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| Final Electrical Specifications LTC1842 Ultralow Power Dual Comparator with Reference August 1998 FEATURES s s s DESCRIPTION The LTC (R)1842 is an ultralow power dual comparator with built-in reference. The comparator features less than 5.7A supply current over temperature, a 1.182V 1% reference, programmable hysteresis and open-drain outputs that sink current. The reference output can drive a bypass capacitor of up to 0.01F without oscillation. The comparator operates from a single 2.5V to 11V supply or a dual 1.25V to 5.5V supply. Comparator hysteresis is easily programmed by using two resistors and the HYST pin. The comparator's input operates from the negative supply to within 1.3V of the positive supply. The comparator output stage can typically sink greater than 20mA. By eliminating the cross-conduction current that normally happens when the comparator changes logic states, power supply glitches are eliminated. The LTC1842 is available in 8-pin PDIP and SO packages. , LTC and LT are registered trademarks of Linear Technology Corporation. s s s s s s Ultralow Quiescent Current: 3.5A Typ Open-Drain Outputs Typically Sink > 20mA Wide Supply Range: Single: 2.5V to 11V Dual: 1.25V to 5.5V Input Voltage Range Includes the Negative Supply Reference Output Drives 0.01F Capacitor Adjustable Hysteresis 12s Propagation Delay with 10mV Overdrive No Crowbar Current Pin Compatible Upgrade for MAX982 APPLICATIONS s s s s Battery-Powered System Monitoring Threshold Detectors Window Comparators Oscillator Circuits TYPICAL APPLICATION Battery Switchover Circuit WALL ADAPTER 9V Si9433 7 4-CELL BATTERY 1.1M 3 130k 562k IN A+ V+ LTC1842 1M LTC1474 STEP-DOWN REGULATOR 1M OUTPUT 3.3V 1N5818 + LBO - 5 HYST 4 IN B+ SUPPLY CURRENT (A) OUT A 1 + OUT B 8 6 REF 0.01F 20k V- 47k 2.4M 2 - 0 0 2 6 8 4 SUPPLY VOLTAGE (V) 10 12 1842 TA02 1842 TA01 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. U U U LTC1842 Supply Current vs Supply Voltage 5 TA = 25C 4 3 2 1 1 LTC1842 ABSOLUTE MAXIMUM RATINGS (Note 1) PACKAGE/ORDER INFORMATION TOP VIEW OUT A 1 V - Voltage V + to V - ................................................12V to - 0.3V IN +, IN -, HYST ................. (V + + 0.3V) to (V - - 0.3V) REF ................................... (V + + 0.3V) to (V - - 0.3V) OUT ................................................ 12V to (V - - 0.3V) Current IN +, IN -, HYST ................................................. 20mA REF ................................................................... 20mA OUT .................................................................. 50mA OUT Short-Circuit Duration (V + 5.5V) ...... Continuous Power Dissipation............................................. 500mW Operating Temperature Range LTC1842C............................................... 0C to 70C LTC1842I........................................... - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C ORDER PART NUMBER 8 7 6 5 OUT B V + 2 LTC1842CS8 LTC1842IS8 S8 PART MARKING 1842 1842I IN A+ 3 IN B + 4 REF HYST S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 175C/ W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER Power Supply V+ ICC VOS IIN VIN PSRR NOISE VHYST tPD ILEAK VOL Reference VREF Reference Voltage No Load Supply Voltage Range Supply Current Comparator Input Offset Voltage Input Leakage Current (IN +, IN -) Comparator Input Voltage Range Power Supply Rejection Ratio