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
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 volt-
age 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 con-
versions. 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
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
The AD650JN and AD650KN are offered in a plastic 14-lead
DIP package. 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 (0°C to +70°C) tempera-
ture range. For industrial temperature range (–25°C to +85°C)
applications, the AD650AD and AD650BD are offered in a
ceramic package. The AD650SD is specified for the full –55°C
to +125°C extended temperature range.
1. In addition to very high linearity, the AD650 can operate at
full-scale output frequency up to 1 MHz. The combination of
these two features makes the AD650 an inexpensive solution
for applications requiring high resolution monotonic A/D
2. The AD650 has a very versatile architecture that can be con-
figured to accommodate bipolar, unipolar, or differential
input voltages, or unipolar input currents.
3. TTL or CMOS compatibility is achieved using an open
collector frequency output. The pull-up resistor can be
connected to voltages up to +30 V, or +15 V or +5 V for
conventional CMOS or TTL logic levels.
4. The same components used for V/F conversion can also be
used for F/V conversion by adding a simple logic biasing net-
work and reconfiguring the AD650.
5. The AD650 provides separate analog and digital grounds.
This feature allows prevention of ground loops in real-world
6. The AD650 is available in versions compliant with MIL-
STD-883. Refer to the Analog Devices Military Products
Databook or current AD650/883B data sheet for detailed
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© Analog Devices, Inc., 2000