TPS5402 COMP pin

Mario Avila

Other Parts Discussed in Thread: TPS5402, TPS54040

Hi,

I am designing a buck converter based on TPS5402 chip. By reading the datasheet I don't understand the criteria to choose Rc and Cc values.

It says " Error amplifier output and input to the PWM comparator. Connect frequency compensation components to COMP 6 this pin"

Can someone help me with this issue?

Thank you.

over 9 years ago

0 JohnTucker over 9 years ago

TI__Guru**** 191445 points

They don't really cover that at all in the datasheet do they? The TPS5402 is just current mode control. Are you an experienced dc/dc converter designer? If so you can just design the compensation as you normally would. If not I can possibly help you with it. Let me know your input and output voltage and current requirements. Have you already chosen Cout and Lout?

0 Mario Avila over 9 years ago in reply to JohnTucker

Prodigy 140 points

I have no experience designing dc/dc converter. This is my first design. I dont want you to spend much time with this, so as long as you can provide me a guide to understand this problem it will be fine.

My requeriments are input voltage between 5-24v and fixed output voltage around 4-5v (I am not sure if it can work with 5v input voltage and 5v output voltage) . Output current around 1A its fine.

Basically what I'm designing is the power stage of a battery powered device which should work with either a solar cell or wide voltage DC conection (5-24v)

Thank you.

0 JohnTucker over 9 years ago in reply to Mario Avila

TI__Guru**** 191445 points

I would probably use this document to calculate compensation:
http://www.ti.com/lit/ds/symlink/tps54040.pdf
Start on page 33. Make sure to use the parameters from TPS5402, gmps = 9 A/V, gmea = 92E-6 and vref = 0.8 V.
Let me know if you have problems.

0 Mario Avila over 9 years ago in reply to JohnTucker

Prodigy 140 points

Thank you so much! This application note was really helpful.

I have a last question. Those equations are related with Vout. What happen if Vout is not fixed?

0 JohnTucker over 9 years ago in reply to Mario Avila

TI__Guru**** 191445 points

That's one of the disadvantages of current mode control. The loop response will change with Vout. If your Vout does not change much you can design a circuit that is stable over the range of output voltages. If you need a wide range of adjust ability, you may be better off with voltage mode control.

0 Mario Avila over 9 years ago in reply to JohnTucker

Prodigy 140 points

Thank you again! Very helpful.

Power management

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TPS5402 COMP pin