TPS543C20: RAMP resistor value with 2 phase condition

K. Sasaki14

Guru 10200 points

Part Number: TPS543C20

Generally, we use same resistor value for Master and Slave TPS543C20 RAMP pin.

What kind of problem does it occur if different resistor value is set between master and slave?

We would like to know possible phenomena.

Best Regards,
Kohei Sasaki

over 6 years ago

0 JohnTucker over 6 years ago

TI__Guru**** 191445 points

Sasaki-san,
The RAMP resistor sets the internal control loop ramp amplitude. It is used to stabilize the control loop for different output filter L and C values. The master and slave should have the same output filter, so the RAMP value should be the same also. Why are you concerned about the different values? I doubt that we have tried it that way (why would we purposely design it wrong?). I can check about it after the new year further.

0 K. Sasaki14 over 6 years ago in reply to JohnTucker

Guru 10200 points

John-san,

Thank you for your answer.

We understand master and slave should have same RAMP resistor value. However our customer forgot to change slave RAMP resistor when they adjusted master RAMP resistor value.

So they would like to know the influence that master RAMP resistor value is different from slave RAMP resistor value.

Please check further. We would like to know possible phenomena which may occur when master and slave have different RAMP resistor value.

Best Regards,
Kohei Sasaki

0 JohnTucker over 6 years ago in reply to K. Sasaki14

TI__Guru**** 191445 points

Sasaki-san,

We will look into it next week after the holiday.

0 K. Sasaki14 over 6 years ago in reply to JohnTucker

Guru 10200 points

John-san,

How is the progress for this post?

Best Regards,
Kohei Sasaki

0 JohnTucker over 6 years ago in reply to K. Sasaki14

TI__Guru**** 191445 points

Sasaki-san,

Kit from our team will respond later today.

0 K. Sasaki14 over 6 years ago in reply to JohnTucker

Guru 10200 points

Kit-san,

Sorry for pushing you.
Could you give me answer for my post?

Best Regards,
Kohei Sasaki

0 Henry Nguyen over 6 years ago in reply to K. Sasaki14

TI__Intellectual 2460 points

Hi Sasaki,
The resistor value at RAMP pin needs to be the same for both master and slave. The tolerance resistor values are in that excel design tool that I sent to you. The VSHARE is the control voltage for both master and slave. The RAMP signal in each device will intersect the VSHARE signal to command the duty cycle. If the RAMP resistor are different, the duty cycle and current balance will be different.
Kit

Power management

Power management forum

TPS543C20: RAMP resistor value with 2 phase condition