LM231N/NOPB National Semiconductor, LM231N/NOPB Datasheet - Page 8
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LM231N/NOPB
Manufacturer Part Number
LM231N/NOPB
Description
IC CONVERTER PREC V TO FREQ 8DIP
Manufacturer
National Semiconductor
Type
Voltage to Frequencyr
Datasheet
1.LM331NNOPB.pdf
(15 pages)
Specifications of LM231N/NOPB
Frequency - Max
100kHz
Full Scale
±150ppm/°C
Linearity
±0.01%
Mounting Type
Through Hole
Package / Case
8-DIP (0.300", 7.62mm)
Converter Function
VFC
Full Scale Frequency
100
Power Supply Requirement
Single
Single Supply Voltage (typ)
5/9/12/15/18/24/28V
Single Supply Voltage (max)
40V
Single Supply Voltage (min)
4V
Dual Supply Voltage (typ)
Not RequiredV
Dual Supply Voltage (min)
Not RequiredV
Dual Supply Voltage (max)
Not RequiredV
Operating Temperature (min)
-25C
Operating Temperature (max)
85C
Operating Temperature Classification
Commercial
Package Type
MDIP
Supply Voltage (max)
40 V
Supply Voltage (min)
4 V
Maximum Operating Temperature
+ 85 C
Minimum Operating Temperature
- 25 C
Linearity Error
+/- 0.14 %FSR
Mounting Style
Through Hole
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
*LM231N
*LM231N/NOPB
LM231
LM231N
*LM231N/NOPB
LM231
LM231N
www.national.com
Applications Information
A 47Ω resistor, in series with the 1 µF C
esis, which helps the input comparator provide the excellent
linearity.
*Use stable components with low temperature coefficients. See Typical
Applications section.
**0.1µF or 1µF, See “Principles of Operation.”
*Use stable components with low temperature coefficients. See Typical Applications section.
**This resistor can be 5 kΩ or 10 kΩ for V
***Use low offset voltage and low offset current op-amps for A1: recommended type LF411A
with
FIGURE 3. Simple Stand-Alone V-to-F Converter
±
0.03% Typical Linearity (f = 10 Hz to 11 kHz)
FIGURE 4. Standard Test Circuit and Applications Circuit, Precision Voltage-to-Frequency Converter
S
=8V to 22V, but must be 10 kΩ for V
L
, provides hyster-
(Continued)
00568001
8
S
=4.5V to 8V.
Details of Operation: Precision V-To-F Converter
(Figure 4)
In this circuit, integration is performed by using a conven-
tional operational amplifier and feedback capacitor, C
When the integrator’s output crosses the nominal threshold
level at pin 6 of the LM231/331, the timing cycle is initiated.
The average current fed into the op-amp’s summing point
(pin 2) is i x (1.1 R
−V
input comparator does not affect the offset or accuracy of the
V-to-F converter as it does in the stand-alone V-to-F con-
verter; nor does the LM231/331 bias current or offset cur-
rent. Instead, the offset voltage and offset current of the
operational amplifier are the only limits on how small the
signal can be accurately converted. Since op-amps with
voltage offset well below 1 mV and offset currents well below
2 nA are available at low cost, this circuit is recommended for
best accuracy for small signals. This circuit also responds
immediately to any change of input signal (which a stand-
alone circuit does not) so that the output frequency will be an
accurate representation of V
spacing can be measured.
In the precision mode, excellent linearity is obtained be-
cause the current source (pin 1) is always at ground potential
and that voltage does not vary with V
stand-alone V-to-F converter, a major cause of non-linearity
is the output impedance at pin 1 which causes i to change as
a function of V
The circuit of Figure 5 operates in the same way as Figure 4,
but with the necessary changes for high speed operation.
IN
/R
IN
. In this circuit, the voltage offset of the LM231/331
IN
).
t
C
00568005
t
) x f which is perfectly balanced with
IN
, as quickly as 2 output pulses’
IN
or f
OUT
. (In the
F
.