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TPS650350-Q1: BUCK1 UVLO QUESTION

Florens Liang
Prodigy 110 points
Part Number: TPS650350-Q1

Tool/software:

Hi team,

Here are some questions about TPS650350-Q1, pls help me, thanks.

1. Why we need to meet the requirement about "The PVIN_B1 UVLO falling threshold must be set at least 0.5 V less than the rising threshold."?

2. What happen if the PVIN_B1 UVLO falling threshold set within 0.5 V less than the rising threshold.

3. What happen if I set BUCK1_UVLO = 00?

4. If BUCK_UVLO cannot be set to 00, what is the significance of BUCK_UVLO = 00?

  • +1
    TI__Mastermind 48991 points

    Hi Florens,

    Please see my answers below:

    1. It's because the PVIN_B1 has certain level drop caused by the DCR of the path of PoC during its powering up; to avoid the device cycling between power on/off; the 0.5V min difference is necessary.
    2. The device can't power on normally; could be in cycling between power on/off.
    3. PVIN_B1 UVLO=0 is not an option.
    4. PVIN_B1 UVLO=0 is not an option.

      You can schedule a WebEx meeting for further explanation if like. 

    Thanks!

    Phil

  • 0 in reply to Phil Yi
    TI__Prodigy 110 points

    Hi Phil,

    Thanks for your explanation, there are still two small questions need your help:

    1. Does it mean that the TPS65035x cannot work at VIN=4V?

    2. Can this socket work when PVIN_B1 UVLO=01?

    Thanks!

    Florens

  • +1 in reply to Florens Liang
    TI__Mastermind 48991 points

    Hi Florens,

      A1. It depends on the VBUCK1 level and the load on the Buck1.

      A2: What do you mean "PVIN_B1 UVLO=01"? I guess you mean BUCK1_UVLO=0x01 as following. If so, same answer as A1. 

    Thanks!

    Phil

  • 0 in reply to Phil Yi
    TI__Prodigy 110 points

    Hi Phil,

    Thanks for your explanation, For Q1, When the input voltage is 4V, we should set the PVIN_B1 UVLO=0x00, which means the rising voltage is 3.64V and falling voltage is 3.5V, but its difference is within 0.5V, so is it possible for TPS65035x works in VIN=4V?

    Thanks a lot!

    Florens

  • 0 in reply to Florens Liang
    TI__Mastermind 48991 points

    Hi Florens,

     As I've answered; it depends on the VBUCK1 level and the load on the Buck1. For example; TPS65035x works well when PVIN_B1=4V if VBUCK1=3.3V with 0.5A load; it doesn't work for VBUCK1>3.3V with >0.5A load. 

    Thanks!

    Phil

  • 0 in reply to Phil Yi
    TI__Prodigy 110 points

    Hi Phil,

    Please check my understanding. During power-up, transient currents cause voltage drops, so the rising voltage must be 0.5V greater than the falling voltage to avoid device cycling between power on and off. However, if the output load current is less than 0.5A, this requirement for the rising voltage to be 0.5V greater than the falling voltage is not necessary, right?

    Thanks a lot!

    Florens

  • 0 in reply to Florens Liang
    TI__Mastermind 48991 points

    Hi Florens,

      Yes; only if device doesn't cycle between power on and off.

      No; if the DCR from PoC connector to PVIN_B1 is too much to cause the Vdrop>0.5V.

      

    Thanks!

    Phil