Document
LM131A LM131 LM231A LM231 LM331A LM331 Precision Voltage-to-Frequency Converters
December 1994
LM131A LM131 LM231A LM231 LM331A LM331 Precision Voltage-to-Frequency Converters
General Description
The LM131 LM231 LM331 family of voltage-to-frequency converters are ideally suited for use in simple low-cost circuits for analog-to-digital conversion precision frequencyto-voltage conversion long-term integration linear frequency modulation or demodulation and many other functions The output when used as a voltage-to-frequency converter is a pulse train at a frequency precisely proportional to the applied input voltage Thus it provides all the inherent advantages of the voltage-to-frequency conversion techniques and is easy to apply in all standard voltage-to-frequency converter applications Further the LM131A LM231A LM331A attains a new high level of accuracy versus temperature which could only be attained with expensive voltage-to-frequency modules Additionally the LM131 is ideally suited for use in digital systems at low power supply voltages and can provide low-cost analog-to-digital conversion in microprocessor-controlled systems And the frequency from a battery powered voltage-to-frequency converter can be easily channeled through a simple photoisolator to provide isolation against high common mode levels The LM131 LM231 LM331 utilizes a new temperaturecompensated band-gap reference circuit to provide excellent accuracy over the full operating temperature range at power supplies as low as 4 0V The precision timer circuit has low bias currents without degrading the quick response necessary for 100 kHz voltage-to-frequency conversion And the output is capable of driving 3 TTL loads or a high voltage output up to 40V yet is short-circuit-proof against VCC
Features
Y Y
Y Y Y Y Y Y
Y Y
Guaranteed linearity 0 01% max Improved performance in existing voltage-to-frequency conversion applications Split or single supply operation Operates on single 5V supply Pulse output compatible with all logic forms Excellent temperature stability g 50 ppm C max Low power dissipation 15 mW typical at 5V Wide dynamic range 100 dB min at 10 kHz full scale frequency Wide range of full scale frequency 1 Hz to 100 kHz Low cost
Typical Applications
fOUT e
VIN R 1 S 2 09 V RL RtCt
TL H 5680 – 1
Use stable components with low temperature coefficients See Typical Applications section 0 1mF or 1mF See ‘‘Principles of Operation ’’
FIGURE 1 Simple Stand-Alone Voltage-to-Frequency Converter with g 0 03% Typical Linearity (f e 10 Hz to 11 kHz)
C1995 National Semiconductor Corporation
TL H 5680
RRD-B30M115 Printed in U S A
Absolute Maximum Ratings (Note 1)
If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage Output Short Circuit to Ground Output Short Circuit to VCC Input Voltage Operating Ambient Temperature Range Power Dissipation (PD at 25 C) and Thermal Resistance (ijA) (H Package) PD ijA (N Package) PD ijA (M Package) PD iJA Lead Temperature (Soldering 10 sec ) Dual-In-Line Package (Plastic) Metal Can Package (TO-5) ESD Susceptibility (Note 4) Metal Can Package (TO-5) Other Packages LM131A LM131 40V Continuous Continuous b 0 2V to a VS TMIN TMAX b 55 C to a 125 C LM231A LM231 40V Continuous Continuous b 0 2V to a VS TMIN TMAX b 25 C to a 85 C LM331A LM331 40V Continuous Continuous b 0 2V to a VS TMIN TMAX 0 C to a 70 C
670 mW 150 C W 1 25W 100 C W 1 25W 85 C W 260 C 260 C 2000V 500V 500V 260 C 1 25W 100 C W
260 C
Electrical Characteristics TA e 25 C unless otherwise specified (Note 2)
Parameter VFC Non-Linearity (Note 3) Conditions 4 5V s VS s 20V TMIN s TA s TMAX VFC Non-Linearity In Circuit of Figure 1 Conversion Accuracy Scale Factor (Gain) LM131 LM131A LM231 LM231A LM331 LM331A Temperature Stability of Gain LM131 LM231 LM331 LM131A LM231A LM331A Change of Gain with VS Rated Full-Scale Frequency Gain Stability vs Time (1000 Hrs) Overrange (Beyond Full-Scale) Frequency INPUT COMPARATOR Offset Voltage LM131 LM231 LM331 LM131A LM231A LM331A Bias Current Offset Current Common-Mode Range TMIN s TA s TMAX
b0 2
Min
Typ
g 0 003 g 0 006 g 0 024
Max
g 0 01 g 0 02 g 0 14
Units % FullScale % FullScale %FullScale kHz V kHz V ppm C ppm C % V % V kHz % FullScale %
VS e 15V f e 10 Hz to 11 kHz VIN e b10V RS e 14 kX 0 95 0 90 TMIN s TA s TMAX 4 5V s VS s 20V
1 00 1 00
g 30 g 20
1 05 1 10
g 150 g 50
4 5VsVS s 10V 10V s VS s 40V VIN e b10V TMIN s TA s TMAX VIN e b11V 10 10 0
0 01 0 006
g 0 02
01 0 06
TMIN s TA s TMAX TMIN s TA s TMAX
g3 g4 g3
g 10 g 14 g 10
mV mV mV nA nA V
b 80
g8
b 300
g 100
VCCb2 0
2
Electrical Characteristics TA e 25 C unless otherwise specified (Note 2) (Continued)
Parameter TIMER Timer Threshold Voltage Pin 5 Input Bias Current Pin 5 All Devices LM131 LM231 LM331 LM131A LM231A LM331A VSAT PIN 5 (Reset) CURRENT SOURCE (Pin 1) Output Current LM131 LM131A LM231 LM231A LM331 LM331A.