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Original question:

TLIN1431-Q1: TLIN14315RGYRQ1

TLIN1431-Q1: TLIN14315RGYRQ1

Lynn Song
Prodigy 70 points
Part Number: TLIN1431-Q1
Other Parts Discussed in Thread: TLIN1431EVM,

In pin mode, HSS pin is controlled by HSSC pin. the datasheet does not specify HSSC = High or Low to turn on HSS pin output. does the below description indicates that HSSC = LOW will turn on HSS pin output and the default configuration is HSS output on since there is a 350k pulldown on HSSC pin.

  • +1
    TI__Prodigy 440 points

    Hi Lynn,

    In pin mode, the HSS pin is default ON in standby mode, normal mode, and fast mode. It has built in current protection so that the pin stops outputting if too much current is being drawn. When that happens, the pin can be reenabled by a falling edge on the HSSC pin. Hope this helps!

    Zach

  • +1
    TI__Mastermind 24275 points

    Hi Lynn,

    Zach is correct. Additionally, to be clear, the HSSC pin is positive-logic, but the point of the screenshot you included and in Zach's answer above is that the high-side switch will remain disabled due to the fault until you transition HSSC to low. This is basically a reset of the high-side switch. It is implied that once the fault is removed by the negative edge on HSSC, you would be able to reapply a logic high on HSSC to re-enable the HSS.

    Best,

    Danny

  • +1 in reply to Zach Schmidt
    Prodigy 70 points

    Thanks, Zach!

    i understand that a falling edge on the HSSC pin reenable HSS output. that's for from fault Off back to ON. what i really want to confirm is that for normal operating, we should keep HSSC = high or low to remain HSS always on since to keep it high or low will be how software control that pin.

  • 0 in reply to Danny Bacic
    Prodigy 70 points

    Thanks, Danny!

    you meant it doesn't matter that we leave HSSC high or low once HSS is ON, it'll keep ON until a fault event takes place.

  • +1 in reply to Lynn Song
    TI__Mastermind 24275 points

    Lynn,

    Yes, correct, HSSC high will keep HSS output on aside from a fault. The risk of hard-tying HSSC high is that you would lose the ability to clear a fault using HSSC when in pin control mode. If you're keeping this pin software-controlled (as it sounds), then default HSSC high would keep the HSS output on assuming no undervoltage/overcurrent condition on HSS.

    Best,

    Danny

  • 0 in reply to Danny Bacic
    Prodigy 70 points

    Thanks, Danny!

    can you guys try it by your demo to see what it'll happen on your side? or you can provide a EVM demo board to me and i'll try it by myself.

    the the below tests:

    test1: Connect HSSC to logical High when power on, what will happen? (note: it will turn on HSS output per your above input)

    test 2: Connect HSSC to logical LOW when power, what will happen? (note: HSS won't be on? i doubt it since your block diagram is showing 350k pull down on this pin)

    test3: if test1 succeeds in getting HSS on. then during normal operating, HSS is normally on, apply a High level voltage to HSSC and keep, what will happen? (note: it will keep on per your above input, but i doubt it, i'm kind of on the low level voltage will keep it on)

    test4: if test1 fails to get HSS on. then apply a High level to HSSC and keep, what will happen? 

    test5: if test1 succeeds in getting HSS on. then during normal operating, HSS is normally on, apply a LOW level voltage to HSSC and keep, what will happen? (note: it will keep on per your above input, but i doubt it, i'm kind of on the low level voltage will keep it on)

    test6: if test1 fails to get HSS on. then apply a LOW level to HSSC and keep, what will happen? 

    test7: Repeat from test3 to test 6 after test 2 done.

    Thanks,

    Lynn

  • +1 in reply to Lynn Song
    TI__Mastermind 24275 points

    Lynn,

    The question here is basically whether HSSC is a positive-logic or negative-logic control pin. Positive-logic control inputs like HSSC mean that an input high signal is interpreted as an ON condition.

    When HSSC is high, HSS is ON. When HSSC is low, HSS is OFF.

    When the device is in Restart, Sleep, or Fail-Safe modes, the HSS is always OFF regardless of the state of HSSC.

    Lynn Song said:
    HSS won't be on? i doubt it since your block diagram is showing 350k pull down on this pin

    There is a pull-down on the pin to disable the HSS in the event that HSSC is left floating. This is the preferred default state when HSSC is disconnected, as is the case with many control input pins. For example, you will notice that EN and DIV_ON also have pull-down resistance, while the negative-logic nRST pin has an internal pull-up.

    Here would be the results of your tests if run:

    1. Conditions: HSSC = High, Mode = Normal/Standby
      Result: HSS = ON
    2. Conditions: HSSC = Low, Mode = Normal/Standby
      Result: HSS = OFF
    3. Conditions: Same as #1 above (no change)
      Result: HSS = ON
    4. Conditions: Same as #1 and #3 above (no change)
      Result: HSS = ON
    5. Conditions: HSSC = High → Low, Mode = Normal
      Result: HSS = ON → OFF
    6. Conditions: Same as #2 (and #5) above
      Result: HSS = OFF

    Our TLIN1431EVM is available for testing the TLIN1431-Q1 if you'd like to take a look at the product folder for it.

    Best,

    Danny