VOLTAGE-TO-FREQUENCY/
FREQUENCY-TO-VOLTAGE CONVERTERS
TC9400
TC9401
TC9402
V+ = 10V to 15V
14
10k
6 GND
6.2V
.01µF
10k
V
DD
TC9400
2 ZERO
ADJUST
V
REF
OUT
I
IN
5
47pF
3
1M
.001µF
V
OUT
500k
100k
Offset
Adjust
Frequency
Input
33k
0.01µF
V+
1.0k
11 DET
AMP OUT 12
GND
6
IN914
1.0M
I
BIAS
V
REF
V
SS
7
4
0.1µF
1.0k
100k
Note: The output is referenced to pin 6, which is at 6.2V (Vz). For frequency meter applications,
a 1 mA meter with a series-scaling resistor can be placed across pins 6 and 12.
Figure 9.
F/V Single Supply F/V Converter
Output Filtering
The output of the TC9400 has a sawtooth ripple super-
imposed on a DC level. The ripple will be rejected if the
TC9400 output is converted to a digital value by an integrat-
ing analog to digital converter, such as the TC7107 or
TC7109. The ripple can also be reduced by increasing the
value of the integrating capacitor, although this will reduce
the response time of the F/V converter.
The sawtooth ripple on the output of an F/V can be
eliminated without affecting the F/V's response time by
using the circuit in Figure 10. The circuit is a capacitance
multiplier, where the output coupling capacitor is multiplied
by the AC gain of the op amp. A moderately fast op amp,
such as the TL071, should be used.
V
REF
OUT 5
47pF
I
IN
3
1M
AMP OUT 12
.001µF
200
TC9400
.01µF
GND
6
2
3
1M
1M
+5
0.1µF
V
OUT
TL071
–
7
6
+
4
–5
Figure 10.
3-298
Ripple Filter
TELCOM SEMICONDUCTOR, INC.
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
