LTC1540 Nanopower Comparator with Reference U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Ultralow Quiescent Current: 0.3µA Typ Reference Output Drives 0.01µF Capacitor Adjustable Hysteresis Available in 3mm x 3mm x 0.8mm DFN Package Wide Supply Range: 2V to 11V Input Voltage Range Includes the Negative Supply Reference Output Sources Up to 1mA TTL/CMOS Compatible Outputs 60µs Propagation Delay with 10mV Overdrive No Crowbar Current 40mA Continuous Source Current Pin Compatible with LTC1440, MAX921, MAX931 U APPLICATIO S ■ ■ ■ ■ Battery-Powered System Monitoring Threshold Detectors Window Comparators Oscillator Circuits , LTC and LT are registered trademarks of Linear Technology Corporation. The LTC ®1540 is an ultralow power, single comparator with built-in reference. The comparator’s features include less than 0.6µA supply current over the commercial temperature range, a 1.182V ±2% reference, programmable hysteresis and TTL/CMOS outputs that sink and source current. The reference output can drive a bypass capacitor of up to 0.01µF without oscillation. The comparator operates from a single 2V to 11V supply or a dual ±1V to ±5.5V supply. Comparator hysteresis is easily programmed by using two resistors and the HYST pin. Each comparator’s input operates from the negative supply to within 1.3V of the positive supply. The comparator output stage can continuously source up to 40mA. By eliminating the cross-conducting current that normally occur when the comparator changes logic states, power supply glitches are eliminated. The LTC1540 is available in the 8-pin MSOP and SO packages. For space limited applications, the LTC1540 is available in a 3mm x 3mm low profile (0.8mm) dual finepitch leadless package (DFN). U TYPICAL APPLICATIO Nanopower 2.9V VCC Threshold Detector LTC1540 Supply Current vs Temperature 3.3V 0.50 R2 3M 1% 7 V+ 3 IN + 0.45 LTC1540 + 8 4 IN– – 5 HYST 6 REF OUT SUPPLY CURRENT (µA) R1 4.32M 1% V + = 5V V – = GND = 0V 0.40 0.35 0.30 0.25 0.20 V– 2 0.15 –40 –20 GND 1 40 20 60 0 TEMPERATURE (°C) 80 100 1540 • TA02 1540 • TA01 sn1540 1540fas 1 LTC1540 W W U W ABSOLUTE MAXIMUM RATINGS Voltage V + to V –, V + to GND, GND 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 ............................... (V + + 0.3V) to (GND – 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 LTC1540C .............................................. 0°C to 70°C LTC1540I ............................................ – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C (DD Package) ................................... – 65°C to 125°C Lead Temperature (Soldering, 10 sec).................. 300°C W U U PACKAGE/ORDER INFORMATION TOP VIEW TOP VIEW TOP VIEW GND 1 8 OUT V+ V– 2 7 V+ 6 REF IN + 3 6 REF 5 HYST IN – 5 HYST GND 1 8 OUT V– 2 7 IN+ 3 IN– 4 LTC1540CDD LTC1540IDD 8 7 6 5 OUT V+ REF HYST TJMAX = 150°C, θJA = 250°C/ W TJMAX = 150°C, θJA = 175°C/ W TJMAX = 125°C, θJA = 160°C/ W (NOTE 2) UNDERSIDE METAL CONNECTED TO V– (PCB CONNECTION OPTIONAL) DD PART MARKING* LAAS 1 2 3 4 MS8 PACKAGE 8-LEAD PLASTIC MSOP S8 PACKAGE 8-LEAD PLASTIC SO DD PACKAGE 8-LEAD (3mm × 3mm) PLASTIC DFN ORDER PART NUMBER 4 GND V– IN + IN – ORDER PART NUMBER LTC1540CS8 LTC1540IS8 S8 PART MARKING 1540 1540I ORDER PART NUMBER MS8 PART MARKING LTC1540CMS8 LTC1540IMS8 LTCE LTADV Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V + = 5V, V – = GND = 0V, TA = 25°C unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 11.0 