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Charge pump vs. phase detector gain for a PLL

When calculating PLL loop filter values, one need to know the phase
detector gain in mA/Hz for a "charge pump phase detector". Very often
the charge pump current is defined if you are using a synthesiser chip.
My question is therefore: What is the relationship between phase
detector gain in mA/Hz and charge pump current in mA?
I often see in literature that they define the ratio between phase
detector gain and charge pump current as a 1:1 ratio. But is this
really correct?
 
J

Jim Thompson

Jan 1, 1970
0
When calculating PLL loop filter values, one need to know the phase
detector gain in mA/Hz for a "charge pump phase detector".

That is not correct... it is mA/radian
Very often
the charge pump current is defined if you are using a synthesiser chip.
My question is therefore: What is the relationship between phase
detector gain in mA/Hz and charge pump current in mA?
I often see in literature that they define the ratio between phase
detector gain and charge pump current as a 1:1 ratio. But is this
really correct?

Nope. Read the data sheet more carefully.

...Jim Thompson
 
M

Mark

Jan 1, 1970
0
Jim said:
That is not correct... it is mA/radian

Yes. the gain is current / phase delta

very often the data sheet will give you the full scale current output
where full scale is +2pi radians (+360 degrees) and -2pi radians (-360
degrees).

Mark
 
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