Other Parts Discussed in Thread: LMX2594
Hi,
I've done some tests with the LMX2594 using several frequencies for the SPI write speed. My results are given below
Time Last Data / CSB Rising Edge [µs] | Time CSB Rising Edge / LD Rising Edge [µs] | Time Last Data / LD Rising Edge | SPI writing speed [kHz] | |
19 | 2,5 | 21,5 | 100 | |
22 | 3,6 | 25,6 | 500 | |
1 | 26 | 27 | 1000 | |
1,4 | 25 | 26,4 | 5000 | |
1,5 | 26 | 27,5 | 10000 | |
1,8 | 26 | 27,8 | 50000 |
Red trace is Data
Yellow trace is CSB
Green trace is Clk
Blue trace is Lock Detect
I have used a Raspberry Pi 3 B+ to control the LMX2594 (instead of the Reference Pro), and the Full Assist mode. As you can see, the time between the last bit of one word and the lock detect rising edge is relatively stable. However that's not the case between the CSB rising edge and the Lock Detect rising edge.
I would like to know what signal triggers the whole processus which allows the PLL to be locked ? Is that the last data bite or the CSB ?
Thanks for the answer
Stéphane