Microchip Technology AC164142 User Manual

© 2011 Microchip Technology Inc.

DS70656A-page 37

Following are the important points to keep in mind while designing a custom hardware 
solution:

C.1.3.1

POWER SUPPLY RATING

It is important to have a power supply with sufficient rating to power the daughter board. 
The daughter board can draw up to 600mA from the power supply. Do not use a pro-
gramming / debugging tool to power up the daughter board.

C.1.3.2

VENTILATION

Sufficient ventilation must be provided to avoid thermal runaway issues with the output 
transistors. The output transistors have to be mounted on a large copper plane to 
dissipate heat efficiently.

C.1.3.3

PCB DESIGN

Due to the very high gain of the receive path, it is very important to carefully design the 
PCB layout. Output signals should not be routed near the inputs of preceding stages. 
Ground return paths should be planned to run in straight lines to the common ground 
reference point and return paths from the last stages should not run under preceding 
stages.

Using less than four Output Compare (OC) channels will reduce the signal power trans-
mitted by the daughter board. Consequently, this can reduce the operating range and 
performance.

Running the dsPIC33F DSC at less than 40 MIPS may change the software timing 
constants, and potentially render the modem software unusable.