Sim7600 G-H generating 750mv with an input voltage of 3.9V, not able to communicate using UART

[Mohammad Farhan]

I have connected the 4 input pads of sim7600G-H to 3.9 voltage. I have followed the datasheet and added the 5 capacitors in parallel to the power supply line and also added a ferrite bead as per the datasheet. But the problem, I am facing is that it is not able to be switched on and be communicated with via UART. In addition, it only produces 750mV from its 1.8V output pin. I have attached my PCB board for reference. It's in Altium. An led to status pin was connected as well, and it was oscillating when the power was switched on for the PCB board. The pcb board takes in 12V, steps it down to 3.8V for the sim7600G-H. It has a level shifter for communcation between MCU and Sim7600G-H via uart. Is there anything wrong that I am doing in my pcb design?

 

[betwixt]

Your TXD and RXD swap at the level shifter, is that intentional?
You could be driving two transmit signals against each other, that would result in low voltage and extra power consumption.

Brian.

 

[Mohammad Farhan]

Your TXD and RXD swap at the level shifter, is that intentional?
You could be driving two transmit signals against each other, that would result in low voltage and extra power consumption.

Brian.

Yes, that's intentional. One end of module TXD goes to MCU RXD @3.3V and the same happens for module RXD. But I doubt that this is the reason why I am getting 750mV out of "1V8 pin" of the Sim7600 module. The MCU is on a different PCB board stacked vertically with this Telemetry PCB board. I have attached the schematic below for reference. But thank you for pointing that out, it does get a bit confusing.

 

[KlausST]

Why uploading PDFs?
the forum editor provides an [Insert Image] button... It´s free to use.

Klaus