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LMR54410: LMR54410DBVR dropout ?

Robert Walker1
Prodigy 80 points
Part Number: LMR54410
Other Parts Discussed in Thread: LMR51420, TPS62932, TPS62933, TPS62933EVM, TPS54202

Can you help please with the drop out in our case for a 11.38V in, what output can we set for at 1A ?

 

Comparing

TI LMR54410DBVR (45V, 1A, 1.1MHz FPWM, SOT23-6 (2.9x1.6mm), Sync, 240mR) (P2P with LMR14010A 1A Sync, or LMR50410 1A Sync

To Diodes AP632000  (32V, 2A, 500KHz FPWM, TSOT26 (3.0x2.8mm), Sync, 125mR)

 

Yes, I know its 1A vs 2A

 

BUT, Dropout is a consideration

We have 12V AC supply, through a Bridge of 2 x MBR230S1F-7 = 0.31V @1A, so Vin is 11.38V

LMR54410DBVR dropout seems to be 0.7V @ 1A

So if we add a LMR54410DBVR 0.7V, we have effective Vrail of 11.38-0.7= 10.68V

 

TI graphe here:       vs Diodes

Diodes AP632000   Below seems to suggest that we would have 5.18V out for a 5.0V in ?  so no dropout at all ?

 

 

  • 0
    TI__Mastermind 27030 points

    HI

    the dropout formular will be around (Vin-Io*Rdson_H)*Dmax-Rdson_L*Io*(1-Dmax)-Rdcr_L*Io

    so AP63200 rdson is 125mohm, even we think  it is 100% duty and no voltage dropout at inductor , it at leas have 125mohm*2A=0.25V dropout. so I think for AP63200 dropout curve, Vin is not 5.18V, it should be larger than 5.5V. 

    for LMR54410, Rdson is 450mohm, max duty is around 98.7%, the output at 11.38V Vin will be around 10.77V without voltage dropout at inductor.

    Thanks



  • 0 in reply to Daniel Li14
    Prodigy 80 points

    yep, 0.61V is too high dropout

    What about Ti TPS62932 ? (– Integrated 76-mΩ and 32-mΩ MOSFETs) so low side is 32mR ? 98% duty cycle, so dropout is ?

  • 0 in reply to Robert Walker1
    TI__Mastermind 27030 points

    HI:

    if you want to lower dropout, Rdson will be key, so I will suggest use LMR51420, which rdson is around 120mohm.  similar with  AP63200

    for TPS62932, let me forward to other colleague for answering your question. 

  • 0 in reply to Daniel Li14
    TI__Genius 15247 points

    Hi Robert,

    I'm the MVB team AE who supports TPS62933/2. As you care about TPS6293x low drop-out application, I have below TPS62933EVM test results for your reference, condition: 15Vin-Set15Vout.

    Vin

    Iout

    Vout

    15.000V

    2A

    14.225V

    15.000V

    0A

    14.539V

    Besides, our MVB team have other 2A part could support 100% duty cycle, like TPS54202.

    Let me know whether TPS62932 or TPS54202 could meet your requirement.

  • 0 in reply to Daniel Li14
    Prodigy 80 points

    Thanks, what is the dropout then for the TPS54202. with 11.38V in and 1A drawn?

    Diodes is Vo ~ Vin - 0.125 – DCR – any connection losses, for 1A load.

    DCR of the internal FET (AP632000 rdson is 125mohm), And loss is I2R, So FET = 1x1*0.125=0.125V

    External inductor, assume 1 of our existing IND: (IND, Choke,10Uh /1.6A/4020/+-20%/0.165R, VDB4020-100M) 

    So 0.165R, VDB4020-100M, so I2R = 1x1*0.165=0.165V 

    So VOUT = 11.38-0.125-0.165=11.09V, so only 0.29V

    is TI TPS54202 the same ?

  • 0 in reply to Robert Walker1
    TI__Genius 15247 points

    Hi Robert,

    I think your estimation is right.

    One thing I want to bring up is that because long time high-side FET turned on, low-side FET turned off, boot cap is always discharged and cannot be charged. The boot cap voltage will trigger UV threshold (2.1V) finally. Then low-side FET will be forced to turn on to charge boot cap. So you still could see switching pulses at 100% duty operation. Below is a TPS54202 waveform for your reference. Condition: 5Vin-Set5Vout-0A

    (Yellow: Vin (overlaid by Vout); Blue: Vout; Pink: SW; Green: IL)