• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 285 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS2121: Chip fails with current configuration as seen in schematic

Michael Drury
Prodigy 30 points
Part Number: TPS2121


I'm using the power mux in the following configuration. When the designed 20V is applied to the board however, the component fails and shorts, drawing excessive current.
Is anyone aware of any issues regarding the schematic that will have caused this? Thanks.

  • 0
    TI__Mastermind 32650 points

    Hi Michael,

    Can you please share a waveform of the failure event? What is the output load for this system? I would like to see VIN1, VOUT, IIN and ST.

    I would like to see how the system behaves during the turn on and rise of VIN1. VIN2 can be left floating.

    Do you have an voltage suppression on the input rails? At 20V and high current, the wire inductance can cause spikes over the abs max rating of the device especially during a hotplug event as described in Section 10.7 in the datasheet. This could damage the device.

  • 0 in reply to Shreyas Dmello
    Prodigy 30 points

    All of our ICs have burnt out at this voltage, so am unable to share the characteristic waveforms etc..

    Are you able to confirm that the dividers and resistor configurations are correct for 20V?

    The load current is 40mA and you I am using power supply with controlled cut off current set to 300mA limit.

    IN2 is floating while testing. When I apply 14V, Vout works fine. Then when Vin is increased to approximately 18V it burns the IC.

    There is no in rush current, no voltage spike and definitely no inductance of wires from power supply.

    Thanks.

  • 0 in reply to Michael Drury
    TI__Mastermind 32650 points

    Hi Michael,

    20V DC is not a concern for the device. The amount of resistance is no a concern here as the ratio of resistors matter more.

    Seeing as how IN2 is left floating (pulled to GND through the CP2 resistor divider), your voltages on the control pins are:

    (assuming VIN1 =20V)

    V_PR1 = 20 * 5/36.6 = 2.73V

    V_OV1 = 20 * 5/112 = 0.89V

    Both these voltages are acceptable The SS capacitor is of an acceptable value (we use 50V rated caps here on the EVM) and so it the R_ILIM.

    Could you please describe the load further? Is is a constant current 40mA load? Is it capacitive or inductive in nature?

    I think we need a waveform of the test you described to understand the system. I am looking to see:

    input voltage

    output voltage

    input current

    and the ST voltage

  • 0 in reply to Shreyas Dmello
    Prodigy 30 points

    Hi Shreyas,

    It appears a capacitor on a voltage regulator input wasn't rated for the 20V, which caused a short in the system. Removing this has solved the issue, so you can mark this as closed.

    Thanks for the help.

    Michael