Secondary Oscillator

The secondary oscillator is a separate oscillator block that can be used as an alternate system clock source. The secondary oscillator is optimized for 32.768 kHz, and can be used with an external crystal oscillator connected to the SOSCI and SOSCO device pins, or an external clock source connected to the SOSCIN pin. The secondary oscillator can be selected during run-time using clock switching.

Figure 1. Quartz Crystal Operation (Secondary Oscillator)
  1. 1.Quartz crystal characteristics vary according to type, package and manufacturer. The user should consult the manufacturer data sheets for specifications and recommended application.
  2. 2.Always verify oscillator performance over the VDD and temperature range that is expected for the application.
  3. 3.For oscillator design assistance, reference the following Microchip Application Notes:
    • AN826, “Crystal Oscillator Basics and Crystal Selection for PIC® and PIC® Devices” (DS00826)
    • AN849, “Basic PIC® Oscillator Design” (DS00849)
    • AN943, “Practical PIC® Oscillator Analysis and Design” (DS00943)
    • AN949, “Making Your Oscillator Work” (DS00949)
    • TB097, “Interfacing a Micro Crystal MS1V-T1K 32.768 kHz Tuning Fork Crystal to a PIC16F690/SS” (DS91097)
    • AN1288, “Design Practices for Low-Power External Oscillators” (DS01288)