LMX2571: Charge pump current setting

Hi,

I have a question about the charge pump current setting of the LMX2571.

In the datasheet, it looks like the charge pump current can be set in 32 steps. However, in actual use it seems to be 24 steps, and in TICS Pro there are settings where the same current value appears in two places.

For example, even when selecting the same “1250 uA”, I can observe a change in phase noise performance between the 1st and the 2nd “1250 uA” entry, as if a different current value is actually being set. Also, the programmed register values are different between these two selections.

1st 1250 uA:
R41 = 0x290808
R40 = 0x28081C

2nd 1250 uA:
R41 = 0x290810
R40 = 0x28101C

Could you please explain:

1. What is the difference between the 1st and 2nd “1250 uA” setting in TICS Pro?

2. Which charge pump current is actually being set in each case (are they truly the same current or different)?

3. Is there any recommendation on which entry/code should be used?

Best regards,

Conor