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About inrush current of TPS61165

watanabe
Expert 1740 points
Other Parts Discussed in Thread: TPS61165

Hi,

My customer have a question.

My customer has sent the following command in the CTRL.

The contents of the signal,

Device address(LHHHLLHL),

RFA(H),

Data Byte(LLLLLLH),

ACK(L).(H=High L=Low)

At the time of the ACK(Low), flows into a current of 1.2A.

What is the cause of this phenomenon?

Best regards,

Watanabe

  • 0
    Expert 1740 points
    P.S.

    Write along the TPS61165 Datasheet(Figure11.EasyScale Protocol Overview).

    STart: High
    DA7 :0
    DA6 :1
    DA5 :1
    DA4 :1
    DA3 :0
    DA2 :0
    DA1 :1
    DA0 :0
    EOS :Low
    STart: High
    RFA: 1
    A1: 0
    A0: 0
    D4: 0
    D3: 0
    D2: 0
    D1: 0
    D0: 1
    EOS :Low
    ACK :Low

    From the setting of the FB voltage 0mV, it sent the above signal.
    1.2A was flowing at the timing of 0.5ms ACK.

    What is the cause of this phenomenon?
    Best regards,

    Watanabe
  • 0 in reply to watanabe
    Expert 1740 points

    P.S.

    Circuit diagram is as follows.

    When it from Vfb=0mV to Vfb=5mV,

    At the moment of ACK,

    Iin is 1.2A from 0A,

    Iout is 320mA from 0A,

    Vin is to 4V from 5V,

    Vout is to 12V from 5V.

    For 1.2A flow,what causes are considered ?

    I'm looking forward to hearing from you.

    Best Regards,

    Watanabe

  • 0 in reply to watanabe
    TI__Intellectual 1780 points

    Hi Watanabe,

    Thank you for providing the details.

    Could you please send us the waveform of the CTRL pin for our debug?

    Thank you,
    -Harini

  • 0 in reply to Harini Sankabattula
    TI__Intellectual 1780 points
    Hi Watanabe,

    It seems there is a known issue with the TPS61165 when using the EasyScale interface to increase the feedback voltage. When VFB is increased from 0 mV to any value above 0 mV, some ICs do not properly soft start during this transition and the voltage on their SW pin overshoots. If the overshoot exceeds the absolute maximum voltage rating on the SW pin, the device is damaged.

    With VFB set below 10 mV through EasyScale, the parasitic offsets on the input pins of the internal transconductance amplifier determine the value of output of the amplifier. Device process variations are causing the offset to be larger and in the opposite polarity than expected. If the amplifier’s output is already high prior to a transition from VFB = 0 mV to any other voltage, then the modulator turns on full, bypassing soft start, and causes the SW pin and output voltage to overshoot.

    To avoid this issue do not use EasyScale to change the feedback voltage from 0 mV, effectively disabling the device, to any other voltage. One alternative is to start with VFB = 10 mV and go to a higher voltage. Another alternative is to disable the device by taking the CTRL pin low for 2.5 ms and then re-enter EasyScale to force a soft start from VFB = 0 mV to the default 200 mV.

    Hope this helps.

    Best,
    -Harini
  • 0 in reply to Harini Sankabattula
    Expert 1740 points
    Hi,Harini-san.

    I appriciate for your support.

    I understand there is known issue.
    Thanks again.

    Best regards.
    -Watanabe