Data Sheet
FEATURES
V/F conversion to 1 MHz
Reliable monolithic construction
Very low nonlinearity
0.002% typ at 10 kHz
0.005% typ at 100 kHz
0.07% typ at 1 MHz
Input offset trimmable to zero
CMOS- or TTL-compatible
Unipolar, bipolar, or differential V/F
V/F or F/V conversion
Available in surface mount
MIL-STD-883 compliant versions available
Voltage-to-Frequency and
Frequency-to-Voltage Converter
AD650
FUNCTIONAL BLOCK DIAGRAM
AD650
V
OUT 1
+IN
2
–IN
3
BIPOLAR
OFFSET
4
CURRENT
–V
S 5
S1
–V
S
OUT
–V
S
COMP
1mA
–0.6V
10
14
OP
AMP
INPUT
OFFSET
TRIM
OFFSET
NULL
OFFSET
NULL
13
12
+V
S
11
ANALOG
GND
DIGITAL
GND
COMPARATOR
INPUT
F
OUTPUT
IN
ONE
FREQ ONE
SHOT
6
SHOT OUT
CAPACITOR
NC
7
NC = NO CONNECT
9
8
Figure 1.
PRODUCT DESCRIPTION
The AD650 V/F/V (voltage-to-frequency or frequency-to-voltage
converter) provides a combination of high frequency operation
and low nonlinearity previously unavailable in monolithic form.
The inherent monotonicity of the V/F transfer function makes
the AD650 useful as a high-resolution analog-to-digital converter.
A flexible input configuration allows a wide variety of input
voltage and current formats to be used, and an open-collector
output with separate digital ground allows simple interfacing to
either standard logic families or opto-couplers.
The linearity error of the AD650 is typically 20 ppm (0.002% of
full scale) and 50 ppm (0.005%) maximum at 10 kHz full scale.
This corresponds to approximately 14-bit linearity in an analog-
to-digital converter circuit. Higher full-scale frequencies or
longer count intervals can be used for higher resolution
conversions. The AD650 has a useful dynamic range of six
decades allowing extremely high resolution measurements.
Even at 1 MHz full scale, linearity is guaranteed less than
1000 ppm (0.1%) on the AD650KN, BD, and SD grades.
In addition to analog-to-digital conversion, the AD650 can be
used in isolated analog signal transmission applications,
phased-locked loop circuits, and precision stepper motor speed
controllers. In the F/V mode, the AD650 can be used in
precision tachometer and FM demodulator circuits.
The input signal range and full-scale output frequency are user-
programmable with two external capacitors and one resistor.
Input offset voltage can be trimmed to zero with an external
potentiometer.
Rev. E
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Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
The AD650JN and AD650KN are offered in plastic 14-lead DIP
packages. The AD650JP is available in a 20-lead plastic leaded
chip carrier (PLCC). Both plastic packaged versions of the
AD650 are specified for the commercial temperature range
(0°C to 70°C). For industrial temperature range (−25°C to
+85°C) applications, the AD650AD and AD650BD are offered
in ceramic packages. The AD650SD is specified for the full
−55°C to +125°C extended temperature range.
PRODUCT HIGHLIGHTS
1.
2.
3.
Can operate at full-scale output frequencies up to 1 MHz
(in addition to having very high linearity).
Can be configured to accommodate bipolar, unipolar, or
differential input voltages, or unipolar input currents.
TTL or CMOS compatibility is achieved by using an open
collector frequency output. The pull-up resistor can be
connected to voltages up to 30 V.
The same components used for V/F conversion can also be
used for F/V conversion by adding a simple logic biasing
network and reconfiguring the AD650.
Separate analog and digital grounds prevent ground loops
in real-world applications.
Available in versions compliant with MIL-STD-883.
4.
5.
6.
00797-001
AD650
TABLE OF CONTENTS
Features .............................................................................................. 1
Functional Block Diagram .............................................................. 1
Product Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings ............................................................ 5
ESD Caution .................................................................................. 5
Pin Configurations and Function Descriptions ........................... 6
Circuit Operation ............................................................................. 7
Unipolar Configuration ............................................................... 7
Component Selection................................................................... 8
Bipolar V/F .................................................................................. 10
Unipolar V/F, Negative Input Voltage ..................................... 10
Data Sheet
F/V Conversion .......................................................................... 10
High Frequency Operation ....................................................... 10
Decoupling and Grounding ...................................................... 12
Temperature Coefficients .......................................................... 12
Nonlinearity Specification ........................................................ 13
PSRR............................................................................................. 14
Other Circuit Considerations ................................................... 14
Applications..................................................................................... 16
Differential Voltage-to-Frequency Conversion ...................... 16
Autozero Circuit ......................................................................... 16
Phase-Locked Loop F/V Conversion ...................................... 17
Outline Dimensions ....................................................................... 19
Ordering Guide .......................................................................... 20
REVISION HISTORY
3/13—Rev. D to Rev. E
Changes to Figure 13 ...................................................................... 11
Updated Outline Dimensions ....................................................... 19
Changes to Ordering Guide .......................................................... 19
3/06—Rev. C to Rev. D
Updated Format .................................................................. Universal
Changes to Product Highlights....................................................... 1
Changes to Table 1 ............................................................................ 3
Added Pin Function Descriptions Table ...................................... 6
Updated Outline Dimensions ....................................................... 18
Changes to Ordering Guide .......................................................... 19
Rev. E | Page 2 of 20
Data Sheet
SPECIFICATIONS
T = 25°C, V
S
= ±15 V, unless otherwise noted.
