Amplifier and Data Converter Selection Guide (Rev. B

Amplifiers23Comparator ICs are specialized op ampsdesigned to compare two input voltages andprovide a logic state output. They can beconsidered one-bit analog-to-digitalconverters.The TI comparator portfolio consists of avariety of products with various performancecharacteristics, including: fast ns responsetime, wide input voltage ranges, extremelylow quiescent current consumption and opamp and comparator combination ICs.Comparator vs. Op AmpComparator Op AmpSpeed (Response time) Yes NoLogic Output Yes NoWide Diff. Input Range Yes YesLow Offset Drift No YesIn general, if a fast response time is required,use a comparator.Design ConsiderationsOutput topology• Open collector—connects to the logicsupply through a pull-up resistor andallows comparators to interface to avariety of logic families.• Push-pull—does not require a pull-upresistor. Because the output swings rail-torail,the logic level is dependent on thevoltage supplies of the comparator.Response time (propagation delay)—applications requiring “near real-time”signal response should consider comparatorswith nanosecond (ns) propagation delay. Notethat as propagation delay decreases, supplycurrent increases. Evaluate what mix ofperformance and power can be afforded. TheTLV349x family offers a unique combinationof speed/power with 5µs propagation delayon only 1µA of quiescent current.Combination comparator and op amp—forinput signals requiring DC level shifting and/orSlower FasterResponse Time Low-to-High (µs)Increasing Speed0.0060.00780.0250.1150.20.311.173680Push-Pull OutputOpen-Drain Output1.41.8LMV331, LMV393, LMV339TLV3491, TLV3492TLC372, TLC374Comparatorsgain prior to the comparator, consider theTLV230x (open drain) or TLV270x (push-pull) opamp and comparator combinations. These dualfunction devices save space and cost.Comparator and voltage reference—comparators typically require a referencevoltage to compare against. The TLV3011is an integrated comparator and voltagereference combination in a space-savingSC70 package.TLV3501 S, 12mA/chTL714 S, 12mA/chTL3016 S, 12.5mA/chTL712TLC352, TLC354LM393, LM339TLC393, TLC339TLC3702, TLC3704S, 20mA/chLM211TLV3701, TLV3702, TLV3704TLV3401, TLV3402, TLV3404S, D, Q, 100µA/chS, D, Q, 1.2µA/chD, Q, 150µA/chD, Q, 150µA/chD, Q, 20µA/chD, Q, 20µA/chS, D, Q, 0.8µA/chS, D, Q, 0.55µA/ch3.3 5 16 30Supply Voltage (V)S, 6mA/chD, Q, 500µA/ch➔High-Speed Comparator in SOT23TLV3501Get samples and datasheets at: www.ti.com/sc/device/TLV3501Key Features• High speed: 4.5ns response at 20mVoverdrive• Beyond-the-rail common-mode input range• Rail-to-rail, push-pull output• Single-supply operation: 2.7V to 5.5V• Packaging: SOT23Applications• Test and measurement• Power supply monitoring• Base stationsThe TLV3501 is a high-speed comparator in a small SOT23 package. Designed for a variety ofapplications, TLV3501 offers very fast response relative to power consumption. It is specifiedover the extended temperature range of –40°C to +125°C.Propagation Delay (ns)987654PROPAGATION DELAY vs. OVERDRIVE VOLTAGEFallRiseV CM = 1VV S = 5VC LOAD = 17pF30 20 40 60 80 100Overdrive Voltage (mV)TLV3501 performancecharacteristics.Texas Instruments 3Q 2007Amplifier and Data Converter Selection Guide