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Electronics => Beginners => Topic started by: Alex on September 12, 2014, 10:03:01 am

Title: Unused oscillator
Post by: Alex on September 12, 2014, 10:03:01 am

I've got a PIC MCU that has RTC functionality programmed into it and uses a typical external 32kHz crystal. The core is clocked using the internal RC oscillator.

In the application I will be using it I do not require the RTC functionality. What is the optimum (electrically) way to disable the internal part of the oscillator? I do not have access to the firmware.

I have attached a schematic of the Pierce-type oscillator.

How about a pulldown resistor to ground at the input of the inverter? 100k?

A

Title: Re: Unused oscillator
Post by: fcb on September 13, 2014, 08:18:29 am

A pull-down will work fine on the input - are you removing the xtal as well?  If not, then you need to make sure your pull-down is low enough to stop it oscillating.