Can 9160 power off before power off the modem?

[zhangchi]

Hi,

In our product, we use 9160 GPIO to control the system power. However, we found we can't power off when 9160's modem is in normal mode. But, the system can power off when modem is in offline mode and power off mode.

We use VDD_3V6 to supply 9160, when modem is not power off, the voltage will hold in 2.6V for a while which made the system can't power off. But when modem is in power off mode, VDD_3V6 can down to 1V immediately. Why? How can we avoid this?

So We can only power off the product when modem is power off. Is it normal in mobile phones or other IOT device? I means, is it popular that the product have to power off the modem before power off?

[Håkon Alseth]

Hi,

 

In our product, we use 9160 GPIO to control the system power. However, we found we can't power off when 9160's modem is in normal mode. But, the system can power off when modem is in offline mode and power off mode.

Can you explain the exact steps you are using here? 

 

We use VDD_3V6 to supply 9160, when modem is not power off, the voltage will hold in 2.6V for a while which made the system can't power off. But when modem is in power off mode, VDD_3V6 can down to 1V immediately. Why? How can we avoid this?

 VDD goes down to 1.0 V? Could you show a minimal schematic of what you are doing here?

 

So We can only power off the product when modem is power off. Is it normal in mobile phones or other IOT device? I means, is it popular that the product have to power off the modem before power off?

 Yes, you can shut down the modem, but it sounds like you are physically cutting the power (disconnecting the VDD_NRF) ?

 

Kind regards,

Håkon

[zhangchi]

when customer press the button to power off the system, GPIO30 from 9160 will pull high to open the N_Mos. But when 9160 is power off, GPIO30 will be low, the N_mos will be closed. In this moment, when modem is in normal mode, VDD_3V6 will only decrease to  2.5V. This 2.5V will power on the system again. We have discharge circuit for 3V6. When modem is power off 3V6 can down to 1V but when modem is open, the voltage can only down to 2.5V.

We charge the mode of the modem by AT command.

[Håkon Alseth]

Do you have a schematic to show how this is all connected?

[zhangchi]

Thank you for your reply. I create a new private case and put schematic in it. 

Case ID: 240139

[Håkon Alseth]

Thank you, let's continue in the new case.

 

Kind regards,

Håkon