controlling reset pin of A6 gsm

Thread Starter

vtc

Joined Apr 3, 2018
37
Hi,

Iam using A6 Gsm module with arduino uno to send and receive messages
A6 gsm.jpg

I need to reset the module from the code,i read the datasheet and find the following for reset pin

rst.png

But i don't understand what NMOS control ,could anyone explain it>

A6 Datasheet

Regards
 

Irving

Joined Jan 30, 2016
947
What I think its trying to say is that you need to pull this below 0.05v to ensure it resets the module, and when not resetting you must have very low leakage, therefore use an N-channel MOSFET rather than a transistor.

eg in circuit below, D11 HIGH pulls \RESET down to 1mV, D11 LOW, leakage is <0.5uA

1595329269445.png
 
Last edited:

jpanhalt

Joined Jan 18, 2008
10,087
It is hard to decipher that instruction. My impression is that pulling the pin low creates a reset. The 70 mA current seems strangely large. Maybe 70 uA is meant?

Checked a device that has similar capabilities (SIM808 Module GSM GPRS GPS). Its datasheet describes reset a little better (See: Attached pdf, page 27).
 

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Irving

Joined Jan 30, 2016
947
It is hard to decipher that instruction. My impression is that pulling the pin low creates a reset. The 70 mA current seems strangely large. Maybe 70 uA is meant?

Checked a device that has similar capabilities (SIM808 Module GSM GPRS GPS). Its datasheet describes reset a little better (See: Attached pdf, page 27).
Yes, I looked at a couple of other devices, but they all seem to have fairly normal logic levels. You may well be right about the 70mA -> 70uA, that makes more sense, but needing <0.05v is unusual. The circuit I show, with that particular MOSFET Rds_on < 180mOhm @ 1mA Ids, Vgs=3v, meets that requirement easily.
 

jpanhalt

Joined Jan 18, 2008
10,087
I agree, the mosfet is safer, if the reset current is really 70 mA. The datasheet is pretty vague about such values, except apparently the whole device can require up to 2 A. My comment was of course was based on the comment about using a GPIO in the other device.

Maybe the TS can confirm with tech service at the manufacturer (Ai ).
 

Irving

Joined Jan 30, 2016
947
Well the MOSFET I suggested will easily handle 70mA, and there are no overheating concerns. Still seems high, poor design I guess, maybe that']s why they are discontinuing it.
 

Thread Starter

vtc

Joined Apr 3, 2018
37
Well the MOSFET I suggested will easily handle 70mA, and there are no overheating concerns. Still seems high, poor design I guess, maybe that']s why they are discontinuing it.
Can i use any mosfet transistor ?

I appreciate your effort

vtc
 

Irving

Joined Jan 30, 2016
947
It must be a logic level MOSFET

Gate threshold Vth <2v
Drain current Max Ids(max) >200mA @ Vgs=3v
On resistance Rds < 200mOhm @ Vgs=3v
 
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