LM231AN National Semiconductor, LM231AN Datasheet - Page 9

• Manufacturer Part Number: LM231AN
• Description: Voltage / Frequency (V/F & F/V) Converter IC
• Manufacturer: National Semiconductor

Specifications of LM231AN

• Frequency: 100kHz
• No. Of Pins: 8
• Mounting Type: Through Hole
• Converter Type: Voltage/Frequency
• Operating Temperature Max: 85°C
• Peak Reflow Compatible (260 C): No
• 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
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Applications Information
DETAILS OF OPERATION: F-to-V CONVERTERS
(Figure 6 and Figure 7)
In these applications, a pulse input at f
a C-R network and the negative-going edge at pin 6 causes
the input comparator to trigger the timer circuit. Just as with
a V-to-F converter, the average current flowing out of pin 1 is
I
In the simple circuit of Figure 6, this current is filtered in the
network R
mV peak, but the response will be slow, with a 0.1 second
time constant, and settling of 0.7 second to 0.1% accuracy.
*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 types LF411A or LF356.
AVERAGE
= i x (1.1 R
L
= 100 kΩ and 1 µF. The ripple will be less than 10
t
C
t
) x f.
S
=8V to 22V, but must be 10 kΩ for V
FIGURE 5. Precision Voltage-to-Frequency Converter,
IN
100 kHz Full-Scale,
is differentiated by
(Continued)
±
9
S
0.03% Non-Linearity
=4.5V to 8V.
In the precision circuit, an operational amplifier provides a
buffered output and also acts as a 2-pole filter. The ripple will
be less than 5 mV peak for all frequencies above 1 kHz, and
the response time will be much quicker than in Figure 6.
However, for input frequencies below 200 Hz, this circuit will
have worse ripple than Figure 6. The engineering of the filter
time-constants to get adequate response and small enough
ripple simply requires a study of the compromises to be
made. Inherently, V-to-F converter response can be fast, but
F-to-V response can not.
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