Other Parts Discussed in Thread: LMX2595,
Hi Team!
I have previously used the LMX2595, and manage to control it well.
When I now use the LMX2572, it seems that I can not control the f_VCO.
First we use a default configuration that we found on Texas Instruments, that is modified slightly:
MUXOUT_LD_SEL = 0 (Readback)
v_OSC = 125 MHz
PreR = 2
FCAL_HPFD_ADJ = 1 (37.5 MHz < f_PD <= 75 MHz)
MASH_ORDER = 3 (3rd Order Modulator)
OUTA_PD = 1
OUTB_PD = 0
(RFoutB = 100 MHz)
The file thats is programmed to the LMX2572 at startup:
We then read back all register values, which can be found in LMX2572_ReadBackConfiguration.txt, and it seems correct when using the TICS Pro.
The readback file:
When this configuration is programed, we measure 108 MHz, which is not exactly what we expected though, but at least close.
After further experimentation, it seems that only our choice of channel divider seem to affect the RFoutB frequency.
When I change the register values to get RFoutB = 500 MHz, for example, the channel divider value is set to 8, and the frequency I measure is around 880 MHz,
close to 8 times the frequency that was measured when the channel divider value was 64.
The read back file after setting RFoutB to 500MHz:
/cfs-file/__key/communityserver-discussions-components-files/48/LMX2572_5F00_500MHz.txt
It seems that changing PLL_N does not affect RFoutB at all, even after writing FCAL_EN high.
OUTA_PD, OUTB_PD, OUTA_PWR, OUTB_PWR, and CHDIV all seem to work for us, and the register values for PLL_N seem correct when we readback all register values.
TICS Pro has been tremendously useful for finding errors in our register setup for the LMX2595, but now we do not get any errors, but we still can not control RFoutB properly.
Is there something we are doing wrong?
/Simon
