AD652AQ/+ Analog Devices Inc, AD652AQ/+ Datasheet - Page 20

• Manufacturer Part Number: AD652AQ/+
• Description: IC,Voltage-to-Frequency Converter,DIP,16PIN
• Manufacturer: Analog Devices Inc
• Type: Voltage to Frequencyr

Specifications of AD652AQ/+

• Rohs Status: RoHS non-compliant
• Frequency - Max: 2MHz
• Full Scale: ±50ppm/°C
• Linearity: ±0.02%
• Mounting Type: Through Hole
• Package / Case: 16-CDIP (0.300", 7.62mm)

AD652
SVFC Demultiplexer
The demultiplexer needed to separate the combined signals is
shown in Figure 30. A phase-locked loop drives another 4-phase
clock chip to lock onto the reconstructed clock signal. The sync
pulses are distinguished from the data pulses by their shorter
duration. Each falling edge on the multiplex input signal
triggers the one-shot; at the end of this one-shot pulse, the
multiplex input signal is sampled by a D-type flip-flop. If the
signal is high, the pulse was short (a sync pulse) and the Q
output of the D-flop goes low. The D-flop is cleared a short time
(two gate delays) later, and the clock is reconstructed as a
stream of short, low-going pulses. If the multiplex input is a data
pulse, then the signal will still be low and no pulse will appear at
the reconstructed clock output when the D-flop samples at the
end of the one-shot period. See Figure 29.
If it is desired to recover the individual frequency signals, the
multiplex input is sampled with a D-flop at the appropriate
time, as determined by the rising edge of the various phases
generated by the clock chip. These frequency signals can be
counted as a ratio relative to the reconstructed clock, so it is not
even necessary for the transmitter to be crystal-controlled as
shown in Figure 30.
INPUT
MPX
f2
D
Q
CLOCK
'74 (1/2)
+5V
CLOCK
D
GND
FREQUENCY OUTPUTS
NC
A1
A2
RECONSTRUCTED
Q
Q
1/2 '74
φ
2
1
2
3
4
5
6
7
CLEAR
RECONSTRUCTED
f3
D
Q
CLOCK OUTPUT
CLOCK
Q
ONE SHOT
'74 (1/2)
Q
'00
'00
'121
Q
φ
3
Figure 30. SVFC Demultiplexers
14
13
12
11
10
9
8
f4
D
Q
CLOCK
'74 (1/2)
V
NC
NC
R
C
R
NC
Rev. C | Page 20 of 28
CC
EXT
EXT
INT
/C
1
3
50pF
+5V
EXT
2kΩ
14
4
PHASE LOCK LOOP
390pF
+5V
φ
4
13
2
MC4044
φ
φ
150Ω
3
4
130Ω
4
11
5
10
1
2
3
4
5
6
7
8
9
TANK 1
TANK 2
GND 1
FFQ
FFD
φ
φ
φ
φ
GND 2
8
4 PHASE CLOCK
10
4 TTL
3 TTL
3
4
9
TIM 9904A
NC = NO CONNECT
+5V
SYNC
3.01kΩ
719Ω
1kΩ
φ
0.1µF
1
OSCOUT
Figure 29. Demultiplexer Waveforms
XTAL 2
XTAL 1
φ
φ
Figure 28. Multiplexer Waveforms
OSCIN
2 TTL
1 TTL
V
V
2
CC
DD
φ
φ
1
2
3
6
φ
+5V
20
19
18
17
16
15
14
13
12
11
'LS629
2
16
VCO
8
+5V
DATA
15
9
φ
φ
φ
3
1
2
11
7
4
5
50pF
φ
4
MULTIPLEX
INPUT
ONE SHOT
RECONSTRUCTED
CLOCK
φ
(PHASE LOCKED TO
RECONSTRUCTED
CLOCK)
1
φ
φ
φ
φ
1MULTIPLEX
OUTPUT
1
2
3
4