Other Parts Discussed in Thread: LMX2594
I having problem with running the chip. PLL sets LOCK but frequency is not locked.
Using VCO force i was able to run chip only for VCO4 and VCO6 subranges.
What can be a reason for such behavior?
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Hi Dean,
1. Reference clock is OK.
2,4,5 SPI is OK, I write frequency setup every second, no missed setups for 2-3 hours.
At first i have used my register setup, then register setup generated by TICSPRO. I can readback
all registers and they behave as expected - write and read values are the same(except readonly registers).
I have tried self clearing RESET and explicit write with RESET=0, no avail.
3. It seems, this is the power problem or hardware wiring.
The chip is powered from two ADP150AUJZ-3.3, one branch connected to VCCBUF, second powers all other pins.
Visually (by oscilloscope) there are no problems in power supply.
Questions:
1. There is bunch of "bypass" pins, what are expected levels on those pins?
2. "LOCK" is locked mostly, no matter that frequency is wrong or unstable,
sometimes, though, it is not locked..?
6175.LMX2594 Initialization Power Up and Calibration.pdfVladimir,
OK, it sounds like some of the basic things are running. It's tricky to think of what would make only two cores work, unless you are misprogramming the device. When you force the ranges did you try?
1. VCO_DACISET_FORCE=1, VCO_DACISET=200
2. VCO_CAPCTRL_FORCE=1, VCO_CAPCTRL=100
3. VCO_SEL_FORCE=1, VCO_SEL = 1,2,3,4,5,6
For "Lock", if this is based on the "VCO calibration Status" lock detect, maybe this is the issue as you can lose lock with this style and it will not indicate it.
I don't have a bias level document with the LMX2572, but I have one for the LMX2594, which should be very similar and I am attaching.
REgards,
Dean
Dean Banerjee said:1. VCO_DACISET_FORCE=1, VCO_DACISET=200
2. VCO_CAPCTRL_FORCE=1, VCO_CAPCTRL=100
3. VCO_SEL_FORCE=1, VCO_SEL = 1,2,3,4,5,6
Can you clarify - run this settings with default N,NUM,DENOM, Fpfd path registers or with some settings?
For "Lock" I use LED connected to MUXOUT (output functionality "Lock detect"), can you clarify about "VCO calibration Status"?
I have checked voltages given in "LMX2594 Initialization.." file. The voltages are very close, it seems, they are ok.
Questions:
1 . FCAL_EN=0 was mentioned in the given file. But LMX2572 datasheet states:
"Enables and activates VCO frequency calibration. Writing register R0 with this bit set
to a 1 enables and triggers the VCO frequency calibration. Writing 0 to this field is
prohibited."
2. In initialization procedure -
"4. Program all registers in REVERSE order from highest to lowest
5. Wait 10 ms
6. Program register R0 one additional time with FCAL_EN to ensure VCO calibration runs from a steady state".
So two R0 writes are implied separated by 10 ms. Is this right?
Update: I was able to run PLL with TICS Pro register datasets for all VCOs.
It seems, PFD_DLY_SEL has big impact on functionality.
I can not grasp idea of selecting this parameter from Table 3.(LMX2572 datasheet )
I will use N in range 256...512 (3200...6400 Mhz / 12.5 Mhz).
Can you, please, provide more detailed selection guide.