adf4212l Analog Devices, Inc., adf4212l Datasheet - Page 9

• Manufacturer Part Number: adf4212l
• Description: Dual Low Power Pll Frequency Synthesizer
• Manufacturer: Analog Devices, Inc.

CIRCUIT DESCRIPTION
Reference Input Section
The Reference Input Stage is shown in Figure 2. SW1 and SW2
are normally closed switches. SW3 is normally open. When
power-down is initiated, SW3 is closed and SW1 and SW2 are
opened. This ensures that there is no loading of the REFIN pin
on power-down.
REV. A
–100
–120
–100
–120
–20
–40
–60
–80
–20
–40
–60
–80
0
0
–40
–40
REF
TPC 19. RF Spurs vs. Temperature
TPC 20. IF Spurs vs. Temperature
IN
Figure 2. Reference Input Stage
–20
–20
NC
POWER-DOWN
SW1
CONTROL
0
0
NO
NC
TEMPERATURE – C
TEMPERATURE – C
SW3
SW2
20
20
100k
40
40
NC = NO CONNECT
BUFFER
60
60
80
80
TO R COUNTER
100
100
–9–
RF/IF Input Stage
The RF/IF Input Stage is shown in Figure 3. It is followed by a
two-stage limiting amplifier to generate the CML (Current
Mode Logic) clock levels needed for the prescaler.
TPC 21. S Parameter Data for the RF Input
FREQ
(MHz)
50
150
250
350
450
550
650
750
850
950
1050
1150
1250
1350
1450
RF
RF
IN
IN
A
B
s11.REAL
0.97692
0.942115
0.961217
0.920667
0.897441
0.888164
0.850012
0.760189
0.767363
0.779511
0.761034
0.624825
0.635364
0.630242
0.634506
Figure 3. RF/IF Input Stage
GENERATOR
BIAS
–0.110459
–0.085802
–0.185830
–0.245482
–0.282399
–0.305457
–0.358884
–0.541032
–0.585687
–0.482539
–0.530108
–0.590526
–0.592498
–0.655932
s11.IMAG
–0.021077
2k
FREQ
(MHz)
1550
1650
1750
1850
1950
2050
2150
2250
2350
2450
2550
2650
2750
2850
2950
1.6V
s11.REAL
0.561872
0.529742
0.514244
0.405754
0.379354
0.312959
0.322646
0.288881
0.199294
0.206914
0.168344
0.092764
0.036125
0.037007
–0.053842
2k
ADF4212L
AGND
AV
–0.648879
–0.668172
–0.702192
–0.714541
–0.703593
–0.802878
–0.803970
–0.807055
–0.758619
–0.725029
–0.770837
–0.778619
–0.706197
–0.716939
–0.736527
s11.IMAG
DD