TPS7A57: Design Implementation Issue

Sean Mullins

Prodigy 10 points

Part Number: TPS7A57

Hello,

I am using a TPS7A5701RTER on a new board and it will not power on. Here is the pinout and how I have it setup.

Pin 1, 2, 3, 4, 5, and 16 - Tied to 3V8 with 22uF decoupling cap.

Pin 7 - Pulled down with a 65.5k resistor to give roughly a 3V3 output.

Pin 8 - Pulled down with a 4.7uF cap.

Pin 9, 10, 11, 12, 13 - Tied to the output being 3V3.

Pin 14 - Tied to a 3v3_PG signal with a pull up resistor to 3v3 and a 22uF decoupling cap.

Pin 15, 6, and 17 - Tied to GND.

Taking measurements of the board I don't have an output but nothing looks bizarre and there are no shorts going into the chip. The input is valid at 3V8 to pins 1, 2, 3, 4, 5, and 16.

Thank you!

over 1 year ago

0 Stephen Ziel over 1 year ago

TI__Mastermind 37065 points

Hi Sean,

I'm pretty sure the issue is the UVLO on the BIAS rail which needs to be approximately 3V higher than Vout if you wish to turn off the internal charge pump. In your design it is only 500mV differential between Vin=Vbias and Vout. To get your design working, please use at least 6V on the bias pin, or alternatively you can tie the CP pin high to engage the charge pump.

Thanks,

Stephen

0 Sean Mullins over 1 year ago

Prodigy 10 points

Thank you for your help Stephen! I'll report back tomorrow with my findings and if this is the solution. After reading back through the datasheet it sure seems to be the issue.

0 Stephen Ziel over 1 year ago in reply to Sean Mullins

TI__Mastermind 37065 points

Sounds good, let us know if you need anything else.

Thanks,

Stephen

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TPS7A57: Design Implementation Issue