V 0.68 0.71 µA µA ±12 ±15 ±16 mV mV mV ±1.0 ±1.0 nA nA V + – 1.3V V Power Supply V+ ICC ● Supply Voltage Range Supply Current IN + = IN – = 80mV, HYST = REF, C-Grade IN + = IN – = 80mV, HYST = REF, I-Grade 2.0 ● ● 0.3 Comparator VOS Comparator Input Offset Voltage VCM = 2.5V LTC1540CMS8/IMS8 IIN Input Leakage Current (IN +, IN –) VIN + = VIN – = 2.5V Input Leakage Current (HYST) VCM CMRR PSRR ● ● ● ● ● Comparator Input Common Mode Range ±0.01 ±0.02 V– Common Mode Rejection Ratio V– to V + – 1.3V 0.1 1 mV/V Power Supply Rejection Ratio V+ = 2V to 11V 0.1 1 mV/V sn1540 1540fas 2 LTC1540 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V + = 5V, V – = GND = 0V, TA = 25°C unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP ● REF – 50mV VHYST Hysteresis Input Voltage Range tPD Propagation Delay COUT = 100pF VOH Output High Voltage IO = – 13mA ● VOL Output Low Voltage IO = 1.8mA ● VREF Reference Voltage No Load ∆VREF Load Regulation 0 ≤ ISOURCE ≤ 100µA Overdrive = 10mV Overdrive = 100mV MAX UNITS REF V 60 50 µs µs V + – 0.4V V GND + 0.4V V 1.182 1.182 1.182 1.206 1.208 1.212 V V V 0.5 2.5 mV 0.5 1.5 5 mV mV TYP MAX UNITS 11 V 0.28 0.61 0.64 µA µA ±12 ±15 ±16 mV mV mV ±1 ±1 nA nA V + – 1.3V V Reference (SO-8)/(DFN) Commercial MS8 Commercial (SO-8)/(MS8)/(DFN) Industrial ● ● ● 1.158 1.156 1.152 ● 0 ≤ ISINK ≤ 10µA ● V + = 3V, V – = GND = 0V, TA = 25°C unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN Power Supply V+ Supply Voltage Range ICC Supply Current ● IN + = IN – = 80mV, HYST = REF, C-Grade IN + = IN – = 80mV, HYST = REF, I-Grade 2 ● ● Comparator VOS Comparator Input Offset Voltage VCM = 2.5V ● ● LTC1540CMS8/IMS8 IIN VCM Input Leakage Current (IN +, IN –) VIN + = VIN – = 1.5V Input Leakage Current (HYST) ● ● Comparator Input Common Mode Range ● to V + ±0.01 ±0.02 V– CMRR Common Mode Rejection Ratio V– – 1.3V 0.1 1 mV/V PSRR Power Supply Rejection Ratio V + = 2V to 11V 0.1 1 mV/V VHYST Hysteresis Input Voltage Range tPD Propagation Delay COUT = 100pF VOH Output High Voltage IO = – 8mA ● VOL Output Low Voltage IO = 0.8mA ● VREF Reference Voltage No Load ∆VREF Load Regulation 0 ≤ ISOURCE ≤ 100µA ● REF – 50mV Overdrive = 10mV Overdrive = 100mV REF V 70 60 µs µs V + – 0.4V V GND + 0.4V V 1.182 1.182 1.182 1.206 1.208 1.212 V V V 0.75 3.5 mV 0.5 1.5 5 mV mV Reference (SO-8)/(DFN) Commercial MS8 Commercial (SO-8)/(MS8)/(DFN) Industrial ● ● ● ● 0 ≤ ISINK ≤ 10µA ● Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 1.158 1.156 1.152 Note 2: The θJA specified for the DD package is with minimal PCB heat spreading metal. Using expanded metal area on all layers of a board reduces this value. sn1540 1540fas 3 LTC1540 U W TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Temperature 0.5 1.190 V + = 5V V – = GND = 0V 0.3 V + = 2V V – = GND = 0V 0.2 0.1 0 – 60 – 40 –20 0 20 40 60 TEMPERATURE (°C) 80 100 8 1.186 7 1.184 1.182 1.180 1.178 2 1 0 TA = 25°C 2.0 OUTPUT VOLTAGE (V) 4 0 3 V+ = 3V 2 10 20 30 40 50 60 LOAD CURRENT (mA) 60 55 45 40 20 35 30 1 2 3 4 5 6 7 8 SUPPLY VOLTAGE (V) 9 10 1540 G07 tPLH 50 40 0 70 80 1540 G06 DIFFERENTIAL INPUT VOLTAGE (V) 60 20 30 40 50 60 LOAD CURRENT (mA) Hysteresis Control 65 OUTPUT CONNECTED TO V +; SINK CURRENT 10 80 TA = 25°C 75 V + = 5V V – = GND = 0V 70 100 80 0 80 80 TIME (µs) 120 70 Comparator Response Time vs Input Overdrive TA = 25°C 140 1.0 1540 G05 Comparator Short-Circuit Current vs Supply Voltage OUTPUT CONNECTED TO – = GND = 0V; V SOURCE