CC2530: What is the advantage of using a 32kHz crystal vs. internal RC oscillator?

Hi Derek,

A 32kHz crystal will be much more accurate and stable than the internal RC oscillator. A crystal should be within +/- 40ppm and the RC oscillator is specified in the datasheet at +/-0.2% accuracy after calibration, which equals +/- 2000ppm. So which you use will depend on your application and it's timing requirements while using the low frequency clock. If you are using Zigbee the 802.15.4 standard requires the accuracy of a crystal. If not then it is up to you.

Russ

I realize that the CC2530 (and '15.4 spec) requires the 32 MEGAHERTZ crystal for accurate timing, but the spec doesn't require the 32 KILOHERTZ crystal. Is this only used for sleep timing?

--Derek

That is what I thought ! In fact Abracon (I am not associated with them in any way, just use their parts)

indicates some 32Mhz parts as specifically suited for Zigbee. So I figures the 32Mhz specs

are crucial for  Zigbee apps  in terms of ppm etc. Was not sure why the 32khz mattered.

i would love to reduce sleep power since the 2530 will be asleep most of the

time but I have a tiny circular PCB with an RFID controller, Zigbee controller and a

host controller ! No space ...

Madhu

Hi,

The 32 kHz crystal oscillator is only used for accurate timing in PM1 and PM2.

RF accuracy is dependent on the 32 MHz oscillator.

/F

If your application is extensively using sleep mode of operation, an accurate 32Khz crystal will improve the battery life as it stays well controlled with change of temperatures. Thats the best reason i can think of for using the 32KHz crystal

Is the amount of energy saved by the accuracy of 32KHz crystal enough to be higher than the extra energy consumed by istelf?  At CC253x user´s guide the use of 32KHz RCOSC is recommended for energy saving...