Voltage Noise Hysteresis Input Voltage Range Propagation Delay Output Leakage Current Output Low Voltage V + = 2.5V to 11V 100Hz to 100kHz CONDITIONS V + = 5V, V - = 0V, TA = 25C unless otherwise noted. MIN q TYP MAX 11 UNITS V A mV nA V mV/V VRMS V s s 2.5 3.5 3 0.01 V- 0.1 100 HYST = REF (Note 2) VCM = 2.5V IN + = IN - = 2.5V q 5.7 10 1.0 V + - 1.3V 1 VREF Comparator q q q q VREF - 50mV 12 4 COUT = 10pF, RPULL-UP = 100k Overdrive = 10mV Overdrive = 100mV VOUT = 12V (Note 2) IOUT = 1.8mA 25C C Temp Range I Temp Range q q q q q q 1 100 V - + 0.4V 1.174 1.170 1.164 1.182 1.190 1.194 1.200 VREF Load Regulation ISOURCE = 1mA ISINK =10A 1 1.75 100 3 4 6 en Voltage Noise 100Hz to 100kHz VRMS 2 U W U U WW W nA V V V V mV mV mV LTC1842 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER Power Supply V+ ICC VOS IIN VIN PSRR NOISE VHYST tPD ILEAK VOL Reference VREF Reference Voltage No Load Supply Voltage Range Supply Current Comparator Input Offset Voltage Input Leakage Current (IN +, IN -) Comparator Input Voltage Range Power Supply Rejection Ratio Voltage Noise Hysteresis Input Voltage Range Propagation Delay Output Leakage Current Output Low Voltage V+ = 2.5V to 11V 100Hz to 100kHz CONDITIONS V + = 3V, V - = 0V, TA = 25C unless otherwise noted. MIN q TYP MAX 11 UNITS V A mV nA V mV/V VRMS V s s 2.5 3.5 3 0.01 V- 0.1 100 HYST = REF (Note 2) VCM = 1.5V IN + = IN - = 1.5V q 5.5 10 1 V + - 1.3V 1 VREF Comparator q q q q VREF - 50mV 14 5 COUT = 10pF, RPULL-UP = 100k Overdrive = 10mV Overdrive = 100mV VOUT = 12V (Note 2) IO = 0.8mA 25C C Temp Range I Temp Range q q q q q q 1 100 V - + 0.4V nA V V V V mV mV mV VRMS 1.174 1.170 1.164 1.182 1.190 1.194 1.200 VREF Load Regulation ISOURCE = 1mA ISINK =10A 2 1.75 100 6 4 6 en Voltage Noise 100Hz to 100kHz The q denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be imparied. Note 2: IN + = IN - + 80mV, output is in high impedance state. PIN FUNCTIONS OUT A (Pin 1): Comparator A Open-Drain Output. Output can typically sink >20mA. V - (Pin 2): Negative Supply. IN A+ (Pin 3): Noninverting Input of Comparator A. Input common mode range extends from V - to V + - 1.3V. Input current is typically 10pA at 25C. IN B+ (Pin 4): Noninverting Input of Comparator B. Input common mode range extends from V - to V + - 1.3V. Input current is typically 10pA at 25C. HYST (Pin 5): Hysteresis Input. Connect to REF if not used. Input voltage range is from VREF to VREF - 50mV. REF (Pin 6): Reference Output. 1.182V with respect to V -. Can typically source >1mA and sink 10A at 25C. Can drive 0.01F bypass capacitor without oscillation. V + (Pin 7): Positive Supply. 2.5V to 11V. OUT B (Pin 8): Comparator B Open-Drain Output. Output can typically sink >20mA. U U U 1 OUT A 2 LTC1842 OUT B 8 7 V- A B V+ + 3 IN A+ - + - REF 6 HYST 5 4 IN B + V- 1842 PD 3 LTC1842 APPLICATIONS INFORMATION The LTC1842 is a dual micropower comparator with a built-in 1.182V reference. Features include programmable hysteresis, wide supply voltage range (2.5V to 11V) and the ability for the reference to drive up to a 0.01F capacitor without oscillation. The comparator's opendrain outputs can typically sink greater than 20mA and the supply current glitches that normally occur when switching logic states have been eliminated. Power Supplies The comparator operates from a single 2.5V to 11V or dual 1.25V to 5.5V supply. If the reference output is required to source more than 1mA or the supply source impedance is high, V + should be bypassed with a 0.1F capacitor. Comparator Inputs The comparator input can swing from the negative supply V - to within 1.3V (max) of the positive supply V +. The input can be forced 300mV below V - or above V + without damage and the typical input leakage current is only 10pA. Comparator Outputs Each comparator output is an open-drain pull-down to V - typically capable of sinking greater than 20mA. The low output leakage current while in three-state mode allows a high value pull-up resistor to be used. The open-drain outputs can be wire OR-ed or used in level shifting applications. Voltage Reference The internal bandgap reference has an output voltage of 1.182V referenced to V -. The reference accuracy is 1.5% from - 40C to 85C. It can typically source greater than RESISTOR VALUE (k) 10 4 U W U U 1mA and sink up to 10A with a 5V supply. The reference can drive a bypass capacitor of up to 0.01F without oscillation. By inserting a series resistor, capacitance values up to 100F can be used (Figure 1). Figure 2 shows the resistor value required for different capacitor values to achieve critical damping. Bypassing the reference can help prevent false tripping of the comparators by preventing glitches on V + or reference load transients from disturbing the reference output voltage. REFERENCE OUTPUT REF R1 LTC1842 C1 V- 1842 F01 Figure 1. Damping the Reference Output 100 1 0.1 0.001 0.01 0.1 1 CAPACITOR VALUE (F) 10 1842 F02 Figure 2. Damping Resistance vs Bypass Capacitor Value LTC1842 APPLICATIONS INFORMATION Figure 3 shows the bypassed reference output with a square wave applied to the V + pin. Resistors R2 and R3 set a 10mV hysteresis voltage band while R1 damps the reference response. Note that the comparator output doesn't trip. 7 V+ 3 IN A+ LTC1842 1M 1 OUT A 5V + - 5V TO 8V 5 HYST R2 10k R3 2.4M R1 430 C1 1F 6 REF V 2 - 1842 F03a Figure 3a. Power Supply Transient Test Circuit 8V V+ 5V 2mV/DIV VREF OUT 2ms/DIV 1841/2/3 F03b Figure 3b. Power Supply Transient Rejection Hysteresis Hysteresis can be added to the LTC1842 by connecting a resistor (R1) between the REF and HYST pins and a second resistor (R2) from HYST to V - (Figure 4). The difference between the upper and lower threshold voltages, or hysteresis voltage band (VHB), is equal to twice the voltage difference between the REF and HYST pins. R1 294k U W U U As more hysteresis is added, the upper threshold increases the same amount as the low threshold decreases. The maximum voltage allowed between REF and HYST pins is 50mV, producing a maximum hysteresis voltage band of 100mV. The hysteresis band may vary by up to 15%. If hysteresis is not wanted, the HYST pin should be shorted to REF. Acceptable values for IREF range are from 0.1A to 5A. If 2.4M is chosen for R2, then the value of R1 is equal to the value of VHB. 6 R1 5 R2 HYST V - IREF REF LTC1842 R1 = VHB (2)(IREF) R2 = 2 ( 1.182V - IREF VHB 2 ) 1842 F04 Figure 4. Programmable Hysteresis Dual Level Detector The LTC1842 is ideal for use as a micropower dual level detector as shown in Figure 5. The values of R1, R2 and R3 are selected for a 4.5V lower threshold and a 5.5V upper threshold. R4 and R5 set the hysteresis voltage. 