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TPS61094: Using TPS61094 in parallel mode

Christian Schuler
Prodigy 80 points
Part Number: TPS61094
Other Parts Discussed in Thread: LM66100

Tool/software:

Hi TI Team,

we are already using the TPS61094 in an application.
Now, we have the requirement, to generate a higher power output in backup mode (boost operation).

Requirements for Backup Mode:

Output voltage: 4.5V
Output current: 500 mA

We want to use only one SuperCap, due to size limitations and costs.

I'm curious to know, if it is possible to connect directly two or even three TPS61094 in parallel on the VOUT?

Due to slightly differnces in the VOUT voltage, is there a reverse current to expect?

Should both TPS61094 be decoupled with an ORing (ideal diode e.g. LM66100)?

Since the TPS61094 doesn't have a FB input, that can be shared, only OSEL could be set equal.

Should OSEL be connected to the same resistor, if running in parallel? I don't think so...

Thanks for your answer in advance,
Christian

  • 0
    TI__Genius 10105 points

    Hi Christian,

    Thanks for reaching out.

    As for your questions, I don't think ORing is needed here, because I think you want two TPS61094 output power at the same time instead of choosing one of them to output.

    OSEL I think it is not necessary to connect to the same resistor, but TI suggests that the setting resistance accuracy must be 1%.

    About the reverse current, I am not very sure, I think there may be a reverse current but the risk should not be high. For example, if you set OSEL at 3.6V, due to the 

    2% voltage accuracy, it means maybe you have 3.672V and 3.528V two different voltage at worst case. 

    Looking at the operation condition of different modes, the threshold is target Vout+100mV, but the voltage difference may be larger than 100mV at worst case, so it means maybe one device is in Boost mode and the other one is in Buck charge mode. But it is in worst case, the risk should be low.

    Anyway, TPS61094 is not designed for parallel output and we don't have any test result, maybe it can support or will have any potential problem that we don't know.

    We recommend to have try with EVM and make some test at first, especially test the condition when VIN is very close to VOUT.

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 80 points

    Thanks for your feedback and thougths.

    We are using 1% resistors in general, no problem on this point. I think in TPS61094 output setting is not analog controlled by the OSEL, since it is just read in at startup and then latched.

    Tha'ts exactly my point, that the 100mV threshold is quite tight, if the tolerance of the outputvoltages will go to the limits.

    Unfortunately a low risk is still a risk. Testing in the factory for exaclty figuring out this "bad" condition is unacceptable. So, it simply must work in all scenarios, even the worst cases.

    Since VIN will be not present in the power backup scenario, the TPS61094 should not switch at all to "buck mode".

    I will give it a try and will test with all the tolerance.

    The TPS61094 is really one of the best integrated SuperCap Solution ICs I could found, also with a great price.

    Once I'm done, I will come back and share my results.

    Regards,
    Christian

  • 0 in reply to Christian Schuler
    TI__Genius 10105 points

    Hi Christian,

    Ok, understand, waiting for your test results.

    Regards,

    Nathan