers,” said Semtech.

The timer part is very similar to a 555, and there is a guidance document to describe the differences.

“The 555 timer is one of the most popular ICs ever, because it is easy to use, cost-effective and a proven performer,” said Semtech engineering manager Michel Chevroulet. “By embedding unique low-voltage features, the SX8122 extends the versatility of the 555 timer in small light battery-enabled consumer products.”

He also said: “The SX8122 is the industry’s first analogue timer embedding low-voltage features for single AA/AAA cell-powered appliances.”

This last statement is not actually true, as a few years ago Zetex – now part of Diodes – employed original 555 designer Hans Camenzind to develop an 0.9V version from scratch.

This was introduced as the ZSCT1555.

What is unique about Semtech’s offering is the LED driver which, whenever the main (motor-driving) output is high, puts out a square wave.

Sub-1V 555-like timer includes LED driver and charger

Steve Bush

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