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soft power switch on modern gadgets?

pixbroker
Genius 5820 points

Hi,

i would like to find out how most modern gadgets (smartphone, etc) implement their soft power switch. in iPhone for example, has a tactile power button that turns the device on and off. what IC's and circuitry are involved for such a device to implement this? 

in the past, i have implemented such a circuit by controlling the EN pin of a regulator via either a tactile switch or MCU GPIO. i.e. when the device was totally OFF, the EN pin was low and hence power to the system was killed. when the user pressed a tactile button, the EN pin would get pulled up to power the system and the MCU will then hold the EN pin high with a GPIO so that when the user releases the tactile button, the system would still be powered. 

I was wondering how most consumer electronics devices commonly implement such soft power witches and what TI IC's might be a good choice.

thanks in advance

  • 0
    Prodigy 130 points

    First, I suspect that most consumer electronics integrate this sort of 'soft off' functionality into a control-plane microcontroller somewhere in the device, as you described in your post.

    While TI, as far as I know, does not make a device dedicated to such soft-off functionality, LTC has control ICs for this job, namely the LTC295x family.  (There are also Maxim parts for this, but they are limited to a 5.5V Vin, while the LTC295x can accept up to 26V).