Hello,
I was wondering if I can power the RTL8735BDM module with 3.3v instead of 5v.
I checked the module’s schematics, and it looks like the 5V is only used for a buck converter inside the module, which should be happy to take 3.3v also from what I have found. So I did exactly that and powered the module with 3V3, and it was working in my preliminary tests (RTSP streaming via wifi, USB MSC example, etc.).
My question is: What was the design decision to power it with 5V specifically? Can I go with 3V3, or are there any other caveats in doing this?
Hi @k-adarsh ,
After the 5V pin enters the module, there is a DC-DC converter stage that steps the voltage down to 0.9V to power the IC. The input voltage range for this DC-DC converter is 2.7V to 6V, which explains why the customer observed that the module can successfully operate at 3.3V.
However, the PCB layout at the module’s input is specifically designed for the current draw associated with a 5V supply. If the module’s hardware structure remains unchanged and the power supply is manually modified to 3.3V, it will introduce the following risks:
Potential Risks
Mismatched Input PCB Traces
When the supply voltage is lowered to 3.3V, the required current increases to maintain the same power. This larger current will cause a significant increase in impedance losses across the input PCB traces, which were not widened to handle this higher current.
Suboptimal Inductor Matching
The inductor on the backend of the DC-DC converter is not optimally matched for a 3.3V input. This mismatch can result in degraded power conversion efficiency or cause the inductor to overheat.
System Instability Under Full Load
Under full load conditions, using a 3.3V supply may cause the output voltage delivered to the IC to become unstable or abnormal, ultimately leading to system crashes or unexpected lockups.
Thank you.
