AD652AQ Analog Devices Inc, AD652AQ Datasheet - Page 15

• Manufacturer Part Number: AD652AQ
• Description: IV V-F CONVERTER SYNC 16-CDIP
• 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)
• Full Scale Range: 1MHz To 2MHz
• Linearity %: 0.02%
• Supply Voltage Range: ± 6V To ± 18V
• Digital Ic Case Style: DIP
• No. Of Pins: 16
• Frequency Max: 2MHz
• Termination Type: Through Hole
• Converter Function: VFC
• Full Scale Frequency: 2000
• Power Supply Requirement: Single/Dual
• Single Supply Voltage (max): 36V
• Single Supply Voltage (min): 12V
• Dual Supply Voltage (typ): ±15V
• Dual Supply Voltage (min): ±6V
• Dual Supply Voltage (max): ±18V
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Package Type: CDIP
• Converter Type: Voltage to Frequency
• Current, Quiescent Supply: ±11 mA (Typ.)
• Frequency Range: 5 MHz (Typ.)
• Input Impedance: 20 Kiloohms
• Number Of Pins: 20
• Temperature, Operating, Maximum: 85 °C
• Temperature, Operating, Minimum: -40 °C
• Voltage, Range: ±6 to ±18 V
• Voltage, Supply: 36 V
• Filter Terminals: Through Hole
• Rohs Compliant: No
• Calibration Error Fs Typ: 5%
• Lead Free Status / Rohs Status: Not Compliant

FREQUENCY-TO-VOLTAGE CONVERTER
The AD652 SVFC also works as a frequency-to-voltage
converter. Figure 22 shows the connection diagram for F/V
conversion. In this case, the negative input of the comparator is
fed the input pulses. Either comparator input may be used so
that an input pulse of either polarity may be applied to the F/V.
In Figure 22, the + input is tied to a 1.2 V reference and low-
level TTL pulses are used as the frequency input. The pulse
must be low on the falling edge of the clock. On the subsequent
rising edge, the 1 mA current source is switched to the
integrator summing junction and ramps up the voltage at Pin 4.
Due to the action of the AND gate, the 1 mA current is switched
off after only one clock period. The average current delivered to
the summing junction varies from 0 mA to 0.5 mA; using the
internal 20 kΩ resistor, this results in a full-scale output voltage
of 10 V at Pin 4.
The frequency response of the circuit is determined by the
capacitor; the −3 dB frequency is simply the RC time constant.
A tradeoff exists between ripple and response. If low ripple is
desired, a large value capacitor must be used (1 µF); if fast
response is needed, a small capacitor is used (1 nF minimum).
The op amp can drive a 5 kΩ resistor load to 10 V, using a 15 V
positive power supply. If a large load capacitance (0.01 µF) must
be driven, it is necessary to isolate the load with a 50 Ω resistor
V
OUT
+
–
5kΩ
0.01µF
50Ω
CLOCK
VOLTS
FREQ
+V
–V
C
OUT
Figure 22. Frequency-to-Voltage Converter
S
S
IN
1
2
3
4
5
6
7
8
20kΩ
LOADS ON FALLING EDGE OF CK
SHIFTS OUT ON RISING EDGE OF CL
FREQUENCY TO VOLTS CONVERTER
SYNCHRONOUS
VOLTAGE-TO-
FREQUENCY
CONVERTER
AD652
Rev. C | Page 15 of 28
1mA
REFERENCE
as shown. Because the 50 Ω resistor is 0.25% of the full scale,
and the specified gain error with the 20 kΩ resistor is 0.5%, this
extra resistor only increases the total gain error to 0.75% max.
The circuit shown is unipolar and only a 0 V to +10 V output is
allowed. The integrator op amp is not a general-purpose op
amp. Instead, it has been optimized for simplicity and high
speed. The most significant difference between this amplifier
and a general-purpose op amp is the lack of an integrator (or
level shift) stage.
Consequently, the voltage on the output (Pin 4) must always be
more positive than 1 V below the inputs (Pins 6 and 7). For
example, in the F-to-V conversion mode, the noninverting input
of the op amp (Pin 6) is grounded, which means the output
(Pin 4) cannot go below −1 V. Normal operation of the circuit as
shown never calls for a negative voltage at the output.
A second difference between this op amp and a general-purpose
amplifier is that the output only sinks 1.5 mA to the negative
supply. The only pull-down other than the 1 mA current used
for voltage-to-frequency conversion is a 0.5 mA source. The op
amp sources a great deal of current from the positive supply,
and is internally protected by current limiting. The op amp
output may be driven to within 4 V of the positive supply when
not sourcing external current. When sourcing 10 mA, the out-
put voltage may be driven to within 6 V of the positive supply.
AND
5V
D
SHOT
ONE
Q
Q
FLOP
"D"
CK
16
15
14
13
12
11
10
9
FREQ
NC
NC
IN
5V
CLOCK
5kΩ
1N4148
DIGITAL
GND
AD652