TC9402 TELCOM [TelCom Semiconductor, Inc], TC9402 Datasheet - Page 7

• Manufacturer Part Number: TC9402
• Description: VOLTAGE-TO-FREQUENCY/FREQUENCY-TO-VOLTAGE CONVERTERS
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

Output Common
Out are connected to this pin. An output level swing from the
drain voltage to ground or to the V
by connecting this pin to the appropriate point.
R
point for the TC9400. Specifications for the TC9400 are
based on R
beyond 100kHz is limited by the pulse width of the Pulse
Output (typically 3 sec). Reducing R
pulse width and increase the maximum operating frequency,
but linearity errors will also increase. R
to 20k , which will typically produce a maximum full scale
frequency of 500kHz.
Amplifier Out
V/F operation, a negative-going ramp signal is available at
this pin. In the F/V mode, a voltage proportional to the
frequency input is generated.
Zero Adjust
amplifier. The low-frequency set point is determined by
adjusting the voltage at this pin.
I
summing junction when connected in the V/F mode. An
input current of 10 A is specified, but an overrange current
up to 50 A can be used without detrimental effect to the
circuit operation. I
operational amplifier. Voltage sources cannot be attached
directly, but must be buffered by external resistors.
V
V
dependent on the voltage regulation and temperature char-
acteristics of the reference circuitry.
the reference current will be equal to the input current. For
this reason, the DC impedance of the reference voltage
source must be kept low enough to prevent linearity errors.
For linearity of 0.01%, a reference impedance of 200
less is recommended. A 0.1 F bypass capacitor should be
connected from V
VOLTAGE-TO-FREQUENCY/
FREQUENCY-TO-VOLTAGE CONVERTERS
IN
SS
REF
BIAS
The sources of both the Freq/2 out and the Pulse Freq
An external resistor, connected to V
Increasing the maximum frequency of the TC9400
The output stage of the operational amplifier. During
This pin is the noninverting input of the operational
The inverting input of the operational amplifier and the
A reference voltage from either a precision source or the
Since the TC9400 is a charge balancing V/F converter,
supply is applied to this pin. Accuracy of the TC9400 is
TELCOM SEMICONDUCTOR, INC.
BIAS
= 100k
REF
IN
connects the summing junction of an
to ground.
10%, unless otherwise noted.
SS
supply may be obtained
BIAS
BIAS
SS
will decrease the
can be reduced
, sets the bias
or
V
pin. When the op amp output reaches the threshold level,
this pin is internally connected to the reference voltage and
a charge, equal to V
integrator capacitor. After about 3 sec, this pin is internally
connected to the summing junction of the op amp to dis-
charge C
the reference voltage is not directly applied to the summing
junction.
V/F CONVERTER DESIGN INFORMATION
Input/Output Relationships
voltage (V
External Component Selection
R
scale input current of approximately 10 A:
Example:
relationship is defined by the transfer equation. In practice,
the value of R
scale frequency at V
dure"). Metal film resistors with 1% tolerance or better are
recommended for high-accuracy applications because of
their thermal stability and low-noise generation.
C
the relationship:
C
although mica and ceramic devices can be used in applica-
tions where their temperature limits are not exceeded.
Locate as close as possible to pins 12 and 13.
IN
INT
INT
REF
The charging current for C
The output frequency (f
Frequency out =
The value of this component is chosen to give a full-
R
Note that the value is an approximation and the exact
The exact value is not critical but is related to C
3C
Improved stability and linearity are obtained when
IN
Out
REF
4C
REF
IN
V
REF
R
) by the transfer equation:
IN
. Break-before-make switching ensures that
C
IN
INT
IN
Full Scale
. Low-leakage types are recommended,
10 A
typically would be trimmed to obtain full-
10 A
10V
10 C
IN
R
V
REF
IN
IN
full scale (see "Adjustment Proce-
REF
.
= 1M .
OUT
x C
.
(V
) is related to the analog input
REF
REF
REF
, is removed from the
is supplied through this
) (C
1
REF
)
TC9400
TC9401
TC9402
REF
3-293
by
1
2
3
4
5
6
7
8