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TPS62742: TPS62742 overcurrent behaviour

Tino Siebensohn
Prodigy 30 points
Part Number: TPS62742
Other Parts Discussed in Thread: LM3671, , TPS62801, TPS62080, TPS62800EVM-892, TPS62802

Hello,

i'am looking for a Buck Converter with ultralow quiecent current.

The device i want to power in my application draws approx 150mA average. There are current spikes of 500mA for a few milliseconds (max 20ms / duty less than 1%) during RX activity.

At the moment iam using the LM3671 which can supply up to 600mA but draws 16uA quiecent current :( 

So here are my questions:

What will happen if i draw 500mAmps from the TPS62742 in a very short period of time? The efficency is not relevant in that moment.

Is it possible that the output transistor gets damaged due to the high induction voltage or the current? Usually i suppose there may be a output voltage drop only.

Do you have an alternative ultralow quiecent current IC? Unfortunately a "shutdown" is not an option in my application.

Kind regards

Tino

  • 0
    TI__Guru*** 146450 points
    Hi Tino,

    The TPS62742 (and most all devices) have built-in current limit circuits that limit the inductor current (and this the output current) to safe levels. If you try to draw more current than this, the output voltage will drop.

    20 msec is quite a long time for an IC which switches above 1 MHz. So, you should expect to enter current limit in this case. You need a higher power device.

    What Vout do you need? We have TPS62801 which supports 1A and TPS62080 which has a snooze mode for lowest Iq.
  • 0 in reply to Chris Glaser
    Prodigy 30 points

    Hi Chris,

    thank you for your reply.

    I don't know why i igored the TPS62801 so far. Looks like a decent solution, except the package, which is not hand solderable during evaluation.

    There is a Application board TPS62800EVM-892 available, but i can't find a distributor with that in stock. You may have an advice for me?

    Regards

    Tino

  • 0 in reply to Tino Siebensohn
    TI__Guru*** 146450 points
    Hi Tino,

    What Vout do you need? Per the TPS62801 D/S, this family only supports certain Vout ranges.

    You can click 'request' on the page here to request the EVM: www.ti.com/.../tps62800evm-892
  • 0 in reply to Chris Glaser
    Prodigy 30 points

    Hey Chris,

    thank you for that advice. The TPS62801 has a max output voltage of 1,55V. My device needs a voltage of 2,8 :(

    So i have to wait for the TPS62802. Like described in the datasheet the device is still under developement.

    Can you give me something like a quatiation when this device is available?

    I did some tests with the LM3671 as 2,8V and as ajustable version. Looks good so far. But i didnt know that Buck converters create such noise. Even with approx 40uF effective capacity at input and output. The only tradeof for me is the relative high quiecent current of approx 18uA. This is 4 times Higher than the driven device itself in sleep mode.

    I Will put the Layout of the TPS62802 also on my board so i can change that later.

    Regards

    Tino

  • 0 in reply to Tino Siebensohn
    TI__Guru*** 146450 points
    Hi Tino,

    Thanks for confirming your Vout. Yes, TPS62802 will work for you. Can you handle the 0.35mm pitch in your production facility?