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TPS61020: power consumption issue

Gama D
Intellectual 420 points
Part Number: TPS61025
Other Parts Discussed in Thread: TPS610981, TPS61220, TPS61020

Hi,

I have been using this TPS61025DRCR regulator since last few months. It works fine for weeks and then suddenly starts to consume a lot of power. I cross checked the sch and layout with TI reference design and everything seems good. 

standby current when is working good is around 50uA and after few increases to 33mA. This killed my battery just in few days.

any help will be appreciated.

this is a fixed output version, so the FB line is floating ( as instructed in the datasheet).

  • 0
    TI__Mastermind 46905 points
    do the issue still happen if the TPS61025 is replaced by new IC?
    i don't see ceramic capacitor in the output. could you help to check?
  • 0 in reply to Jasper Li
    Intellectual 420 points

    if i replace with a new IC it will start working again and then do the same thing after 3-4 weeks.

    Yes, i have 10uF, 47uF, 0.1uF ceramic caps on vbat as well as on 3.3V lines.

  • 0 in reply to Gama D
    TI__Mastermind 46905 points
    it seem the device is damaged.
    1. please measure the impedance between the SW pin and GND.
    2. Could you share me the layout image.
    3. what is the input voltage range and output current?
  • 0 in reply to Jasper Li
    Intellectual 420 points

    sorry accidentally clicked resoled my issue.

    1. the impedance is 0.729ohm

    2.

    3. Input voltage is 3V and output current is 50uA.

    I though about device damage as well, but then i built 10 of these and ALL behaved in same way.

    In the layout i made sure traces are as short as possible and they also have filter caps on all power in out lines.

  • 0 in reply to Gama D
    TI__Mastermind 46905 points
    1. if 0.729ohm is the impedance between SW and GND, the device is damaged. you can remove the inductor to further check. (make sure it is not assembly issue)
    2. the layout is not good. the routing between output capacitor and the IC is a little long. you can refer this application note to modify the current PCB and check again. "www.ti.com/.../slva773.pdf"
    3. if the output current is only 50uA, the TPS610981 or TPS61220 is better solution because higher efficiency.
  • 0 in reply to Jasper Li
    Intellectual 420 points
    1. when device is on the impedance is almost 0.
    2. it works for couple of weeks then it fails and its not like it will not produce correct voltage, it will just increase the Device Quiescent Current to 35mA.
    3. 50uA is during sleep mode and during wake mode its 70mA. it sleeps 90% of the time.
  • 0 in reply to Gama D
    TI__Mastermind 46905 points
    1.the input will be much larger than 35mA if the impedance is almost 0. So i think your measurement may be not correct.
    2. the behavior you described seem to be that the device is damaged by voltage spike in SW.
    3. Do you have tantalum capacitor in the output? because this device need both ceramic and tantalum capacitor.
  • 0 in reply to Gama D
    TI__Mastermind 46905 points
    you mentioned the device worked weeks before damage. during these time, do you change the external condition? or you just place it there for weeks.
  • 0 in reply to Jasper Li
    Intellectual 420 points
    I dont think its because of any circuit issue, because it works fine for few weeks and supply it dies. there is no change in the environment. It gets its power from a coupe of cells, which eliminates the possibility of any noise on the input side, it has enough decoupling caps on inpt output lines.

    So far tested around 10pcs , all are doing same thing.
  • 0 in reply to Gama D
    TI__Mastermind 46905 points
    1. for boost converter, the output capacitor is most critical, not input capacitor. the tantalum capacitor in output is required to stabilize the TPS61020 series.
    2. the voltage spike in SW could slowly damages (weeks as you mentioned) the IC if it is higher than spec, but not so high to damage the IC immediately.