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PDF AD537 Data sheet ( Hoja de datos )
| Número de pieza | AD537 | |
| Descripción | Integrated Circuit Voltage-to-Frequency Converter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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FEATURES
Low Cost A–D Conversion
Versatile Input Amplifier
Positive or Negative Voltage Modes
Negative Current Mode
High Input Impedance, Low Drift
Single Supply, 5 V to 36 V
Linearity: ؎0.05% FS
Low Power: 1.2 mA Quiescent Current
Full-Scale Frequency up to 100 kHz
1.00 V Reference
Thermometer Output (1 mV/K)
F-V Applications
MIL-STD-883 Compliant Versions Available
Integrated Circuit
Voltage-to-Frequency Converter
AD537*
PIN CONFIGURATIONS
D-14 Package
H-10A Package
LOGIC GND 1
SYNC 2
IIN 3
–VIN 4
+VIN 5
VTEMP 6
VREF 7
LOGIC GND
10
AD537
14 OUTPUT
–VIN 1
AD537
9 OUTPUT
DRIVER
13 +VS +VIN 2
DRIVER
8 +VS
CURR-
BUF TO-FREQ
CONV
VT PRECISION
VOLTAGE
VR REFERENCE
12 CAP
11 CAP
CURR-
TO-FREQ
BUF CONV
10 VOS
9 VOS
8 –VS
3
VTEMP
VT PRECISION
VR
VOLTAGE
REFERENCE
4
VREF
5
7
CAP
6
CAP
–VS
(CONNECTED TO CASE)
PRODUCT DESCRIPTION
The AD537 is a monolithic V-F converter consisting of an input
amplifier, a precision oscillator system, an accurate internal ref-
erence generator and a high current output stage. Only a single
external RC network is required to set up any full-scale (F.S.)
frequency up to 100 kHz and any F.S. input voltage up to
± 30 V. Linearity error is as low as ± 0.05% for 10 kHz F.S., and
operation is guaranteed over an 80 dB dynamic range. The over-
all temperature coefficient (excluding the effects of external
components) is typically ± 30 ppm/°C. The AD537 operates
from a single supply of 5 V to 36 V and consumes only 1.2 mA
quiescent current.
A temperature-proportional output, scaled to 1.00 mV/K,
enables the circuit to be used as a reliable temperature-to-
frequency converter; in combination with the fixed reference
output of 1.00 V, offset scales such as 0°C or 0°F can be generated.
The low drift (1 µV/°C typ) input amplifier allows operation
directly from small signals (e.g., thermocouples or strain gages)
while offering a high (250 MΩ) input resistance. Unlike most
V–F converters, the AD537 provides a square-wave output, and
can drive up to 12 TTL loads, LEDs, very long cables, etc.
The excellent temperature characteristics and long-term stability
of the AD537 are guaranteed by the primary bandgap reference
generator and the low T.C. silicon chromium thin film resistors
used throughout.
The device is available in either a 14-lead ceramic DIP or a 10-lead
metal can; both are hermetically sealed packages.
*Protected by Patent Nos. 3,887,963 and RE 30,586.
REV. C
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 AD537 is available in three performance/temperature
grades; the J and K grades are specified for operation over the
0°C to +70°C range while the AD537S is specified for operation
over the extended temperature range, –55°C to +125°C.
PRODUCT HIGHLIGHTS
1. The AD537 is a complete V-F converter requiring only an
external RC timing network to set the desired full-scale fre-
quency and a selectable pull-up resistor for the open collec-
tor output stage. Any full-scale input voltage range from
100 mV to 10 volts (or greater, depending on +VS) can be
accommodated by proper selection of timing resistor. The
full-scale frequency is then set by the timing capacitor from
the simple relationship, f = V/10RC.
2. The power supply requirements are minimal, only 1.2 mA
quiescent current is drawn from a single positive supply from
4.5 volts to 36 volts. In this mode, positive inputs can vary
from 0 volts (ground) to (+VS – 4) volts. Negative inputs can
easily be connected for below ground operation.
3. F-V converters with excellent characteristic are also easy to
build by connecting the AD537 in a phase-locked loop. Ap-
plication particulars are shown in Figure 6.
4. The versatile open-collector NPN output stage can sink up
to 20 mA with a saturation voltage less than 0.4 volts. The
Logic Common terminal can be connected to any level be-
tween ground (or –VS) and 4 volts below +VS. This allows
easy direct interface to any logic family with either positive or
negative logic levels.
5. The AD537 is available in versions compliant with MIL-
STD-883. Refer to the Analog Devices Military Product
Databook or current AD537/883B data sheet for detailed
specifications.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
1 page  
AD537
NONLINEARITY SPECIFICATION
The preferred method for specifying linearity error is in terms of
the maximum deviation from the ideal relationship after cali-
brating the converter at full scale and “zero”. This error will
vary with the full-scale frequency and the mode of operation.
