nRF9160 ENABLE minimum voltage

[GiulianoFranchetto]

Hi,

In our design, nRF9160 is powered by a LiPo battery, making VDD = 4.2V in a "fully charged" case, and VDD=5V in a "lipo is charging" case.

We would like to be able to turn nRF9160 on and off by using an external MCU, with GPIO level of 3V.

From this post: https://devzone.nordicsemi.com/f/nordic-q-a/47546/nrf9160-enable-pin-voltage-specification , everything should be fine as we are above 1.2V.

However, in page 50 of the specification v2, there is a table talking about a minimum level of VDD*0.8 for V SYSTEM_DISABLED_ON.

I don't really understand this table:

- It seems that ENABLE pin needs to be high to disable the system ("operational voltage to enforce System-Disabled power mode")

- The minimum voltage on that pin shall be 0.8*VDD, and not 1.2V as stated in the post linked above.

Could you please clarify (again , sorry) the minium voltage in ENABLE pin, and what to do with the table in 5.1.1.5.1 of the spec?

Regards

Giuliano

[ketiljo]

Hi Giuliano

The enable pin is referred to VDD. When the enable pin is high, the device is on and when enable is low, the device is off.  

Minimum 1.2 V was true for gen1 of the module. Gen2 have different regulators, so the voltage on the enable pin must be min Vdd*0.8 V. For VDD = 5 V and VDD GPIO = 3.0 V, you need a transistor to control the enable pin to make sure you have high enough voltage. 

https://infocenter.nordicsemi.com/topic/nwp_037/WP/nwp_037/enable.html

best regards,

Ketil Aas-Johansen

[GiulianoFranchetto]

Thank you Ketil!

Do you confirm there is a typo in the 5.1.1.5.1 table of the spec ?

To prevent anymore head scratching, it could be great to mark the post about the "1.2V min" as deprecated or to delete them completly once Gen2 totally replace the Gen1

Regards 

[ketiljo]

Hi Giuliano

The wording in the table is strange. Not sure what they mean to be honest. I'll tell the tech writers.

Gen1 and Gen2 modules will both be produced in case someone has designs that can't use gen2. The datasheet should have info that covers both.

cheers,

Ketil