LM331 ,V-F ConverterLM131A/LM131,LM231A/LM231,LM331A/LM331PrecisionVoltage-to-FrequencyConvertersDecember1994LM131A/LM1 ..
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LM131-LM331
Precision Voltage-to-Frequency Converter
TL/H/5680
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 familyof voltage-to-frequency
convertersare ideally suitedforusein simple low-costcir-
cuitsfor analog-to-digital conversion, precision frequency-
to-voltage conversion, long-term integration, linear frequen- modulationor demodulation,and many other functions.
The output when usedasa voltage-to-frequency convertera pulse trainata frequency precisely proportionaltothe
applied input voltage. Thus,it providesallthe inherentad-
vantagesof the voltage-to-frequency conversion tech-
niques, andis easyto applyinall standard voltage-to-fre-
quency converter applications. Further, the LM131A/
LM231A/LM331A attainsa new high levelof accuracyver-
sus temperature which could onlybe attained with expen-
sive voltage-to-frequency modules. Additionallythe LM131 ideally suitedforusein digital systemsatlow power sup-
ply voltagesandcan provide low-cost analog-to-digital con-
versionin microprocessor-controlled systems. And,thefre-
quency froma battery powered voltage-to-frequency con-
vertercanbe easily channeled througha simple photoisola-
torto provide isolation against high common mode levels.
The LM131/LM231/LM331 utilizesa new temperature-
compensated band-gap reference circuit,to provide excel-
lent accuracy overthefull operating temperature range,at
power suppliesaslowas 4.0V. The precision timer circuit
haslow bias currents without degradingthe quick response
necessaryfor 100 kHz voltage-to-frequency conversion.
Andthe outputis capableof driving3 TTL loads,ora high
voltage outputupto 40V,yetis short-circuit-proof against
VCC.
Features Guaranteed linearity 0.01% max Improved performancein existing voltage-to-frequency
conversion applications Splitor single supply operation Operateson single5V supply Pulse output compatible withall logic forms Excellent temperature stability, g50 ppm/§C max Low power dissipation,15 mW typicalat5V Wide dynamic range, 100dB minat10 kHzfull scale
frequency Wide rangeoffull scale frequency,1Hzto 100kHz Low cost
Typical Applications
TL/H/5680–1
*Use stable componentswithlow temperature coefficients. SeeTypical Applications section.
fOUTeVIN
2.09V#RS#1
RtCt
**0.1mFor1mF, See‘‘Principlesof Operation.’’
FIGURE 1.Simple Stand-Alone Voltage-to-Frequency Converter
with g0.03% Typical Linearity(fe10 Hzto11 kHz)
C1995National SemiconductorCorporation RRD-B30M115/PrintedinU.S.A.
