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TPS2561: TPS2561: USB load on OUT1, loading on OUT2 as well

ANANTHA PADMANABHA
Prodigy 80 points
Part Number: TPS2561
Other Parts Discussed in Thread: TPS2513,

Dear All,

We are using TPS2561 on one of our USB charging  product along with TPS2513 DCP chip. As per datasheet 2.8A  can be load per independent channel. Hope we can use independent channel for individual 2A load. 

But observed USB load on on channel/ OUT1, shows loading on 2nd channel / OUT2 ( even though nothing is connected on OUT2 port) & Vice versa

Example: 1.5A of USB resistive load on channel1 /Out1 shows output voltage of 4.772V with input supply of 5.2V  ( Later I wl increase input voltage to 5.5V n check), but  why Channel 2 / OUT2 output voltage is loading to 4.685V without connecting any load on OUT2 port? & Vice versa

Kindly note: Current limit resistor (ILIM) used as 28Kohm as per datasheet for 2A load.

Can somebody provide valuable feedback on this issue

Thanks & Rgds

Ananth

  • 0
    TI__Expert 8980 points
    Hi, Ananth,

    Those two channel use separated power FET but share same Vin. Could you check if there's Vin drop or power supply current is not enough?

    If you are sure that Vin is above 5V, please attached your schematic and waveform for our analysis.

    Regards,
    Bob
  • 0 in reply to Bob Ma
    Prodigy 80 points

    Dear Bob,

    Thank you for your reply & Sorry for delay in my response.

    As I mentioned on my email above, I have tried with 5.5V supply input & Current limit resistor of 20K ( with 5% tol available with me right now, instead of 1%).

    Yes, there was voltage drop on input side. So I have increased supply voltage to 5.5V from 5.2V. Kindly go thro enclosed file for test report with different load & Schematic for review

    Still there is overloading on channel1 & 2. As per datasheet its 2.8A per channel or 2.8A  per chip.

    Dual Port USB Charger_TPS2561 & TPS2513A_DPUM_A5_v20190114.docx

    Dual port USB Charger readings with load          
                     
    Lab RPS I/P supply @ Conn A/c Inp Cap C5 Top USB port Bottom USB Vbus1 / C2 Vbus2 / C8 Power  Remarks
    in Volts in Volts in Volts Current in Amps Current in Amps in Volts in Volts in Watts Rlim = 20K, 5% (available with us) &
    1 feet Input power cable used.

    Resistive load used
    5.510 5.510 5.510 No Load No Load 5.510 5.510  
    5.510 5.250 5.248 1.000 No Load 5.240 5.180  
    5.510 5.250 5.250 No Load 1.000 5.180 5.240 5.240
    5.510 5.000 4.970 1.000 1.000 4.913 4.900 4.900
    5.510 4.740 4.693 1.500 1.500 4.594 4.594 6.891

    Best Rgds

    Ananth

  • 0 in reply to ANANTHA PADMANABHA
    Prodigy 80 points

    Dear Bob / Hello All,
    Could you please review above schematic page, Tabular column readings & provide your valuable feedback on overloading on channel1 & 2 with 2A load & Rlimit of 20K
    As per datasheet its 2.8A per channel or 2.8A per chip???

  • 0 in reply to ANANTHA PADMANABHA
    TI__Expert 8980 points
    Hi, Ananth,

    I didn't see any problem with TPS2561-Q1, the current is not limited by TPS2561-Q1. If current is limit, the internal powerFET will work at saturation region and Rds will be much bigger than Rds(on) obviously. From your test data, the Rds is very close to Rds(on). (4.693-4.594)/1.5 ~= (4.970-4.913)/1 and it's close to 44mohm Rds(on) in datasheet(Rds from your data is higher than Rds(on) in datasheet is expected because your data include the trace resistance). So I think TPS2561-Q1 current is not limited.

    The Vout voltage drop is obviously caused by Vin voltage drop. Then you need to figure out why there's so much voltage drop on Vin? You can bypass TPS2561-Q1 and connect the same load on Vin connector to see what's wrong.

    Regards,
    Bob
  • 0 in reply to Bob Ma
    TI__Expert 8980 points
    Hi, Ananth,

    Have you get you issue resolved? Because no more reply, I will close this thread for now.
    Feel free to ask any questions.

    Regards,
    Bob