CURRENT V+ = 2V 1.5 0 0 1540 G04 160 V+ = 5V V+ = 3V 0.5 V+ = 2V 0 4 40 2.5 1 180 10 15 20 25 30 35 OUTPUT SINK CURRENT (µA) Comparator Output Voltage (Low) vs Load Current V+ = 5V 3 2 1 OUTPUT SOURCE CURRENT (mA) 5 1540 G03 TA = 25°C OUTPUT VOLTAGE (V) ∆VREF (mV) 0 1540 G02 1 CURRENT (mA) 100 5 2 0 80 Comparator Output Voltage (High) vs Load Current 3 200 4 1.172 20 40 60 – 60 – 40 – 20 0 TEMPERATURE (°C) V + = 5V V – = GND = 0V TA = 25°C 0 5 1.174 Reference Voltage Load Regulation (Source) 4 6 3 1.176 1540 G01 5 V + = 5V V – = GND = 0V TA = 25°C 9 ∆VREF (mV) V + = 3V V – = GND = 0V 10 V + = 5V V – = GND = 0V 1.188 REFERENCE VOLTAGE (V) SUPPLY CURRENT (µA) 0.4 Reference Voltage Load Regulation (Sink) Reference Voltage vs Temperature tPHL 60 40 20 0 – 20 – 40 – 60 – 80 10 20 30 40 50 60 70 80 90 100 110 INPUT VOLTAGE (mV) 1540 G08 0 10 20 30 VREF – VHYST (mV) 40 50 1540 G09 sn1540 1540fas 4 LTC1540 U U U PIN FUNCTIONS GND (Pin 1): Ground. Connect to V – for single supply operation. V + (Pin 7): Positive Supply operating voltage is from 2V to 11V. V – (Pin 2): Negative Supply. Potential should be more negative than GND. Connect to ground for single supply operation. OUT (Pin 8): Comparator CMOS Output. Swings from GND to V +. Output can source up to 40mA and sink 5mA. IN + (Pin 3): Noninverting Comparator Input. Input common mode range from V – to V + – 1.3V. Input current typically 10pA at 25°C. IN – (Pin 4): Inverting Comparator Input. Input common mode range from V – to V + – 1.3V. Input current typically 10pA at 25°C. HYST (Pin 5): Hysteresis Input. Connect to REF if not used. Input voltage range is from VREF to VREF – 50mV. 1 GND LTC1540 – 2 V OUT 8 V+ 7 + 3 IN+ – 4 IN REF (Pin 6): Reference Output. 1.182V with respect to V –. Can source up to 1mA and sink 10µA at 25°C. Drive 0.01µF bypass capacitor without oscillation. – REF 6 HYST 5 1540 • PD U W U U APPLICATIONS INFORMATION The LTC1540 is a nanopower comparator with a built-in 1.182V reference. Features include programmable hysteresis, wide supply voltage range (2V to 11V) and the ability of the reference to drive up to a 0.01µF capacitor without oscillation. The comparator’s CMOS outputs can source up to 40mA while supply current glitches that normally occur when switching logic states, have been eliminated. Power Supplies The comparator operates from a single 2V to 11V supply. The LTC1540 includes a separate ground for the comparator output stage, allowing a split supply ranging from ±1V to ±5.5V. Connecting V – to GND will allow single supply operation. If the comparator output is required to source more than 1mA, or the supply source impedance is high, V + should be bypassed with a 0.1µF capacitor. Comparator Inputs The comparator inputs can swing from the negative supply, V –, to within 1.3V (max) of the positive supply V+. The inputs can be forced 300mV below V– or above V+ without damage and the typical input leakage current is only ±10pA. Comparator Output The comparator output swings between GND and V + to assure TTL compatibility with a split supply. The output is capable of sourcing up to 40mA and sinking up to 5mA while still maintaining nanoampere quiescent currents. The output stage does not generate crowbar switching currents during transitions which helps minimize parasitic feedback through the supply pins. Voltage Reference The internal bandgap reference has a voltage of 1.182V referenced to V –. The reference accuracy