Table 1.
Model
DYNAMIC PERFORMANCE
Full-Scale Frequency Range
Nonlinearity
1
f
MAX
= 10 kHz
f
MAX
= 100 kHz
f
MAX
= 500 kHz
f
MAX
= 1 MHz
Full-Scale Calibration Error
2
100 kHz
1 MHz
vs. Supply
3
vs. Temperature
A, B, and S Grades
at 10 kHz
at 100 kHz
J and K Grades
at 10 kHz
at 100 kHz
BIPOLAR OFFSET CURRENT
Activated by 1.24 kΩ Between
Pin 4 and Pin 5
DYNAMIC RESPONSE
Maximum Settling Time for
Full-Scale Step Input
Overload Recovery Time
Step Input
ANALOG INPUT AMPLIFIER
(V/F CONVERSION)
Current Input Range (Figure 4)
Voltage Input Range (Figure 12)
Differential Impedance
Common-Mode Impedance
Input Bias Current
Noninverting Input
Inverting Input
Input Offset Voltage
(Trimmable to Zero)
vs. Temperature (T
MIN
to T
MAX
)
Safe Input Voltage
COMPARATOR (F/V CONVERSION)
Logic 0 Level
Logic 1 Level
Pulse Width Range
4
Input Impedance
OPEN COLLECTOR OUTPUT
(V/F CONVERSION)
Output Voltage in Logic 0
I
SINK
≤ 8 mA, T
MIN
to T
MAX
Output Leakage Current in Logic 1
Voltage Range
5
Min
AD650J/AD650A
Typ
Max
1
0.002
0.005
0.02
0.1
±5
± 10
−0.015
+0.015
−0.015
0.005
0.02
0.05
0.002
0.005
0.02
0.05
±5
± 10
+0.015
−0.015
Min
AD650K/AD650B
Typ
Max
1
0.005
0.02
0.05
0.1
0.002
0.005
0.02
0.05
±5
± 10
Min
AD650S
Typ
Max
1
0.005
0.02
0.05
0.1
AD650
Units
MHz
%
%
%
%
%
%
% of
FSR/V
+0.015
±75
±150
±75
±150
±75
±150
±75
±150
±75
±200
ppm/°C
ppm/°C
ppm/°C
ppm/°C
0.45
0.5
0.55
0.45
0.5
0.55
0.45
0.5
0.55
mA
1 pulse of new frequency plus 1 μs
1 pulse of new frequency plus 1 μs
1 pulse of new frequency plus 1 μs
1 pulse of new frequency plus 1 μs
1 pulse of new frequency plus 1 μs
1 pulse of new frequency plus 1 μs
0
−10
+0.6
0
2 MΩ||10 pF
1000 MΩ||10 pF
40
±8
100
±20
±4
±30
±V
S
0
−10
+0.6
0
2 MΩ||10 pF
1000 MΩ||10 pF
40
±8
100
±20
±4
±30
±V
S
0
−10
+0.6
0
2 MΩ||10 pF
1000 MΩ||10 pF
40
±8
100
±20
±4
±30
±V
S
mA
V
nA
nA
mV
µV/°C
V
V
V
µs
kΩ
−V
S
0
0.1
250
−1
+V
S
(0.3 × t
OS
)
−V
S
0
0.1
250
−1
+V
S
(0.3 × t
OS
)
−V
S
0
0.1
250
−1
+V
S
(0.3 × t
OS
)
0
0.4
100
36
0
0.4
100
36
0
0.4
100
36
V
nA
V
Rev. E | Page 3 of 20
AD650
Model
AMPLIFIER OUTPUT (F/V CONVERSION)
Voltage Range
(1500 Ω Min Load Resistance)
Source Current
(750 Ω Max Load Resistance)
Capacitive Load
(Without Oscillation)
POWER SUPPLY
Voltage, Rated Performance
Quiescent Current
TEMPERATURE RANGE
Rated Performance
N Package
D Package
1
2
Data Sheet
Min
AD650J/AD650A
Typ
Max
Min
AD650K/AD650B
Typ
Max
Min
AD650S
Typ
Max
Units
0
10
10
0
10
10
0
10
10
V
mA
100
±9
±18
8
±9
100
±18
8
±9
100
±18
8
pF
V
mA
0
−25
+70
+85
0
−25
+70
+85
−55
+125
°C
°C
Nonlinearity is defined as deviation from a straight line from zero to full scale, expressed as a fraction of full scale.
Full-scale calibration error adjustable to zero.
3
Measured at full-scale output frequency of 100 kHz.
4
Refer to F/V conversion section of the text.
5
Referred to digital ground.
Specifications shown in
boldface
are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min
and max specifications are guaranteed, although only those shown in
boldface
are tested on all production units.
Rev. E | Page 4 of 20
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Parameter
Total Supply Voltage
Storage Temperature Range
Differential Input Voltage
Maximum Input Voltage
Open Collector Output Voltage
Above Digital GND
Current
Amplifier Short Circuit to Ground
Comparator Input Voltage
Rating
36 V
−55°C to +150°C
±10 V
±V
S
36 V
50 mA
Indefinite
±V
S
AD650
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. E | Page 5 of 20
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