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TPS2116: Power switching with a drooping DC-DC and battery

Part Number: TPS2116
Other Parts Discussed in Thread: UCC28911, TPS63802,


We are looking to power a device with GSM modem which takes 2A peak current for 0.6 us every 4.6 ms whenever it is communicating (2-3s). The two power sources that we are considering for this application are a buck DC-DC converter such as UCC28911 (70V Vin and 5V out with 0.5A max) and a Li-Ion battery (4.2-3.2V, 3.8V nominal). These two sources are to be selected automatically with DC-DC as higher priority. The output of the PPM is given to a buck-boost TPS63802 to give a stable 4V for GSM module. This is as shown in block diagram below.

Some questions:

1. What is the Vout drooping characteristics of UCC28911 when it is overloaded?

2. Based on this drooping of Vout and battery power path being enabled, how would TPS2116 hysteresis react in the 0.6 ms 2A current draw duration?

3. Would the two power paths come to an equilibrium to share power to the buck-boost regulator?

4. Any other issues possible with this configuration?

Thanks and regards, Prithvi

  • Hi Prithvi,

    1. I cannot comment on the UCC28911 as this is not a Power Switch device. I recommend you make a similar post only about UCC28911 so that the responsible team will be able to help quickly. I could move this thread over but I assume that you may have follow up queries on TPS2116.

    2. Depending on the priority set, TPS2116 can either keep passing the BUCK source or could switch over to the battery. I think the switching in this case would be undesirable and so I would recommend that the priority selection be set up in such a way that allows for these droops to pass without issue. If the voltage were to go lower than these droops, then it would be a fault condition and only then would switchover be necessary.

    3. No. PowerMUXes do not allow for two sources to simultaneously power one output. They will only pas one source to the output at any given time.

    4. I do not expect other issues to come about with this configuration. TPS2116 can be used in many back up systems as this. Feel free to ask further questions if required or if there are any issues down the line with this system.