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LMR33640: schematic review

Feeney Xiao
Intellectual 2470 points
Part Number: LMR33640

Hi expert 

could you please help review the schematic of LMR33640, it's used on the STB, the actually output is 12V 2A

the inductor parameter: I sat =10A，I_TEMP=6A,  DCR=44mohm.

  • 0
    TI__Intellectual 2630 points

    Hi Feeney,

    I suggest raising your inductor to 8.2uH or 10uH according to equation 5 in the data sheet.

    Reduce input capacitance to 2x10uF ceramic and 47uF electrolytic, or you may keep 3x10uF ceramic + 68uF electrolytic. Make sure ESR ~100 mOhms for input dampening.

    I'd suggest adding a feedforward capacitor DNP parallel to R_fbt. You can populate it at a later time. Also use the recommended resistor network R_fbt = 100k Ohms and R_fbb = 9.09k Ohms, as it is common practice not to use R > 100k.

    Cvcc can be reduced to 6.3-10V rating instead of 50V. 

    A capacitor at the EN pin may interfere with proper dropout of the device, so would suggest to remove or DNP C7P53

    Best,

    Ryan