LMK3H0102: Modify Output Frequency

Sky Kao

Part Number: LMK3H0102
Other Parts Discussed in Thread: USB2ANY

Tool/software:

Hi Support Team,

I am using the LMK3H0102A016RERR, and its output is 50 MHz.
However, my actual requirement is 100 MHz.
Therefore, I would like to adjust the output frequency through I²C.
I referred to the datasheet and followed the steps below, but I did not get any output. Could you please help me confirm if there is any issue?

Step 1: Pull REF_CTRL low (to GND) and then power on
Step 2: Read all register values (as shown in Image 1)
Step 3: Write in sequence (as shown in Image 2)
Step 4: Measure OUT1(pin11 pin12) to confirm whether there is output.

1 month ago

0 Kadeem Samuel 1 month ago

TI__Mastermind 22550 points

Sky,

You are setting the digital state machine clock divider to 0, which is not allowed. The digital state machine clock must be set such that the digital state machine clock is as close to 50MHz as possible.

You have I2C access - do you have a USB2ANY available for interfacing the device with TICS Pro? Otherwise, the absolute easiest way to switch from a 50MHz output to a 100MHz output is by using the Edge combiner. The steps for this are as follows:

Unlock the device by writing 91d to R12[7:0].
Average the gain calibration values for FOD0 and FOD1. There are three values for each FOD, in R146 through R148, where x is 1 for FOD0 and 2 for FOD1:
1. DTCx_GAIN_DELTA_HT
2. DTCx_GAIN_RT
3. DTCx_GAIN_DELTA_CT
Select the edge combiner as the source for CH0 (which drives OUT0 and OUT1) by writing CH0_EDGE_COMB_EN (R3[3]) = 1

Thanks,

Kadeem

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LMK3H0102: Modify Output Frequency