TC9400_06 MICROCHIP [Microchip Technology], TC9400_06 Datasheet - Page 17

• Manufacturer Part Number: TC9400_06
• Description: Voltage-to-Frequency/Frequency-to-Voltage Converters
• Manufacturer: MICROCHIP [Microchip Technology]

FIGURE 7-4:
7.4
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 inte-
grating 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 7-1. The circuit is a capaci-
tance 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.
© 2006 Microchip Technology Inc.
-5V
F
IN
2 kΩ
Output Filtering
Offset
Adjust
"Frequency
Input Level
Figure 7-1:
Shifter"
+5V
See
100 kΩ
2.2 kΩ
DC – 10 kHz Converter
2
Zero Adjust
Threshold
Detect
I
BIAS
11
1
10 kΩ
TC9400A
TC9401A
TC9402A
Threshold
Detector
V
SS
4
3msec
Delay
7
V
(Typically -5V)
V
REF
REF
+5V
V
DD
14
FIGURE 7-1:
FIGURE 7-5:
42
–
Amp
+
Op
TC9400
TC9400/9401/9402
GND
V
6
AMP OUT
REF
OUT
I
GND
IN
60 pF Amp
12 pF
5
3
12
Common
6
F
Output
V
OUT
OUT
F
REF
RIPPLE FILTER
Ripple Filter
Out
OUT
1M
I
IN
47 pF
/2
10
9
8
5
3
12
*Optional/If
*
Buffer is Needed
.001 μF
V+
V+
200
R
1 MΩ
1M
C
56 pF
.01 μF 1M
INT
*
REF
*
DS21483C-page 17
2
3
+
+
–
7
4
C
1000 pF
+5
-5
INT
6
V
TL071
0.1 μF
OUT
V
OUT