49.6 Clocks and Crystal Oscillators

The PIC32CM JH00/JH01 family of devises can run from internal or external clock sources, or a mix of internal and external sources. An example of usage will be to use the internal 48 MHz oscillator as source for the system clock, and an external 32.768 kHz crystal as clock source for the Real-Time counter (RTC).

The oscillator circuit must be placed on the same side of the board as the device. Also, place the oscillator circuit close to the respective oscillator pins, not exceeding one-half inch (12 mm) distance between them. The load capacitors must be placed next to the oscillator itself, on the same side of the board. Use a grounded copper pour around the oscillator circuit to isolate them from surrounding circuits. The grounded copper pour must be routed directly to the MCU ground. Do not run any signal traces or power traces inside the ground pour. Also, if using a two-sided board, avoid any traces on the other side of the board where the crystal is placed.

Important: Crystal selection must be done referring to the “Crystal Data Sheet” and the crystal oscillator parameters given in the sections XOSC Electrical Specifications and XOSC32K Electrical Specifications of the Electrical Characteristics chapter.