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Original question:

TPS61022: Device gets shorted very frequently.

TPS61022: IC burned at around 3A output

Haipeng ZHANG
Prodigy 40 points
Part Number: TPS61022

Hello,

We are using TPS61022RWUR to generate 5A@5.1V output. While using DC electronic load to test the output regulation we found that the IC burned at around 3A. It works fine at 1A. Here are the schematic and layout of our TPS61022. We tested two PCB and they all burned. Do you have any clue?

Thank you .

  • 0
    Prodigy 40 points

    We observed with binoscopes the SW pin is completely burned

  • 0 in reply to Haipeng ZHANG
    TI__Mastermind 34231 points

    Hi Haipeng,

    1. We don't recommend customer use thermal relief pattern in layout. 

    The thermal relief pattern in below picture increases the PCB parasitic inductance and resistance, which cause high spikes at SW pin and Vout pin. Higher load current makes the spikes higher at SW pin until the lower switch burns because of EOS. Please remove the thermal relief pattern.

    2. What's the input source VBAT range? If it's a li-ion battery, TPS61022 cannot output 5.1V/5A because of switch current limit would be triggered.

  • 0 in reply to Zack Liu
    Prodigy 40 points

    Hi Zack,

    We are using a 2600mAh Li-ion battery(MPN: ICR18650-26J, Manufacturer: Samsung).

    Could you please explain to us why TPS61022 cannot output 5.1V/5A using li-ion battery as input? In the datasheet of TPS61022 Vin range is 0.5-5.5V which allows us to use Li-ion battery as input, no? 

  • 0 in reply to Haipeng ZHANG
    TI__Mastermind 34231 points

    Hi Haipeng,

    Main reason is not the input voltage, but the maximum output current of 5A.

    The 2600mAh Li-ion battery operating voltage range is 3.0V to 4.2V. The total output power is 5.1A * 5V =25.5W. Assume the efficiency is 90% at full load. The input average current at minimum Vin can be calculated with equation: 25.5W/90%/3.0V=9.44A .That's too big for TPS61022 because the valley current minimum spec is 6.5A. 

    In another word, when Li-ion battery decreases below 3.6V, the switch current limit may be triggered. 

    So want to confirm with you, would you hope a constant 25.5W output power for the whole Li-ion battery range?

  • 0 in reply to Zack Liu
    Prodigy 40 points

    No, we draw 5A at 34kHz, 20% duty cycle within a wave train 500ms/1s.

    At one case, we are drawing 3A using electronic load. The input in this case is power supply(set to 3.7V). The total output power is then 3A * 5.1V = 15.3W, take 90% as effeiciency then the current at input is 15.3W/90%/3.7V = 4.6A, the switch current limit is not triggered but the TPS61022 burned with fire.

  • 0 in reply to Haipeng ZHANG
    TI__Mastermind 34231 points

    Hi Haipeng,

    In this case that should be fine. The average load current is 5A*20%=1A. 

    The root cause of IC burn is the layout as I said in previous email. We did see similar customer's failure cases. Please don't use thermal relief pattern and follow the datasheet layout guideline.