tc9400 Microchip Technology Inc., tc9400 Datasheet - Page 16

• Manufacturer Part Number: tc9400
• Description: Voltage-to-frequency / Frequency-to-voltage Converters
• Manufacturer: Microchip Technology Inc.

TC9400/9401/9402
FIGURE 6-4:
6.4
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
integrating Analog-to-Digital Converter, such as the
TC7107. 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
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.
DS21483D-page 16
-5V
F
IN
2 kΩ
Adjust
Offset
Output Filtering
Figure 7-1:
Input Level
Frequency
Shifter
+5V
See
100 kΩ
2.2 kΩ
DC – 10 kHz Converter.
Figure
2
Zero Adjust
Threshold
Detect
I
6-1. The circuit is a
BIAS
11
1
10 kΩ
TC9400A
TC9401A
TC9402A
Threshold
Detector
V
SS
4
3 ms
Delay
7
V
(Typically -5V)
V
REF
REF
+5V
V
DD
14
FIGURE 6-5:
42
–
Amp
+
Op
TC9400
GND
AMP OUT
V
6
REF
OUT
I
GND
60 pF Amp
IN
12 pF
5
3
12
Common
6
Output
F
V
OUT
OUT
F
REF
Ripple Filter.
Out
OUT
© 2007 Microchip Technology Inc.
1
MΩ
I
47 pF
/2
IN
10
9
8
5
3
12
*Optional If
.001 µF
*
Buffer is Needed
200Ω
V+
V+
1
MΩ
.01 µF 1MΩ
R INT
1 MΩ
C
56 pF
*
*
REF
2
3
+
–
+
7
4
+5
-5
C
1000 pF
6
INT
TL071
0.1 µF
V
OUT
V
OUT