TPS73601DRB Non-deterministic power-up behviour

Peter Watson

We are using the TPS73601DRB on one of our new CMC modules and we are experiencing a power-up behaviour that is not deterministic. See attached scope shots.
Sometimes the Output Voltage (pink) follows the Input Voltage (blue) and sometimes the Output Voltage has a defined power-up ramp as soon as the Input Voltage gets to a caertain level.

What is the reason for this?

over 11 years ago

0 Ryan Eslinger over 11 years ago

TI__Guru 55940 points

Hi Peter,

Would it be possible to share a schematic? It appears that your output actually temporarily exceeds the input voltage slightly on both waveforms. Could you confirm if this is true?

Very Respectfully,

Ryan

0 Peter Watson over 11 years ago in reply to Ryan Eslinger

Prodigy 230 points

The scope shots were taken with the Rotary Selector Switch set to Position 2 (SEL_2.5V)

0 Peter Watson over 11 years ago in reply to Peter Watson

Prodigy 230 points

Attached you find a more detailed scope shot of the power-up behaviour.

0 Ryan Eslinger over 11 years ago in reply to Peter Watson

TI__Guru 55940 points

Hi Peter,

It looks like C43 is a feedforward capacitor. 10uF is extremely large for a feedforward cap (we recommend less than 1uF). Could you remove C43 and retest on another IC?

Very Respectfully,

Ryan

Power management

Power management forum

TPS73601DRB Non-deterministic power-up behviour