tc9400 Microchip Technology Inc., tc9400 Datasheet - Page 10

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

TC9400/9401/9402
4.0
4.1
The output frequency (F
input voltage (V
EQUATION 4-1:
4.2
4.2.1
The value of this component is chosen to give a full
scale input current of approximately 10 µA:
EQUATION 4-2:
EQUATION 4-3:
Note that the value is an approximation and the exact
relationship is defined by the transfer equation. In
practice, the value of R
obtain full scale frequency at V
Section 4.3 “Adjustment Procedure”, Adjustment
Procedure). Metal film resistors with 1% tolerance or
better are recommended for high accuracy applications
because of their thermal stability and low noise
generation.
4.2.2
The exact value is not critical but is related to C
the relationship:
Improved stability and linearity are obtained when
C
although mica and ceramic devices can be used in
applications where their temperature limits are not
exceeded. Locate as close as possible to Pins 12
and 13.
DS21483D-page 10
INT
≤ 4C
Frequency Out
VOLTAGE-TO-FREQUENCY
(V/F) CONVERTER DESIGN
INFORMATION
Input/Output Relationships
External Component Selection
REF
R
C
. Low leakage types are recommended,
IN
INT
3C
IN
R
IN
) by the transfer equation:
R
REF
IN
≅
≅
V
≤
IN
=
IN
10
C
10V
OUT
typically would be trimmed to
INT
V
--------
R
FULL SCALE
μ
10
IN
IN
A
) is related to the analog
≤
•
μ
= 1 M
A
10C
----------------------------------- -
(
V
REF
IN
REF
Ω
) C
1
(
full scale (see
REF
)
REF
by
4.2.3
The exact value is not critical and may be used to trim
the full scale frequency (see Section 6.1 “Input/Out-
put Relationships”, Input/Output Relationships).
Glass film or air trimmer capacitors are recommended
because of their stability and low leakage. Locate as
close as possible to Pins 5 and 3 (see
FIGURE 4-1:
V
4.2.4
Power supplies of ±5V are recommended. For high
accuracy requirements, 0.05% line and load regulation
and 0.1 µF disc decoupling capacitors, located near the
pins, are recommended.
4.3
Figure 3-1
location. Full scale may be trimmed by adjusting R
V
full scale frequency is as follows:
1.
2.
If adjustments are performed in this order, there should
be no interaction and they should not have to be
repeated.
4.4
A TC9400, which operates from a single 12 to 15V
variable power source, is shown in
circuit uses two Zener diodes to set stable biasing
levels for the TC9400. The Zener diodes also provide
the reference voltage, so the output impedance and
temperature coefficient of the Zeners will directly affect
power supply rejection and temperature performance.
Full scale adjustment is accomplished by trimming the
input current.
REF
REF
Set V
to obtain a 10 Hz output frequency.
Set V
to obtain a 10 kHz output frequency.
, or C
.
Adjustment Procedure
Improved Single Supply V/F
Converter Operation
500
400
300
200
100
IN
IN
REF
C
V
0
shows a circuit for trimming the zero
to 10V and trim either R
to 10 mV and trim the zero adjust circuit
DD
REF
. Recommended procedure for a 10 kHz
, V
-1
SS
-2
Recommended C
10 kHz
© 2007 Microchip Technology Inc.
V
-3
100 kHz
REF
-4
(V)
IN
V
V
R
V
T
-5
A
DD
SS
IN
IN
, V
Figure
Figure
= +25°C
= +10V
= 1MW
REF
= -5V
= +5V
-6
REF
, or C
4-2. This
4-1).
-7
vs.
REF
IN
,