About the evaluation board (MCIMX7D-SABRE)

[goto11]

Hello,Community

SNVS_PMIC_ON_REQ pin is connected as follows.

U7 SNVS_PMIC_ON_REQ-PMIC_ON_REQ-U4 PWRON-pullup (R280) -PMIC_PWRON-U37 RST

U37's RESETpin is open-drain output.
SNVS_PMIC_ON_REQ pin of i.MX is a push-pull output.

When SNVS_PMIC_ON_REQ pin of i.MX is high output, does the large drive current flow if the RESET pin of U37 is output low?

There is a description of "PMIC_ON_REQ – push-pull output" in Section 2 of Table 8 of the Hardware Development Guide for i.MX7Dual and 7Solo Applications Processors.

best regards

Goto

[weidong_sun]

Hi,

   The push-pull output stage not only improves the load capacity of the circuit, but also improves the switching speed.

This is the main advantage of push pull design.

    When reset is operated, the current is mainly determined by the pull-up resistor, so you don't have to worry about the problem of large current.

Have a nice day!
BR,

Weidong

[goto11]

Hello,

There is a problem with the circuit I just found in the community.
Even if RESET_B goes low, PWRONpin of PF3000 does not go low.

Below is the revised circuit.

The resistor to be added is an orange square frame.

In this circuit, I thought that PWRON pin of PF3000 would be low when PMIC_ON_REQ pin of i.MX was high and RESET IC was low.
How many Ohms should I add?

best regards

Goto

[weidong_sun]

Hi

>>In this circuit, I thought that PWRON pin of PF3000 would be low when PMIC_ON_REQ pin of i.MX was high and RESET IC was low.

I don't quite understand the meaning of your sentence. If you follow this logic, your board can't be started.

[explaination]

If PWRON pin is low, PMIC will be disabled, no any voltages output.

VSNVS is first output of PMIC, which pulls PMIC_ON_REQ up to HIGH via 100k resistor and pull PWRON pin to High at same time, which enables PMIC's output to supply CPU.

[Comment]

I just finished a hands on Design Based on i.mx7d. 

there is no any problems to follow this part of the circuit design on evk.

Have a nice day!

BR,

weidong

[goto11]

Hello,

I found the following answer in PMIC_ON_REQ design on i.MX7 SABER (https://community.nxp.com/thread/437094).
Should I add a 1 to 10 kOhm resistor to R307?

R307 should be either not populated or be at least some 1 to 10 kOhm resistor to prevent extra current drain when the external watchdog Reset signal goes Low.

best regards

Goto