TPS65218: Issue with Powerup- PWR_EN and nWakeup toggles

Hi Santosh,

Thanks for the post! What is driving the PWR_EN signal? Are all the PMIC output voltages rising to their correct values? Let me know what you think. Thanks!

Regards,

Paul Kundmueller

Thanks for reply

I am surprised after seeing the PMIC behaviour

Initially, input voltage to PMIC was exact 5.0V Dc , and at output rails none. no voltages on any rail

but i decreased the PMIC input voltage to 4.75Vdc and then start by pushing PB button

and all the rails output voltage as per the desired

what is the porblem ? why not 5.0Vdc input to PMIC?

Hi Santosh,

Would you be able to provide scopeshots of the startup waveforms for DCDC1-4 and LDO1? I would like to narrow down what is causing the device to not startup. Let me know if there are any questions. Thanks!

Regards,

Paul Kundmueller

yes, here is scope shots

As I mentioned earlier nWakeup output from PMIC continuously toggles to high to low logics similarly Power enable input to PMIC toggles

but if I reduce the input voltage to 4.80V and use the push button for startup, all the outputs rails reached to desired levels- i.e correct output as per datasheet

Hi

Please reply

 

Hi Santosh,

Sorry for the delay. From the screenshots you provided it seems that DCDC4 is not able to start up. How much total capacitance do you have on the output of DCDC4 across the board? Also would you happen to have a 200pF capacitor or schottky diode handy? If you do, could try placing either the schottky diode or capacitor from GND to L4A? Also would you be able to share your layout? I have sent you a friend request so we can view your design files privately and securely. To send a message, please find the 'messages' icon in the top right of the screen (see below for an example).

Regards,

Paul Kundmueller

Thanks for reply

but then how come DCDC4 startup at 4.80Vdc input? it works fine at 4.80Vdc

When i use 4.80Vdc input voltage to PMIC , all the rails up and working fine