How to TPS659037 power on the automatic start, no button operation

Hi Wei,

You can pull the POWERHOLD pin up to LDOVRTC, and use RESET_IN to turn the PMIC on/off based on input power.  Since LDOVRTC is always on, this will get pulled high when power is supplied.  For RESET_IN, my recommendation is to use a powergood from a pre-regulator, or a supervisor on the input supply, to control RESET_IN in order to allow the power-off sequence to complete when power is removed.

You can look at our blog post How to meet power sequencing requirements, specifically the second half about power-down sequencing, for more details about meeting the power-down requirements with powergood or supervisor.

Regards,
Karl

Hello Karl, 

I just saw this while having the same question. 

I was just wondering if the same auto-turn on can be implemented just by putting a supervisor on PWRON. 

Regards,

KEvin

the POWERHOLD pin up to LDOVRTC,I tried on the EVM board, yes, I design the board can also be

Pull PWRON seems to be not

Kevin,

This exact same logic doesn't work with PWRON. The PWRON pin turns on the device when it is pulled low, and should be released high again. Holding PWRON low for 6-12 seconds causes the device to turn off. So you would need logic that can drive the PWRON pin low and high to do an automatic start. You could try an RC delay circuit from VCC to the PWRON pin, to have the device recognize PWRON=0 after VCC is supplied. This is a little bit more complex, since you need to make sure the tolerances of your RC circuit still delay the VCC signal enough.

The other challenge with using this logic on PWRON is that you need a different way to turn the PMIC off when power is lost. Since you need a controlled shutdown even when power is unexpectedly removed, you may need additional logic to detect power loss and then for example do a software shutdown (writing DEV_ON=0).

The supervisor logic on POWERHOLD does both of these functions in a fairly simple way.

Regards,
Karl