PE9704
Advance Information
Functional Description
The PE9704 consists of a prescaler, counters, a
phase detector, and control logic. The dual
modulus prescaler divides the VCO frequency by
either 10 or 11, depending on the value of the
modulus select. Counters “R” and “M” divide the
reference and prescaler output, respectively, by
integer values stored in a 20-bit register. An
additional counter (“A”) is used in the modulus
select logic. The phase-frequency detector
generates up and down frequency control signals.
The control logic includes a selectable chip
interface. Data can be written via a serial bus or
hardwired directly to the pins. There are also
various operational and test modes and a lock
detect output.
Main Counter Chain
Normal Operating Mode
Setting the PB control bit “low” enables the ÷10/11
prescaler. The main counter chain then divides the
RF input frequency (F
IN
) by an integer derived from
the values in the “M” and “A” counters.
In this mode, the output from the main counter
chain (f
p
) is related to the VCO frequency (F
IN
) by
the following equation:
f
p
= F
IN
/ [10 x (M + 1) + A]
where A
≤
M + 1, 1
≤
M
≤
511
(1)
Prescaler Bypass Mode
Setting the frequency control register bit PB “high”
allows F
IN
to bypass the ÷10/11 prescaler. In this
mode, the prescaler and A counter are powered
down, and the input VCO frequency is divided by
the M counter directly. This mode is only available
when using the serial port to set the frequency
control bits. The following equation relates F
IN
to
the reference frequency F
R
:
F
IN
= (M + 1) x (F
R
/ (R+1)) )
where 1
≤
M
≤
511
(3)
Reference Counter
The reference counter chain divides the reference
frequency F
R
down to the phase detector
comparison frequency f
c
.
The output frequency of the 6-bit R Counter is
related to the reference frequency by the following
equation:
f
c
= F
R
/ (R + 1)
where 0
≤
R
≤
63
(4)
Note that programming R with “0” will pass the
reference frequency (F
R
) directly to the phase
detector.
When the loop is locked, F
IN
is related to the
reference frequency (F
R
) by the following equation:
F
IN
= [10 x (M + 1) + A] x (F
R
/ (R+1))
where A
≤
M + 1, 1
≤
M
≤
511
(2)
A consequence of the upper limit on A is that F
IN
must be greater than or equal to 90 x (F
R
/ (R+1)) to
obtain contiguous channels. The A counter can
accept values as high as 15, but in typical operation
it will cycle from 0 to 9 between increments in M.
Programming the M counter with the minimum
allowed value of “1” will result in a minimum M
counter divide ratio of “2”.
PEREGRINE SEMICONDUCTOR CORP.
|
http://www.peregrine-semi.com
Copyright
Peregrine Semiconductor Corp. 2003
Page 7 of 12
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