Initial surge current nRF52832

[Lakshmikanth Satyavolu]

Hi,

I am using TPS61021DSG in my design which is a data acquisition system using nRF52832 BLE module. I am using 1.4V Zinc-air battery to power up my circuit to generate 3VDC at output. 

The circuit not being powered up when using Zinc-air 1.4V. After I investigate more by testing it with DC power supply, I realized the initial current when we apply 1.4V to the circuit goes upto 53mA and settles down at 20mA which is causing my battery to not support that initial surge. 

Attached is my power supply section and the video I have captured which explains the scenario. Can someone please review the design and help me understand why is this happening? 

Best

Lakshmikanth

[Turbo J]

Measure Voltage across U8. According to the datasheet, the FET may not be fully "ON" - especially when the battery voltage is "loaded down".

BTW: I would rather just use a reversed diode here as polarity protection - the zinc air cell has not much current output when shorted.

There is no way around the initial 5-7mA during POR.

Consider putting a large capacitor - say 470µF or more - on the primary side in addition to C47. Also use an RC-delay on the EN line of the voltage ragulator in order to allow this capacity to be fully loaded before the regulator turns on. This may buy you just enogh time to go through POR and into the application - only then you are able to go in lower power states.