is ±2.0% from 0°C to 70°C. It can source up to 1mA and sink up to 10µA with a 5V supply. The reference can drive a bypass capacitor of up to 0.01µF without oscillation and by inserting a series resistor, capacitance values up to 10µF 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. sn1540 1540fas 5 LTC1540 U U W U APPLICATIONS INFORMATION REFERENCE OUTPUT 7 V+ REF R1 3 IN + LTC1540 LTC1540 + 8 C1 4 IN– V– 5V TO 8V 1540 • F01 OUT – 5 HYST R2 10k 6 REF Figure 1. Damping the Reference Output R3 2.4M R1 430Ω RESISTOR VALUE (kΩ) 1000 V– 2 C1 1µF GND 1 100 1540 • F03a Figure 3a. Power Supply Transient Test Circuit 10 1 8V V+ 0.01 0.1 1 CAPACITOR VALUE (µF) 10 1540 • F02 5V 2mV/DIV 0.1 0.001 VREF Figure 2. Damping Resistance vs Bypass Capacitor Value Figure 3 shows the bypassed reference output with a square wave applied to the V + pin. Resistors R2 and R3 set 10mV of hysteresis voltage band while R1 damps the reference response. Note that the comparator output doesn’t trip. OUT 2ms/DIV Figure 3b. Power Supply Transient Rejection Low Voltage Operation: V + = 1.6V 5 V – = GND = 0V IN+ = 0V IN – = REF = HYST TA = 25°C 4 SUPPLY CURRENT (µA) The guaranteed minimum operating voltage is 2V (or ±1V). As the total supply voltage is reduced below 2V, the performance degrades and the supply current falls. At low supply voltages, the comparator’s output drive is reduced and the propagation delay increases. The VREF and VOS are also slightly worse. The useful input voltage range extends from the negative supply to 0.9V below the positive supply. Test your prototype over the full temperature and supply voltage range if operation below 2V is anticipated. Because of the increase in supply current, operation below 1.5V is not recommended (Figure 4). 1540 F03b 3 2 1 0 0 0.5 1.5 2.0 1.0 SUPPLY VOLTAGE (V) 2.5 1540 F04 Figure 4. Supply Current vs Supply Voltage sn1540 1540fas 6 LTC1540 U W U U APPLICATIONS INFORMATION Hysteresis Hysteresis can be added to the LTC1540 by connecting a resistor (R1) between the REF and HYST pins and a second resistor (R2) from HYST to V – (Figure 5). up to 15%. If hysteresis is not wanted, the HYST pin should be shorted to REF. Acceptable values for IREF range from 0.1µA to 5µA. If 2.4M is chosen for R2, then the value of R1 (kΩ) is equal to the value of VHB (mV). 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. 6 IREF LTC1540 R1 5 When 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 R1 = REF HYST R2 = VHB (2)(IREF) ( V– 2 R2 1.182V – VHB 2 ) IREF 1540 • F05 Figure 5. Programmable Hysteresis U TYPICAL APPLICATIONS Level Detector The LTC1540 is ideal for use as a nanopower level detector as shown in Figure 6. R1 and R2 form a voltage divider from VIN to the noninverting comparator input. R3 and R4 set the hysteresis voltage, and R5 and C1 bypass the reference output. The following design procedure can be used to select the component values: 1. Choose the VIN voltage trip level, in this example 4.65V. 2. Calculate the required resistive divider ratio. Ratio = VREF/ VIN Ratio = 1.182V/4.65V = 0.254 3. Choose the required hysteresis voltage band at the input VHBIN, in this example 60mV. Calculate the hysteresis voltage band referred to the comparator input VHB. VHB = (VHBIN)(Ratio) R1 = VREF 1.182V = = 1.18M IBIAS 1µA VIN R2 = R1 V VREF + HB 2 4.65V –1 R2 = 1.18M 15mV 1.182V + 2 R2 = 3.40M VIN 5V 7 R2 3.4M 1% V+ 3 IN + 4. Choose the values for R3 and R4 to set the