Posts: 1
Registered: ‎05-21-2015
Accepted Solution

Si5351C not generating programmed frequencies

We are using Si5351C I2C programmable clock synthesizer. Generated register map from clock builder, then programmed according i2c programming procedure as mentioned in datasheet. We are not getting expected frequencies and voltage levels.
Please find attached files:
1. clk_syn_clk_builder.txt ---> File generated from clock bulder
2. register_config_sequence.txt ---> Sequence of register write done through i2c
3. CLK_SYN_observe.xlsx ---> Observations of programmed and measured values

Looking forward for your quick reply. Thanks.

Posts: 19
Registered: ‎11-21-2014

Re: Si5351C not generating programmed frequencies



I tested your plan on one of our Si5350/51 evaluation boards and was able to generate the correct frequencies according to what is outlined in your plan. As a side note, I also noticed that the frequencies in your excel file are reversed compared to your plan.


The issue may lie with your register write sequence. I agree the registers you listed are correct and need to be written, but are these the only registers you are writing? Please ensure you are programming all registers outlined in Figure 12 on Page 19 of the Si5351 datasheet not just the registers with non-zero values. In addition, the registers need to be programmed in numerical order.


Also if possible, could you perform a register read back to ensure everything is being correctly written?