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TPS40322: [TPS40332]TPS40322 no output issue

HAN LEE
Expert 1515 points
Part Number: TPS40322

Hi all,

Good day, i though i met something abnormal at EN1/SS1 pin,as figures below,is there anything that we should pay special attention to? thanks.

Can you help to review TPS40322 schematic  and give your comments?thanks.

Vin :    12V  （typical）

Vout ： 5V

Iout(max) : 40A

 

CH1:EN1/SS1 ,no load test

VDD & UVLO waveform

CH1:VDD , CH2:UVLO

CH1:HDRV1 , CH2:LDRV1

CH1:HDRV1 , CH2:LDRV1

CH2:Vout

CH1:ILIM1 CH2:FB1

SCH file,

  • 0
    TI__Mastermind 24075 points

    Hi Han,

    What's Vout? If Vout is 1.2V, the resistor divider  (R621 and R622) values are not correct.

    Vout net is +5VI, VSNS is connected to +5VRS. What is +5VRS?

    Based on R638 and R639 values, the UVLO voltage should be around 1.56V when Vin is 12V, but your waveform shows UVLO voltage is 4V.

    Can you double check?

    Also, can you check if BP6 voltage is normal, if boot capacitor (C604 and C605) values are correct?

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Expert 1515 points

    Hi Qian,

    Sorry , I revise Vout for 5V.

    BTW, R639 was revise to 38.2K, then UVLO is 3.5V  

    BP6 is 7.1V,the figure as  follows


    +5VRS is remote sense on main board ，but we are testing PCB card so R643 change to R646，R648 change to R649,thanks.

  • 0 in reply to HAN LEE
    TI__Mastermind 24075 points

    Hi Han,

    FB1 voltage is abnormal. Why there is around 80mV DC voltage.

    Can you check DIFFO1 waveform? Also, can you provide SW1 and SW2 waveform?

    The schematic looks fine. I suspect the problem is related to BOM error or layout. Can you check if AGND and PGND is shorted?

    Btw, when R639 is 38.2k, Vin turn-on threshold is 1.25V*(38.2k+100k)/38.2k=4.52V. This is not reasonable, because Vin turn-on threshold should be higher than Vout with some margin.

    Thanks

    Qian