5V VIN 7 R3 1M 3 IN A+ V+ LTC1842 1M 1M + OUT A 1 - R2 62.2k R5 10k 4 IN B+ R4 2.4M V- 2 1842 F05 5 HYST 6 REF - OUT B 8 + VUTH = 5.5V VLTH = 4.5V Figure 5. Dual Level Detector 5 LTC1842 APPLICATIONS INFORMATION The following design procedure can be used to select the component values: 1. Choose the required hysteresis voltage band and calculate values for R4 and R5 according to the formulas in the hysteresis section. In this example, 5mV of hysteresis has been added at the comparator input (VH = VHB/2). Note that the hysteresis apparent at VIN will be larger because of the input resistor divider. 2. Select R1. The leakage current into IN B - is under 1nA so the current through R1 should exceed 100nA, to ensure threshold accuracy. R1 values up to about 10M can be used, but values in the 100k to 1M range are usually easier to deal with. In this example choose R1 = 294k. 3. Calculate R2 + R3. The upper threshold should be set at 5.5V. The design equation is as follows: VUTH - 1 R2 + R3 = R1 VREF + VH 5.5 = 294k - 1 1.182 + 0.005 = 1.068M 4. Calculate R2. The lower threshold should be set at 4.5V. The design equation is as follows: R2 = R1 + R2 + R3 ( )V V -V REF LTH H - R1 = 294k + 1.068M = 62.2k ( ) 1.1824-.50.005 - 294k Choose R2 = 61.9k (1% standard value) 6 U W U U 5. Calculate R3: R3 = (R2 + R3) - R2 = 1.068M - 61.9k = 1.006M Choose R3 = 1M (1% standard value) 6. Verify the resistor values. The equations are as follows, evaluated for the above example: Upper threshold: VUTH = VREF + VH = 5.474V Lower threshold: VLTH = VREF - VH = 4.484V ( ) R1+ R21+ R3 R ( + ) R1R1R+2R+2R3 R5 where the hysteresis voltage VH = VREF R4 () LTC1842 PACKAGE DESCRIPTION 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP 0.016 - 0.050 0.406 - 1.270 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE U Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 - 0.197* (4.801 - 5.004) 8 7 6 5 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157** (3.810 - 3.988) 1 0.053 - 0.069 (1.346 - 1.752) 2 3 4 0.004 - 0.010 (0.101 - 0.254) 0.014 - 0.019 (0.355 - 0.483) 0.050 (1.270) TYP SO8 0996 7 LTC1842 RELATED PARTS PART NUMBER LT(R)1178/LT1179 LT1351 LT1352/LT1353 LTC1440/LTC1540 LTC1441/LTC1442 LTC1443/LTC1444/LTC1445 LTC1474 LT1495 LT1521 LTC1541/LTC1542 LT1634 DESCRIPTION Dual/Quad 17A Precision Single Supply Op Amps Single 250A, 3MHz, 200V/s Op Amp with Shutdown Dual/Quad 250A, 3MHz, 200V/s Op Amps Micropower Comparator with 1% Reference Micropower Dual Comparator with 1% Reference Micropower Quad Comparator with 1% Reference Low Quiescent Current High Efficiency Step-Down Switching Regulator 1.5A Max, Dual Precision Rail-to-Rail Input and Output Op Amp 300mA Low Dropout Regulator with Micropower Quiescent Current and Shutdown Micropower Op Amp, Comparator and Reference Micropower Precision Shunt Voltage Reference COMMENTS 70V Max VOS, 5nA Max IBIAS C-LoadTM Op Amp Stable Driving Any Capacitive Load C-Load Op Amps Stable Driving Any Capacitive Load 1.182V 1% Reference, 10mV (Max) Input Offset 1.182V 1% Reference (LTC1442) LTC1443 Has 1.182V Reference, LTC1444/LTC1445 Have 1.221V Reference and Adjustable Hysteresis 10A Standby Current, 92% Efficiency, Space Saving 8-Pin MSOP Package 375V Max VOS, 250pA IBIAS, 25pA IOS 0.5V Dropout Voltage, 12A Quiescent Current, Adjustable Output 3V, 3.3V and 5V Fixed 1.200V 0.8% Reference (LTC1541) Op Amp Outputs Stable with 1000pF Load 1.25V Output, 10A Operating Current, 0.1% Initial Accuracy 10ppm/C Max Drift C-Load is a trademark of Linear Technology Corporation. 8 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com 1842I LT/TP 0898 4K * PRINTED IN USA (c) LINEAR TECHNOLOGY CORPORATION 1998 |
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