TPS63031 does not enable

Andreas Zimmer

I have the following problem with the DC-DC TPS63031 converter operating in a Li-On battery MSP430 circuit. I'll turn on theTPS63031 with the EN input.
When at the input a voltage applied between 3.3 and 4.2V, the DC-DC does not turn on the output, there are only 0.7V. At a input voltage below 3.3V, the switching on the En input works, there are the 3.3V.

Why might that be?

8424.Schaltplan.pdf

over 11 years ago

0 Chris Glaser over 11 years ago

TI__Guru**** 150790 points

Could you post your board layout and waveforms of Vin, Vout, and EN when it does not work?

0 Andreas Zimmer over 11 years ago in reply to Chris Glaser

Prodigy 40 points

the waveforms I have not measured, but here is the layout:

7585.Layout.pdf

0 Chris Glaser over 11 years ago in reply to Andreas Zimmer

TI__Guru**** 150790 points

Thanks for posting this.

To me, it's not surprising this isn't regulating. The layout is unacceptable. The input and output caps are very far away from the IC. I can't even find the traces that connect the input cap on the back of the board to the VIN pin. This connection must be short and direct for any SMPS. Please look at the EVM's layout as a guideline and copy it: http://www.ti.com/lit/ug/slvu275/slvu275.pdf

I would recommend ordering the EVM and wiring it into your board to evaluate the performance. This is quicker and lower risk than spinning a new PCB.

As well, you should test the EVM with your 10uH and 47uH output filters. These secondary filters are well known to cause stability issues with SMPSs.

0 Andreas Zimmer over 11 years ago in reply to Chris Glaser

Prodigy 40 points

thanks a lot.

I have now placed the input and output caps near the SMPS, similar to the EVM. Now it regulates well :-).

Also, the input EN doing now what it should, even with the secondary output filters.

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TPS63031 does not enable