LMX2355SLB National Semiconductor, LMX2355SLB Datasheet - Page 19

• Manufacturer Part Number: LMX2355SLB
• Description: PLLatinum Fractional N RF/ Integer N IF Dual Low Power Frequency Synthesizer
• Manufacturer: National Semiconductor

Programming Description
5.3 QUADRATURE MODULUS PRESCALER
The LMX2354 contains a quadrature modulus prescaler, consisting of a prescaler, A counter, B counter and C counter. Once the
N value is known, the A, B, and C values can be calculated by:
C = N div P
B = (N–C • P) div 4
A = N mod 4
For the divide ratio to be legal, it is also required:
C
fvco = [N + F] x [fosc / R ]
N = P • C + 4 • B + A
F:
f
C:
B:
A:
f
R:
P:
5.4 SERIAL DATA INPUT TIMING
Note: Data shifted into register on clock rising edge. Data is shifted in MSB first.
vco
osc
>
: Output frequency of external voltage controlled oscillator (VCO)
: Output frequency of the external reference frequency oscillator
=max {A, B} + 2
TEST CONDITIONS: The Serial Data Input Timing is tested using a symmetrical waveform around V
with amplitudes of 2.2V
Fractional ratio (contents of FRAC_CNTR divided by the fractional modulus)
Preset value of the C counter
Preset value of the B counter
Preset value of the A counter
Preset divide ratio of binary 15-bit programmable reference counter (3 to 32,767)
Preset modulus of quadrature modulus prescaler
8/9/12/13 550 MHz–1.2 GHz
16/17/20/21 1.2 GHz–2.5 GHz
@
V
CC
=2.7V and 2.6V
@
V
CC
(Continued)
= 5.5V.
19
CC
/2. The test waveform has an edge rate of 0.6 V/ns
20004803
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