hysteresis. R4 = 2.4M R3 (kΩ) = 15k, VHB (mV) = 15mV 5. Choose the values for R1 and R2 to set the trip point. LTC1540 + 8 R1 1.18M 1% 4 IN– VHB = (60mV)(0.254) VHB = 15.24mV –1 OUT – 5 HYST R3 15k 1% R4 2.4M 1% 6 REF R5 430Ω 5% C1 1µF V– 2 GND 1 1540 F06 Figure 6. Glitch-Free Level Detector with Hysteresis sn1540 1540fas 7 LTC1540 U TYPICAL APPLICATIONS 3.3V Output Low Dropout Linear Regulator The LTC1540 can be connected as a micropower (IQ = 5.5µA at VIN = 5V) low dropout linear regulator (Figure 7). When the output is low, Q1 turns on, allowing current to charge output capacitor C1. Local feedback formed by R4, Q1 and Q2 creates a constant-current source from the 5V input to C1. R4, R1 and Q2’s VBE also provide current limiting in the case of an output short-circuit to ground. C2 reduces output ripple, while the R2-R3 feedback voltage divider establishes the output voltage. output is the switched power supply output. With a 10mA load, it typically provides a voltage of (VBAT – 0.17V). The whole circuit draws a mere 0.8µA of quiescent current with VBAT = 5V. The three resistor voltage divider programs 50mV of hysteresis for the comparator, and sets the IN – voltage at 200mV. This gives an IN + trip threshold of approximately 150mV The RC time constant determines the maximum power-on time of the OUT pin before power down occurs. This period can be approximated by: t = 4.6RC (seconds) Auto Power-Off Source Figure 8 shows the circuit for a 30mA power supply that has a timed auto power-off function. The comparator The actual time will vary with both the leakage current of the capacitor and the input current at the IN + pin. V BAT V IN = 5V 7 V 3 IN + + LTC1540 R1 47k + OUT 8 4 IN– R4 10Ω Q2 2N3906 7 C1 10µF – LTC1540 Q1 TP0610L 6 REF R2 430k 1% C3 GND 1 V – MOMENTARY SWITCH R + 5 HYST C2 2.2nF IN + 3 C V OUT 3.3V 432k R3 750k 1% V+ OUT 8 4 IN – (VBAT – 0.17V) 10mA – 2M 5 HYST 121k 6 REF 2 V– 1540 F07 Figure 7. 3.3V Output Low Dropout Linear Regulator 2 GND 1 1540 F08 Figure 8. Auto Power-Off Switch Operates on 0.8µA Quiescent Current sn1540 1540fas 8 LTC1540 U TYPICAL APPLICATIONS Low-Battery Detect operation down to a supply voltage of 2V, but it is still functional with the supply as low as 1.6V. Some parameters, such as VREF and VOS, will be degraded on lower supply voltages. The input voltage range extends from 0.9V below the positive supply to the negative supply. Figure 9 shows how to use the LTC1540 for a low-battery detect, drawing only 1.4µA at VBAT = 2V. The circuit is powered by a 2-cell NiCd battery. The VBAT pin could be as low as 1.6V when the batteries are completely depleted. The electrical specifications of the LTC1540 guarantee VBAT = ~1.6V TO 2.5V 2-CELL NiCd 7 R1 3M V 3 IN + + LTC1540 + OUT R2 1.1M 4 IN– 8 LBO – 6 REF R3 40k R4 1.2M R5 1M 5 HYST V– 2 GND 1 1540 F09 Figure 9. Low-Battery Detect Works Down to 1.6V sn1540 1540fas 9 LTC1540 U PACKAGE DESCRIPTION DD Package 8-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1698) R = 0.115 TYP 5 0.38 ± 0.10 8 0.675 ±0.05 3.5 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 1.65 ± 0.10 (2 SIDES) 3.00 ±0.10 (4 SIDES) PACKAGE OUTLINE PIN 1 TOP MARK (DD8) DFN 0203 0.75 ±0.05 0.200 REF 0.28 ± 0.05 4 0.28 ± 0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) 1 0.50 BSC 2.38 ±0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 2. ALL DIMENSIONS ARE IN MILLIMETERS 3. