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TPS65910: Backup Battery Charger

Angelo Bertuletti
Prodigy 110 points
Part Number: TPS65910

Hi,

I want to connect a superCap of 0.22F 5.5V (p/n FGH0H224ZF) to the pin VBACKUP of the TPS65910A3A1RSLR.

At page 19 of the datasheet i read the *(1) Note:

• BBSEL = 10, 00, or 01 intended to charge battery or superCap

• BBSEL = 11 intended to charge capacitor

In my application VCC7 is a regulated voltage at +5.0V and I want to charge the superCap at 5V (BBSEL[1:0] = 11 : VBAT).

According to the previous note, it's better to not connect a superCap on the pin VBACKUP, because is selected BBSEL=11. Why?

The superCap that I have selected is compatible with the output voltage of 5.0V.

Best regards,

Angelo

  • 0
    TI__Mastermind 30280 points

    It is common for SuperCaps to have a maximum voltage of 2.5-2.7V, so it would be ideal to select BBSEL[1:0] = 01 : 2.52 V which would be similar to a re-chargeable Li-Ion coin cell.

    From this website, "All capacitors have voltage limits. While the electrostatic capacitor can be made to withstand high volts, the supercapacitor is confined to 2.5–2.7V. Voltages of 2.8V and higher are possible, but at a reduce service life. To get higher voltages, several supercapacitors are connected in series."

    Maybe the SuperCap you have selected is actually multiple SuperCaps in series to increase max voltage and multiple SuperCaps in parallel to increase overall capactiance. I cannot say without knowing the part # of the SuperCap that is being used. Either way, you will need to test with the TPS65910 to verify the performance meets your expectations and does not cause damage.

    You can use the TPS65910A3EVM-583 to evaluate the performance of the PMIC and SuperCap for your system.

  • 0 in reply to Brian Berner
    Prodigy 110 points

    Thank you Brian for your prompt reply.

    I understand that the note in the datasheet is a simple warning, that highlight to pay attention to the electrical characteristics of the superCap.

    If the superCap is compatible there aren't other reasons to not use it with BBSEL = 11... of course I will check the performance of the superCap with the TPS65910.

    FYI the p/n of the superCap is FGH0H224ZF.

    Thank you again and best regards,

    Angelo

  • 0 in reply to Angelo Bertuletti
    TI__Mastermind 30280 points

    Angelo,

    Indeed. I see FGH0H224ZF is of the -OH type in the datasheet, where -OH indicates a Maximum Operating Voltage of 5.5VDC.

    As a result, it seems OK to set  BBSEL = 11b if the input voltage, VCC7 (or VBAT) is <= 5.5V

    For the most part, I would say that battery & SuperCap chemistries are continuously improving and the maximum charge voltage/current is increasing at a rate faster than most PMICs and this is the reason for the somewhat misleading statement in the datasheet.

    Just to be sure that your system will work, I still recommend using a TPS65910A3EVM-583, connecting your SuperCap to VBACKUP and evaluating your implementation before building the PCB.