TPS62140: Using tps62140 to get 1.2V but get 2.0V

vlad listov

Part Number: TPS62140
Other Parts Discussed in Thread: TPS62142,

Using the same resistor divider for tps62140 as in datasheet for 1.2V but get 2.0V (75 kOhm and 150 kOhm). After tps62140 enabled tps62142 (from PG pin of tps62140 to tps62142). From tps62142 get 3.3V exactly. What could be reason?

over 8 years ago

0 vlad listov over 8 years ago

Prodigy 30 points

Connected load 30 Ohm to tps62140 and now output voltage is 1.2V (correct)

0 Chris Glaser over 8 years ago in reply to vlad listov

TI__Guru**** 150930 points

A load is not required to get the correct output voltage. Can you post a waveform of Vin, Vout, and SW when Vout is 2V?

0 vlad listov over 8 years ago in reply to Chris Glaser

Prodigy 30 points

Oscilloscope is not available now. But used multimeter. For Vin 5.57V and 12V (tested with two fixed Vin) the same result Vout = 2V. On SW output voltage increasing from 1.15V to 2V. On FB pin Vfb=1.34V (and due to resistor devider formula it is correct why we have 2V).

But with external load we have Vout=1.2 and Vfb=0.8V as in datasheet (Vref)

0 Chris Glaser over 8 years ago in reply to vlad listov

TI__Guru**** 150930 points

Due to the switching waveforms in any DC/DC converter, we need to use a scope to debug the circuit.

Is this circuit in your system or on its own board by itself? If it's within a system, it is likely that another rail is backfeeding its voltage onto the output. This can be confirmed with a scope.

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TPS62140: Using tps62140 to get 1.2V but get 2.0V