MC1320x RF Circuit Question...

[RichTestardi]

Hi,

Sorry if this is the wrong place to post this question, but I didn't see other forums with 1320x information.

My question is what is the recommended value of the inductor between the balun inputs when using the Murata LDB212G4005C-001 balun?

In the MC1320x RF Daughter Card User's Guide, this is listed in section 5 (or 6) as L103 with a value of 3.9nH.

In the MC13201 Data Sheet, on the other hand, this is listed in section 8.8 as L2  with a value of 6.8nH.

Other than this, the two circuits are identical.

Thanks for any pointers!

-- Rich

[RichTestardi]

Just to add a bit more ambiguity, I found this in AN3248.PDF dated 03/2006:

Freescale has analyzed several network configurations and recommends that the best network to use for the MC1321x transceivers are two series coils and a shunt coil followed by a 1:1 balun. This configuration, as shown in Figure 7, provides the best bandwidth and least performance degradation. This match is optimized for best RX performance with some degradation in maximum TX power output.

For best performance, L102 and L103 should be 1.5 nH (Murata LQG15HN1N5S00) and L100 and L101 should be 3.9 nH (Murata LQG15HN3N9S00) and C103 should be 1.0 pF.

Note that the L numbers are different in this circuit vs. both of the others.

I'll probably just try all three combinations and see if I notice any difference -- it might well be in the noise vs. the other board parameters.