TPS54294: TPS54294PWP

Asiya Asiya

Part Number: TPS54294

In our circuit, we are generating 5V & 3.3V outputs by giving input voltage 7V. Same circuit is working fine with P/No:TPS542941PWP but when we replace with part:TPS54294PWP it is not generating the output voltage-5V.

The difference in functionality we observed are,

1. By increasing input voltage gradually TPS54294PWP IC is not generating output voltage till 10V. Observed at 4V the output voltage is increasing from 0V to 2V & then again decreasing to 0V. At this time some humming noise observed from the IC. If we make power-supply On/Off by increasing the input voltage, then at 7.5V it is generating 5V o/p.

2. Also observed when we keep any conductor/measuring probe on VFB1 & VFB2 pins then the Output is getting decreased from 5V to 0V.

Please let me know the difference between these two parts P/No: TPS54294PWP & TPS542941PWP & why i am not getting the output voltage 5V.

over 1 year ago

0 Amod Vaze over 1 year ago

TI__Mastermind 25060 points

TPS54294 is rated 2A current on both channels while TPS542941 has 2A/3A channel ratings. This changes the current limit spec on one of the channels. Can you share the schematic? Also, which packages are you using on both these devices? Please share VIN, SW, VOUT waveforms in as much detail as possible.

0 Asiya Asiya over 1 year ago in reply to Amod Vaze

Prodigy 30 points

I have verified in no load condition only. Attached the circuit.

0 Amod Vaze over 1 year ago in reply to Asiya Asiya

TI__Mastermind 25060 points

Schematic looks fine for most part. 22pF feedforward needs to be across the two resistors adding up on the top divider resistor. 5V channel inductor can be 3.3uH. Bottom divider on 5V design can be 22.1kohm.

Thanks,

Amod

0 Asiya Asiya over 1 year ago in reply to Amod Vaze

Prodigy 30 points

Verified as per the above modification but same problem observed.

0 Amod Vaze over 1 year ago in reply to Asiya Asiya

TI__Mastermind 25060 points

Is it possible to share VIN, SW and VOUT waveforms during these observations? Need to use pigtail or tip and barrel technique to measure on the scope with full bandwidth.

Thanks,

Amod

0 Asiya Asiya over 1 year ago in reply to Amod Vaze

Prodigy 30 points

Dear Sir,

Please find the attached images. Input voltage is 7V but IC is not generating output voltage 5V.

0 Amod Vaze over 1 year ago in reply to Asiya Asiya

TI__Mastermind 25060 points

Asiya,

I see 5V (4.86V mean) on one of the scope shots. Is that the VOUT? I see two other scope shots with 0V which I suspect you are pointing to. Any chance of confirming the EN voltage and SW voltage? Does the design work if you replace the TPS54294 IC with a new one?

Thanks,

Amod

0 Asiya Asiya over 1 year ago in reply to Amod Vaze

Prodigy 30 points

Sir, the voltage 4.86V is at VBST1 pin. The other 2 wave forms are of SW1 & VOUT.

0 Amod Vaze over 1 year ago in reply to Asiya Asiya

TI__Mastermind 25060 points

Asiya,

Considering there is no switching, it is likely the IC has potentially damaged. Do you mind sharing the schematic, BOM and layout for this design? Have you custom manufactured or testing this on an EVM? Has the design ever worked before and then stopped working?

Thanks,

Amod

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TPS54294: TPS54294PWP