1k Series restors on ADF4351 and PE43703

[heatherlomond]

I want to have an ADF4351 and an attenuator in my Portsdown 4.
I am unsure about the 1k resistors. I think it comes down to a choice between these 2 options?

Code: Select all

              |-- 1k -- ADF4351 CLK
Pin 29: CLK --|
              |-- 1k -- PE43703 CLK

or

Code: Select all

                    |-- ADF4351 CLK
Pin 29: CLK -- 1k --|
                    |-- PE43703 CLK

And presumably the same for Data on pin 31?
Also I assume I need a 1k in the line from to pin 33 to ADF4351 LE and another for pin 10 to the PE43703 LE so:

Code: Select all

Pin 33: LE -- 1k -- ADF4351 LE

Pin 10: LE -- 1k -- PE43703 LE

Can someone confirm which option to use for CLK and DATA and if I have the LE 1ks correct?

Heather

[G8GKQ]

Hi Heather

It's all about damping reflections of the sharp edges on the data/clock lines, so it's all a bit of a black art (unless you have a very high speed low capacitance 'scope).

I tend to use 220 ohm resistors at the Raspberry Pi end (only) of any data/clock/switching line. If you are running 2 parallel wires to the adf4351 and the PE43703 then that's 2 resistors for each line. If they are both remote in the same box, only one resistor for each line.

But don't make them too remote - 20cm seems to be a reasonable limit.

Dave