SM5166AV
FUNCTIONAL DESCRIPTION
Operating Frequency Divider
(N-counter) Structure
The operating frequency divider generates a
comparator frequency signal (FV), which is input to
the phase comparator, by dividing the VCO signal
input on pin FIN.
The operating frequency divider is comprised by
dual modulus prescalers, a 5-bit swallow counter and
a 11-bit main counter.
The settings for the prescaler (P and P + 1), swallow
counter (S) and main counter (M) are related to the
comparator frequency divider ratio by:
N =
(
P + 1
) ×
S + P
(
M – S
)
= PM + S
The counter value ranges are P = 32, P + 1 = 33, S =
0 to 31, and M = 32 to 2047. Therefore, the operating
frequency divider ratio range N is 1056 to 65535.
Input Data
The input data should be specified keeping in mind
the V
DD2
supply. The data is input using CLK,
DATA and LE pins into the shift register and latch
which operate from the V
DD2
supply. However, the
V
DD1
supply level can vary.
The control data input uses a 3-line 17-bit serial
interface comprising the clock (CLK), data input
(DATA) and latch enable (LE). The data is input with
the MSB first. The last (17th) bit is used as the latch
select control bit. Data is written to the shift register
on the rising edge of the clock signal. Accordingly,
the data should change state on the falling edge of
the clock signal. Data is transferred from the shift
register to the latch when the latch enable (LE)
signal goes HIGH. Accordingly, the latch enable
signal should be held LOW while data is being
written to the shift register.
The clock and data input signals are both ignored
when the latch enable signal goes HIGH. Also, the
CLK, DATA and LE inputs should be tied LOW
when not setting data.
Reference Frequency Divider
(R-counter) Structure
The reference frequency divider generates a
comparator frequency signal (FR), which is input to
the phase comparator, by dividing the reference
frequency input either from an external signal on
XIN or from a crystal connected between XIN and
XOUT.
The reference frequency divider is comprised by a
fixed divide-by-8 prescaler and an 13-bit reference
counter.
The settings for the prescaler (A = 8) and reference
counter (R) are related to the reference frequency
divider ratio by:
R = AB = 8B
The counter value ranges are A = 8 and B = 5 to
8191. Therefore, the reference frequency divider
ratio range is R = 40 to 65528.
NIPPON PRECISION CIRCUITS—5
NPC [ NIPPON PRECISION CIRCUITS INC ]
