Datasheet

© 2007 Microchip Technology Inc. DS21483D-page 11
TC9400/9401/9402
Trimming the reference voltage is not recommended
for high accuracy applications unless an op amp is
used as a buffer, because the TC9400 requires a low-
impedance reference (see Section 2.5 “Voltage Ref-
erence (VREF)”, V
REF
pin description, for more infor-
mation).
The circuit of Figure 4-2 will directly interface with
CMOS logic operating at 12V to 15V. TTL or 5V CMOS
logic can be accommodated by connecting the output
pull-up resistors to the +5V supply. An optoisolator can
also be used if an isolated output is required; also, see
Figure 4-3.
FIGURE 4-2: Voltage-to-Frequency.
R1
910 kΩ
R4
F
D2
5.1 VZ
R2
910 kΩ
R5
91 kΩ
Rp
Offset
20 kΩ
100 kΩ
D1
5.1 VZ
0.1 µF
100 kΩ
C
REF
C
INT
1.2 kΩ
+12 to +15V
10 10 kΩ
Output
Frequency
Digital
Ground
Analog Ground
Input
Voltage
(0 to 10V)
R3
Gain
TC9400
11
12
5
3
2
6
7
1
4
14
9
10
8
Threshold
Detect
Amp Out
C
REF
I
IN
Zero Adjust
GND
V
REF
I
BIAS
Output
Common
F
OUT
/2
F
OUT
V
DD
V
SS
100 kΩ
kΩ
Component Selection
F/S Freq. C
REF
C
INT
1 kHz 2200 pF 4700 pF
10 kHz 180 pF 470 pF
100 kHz 27 pF 75 pF