Datasheet
VFC320
8
SBVS017A
Selecting R
2
R
2
= V
PULLUP
/(8mA – I
LOAD
)
=5V/(8mA – 1.6mA), one TTL-load = 1.6mA
=781Ω
Choose a 750Ω 1/4-watt carbon compensation resistor with
±5% tolerance.
FREQUENCY-TO-VOLTAGE CONVERSION
To operate the VFC320 as a frequency-to-voltage converter,
connect the unit as shown in Figure 9. To interface with
TTL-logic, the input should be coupled through a capacitor,
and the input to pin 10 biased near +2.5V. The converter will
detect the falling edges of the input pulse train as the voltage
at pin 10 crosses zero. Choose C
3
to make t = 0.1t (see
Figure 9). For input signals with amplitudes less than 5V,
pin 10 should be biased closer to zero to insure that the input
signal at pin 10 crosses the zero threshold.
Errors are nulled using 0.001 • full scale frequency to null
offset, and full scale frequency to null the gain error. The
procedure is given on this page. Use equations from V/F
calculations to find R
1
, R
3
, R
4
, C
1
and C
2
.
TYPICAL APPLICATIONS
Excellent linearity, wide dynamic range, and compatible
TTL, DTL, and CMOS digital output make the VFC320
ideal for a variety of VFC applications. High accuracy
allows the VFC320 to be used where absolute or exact
readings must be made. It is also suitable for systems
requiring high resolution up to 14 bits
Figures 10-14 show typical applications of the VFC320.
FIGURE 9. Connection Diagram for F/V Conversion.
FIGURE 10. Inexpensive A/D with Two-Wire Digital Transmission Over Twisted Pair.
FIGURE 11. Inexpensive Digital Panel Meter.
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Input
Amp
Switch
One-
shot
NC
NC
–V
CC
(1)
NC
NC
NC
+V
CC
(1)
C
2
Integrator Capacitor
R
1
R
3
R
5
R
4
+15V
–15V
One-shot
Capacitor
C
1
f
OUT
NOTE:
(
1
)
B
y
pass with 0.01
µ
F
Pin numbers in squares
refer to DIP packa
g
e.
R
6
12kΩ
2.5V
R
7
2.2kΩ
0.001µF
C
3
f
IN
V
OUT
+1V
0V
(t)
T
F
FS
= 100kHz
Sensor
INA101
+
–
VFC320
V
IN
f
OUT
Clock
Counter
Computer
Parallel
Data
High Noise
Immunity
Instrumentation
Amp
VFC320
V
IN
f
OUT
Clock
BDC
Counter
Driver/Display
e
1
e
2
Differential
Input