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LMR51610: DCDC power section review

Shashank TS
Prodigy 160 points
Part Number: LMR51610

Tool/software:

Hello,

This design is for a automotive application and Vin would be 29V to 42V, Nominal 36V.

1. Can you please let me know if the below schematic looks ok to Output 5V? 

2. Is it necessary for me to have provision for C5 and C6 as per evaluation board schematics as this occupies more space on the board?

3. What is the significance of C9 here? 

  • 0
    TI__Mastermind 31225 points

    Hi Shashank,

    I think 100uH inductor might be too large for a 1100kHz switching frequency. 10-20uH is actually ok here. 

    You may put C5 and C6 there for additional input capacitance if needed. I would recommend it if you are prototyping since you can remove it later.

    I noticed in the feedback network that you have a 49.9Kohm resistor (R4). Are you planning on taking loop measurements? It is usually recommended to do 49.9 Ohm.

    The datasheet also has values for the feedback network to generate 5V, a top feedback resistor of 118kOhm and bottom of 22.1kOhm is suitable. 

    C9 is adding feedforward capacitance to help improve phase margin if needed. 

    Thanks,

    Richard

  • 0 in reply to Richard Fu22
    Prodigy 160 points

    L1 is 10uH and not 100uH. Can I completely remove R4(Yes I will change to 49.9) if it is not affecting the performance. Additionally, can I remove C9 as well? The reason is to save board space. Also can R6 and R9 be 0402 (1/16W) instead of 0603(1/10W).

  • +1 in reply to Shashank TS
    TI__Mastermind 31225 points

    HI Shashank,

    Sorry, I misread the inductor value. 

    If you are not planning on taking loop measurements, it is ok to remove R4. 

    C9 is also ok to be removed, and R6 & R9 should be ok to use 0402. Just make sure you update R6 value. 

    Thanks,

    Richard