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TPS552892-Q1: Buck-Boost Converter Schematic Review

Jackson Werner
Prodigy 10 points
Part Number: TPS552892-Q1

Tool/software:

Hello, I'm a student completing my first buck-boost converter design. My specs are as follows:

Vin = 10-19 V

Vout = 12V

I(max) = 5A

Before I ordered my PCB, I wanted to verify a few things I had questions on:

1. Is the resistor + capacitor at the COMP pin adequate? This is what the Webench circuit designer created for me, but other schematics I have found online have higher resistance values as well as a capacitor in parallel with the series RC.

2. Do I need a snubber circuit on each side of the inductor?

3. Is the output capacitance adequate for a switching frequency of about 400 kHz? I want ripple to be as minimal as possible.

4. Does the DITH/SYNC pin require a capacitor between it and GND?

Please let me know if anything else about the schematic looks off. Thank you!

  • 0
    TI__Genius 14950 points

    Hi Jackson,

    Thank you for reaching out. Below is my comments.

    1. Recommend to add one E-CAP in input side to stabilize input voltage.

    2. Recommend to use >16 rated voltage cap for C3 to ensure 2uF effective capacitance with 5V DC bias.

    Jackson Werner said:
    1. Is the resistor + capacitor at the COMP pin adequate? This is what the Webench circuit designer created for me, but other schematics I have found online have higher resistance values as well as a capacitor in parallel with the series RC.

    Can you provide part number of output caps for me to check effective capacitance and ESR? Need these parameters to calculate compensation parameters.

    Jackson Werner said:
    2. Do I need a snubber circuit on each side of the inductor?

    Yes, recommend to add RC snubber in SW1 and SW2. 2.2nF+2.2ohm(1206).

    Jackson Werner said:
    3. Is the output capacitance adequate for a switching frequency of about 400 kHz? I want ripple to be as minimal as possible.

    I think it is enough.

    Jackson Werner said:
    4. Does the DITH/SYNC pin require a capacitor between it and GND?

    If dithering function is needed, add a 10nF cap here. If it is not needed, just connect to GND.

    Please refer to EVM user guide and layout guideline in homepage.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 10 points

    Thank you for the reply. Here is my updated design:

    Regarding your comments:

    1. Added a 100uF E-CAP on input voltage, the same as the one on output voltage.

    2. C3 is part number 1206B475K500NT, rated for 50V.

    Regarding my questions:

    1. Please feel free to suggest alternate parts that are recommended by TI for any of these.

    Output cap part numbers:

    22uF, COUT1-3: GCM32EL8EF226KE08L

    100nF, CDECOUP: GRM155R71H104ME14D

    100uF,COUT_ELEC, E-CAP: EEH-ZK1V101XP

    47 nF, CCOMP: GRM31M5C1H473JA01L

    300 ohm, RCOMP: ERA3AEB301V

    2. Added snubber circuit.

    Again, thank you for the advice.

  • 0 in reply to Jackson Werner
    TI__Genius 14950 points

    Hi Jackson,

    1.To minimize input power loop, recommend to add a 0402 0.1uF cap in input side.

    2.1206 package for C3 is too large. C3 should be placed close to IC. You can choose a 16V/0805 cap.

    3.Recommended compensation parameters: Rcomp=10kohm, Ccomp=6.8nF, parallel with a CHF=100pF.

    4. Make sure follow layout guideline.

    Regards,

    Mulin