The AD537 operates best at a 10 kHz full-scale frequency with
a negative voltage input; the linearity is typically within ± 0.05%.
Operating at higher frequencies or with positive inputs will
degrade the linearity as indicates in the Specification table. The
shape of a typical linearity plot is given in Figure 4.
0.18
0.16 TEST CONDITIONS:
0.14
+VS = +15V
–VS = 0V
0.12 CT = 0.01µF
0.10
RT = 10kΩ
VFS = ±10V
0.08 POS INPUT – FIG. 3
NEG INPUT – FIG. 4
0.06
AD537J
0.04
0.02
0
–0.02
–0.04
AD537K, S
–0.06
–0.08
1
10 100 1k
OUTPUT FREQUENCY – Hz
10k
Figure 4a. Typical Nonlinearity Error Envelopes with
10 kHz F.S. Output
0.18
0.16
0.14
0.12
0.10
0.08
0.06
TEST CONDITIONS:
+VS = +15V
–VS = 0V
CT = 0.001µF
RT = 10kΩ
VFS = ±10V
POS INPUT – FIG. 3
NEG INPUT – FIG. 4
AD537J
0.04
0.02
0
–0.02
AD537K, S
–0.04
–0.06
–0.08
10
100 1k 10k
OUTPUT FREQUENCY – Hz
100k
Figure 4b. Typical Nonlinearity Error with 100 kHz F.S.
Output
OUTPUT INTERFACING CONSIDERATIONS
The design of the output stage allows easy interfacing to all digi-
tal logic families. The collector and emitter of the output NPN
transistor are both uncommitted; the emitter can be tied to any
voltage between –VS and 4 volts below +VS. The open collector
can be pulled up to a voltage 36 volts above the emitter regard-
less of +VS. The high power output stage can supply up to
20 mA (10 mA for “H” package) at a maximum saturation volt-
age of 0.4 volts. The stage limits the output current at 25 mA; it
can handle this limit indefinitely without damaging the device.
Figure 5 shows the AD537 with a standard 0 to +10 volt input
connection and the output stage connections. The values for the
logic common voltage, pull-up resistor, positive logic level, and
–VS supply are given in the accompanying chart for several logic
forms.
10k
VIN
AD537
LOGIC COM
VEE
1 14 fOUT
RL LOGIC VCC
2 DRIVER 13
+VS
(+15V)
3 12
4
CURR-
BUF TO-FREQ
11
C
TTL/DTL
VCC VEE RL
+5 GND 5k
–VS
GND
CONV
5 10 5V CMOS +5 GND 20k GND
15V CMOS/ +15 GND 10k GND
6 VT PRECISION
VOLTAGE
9 VOS
20k
HNIL
ECL 10k 0 –8 5k –8 TO
7 VR REFERENCE 8 –VS
–15
ECL2.5k +1.3 –2 5k –5
PMOS
0 –15 10k –15
Figure 5. Interfacing Standard Logic Families
APPLICATIONS
The diagrams and descriptions of the following applications are
provided to stimulate the discerning engineer with alternative
circuit design ideas. “Applications of the AD537 IC Voltage-
to-Frequency Converter”, available from Analog Devices on
request, covers a wider range of topics and concepts in data
conversion and data transmission using voltage-to-frequency
converters.
TRUE TWO-WIRE DATA TRANSMISSION
Figure 6 shows the AD537 in a true two-wire data transmission
scheme. The twisted-pair transmission lines serves the dual pur-
pose of supplying power to the device and also carrying fre-
quency data in the form of current modulation. The PNP circuit
at the receiving end represents a fairly simple way for converting
the current modulation back into a voltage square wave which
will drive digital logic directly. The 0.6 volt square wave which
will appear on the supply line at the device terminals does not
affect the performance of the AD537 because of its excellent
supply rejection. Also, note that the circuit operates at nearly
constant average power regardless of frequency.
RCAL
VIN
RSCALE
10
1
AD537
LOGIC
GND
9
DRIVER
+VIN
2
BUF
CURR-
TO-FREQ
CONV
VTEMP 3
VT PRECISION
VOLTAGE
VR REFERENCE
VREF 4
6
5
–VS
(CONNECTED TO CASE)
RL
+VS
8
120
7 RS
C
TWO-WIRE
LINK
220Ω
VS RS RL
+5 0 1k
+15 1k 3.3k
Figure 6. True Two-Wire Operation
+VS
OUTPUT
REV. C
–5–
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet AD537.PDF ] | |
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