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TPS61022: mass product problem

Grigory Vaulin
Prodigy 40 points
Part Number: TPS61022

Hi,

we have mass problem with TPS61022 used with supercap.

Output load 5V, 500mA. Supercap 200F 2,7V. When supercap is charging then boost En is 0V.

First charge supercap and start boost: all ICs from about 500ps functional right and discharge supercap to 0,8-0,9V.

Second charge show: 65% ICs are can not work and output voltage is 0V and ICs is hot. 

Other 35% work right infinity cycles.

Previous manufacture process we had 50% IC  broken but IC was buy not in TI. We thought it was the seller's fault. Now we buy from TI directly and have 65% broken,

For design we used evaluation board and don't have problem with a lot of tests.

  • 0
    TI__Mastermind 34231 points

    Hi Vaulin,

    In order to quickly find out the root cause, can you share the schematic and layout? For dc/dc high switching frequency, high current boost converter, the layout is an important step.

    For design we used evaluation board and don't have problem with a lot of tests. Here do you mean the TI's EVM?

  • 0 in reply to Zack Liu
    Prodigy 40 points

    schematic and gerbers in attached file. DKST 51.20.2 DOCS TI 04_2020.zip

  • 0 in reply to Grigory Vaulin
    TI__Mastermind 34231 points

    Hi Grigory,

    Thanks for the shared schematic and layout.

    It's quite strange that the first charge all IC are functional but second charge part of IC not working. If this relates to the boost converter, the problem should shows up at first charge. 

    For the schematic and layout, below are my comments:

    1. The 2.2uF ceramic capacitor C11 is suggested to be placed close to TPS61022 Vin pin to filter noise. This is just a suggestion but may not be the root cause. Please fix it in next version layout.

    2. For a single super capacitor application, as the super capacitor voltage decreases from 2.7V down to 0.8V until triggering TPS61022 switch current limit, TI suggest add a feedforward capacitor in parallel with upper feedback resistor R14. Otherwise there is loop stability problem.

    3. What's the inductor L1 saturation current spec? TPS61022 employs valley switch current limit 8 A typically. The chosen inductor saturation current spec is better higher than 10A. 

    Below is the tips of debugging:

    1. Firstly make sure during the second charge, the board other circuits are working correctly. No over voltage happens and applied at TPS61022 pins.

    2. Like the 2nd comments, Solder R17 with a 2kohm resistor, Solder T6 with a 1nF feedforward capacitor. So that the zero frequency (fFFZ) is around 2kHz. 

    3. Try to capture the key waveform during the second charge, for example, high voltage at Vout pin, Vin pin. 

  • 0 in reply to Zack Liu
    Prodigy 40 points

    Hi,

    inductor L1 is VLS5045EX-1R0N

    R17 and CAP in process.

  • 0 in reply to Grigory Vaulin
    TI__Mastermind 34231 points

    Hi Grigory,

    Thanks. Let me know if there is new finding on bench.

  • 0 in reply to Zack Liu
    Prodigy 40 points

    Solder R17 with a 2kohm resistor, Solder T6 with a 1nF feedforward capacitor. - SOLVED PROBLEM

    Thank you.