1-10 THEORY OF OPERATION
Both the normal and adapt charge pumps get their supply from the capacitive voltage multiplier
which is made up of C3701 to C3704 and triple diodes D3701, D3702. Two 3.3V square waves (
180 deg out of phase) are first multiplied by four and then shifted, along with regulated 5V, to build
up 13.5V at pin 47 of U3701.
Figure 5-2 Synthesizer Block Diagram
DATA
CLK
CEX
MODIN
VCC, DC5V
XTAL1
XTAL2
WARP
PREIN
VCP
REFERENCE
OSCILLATOR
VOLTAGE
MULTIPLIER
VOLTAGE
CONTROLLED
OSCILLATOR
2-POLE
LOOP
FILTER
DATA (U409 PIN 100)
CLOCK (U409 PIN 1)
CSX (U409 PIN 2)
MOD IN (U404 PIN 40)
+5V (U3711 PIN 4)
7
8
9
10
13, 30
23
24
25
32
47
VMULT2 VMULT1
BIAS1
SFOUT
AUX3
AUX4
IADAPT
IOUT
GND
FREFOUT
LOCK
4
19
6, 22, 23, 24
43
45
3
2
28
14
15
40
FILTERED 5V
STEERING
LINE
LOCK (U409 PIN 56)
PRESCALER IN
LO RF INJECTION
TX RF INJECTION
(1ST STAGE OF PA)
FREF (U3220 PIN 21 & U404 PIN 34)
39
BIAS2
41
DUAL
TSTRS
48
5V
R5
5, 20, 34, 36
(U3201 PIN 5)
AUX1
VDD, 3.3V
MODOUT
U3701
LOW VOLTAGE
FRACTIONAL-N
SYNTHESIZER
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