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LMQ61460-Q1: Inverting Buck Boost SCH review

Rocky Chen
Expert 7775 points
Part Number: LMQ61460-Q1
Other Parts Discussed in Thread: LMQ61460

Dear

I proposed LMQ61460 as IBB for customer OLED ELVSS supply. Could you please help review below SCH? Thanks a lot!

Vin 12V, -VOUT -10V

  • 0
    TI__Guru 50120 points

    Hi,

    The schematic connections look correct for converting buck to IBB. More details about this conversion can be seen in this app note (https://www.ti.com/lit/an/snva856a/snva856a.pdf). 

    How much current do you expect for this application? The voltage stress here is well below 36V, but we need to understand if the current is appropriate or not for this conversion.

    Regards,

    Jimmy

  • 0
    TI__Expert 7775 points

    Hi Jimmy

    My customer is doing re-work on EVM. But there is no output, could you help double confirm if LMQ61460 can be used as IBB?

    Detail re-work:

    - Make C1/C2 connected between VIN-12V and VIN-GND.

    - Make EVM-GND as Vout

    - Make EVM-VOUT connected with VIN-GND

  • 0 in reply to Rocky Chen
    TI__Guru 50120 points

    Hi,

    To just get the default EVM working in IBB, you can just add an external electrolytic capacitor 47uF-100uF between input supply (VIN+) and input ground (GND). The supply would then be connected between VIN and VOUT of the EVM. 

    If the connection is correct, the customer should see -5V output. Then the bottom resistor can be adjusted to get the desired -10V output.

    Regards,

    Jimmy