• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Subscribers 63 subscribers
  • Views 2012 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TPS65142 / WLED BOOST REGULATOR is not enabled

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: TPS65142

Hello,

TPS65142 WLED BOOST REGULATOR is not enabled with below sequence.
-Vin input  --> Vbat input(controled by external load SW) --> PWM --> EN
The WLED BOOST Converter is operated when the loadsw is changed from 1.5ms start up device to 0.5ms start up device.

Could you please let me know this reason?




Should We input the Vbat before VREF is regulated?
Are there any timing requirement during from Vref regulated to Vbat input? 


Best Regards,
Ryuji Asaka



  • 0
    Guru 20090 points

    Hello,

    I have additional question.

    Vsc(dly) Short circuit detection delay during start up
    Is the start up is Vbat voltage ? or Vsup Voltage?
    If the start up is Vsup, is there timing requirement from Vsup to Vbat?

    Best Regards,
    Ryuji Asaka

  • 0
    TI__Expert 8010 points

    Hi Ryuji,

    There are four conditions which has to be met before WLET Boost converter will start:

    1. the VBAT input voltage is higher than its under-voltage-lockout (UVLO) threshold (~4.4V)

    2. the REF regulator output is higher than its power-good threshold 

    3. the output voltage VO is within 2V of the input voltage VBAT;

    4. and the enable input from the EN pin is high.

    I assume that in your scope Vout is the output of the boost converter (AVDD). What signal is PWM?
    I do not see the output voltage of the WLED boost converter, therefore i am not completely aware of your problem.

    Thank you,

    Best regards,

    Ilona

  • 0 in reply to Ilona
    Guru 20090 points

    Hello Ilona san,

    VOUT is the output of the WLED boost converter and PWM is signal of DCTRL.
    Since the WLED Boost converter is not enabled, the Vbat is equal to WLED boost output.

    I get the additional information.
    The customer use the high side switch(please see the attached file)



    Vin=5V,
    Pout=21W (LED = 8series, 3parallell)
    HSSW current limit is 750mA(typ),630mA(min) , device name is BD2246G.
    Time from the Vref regulated to Vbat input is about 270ms

    When they change the HSSW which has cullent limit is 1.5A(typ), the WLED Boost converter was operated.
    Also, the WLED boost converter was operated when the Vbat was increased to 5.2V.

    If the HSSW current limit is occured , is the WLED Boost driver not enabled?


    Best Regards,
    Ryuji Asaka

  • 0 in reply to Ryuji
    TI__Expert 8010 points
    Hello Ryuji-san,

    I am really sorry, but i do not understand the question. What do you mean with this question: "Is the start up is Vbat voltage ? or Vsup Voltage?"
    Do you mean, whether VBAT or VSUP turns off when short circuit is detected? The IC turns off when overcurrent is detected for more than 16ms. After it shuts down and restarts after input power-on reset or enable toggles.
    Is this helpful for you?
    Best regards,
    Ilona
  • 0 in reply to Ryuji
    TI__Expert 8010 points
    If current limit of 1.5A sustains for more than 16ms than the IC will shut down and therefore WLED boost driver will be shut down. Does this answer your question?
  • 0 in reply to Ilona
    Guru 20090 points
    Hello IIona san,

    Sorry for my miss expalation.
    There is the paramter Vsc(dly) 32ms(typ) in the datasheet P.8 and the description of Vsc(dly) is the "Short circuit detection delay during start up".
    I would like to know the period of this 32ms.

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ilona
    Guru 20090 points
    Hello IIona san,

    Thank you for the reply.
    In the customer, current limit is not occured at the TPS65142 Boost converter.

    If the VBAT slewrate is slow (1.5ms or longer) , are there possibility of the Power On Reset is not completed?
    Is the VBAT Power On Reset completed when the VBAT power will be higher than UVLO?
    The customer concern that Power On Reset is not completed when the VBAT slewrate is slow(or other reason).

    Currently , the power on sequence is the following.

    Vsup and Vref start up --(260ms) --> Vbat input(1.5ms slew rate) --(30ms)--> DCTRL is High(100% duty) --(20ms)-->EN is High

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Expert 8010 points
    Hello Ryuji-san,

    To close this discussion i would like to summarize that the converter can only work properly by sequencing VBAT before VIN. This requirement has been updated in the d/s.

    Best Regards,
    Ilona