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LM5148: LM5148RGYR schematics review

Kevin Huang8
Genius 5211 points

Part Number: LM5148
Other Parts Discussed in Thread: LM61460, LM25148, LM65680

Hi 

Please help review LM5148RGYR schmatics.

Input voltage: 9~36V
Output voltage: 14.6V
OCP setting: 7A

M820Pro_RA2_mmWave_power.pdf 

  • 0
    TI__Guru* 87657 points

    Hi Kevin,

    Send on a completed quickstart file for this.

    Given the Vin-max here, you can use the LM25148 42V version. Even better, consider using a converter with integrated FETs, e.g. LM65680 65V/6A converter. LM61460 36V/6A would work here as well if 36V input rating is deemed adequate.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    TI__Guru* 87657 points

    Some comments on the schematic:

    1. Remove the resistor on the VOUT sense line - we can't have resistance here, as the bias current will affect the current sense.
    2. Same for LO - never a resistance here.
    3. No need for the gate resistor on HO either - just use the resistor in series with the boot cap to slow the turn on if needed. As this is a 5V gate driver, you shouldn't need to slow it down (assuming the layout is good).
    4. Add more ceramic output capacitance to reduce the effective ESR. In fact, 3-4pcs of 22uF/25V is ideal here - no need for the electrolytic.
    5. Make sure the FET is logic-level gate drive (Rdson rated at Vgs = 4.5V).
    6. Boot cap of 100nF should be fine. 4.7uF on VCC is better
    7. Any input filter for EMI? If so, add an electrolytic damping cap as well.