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TPS2113: Behaviour in burted GSM environment (2.5A burst current with duty cycle of 12.5%)

Stefan Baumann
Prodigy 70 points
Part Number: TPS2113
Other Parts Discussed in Thread: TPS2120,

Hi E2E,

we would like to use the TPS2113 in an environment where IN1 is connected to a DCDC converter (2.5A) and a Li-Ion battery on IN2. The output drives a CPU someperiphals and a GSM modem. This modem draws in transmit mode worst case up to 2.5A for a duty cycle of 12.5%. The overall, with CPU and some other peripherals, current would be 2.7 to 2.8A in transmit mode and 200-300mA in receive mode of the modem.

I've checked the datasheet and on average we neither hit the 1.25A current limit nor the dissipation ratings.

  1. Can you recommend this part for those operationg conditions?
  2. Anything else to consider if we want to use this part in this environment, like setting the Ilim correctly?
  3. The figure for "Current limit settling time" suggests that 577us should not be a problem, correct?
  4. I've already checked some other devices from your portfolio, but e.g. the Iq of the TPS2120 is too high. Any other solution you can propose?

Thanks and best regards

Stefan

  • 0
    TI__Genius 10855 points

    Hi Stefan, 

    Thanks for reaching out on E2E!

    I'm not quite sure I understand the message: "I've checked the datasheet and on average we neither hit the 1.25A current limit nor the dissipation ratings." Could you help clarify my understanding of the application:

    • What is the duration of the 2.5A event? How long will it last for?
    • You can calculate the correct resistor setting by using the equation: 500 / RILIM

    Thanks,

    Arthur Huang

  • 0 in reply to Alpha H
    Prodigy 70 points

    Hi Arthur,

    in the meantime I've noted that you haven an improved version of the TPS2113 which is called TPS2113A which has a current limit of 2A (in SON-8 package). So please ignore my comment about the "hit the 1.25A current limit". It is actually 2.0A for the TPS2113A

    Our application is: we have an GSM modem after the TPS2113 which draws periodically up to 2.8A for 577us and then 0.3A for 4ms (the duty cycle is 12.5%). 

    Is the TPS2133 still suited for this application where the peak currenct exceeds the specification, but the average current does not? (That what I meant with "on average we don't hit the 1.25A current limit")

    I guess I have to adjust then the current limit beyond the specification, but the formula 500/RILIM still holds? So if I want to set the current limit to 3.0A I'll use RIlim=167Ohm. I'm asking because this limit and resistor setting is exceeding the specification.

    Hope this helped to clarify things

    Stefan

  • 0 in reply to Stefan Baumann
    TI__Genius 10855 points

    Hi Stefan, 

    Yes, this configuration should be ok. The TPS2113ADRB package can support 2.5A continuous as long as the Tj is below 105C, so there shouldn't be an issue with running the device at 2.8A for a short 577uS duration. 

    You are correct, the RILIM equation still holds. Keep in mind that the RILIM equation has some hysteresis in the accuracy.

    Thanks,

    Arthur

  • 0 in reply to Alpha H
    Prodigy 70 points

    Hi Arthur,

    thanks for resolving this.

    Have fun

    Stefan