Product Specification
PE83336
Page 8 of 12
©2010-2012 Peregrine Semiconductor Corp. All rights reserved. Document No. 70-0137-05 │ UltraCMOS
®
RFIC Solutions
Main Counter Chain
The main counter chain divides the RF input
frequency, F
in
, by an integer derived from the user
defined values in the “M” and “A” counters. It is
composed of the 10/11 dual modulus prescaler,
modulus select logic, and 9-bit M counter. Setting
Pre_en “low” enables the 10/11 prescaler. Setting
Pre_en “high” allows F
in
to bypass the prescaler
and powers down the prescaler.
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] (1)
where A
M + 1, 1
M
511
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)) (2)
where A
M + 1, 1
M
511
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. Programming the M
Counter with the minimum value of “1” will result in
a minimum M Counter divide ratio of “2”.
When the prescaler is bypassed, the equation
becomes:
F
in
= (M + 1) x (f
r
/ (R+1)) (3)
where 1
M
511
In Direct Interface Mode, main counter inputs M
7
and M
8
are internally forced low.
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) (4)
where 0
R
63
Note that programming R equal to “0” will pass the
reference frequency, f
r
, directly to the phase
detector.
In Direct Interface Mode, R Counter inputs R4 and
R5 are internally forced low (“0”).
Register Programming
Parallel Interface Mode
Parallel Interface Mode is selected by setting the
Bmode input “low” and the Smode input “low”.
Parallel input data, D[7:0], are latched in a
parallel fashion into one of three, 8-bit primary
register sections on the rising edge of M1_WR,
M2_WR, or A_WR per the mapping shown in
Table 7 on page 9. The contents of the primary
register are transferred into a secondary register
on the rising edge of Hop_WR according to the
timing diagram shown in Figure 5. Data are
transferred to the counters as shown in Table 7
on page 9.
The secondary register acts as a buffer to allow
rapid changes to the VCO frequency. This
double buffering for “ping-pong” counter control
is programmed via the FSELP input. When
FSELP is “high”, the primary register contents
set the counter inputs. When FSELP is “low”, the
secondary register contents are utilized.
Parallel input data, D[7:0], are latched into the
enhancement register on the rising edge of
E_WR according to the timing diagram shown in
Figure 5. This data provides control bits as
shown in Table 8 on page 9 with bit functionality
enabled by asserting the Enh input “low”.
Serial Interface Mode
Serial Interface Mode is selected by setting the
Bmode input “low” and the Smode input “high”.
While the E_WR input is “low” and the S_WR
input is “low”, serial input data (Sdata input), B
0
to B
19
, are clocked serially into the primary
register on the rising edge of Sclk, MSB (B
0
)
first. The contents from the primary register are
transferred into the secondary register on the
rising edge of either S_WR or Hop_WR
according to the timing diagram shown in
Figures 5-6. Data are transferred to the counters
as shown in Table 7 on page 9.
The double buffering provided by the primary
and secondary registers allows for “ping-pong”
counter control using the FSELS input. When
FSELS is “high”, the primary register contents
set the counter inputs. When FSELS is “low”, the
secondary register contents are utilized.
