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TPS65070: Ripple in TPS65070 step-down converters

Madhu Wesly
Intellectual 280 points
Part Number: TPS65070
Other Parts Discussed in Thread: , BQ24079, TPS65263

Hello,

I would like to use TPS65070 in my application. My application requires 2A current @3.5V for every 5mins, and that I want to provide it from DCDC2 of TPS65070. But, the maximum output current of the DCDC2 is 1.5A(given in datasheet under min. current rating column).

My doubts are:

1. Will there be an increase in ripple(or Noise) value at output supply when the load takes Surge current of 2A??

2. Will there be a huge impact in the efficiency of the DCDC2 converter in the TPS65070 PMIC when the load is taking 2A surge current??

3. If there will be an increase in ripple/noise, how to avoid/mitigate it??

Thanks in advance.

  • 0
    TI__Expert 8730 points
    Hi,

    DCDC2 has a forward current limit of 2.1A (min) and considering the inductor ripple current, at 2A load current, device may be already in current limit and hence it may not work. However, i have forwarded your request to application expert of this device and he will get back to you if he has more information on this.

    Regards,

    Murthy
  • 0 in reply to Krishnamurthy Hegde
    Intellectual 280 points

    Hi Murthy,

    Thanks for the quick reply.
    Actually,  the mentioned load current is "Not continuous load current", the load takes surge current of 2A with a duration of around 300msec once in every 5mins.

    How about if I choose the Inductor at DCDC2 with maximum DC current 2A(As I required 2A surge)??

    My fundamental doubt is: In general, will there be any increase in ripple(or Noise) value at output voltage when the load takes Surge current of 2A in this case??

    Thanks in advance.

  • 0 in reply to Madhu Wesly
    TI__Mastermind 30260 points
    Madhu,

    As my colleague mentioned, the TPS65070 device might reach the 2.1A forward limit of the FET before the output of 2A is reached by the output. The current through the inductor will be higher than the output.

    Before considering your follow-up questions, you will need to determine if the DC-DC converter shuts itself off when the surge occurs. The only way to test this is on the TPS65070EVM-430 board. You will need to evaluate the device to see if it meets the needs of your application.

    In addition, the answer to your follow-up questions can only be answered by testing on the EVM, as this load current is outside of the spec. Although it is possible for you to test the TPS65070, it does not sound like the best fit.

    You might want to consider an externally configurable PMU and a discrete battery charger to solve your problem.
    I would recommend the TPS65263 as the PMU, and you can select the battery charger based on your battery chemistry and required charging current. The BQ24079 is a 1.5A battery charger with Power Path management that will charge the battery to 4.1V, but there are many solutions to choose from.
  • 0 in reply to Brian Berner
    Intellectual 280 points
    Thank you very much for the alternate and good solution.