CDCE913: How to change fout on the fly

shibatani

Part Number: CDCE913
Other Parts Discussed in Thread: CLOCKPRO

Hello

Would you please let me know the way how to change the fout on the fly without lost of fout / or unexpected frequency of fout?

How can I change fout(MHz) on the fly by changing N,P,Q,R without lost of fout or unexpected frequency ?

I wonder PLL unlock.

My idea is to change PLL1_0 and PLL1_1 by changing OFFSET 13h 00h or 02h .

In this procedure, can I expect linear transition of frequency from PLL1_0 to _1?

Procedure:

1 write 18~1Bh; set PLL1_0 in advance
2 write 1C~1Fh; set PLL1_1 in advance
3 write 13h ;select PLL1_0 or PLL1_1

Please advise

Best Regards

CDCE913_change_fout_on the fly.pptx

over 3 years ago

0 Aaron Black over 3 years ago

TI__Expert 7745 points

Hello Shibatani,

Q1.

This device is not meant to be a glitchless device and will have down-time (unexpected frequency) when changing N,P,Q,R values whether that be by I2C programming or control pins.

While programming the device this will require to write to PLL1_x registers. This communication timing can be seen in the datasheet as well.

PLL lock time on this device requires ~ 10 us please see section 11.2.2.3 'Crystal Oscillator Start-Up' for this definition.

Q2.

Please note again that using Control Pins also is not guaranteed to have glitchless performance.

If you plan to use PLL1_0 and PLL1_1 separately controlled by pin selections this should be the fastest change. Please note that the device requires the device to be programmed initially with different frequency plans for PLL1_0 and PLL1_1 as well as a SPICON bit in Reg2.

S0, S1, S2 combinations would then determine FS1_x: PLL1 Frequency Selection. Please see ClockPro Direct Registers View tool as well for this combination as calculations can be done for different Multi/Div definitions.