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 4. EXPOSED PAD SHALL BE SOLDER PLATED RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 0.42 ± 0.04 (.0165 ± .0015) TYP 3.2 – 3.45 (.126 – .136) 0.65 (.0256) BSC 0.254 (.010) 8 7 6 5 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.90 ± 0.15 (1.93 ± .006) DETAIL “A” 0.52 (.206) REF 0° – 6° TYP GAUGE PLANE 1 0.53 ± 0.015 (.021 ± .006) RECOMMENDED SOLDER PAD LAYOUT DETAIL “A” 1.10 (.043) MAX 2 3 4 0.86 (.034) REF 0.18 (.077) NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX SEATING PLANE 0.22 – 0.38 (.009 – .015) TYP 0.65 (.0256) BSC 0.13 ± 0.076 (.005 ± .003) MSOP (MS8) 0802 sn1540 1540fas 10 LTC1540 U PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 .245 MIN 7 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 3 4 .053 – .069 (1.346 – 1.752) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN 2 .014 – .019 (0.355 – 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) .050 (1.270) BSC SO8 0303 sn1540 1540fas 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. 11 LTC1540 U TYPICAL APPLICATION RF Field Detector Figure 10 shows the complete circuit for a field detector which was tested at 445MHz. A transmission line is used to match the detector diode (1N5712) to a quarter-wave whip antenna. The 0.23λ wavelength transmission line section transforms the 1pF (350Ω) diode junction capacitance to a virtual short at the base of the antenna. At the same time it converts the received antenna current to a voltage loop at the diode, giving excellent sensitivity. The rectified output is monitored by the LTC1540 comparator. The internal reference is used to set up a threshold of about 18mV at the inverting input. A rising edge at the comparator output triggers a one shot that temporarily enables answer back and any other pulsed functions. The total supply current is 400nA. Among other monolithic one shots, the CD4047 draws the least amount of transient current. 2V TO 11V λ /4 FB 12M 10k 5 3 + 10nF LTC1540 4 0.23λ 10nF 6 – 180k 7 8 CMOS ONE SHOT (CD4047) Q Q 1 2 1540 F10 1N5712 Figure 10. Nanopower Field Detector RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT 1178/LT1179 Dual/Quad 17µA Precision Single Supply Op Amps 70µV Max VOS, 5nA Max IBIAS LT1351 Single 250µA, 3MHz, 200V/µs Op Amp with Shutdown C-LoadTM Op Amp Stable Driving Any Capacitive Load LT1352/LT1353 Dual/Quad 250µA, 3MHz, 200V/µs Op Amps C-Load Op Amps Stable Driving Any Capacitive Load LTC1440 Micropower Comparator with 1% Reference 1.182V ±1% Reference, ±10mV (Max) Input Offset LTC1443/LTC1444/LTC1445 Micropower Quad Comparators with 1% Reference LTC1443 Has 1.182V Reference, LTC1444/LTC1445 Have 1.221V Reference and Adjustable Hysteresis LTC1474 Low Quiescent Current High Efficiency Step-Down Converter 10µA Standby Current, 92% Efficiency, Space Saving 8-Pin MSOP Package LT1495 1.5µA Max, Dual Precision Rail-to-Rail Input and Output Op Amp 375µV Max VOS, 250pA IBIAS, 25pA IOS LT1521 300mA Low Dropout Regulator with Micropower Quiescent Current and Shutdown 0.5V Dropout Voltage, 12µA Quiescent Current, Adjustable Output 3V, 3.3V and 5V Fixed LT1634 Micropower Precision Shunt Voltage Reference 1.25V, 2.5V, 4.096V, 5V Outputs, 10µA Operating Current, 0.05% Initial Accuracy 25ppm/°C Max Drift, SO-8, MSOP and TO-92 Packages ® C-Load is a trademark of Linear Technology Corporation. sn1540 1540fas 12 Linear Technology Corporation LT/TP 0403 1K REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1997