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TPS4361 doesn't step up under 20V and BQ24610 with low output

Ran Aloni
Expert 2386 points
Other Parts Discussed in Thread: BQ24610, TPS43061

Dear all,

I attached a schematics of a PCB we made recently.

this sch has 2 tiers.

first tier is stepping up (TPS4361) inputs from 12V to 23V to 25V, and second tier is a charger (BQ24610), which charges in 21.5V.

1st Tier:

only stepping up 20V and up to 25V. when you lower the voltage, the output voltage goes down as well.

2nd Tier:

I'm checking the output with no battery, and I get 1.2V on the output.

I can measure 1.6V on TS pin, so this is not a bad NTC problem.
I applied 24V on Cin (C7,C8), to isolate the step up influence, and still, no output.

please tell me if anymore measurements and data are needed.

any suggestions?

best regards,

input & charge A6.pdf
  • 0
    Expert 2386 points

    Dear all,

    attached my PCB layout as well,
    I went through trace by trace, matches schematics.

    few thoughts:

    1. ACN-ACP pins are shorted together, in the EVM they are also connected to VCC.
      other them BATFET operation (which is not used here), don't see any meaning, do you?
    2. layout: Cout, M1, M2 are close to one another, but far from the TPS43061, can this cause bat step up operation?

    any more suggestions? I'm kind of lost on why the BQ24610 doesn't work...

    thanks for any assistance...

    Solarian A5 Layout Design(v2.0).zip
  • 0 in reply to Ran Aloni
    Expert 2386 points

    Dear all,

    few things I noticed.

    1)TPS43061: my EN PIN is attached to Vin. from what I understood, as long as it is above 1.2V and under 38V, chip should be enabled. so don't see a problem here as well, right?

    2) I have a problem that my step up Iout is 2A and the Icharge of the BQ24610 is 3A.
    I will need to either lower I charge by changing ISET1 to be 1A or replacing the Iout by changing R6,R7 to 8mOhm each, giving a 3A/4A support.
    any way, I tested the circuit with no battery attached, which means that I at least need to see 25V after the step up with no Load.

    3) I disconnected L1, in order to separate the tier, and supplies 25V across Cin.
    still I get ~0.7V on the charger IC outputs with no battery connected.

    kindly waiting for your reply,

    Ran Aloni

  • 0 in reply to Ran Aloni
    Expert 2386 points

    Dear all,

    Step up:

    1. by reducing the Rsense to 5 Ohm (Iout 4.3A), I'm able to get better results, since the initial charging of Cout requires more more current than the design 2.2A.
    2. EN pin is connected to Vin, it should be connected to a resistor divider to over come start-up issues.

    charger:

    here lies the big mystery:

    my STAT2 pin is on as soon as I insert an input, even if my battery is not present.

    can anyone suggest an explanation on why this could be, other than IC malfunction?

    this happens on 3 different PCBs.

    regards,

  • 0 in reply to Ran Aloni
    Expert 2386 points

    Dear all,

    I kindly request your assistance.


    many thanks,