LMX2594: frequency setting issue

user6325641

Part Number: LMX2594
Other Parts Discussed in Thread: LMK04832

CTM use LMK04832 supply 200MHz clock for LMX2594, VCO(1-7) is PLL output in the chip, and FVCO is an output signal which can mux from the VCO(1-7). The FVCO output is normal when switched to VCO(5-7) while abnormal when switched to VCO(1-4) . How to solve this problem?

over 5 years ago

0 Noel Fung over 5 years ago

TI__Guru** 115380 points

Hi There,

I am afraid we do not have sufficient information to make a guess, would you please describe the failure symptom in details? Thank you.

0 user6386615 over 5 years ago in reply to Noel Fung

Prodigy 10 points

We use LMK04832 supply 200MHz clock for LMX2594

VCO can be locked only when freq is min of the core range. For example, it's able to lock VCO2 if Fvco is 8600, but was not able to lock if Fvco is 8800 while 8800 is in VCO2's core range [8600 9800].

I am sure VCO CapCode and VCO amplitude were both calculate correctly according to the manual.

Can anyone help on this?

0 Noel Fung over 5 years ago in reply to user6386615

TI__Guru** 115380 points

Hi There,

Could you show me your programming sequence when you change the frequency from 8600MHz to 8800MHz?

For example,

step 1. Program PLL_N

step 2. Program PLL_NUM

.......

Clock & timing

Clock & timing forum

LMX2594: frequency setting issue