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!
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.
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!
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
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?
Hi Allen,
Your understanding of the scaling feature is correct.
Best regards,
Ridge Lahti
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.
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