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TPS1HA08-Q1: TPS1HA08-Q1 Action Issues.

Chun Youngsu
Expert 2485 points
Part Number: TPS1HA08-Q1

Dear TI Team,

The TPS1HA08A-Q1 was designed and tested.

Our usage specifications are as follows.

1. Vin: 24V

2. Lout: Max 6A (LED Panel Back Light) , Continuous load current 4A

3. Do not use MCU

4. Fault function is used. (Output cutoff)

5. Symptom :

    1) Fault occurs at initial start

    2) The ST pin operates normally up to 1A when the pull-up resistor is removed, but a fault occurs at the 4A load.

    3) Removing the diode connected to GND causes the same symptom as item 2

6. Requests :

    1) schematic Review

    2) Do you have a TPS1TA08-Q1 product?

         In the data sheet, 12V is TPS1HA08-Q1 and 24V is TPS1TA08-Q1.

    3) Please ask us if it is appropriate for the structure we are using.

7. Below is the schematic we designed & waveform.

* Waveform of ST pin designed according to circuit diagram

When the diode of GND is removed and 4A Load is given, the waveform (ST Pin)

Please review.

  • 0
    TI__Genius 12410 points
    Hello,
    I see this is a question in a different thread so I will close that one and keep with this one,
    Can you give me a current measurement on the output? I am wondering if there is any type of inrush currentsince this is LED backlight I assume it would have some decent sized capacitors?

    Also the resistor divider method that you are using for the 3.3V rail is not ideal as during start up if VCC gets pulled a little bit lower then it will not be high enough to keep the enable pin high. to test this I would recommend supply a separate 3.3V rail and see if it fixes this issue. Could you get a waveform of VCC like you did for ST to see what it is doing during the turn on time and see if it is falling below where your resistor divider is no longer high enough to keep the device on.

    Unfortunately we do not have a TPS1TA08-Q1 device.
  • 0 in reply to Cameron Phillips
    Expert 2485 points
    Dear Phillips

    I did not solve the problem, but I pressed the wrong button on the top.

    We modified the circuit of EN pin and tested it.

    However, there is no improvement.

    If EN is set high after stabilization after power is applied, fault will occur.

    It seems to be a problem because EN is not set to Soft Start when it goes High.

    We have LCD back light connected to the load.

    Did you find any problems in the schematic other than the EN circuit?

    We do not know why Fault occurs.

    The conditions we use are confirmed to be used within the Chip Spec.

    Is there more material to review?

    Thanks.
  • 0 in reply to Chun Youngsu
    TI__Genius 12410 points

    Hello,

    What is the capacitance on the input of the LCD display load?

    Can you please send the current waveform when you power it up? Do you see an inrush profile that is causing the device to current limit?

  • 0 in reply to Cameron Phillips
    Expert 2485 points
    Hello,

    The capacitance of the LCD panel backlight is unknown.

    Is the waveform of the current when the power is on?

    Tested with adapter and power supply.

    The adapter has failed each time and the power supply has not failed.

    However, it has been confirmed that if the EN is turned on / off, the same error occurs.

    Thanks.