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TPS35-Q1: Use case confirmation

Allen Lu
Intellectual 1910 points
Part Number: TPS35-Q1

Hi team:

 my customer have a use case want to use TPS35-Q1 version, base on the PPS35AA38AGADDFRQ1 available part# in the spec.

 I post the my understanding & questions as attached.

 can you help to review and get feedback to me ? tks!

use case of tps35.pptx

  • 0
    TI__Genius 13495 points

    Hi Allen,

    I have listed your questions with my Answers underneath:

    1. so we can only by changing the cap of  Crst?

    For the PPS35AA38AGADDFRQ1 you cannot change the Startup delay. However, the timing diagram in Figure 7-1 shows that reset will be LOW for tstart + tD when the device first powers on. Since you require 8sec of reset delay anyways, your requirement during power should be met. You can set the reset delay using Equation 2 in Section 8.3.4. The RESET and WDO outputs use the same reset delay (responding to the comment on slide 3).

    2. What s the meaning of 10ms in SET0=0 and 1280ms in SET0=1?

    The value of SET0 selects which scaling you would use for the watchdog timer. Table 8-1 uses the a fixed WD timer of 10ms for the example. For the PPS35AA38AGADDFRQ1, SET0=0 configures 1x scaling and SET0=1 configures 128x scaling. The value of the WD timer is set using a capacitor on the Cwd pin.

    3. How to calculate the n?

    For the PPS35AA38AGADDFRQ1, the scaling options are 1x and 128x, chosen by the SET0 pin. Figure 5-1 shows which scaling options are associated with each OPN.

    Best regards,

    Ridge Lahti

  • 0 in reply to Ridge Lahti
    TI__Intellectual 1910 points

    Hi Ridge:

     Tks for your reply, it is clear for my first question.

     but combine the 2 & 3 question, here is my understanding of the scaling ,can you help to correct me?

    1. The Td and Twd share the same Calculation formula

    2. so base on the Table 9-1, when i set the Ccwd as 100nF, the type Twd is 495ms, so when is set SET0=0 configures 1x scaling, The Twd = 495ms x1 =495ms.

     if i set SET0=1 configures 128x scaling, then the final Twd = 495ms x128 =63,360ms?

     

  • 0 in reply to Allen Lu
    TI__Genius 13495 points

    Hi Allen,

    Your understanding of the scaling feature is correct.

    Best regards,

    Ridge Lahti

  • 0 in reply to Ridge Lahti
    TI__Intellectual 1910 points

    Hi Ridge:

     Tks for your confirmation, i have one more question for the reset status and WDI logic:

     

    for the above red mark area, when i set the Td as 10s, what if i recover the WDI signal as 5s , does the reset signal will become high or we have to wait after 10s?

     tks for your checking.

  • 0 in reply to Allen Lu
    TI__Genius 13495 points

    Hi Allen,

    During a RESET or WDO fault, the watchdog will ignore the WDI. You will have to wait the entire reset delay before a new watchdog timeout starts.

    Best regards,

    Ridge Lahti