LTC1998 2.5µA, 1% Accurate SOT-23 Comparator and Voltage Reference for Battery Monitoring DESCRIPTION FEATURES n n n n n n n High Accuracy Trip Voltage: 1% Max Error Using External 1% Resistors Adjustable Threshold Voltage and Hysteresis Quiescent Current: 2.5μA Typ Output Swings Rail-to-Rail Thresholds Programmable from 2.5V to 3.25V Output State Guaranteed for VBATT ≥1.5V Low Profile (1mm) ThinSOT™ Package The LTC®1998 is a micropower comparator and a precision adjustable reference in a 6-pin SOT-23 package that is optimized for lithium-ion low battery detection circuits. The LTC1998 features a voltage detection circuit with an adjustable threshold voltage and hysteresis. The threshold voltage can be programmed from 2.5V to 3.25V with two external resistors. A 10mV to 750mV hysteresis can be added with a third external resistor. A proprietary internal architecture maintains 1% threshold voltage accuracy over temperature with low cost 1% external resistors. APPLICATIONS n Lithium-Ion Battery-Powered Equipment PDAs Cell Phones Handheld Instruments Battery Packs Pagers Palm Top Computers POS Terminals A separate power supply pin, VLOGIC, allows the battery-low logic output to operate below the battery voltage, allowing compatibility with low voltage microprocessors without a pull-up resistor. Power supply glitches are eliminated by preventing the cross-conducting current which occurs when the output changes state. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. The LTC1998 operates with battery or supply voltages up to 5.5V and its battery-low output is valid for battery voltages above 1.5V. BLOCK DIAGRAM Threshold Voltage Error vs Temperature 1.0 BATT 0.9 VLOGIC 0.7 THRESHOLD ADJUST BATTLO R VTH.A % ERROR 1.1R VHYST.A VTH.A SET BY 1% EXTERNAL R, THRESHOLD = 3V 0.8 0.6 0.5 0.4 VTH.A = 1V THRESHOLD = 3V 0.3 1.2V 0.2 VTH.A SHORTED TO GROUND, THRESHOLD = 2.5V 0.1 1998 BD 0 –45 –25 35 15 55 –5 TEMPERATURE (°C) 75 95 1998 TA02 1998fa 1 LTC1998 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW Total Supply Voltage (BATT or VLOGIC to GND)............6V Voltage VTH.A, VH.A ....................... BATT + 0.3V to GND – 0.3V BATTLO ..........................VLOGIC + 0.3V to GND – 0.3V Operating Temperature Range (Note 3).... –40°C to 85°C Specified Temperature Range (Note 4) LTC1998C ............................................ –40°C to 85°C LTC1998I.............................................. –40°C to 85°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C BATT 1 6 BATTLO GND 2 5 VLOGIC VTH.A 3 4 VH.A S6 PACKAGE 6-LEAD PLASTIC SOT-23 TJMAX = 150°C, θJA = 250°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC1998CS6#PBF LTC1998CS6#TRPBF LTTY 6-Lead Plastic SOT-23 –40°C to 85°C LTC1998IS6#PBF LTC1998IS6#TRPBF LTTY 6-Lead Plastic SOT-23 –40°C to 85°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC1998CS6 LTC1998CS6#TR LTTY 6-Lead Plastic SOT-23 –40°C to 85°C LTC1998IS6 LTC1998IS6#TR LTTY 6-Lead Plastic SOT-23 –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 1998fa 2 LTC1998 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VGND = 0V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Power Supply Supply Voltage Range-BATT l 1.5 Supply Voltage Range-VLOGIC l 1 5.5 V VBATT V 2.5 3.5 4.2 4.5 μA μA μA 3 4.3 5.2 5.5 μA μA μA l 0.6 0.8 0.85 1 % % VBATT.Th = 3V, Pin 3 Driven by Precision Voltage Source to 1V LTC1998C LTC1998I l l 0.5 0.6 0.61 0.71 % % VBATT.Th = 3V, VTH.A = 1V (Note 5) Programmed with 1% Max External Resistors LTC1998C LTC1998I l l 0.8 0.9 1 1.1 % % VBATT.Th = 3.25V, Pin 3 Driven by Precision Voltage Source to 1.5V LTC1998C LTC1998I l l 0.6 0.7 0.65 0.85 % % VBATT.Th = 3.25V, VTH.A = 1.5V (Note 5) Programmed with 1% Max External Resistors LTC1998C LTC1998I l l 0.9 1 1.1 1.3 % % VHYST ≤ 250mV 250mV ≤ VHYST ≤ 750mV l l –5 5 mV mV l 10 750 mV Supply Current, VBATT = 3V, VTH.A = 1.5V TA = 25°C LTC1998CS6 LTC1998IS6 l l Supply Current, VBATT = 5.5V, VTH.A = 1.5V TA = 25°C LTC1998CS6 LTC1998IS6 l l Monitor Threshold Accuracy Hysteresis Accuracy VBATT.Th = 2.5V, Pin 3 Shorted to Ground Allowable Hysteresis Range (Note 2) Propagation Delay ±5 COUT = 100pF Overdrive = 10mV Overdrive = 100mV 350 150 μs μs VTH.A ≤ 1.5V l 0.01 1 nA VH.A ≤ 1.5V l 0.01 1 nA BATTLO High Voltage IOUT = –1mA, VLOGIC ≥ 1.5V l BATTLO Low Voltage IOUT = 1mA, VBATT ≥ 2V l 0.2 V BATTLO Low Voltage IOUT = 0.25mA, VBATT = 1V l Threshold Adjust Pin Leakage, ITH.A Hysteresis Adjust Pin Leakage, IH.A Output Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: Maximum allowable hysteresis depends on desired trip voltages. See application notes for details. Note 3: LTC1998C and LTC1998I are guaranteed functional over the operating temperature range of –40°C to 85°C. VLOGIC – 0.3 V 0.3 V Note 4: The LTC1998C is guaranteed to meet specified performance from 0°C to 70°C. The LTC1998C is designed, characterized and expected to meet specified performance from –40°C to 85°C but is not tested or QA sampled at these temperatures. The LTC1998I is guaranteed to meet specified performance from –40°C to 85°C. Note 5: This parameter is not 100% tested. 1998fa 3 LTC1998 TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Supply Current vs Supply Voltage 3.0 3.5 TA = 25°C VLOGIC = VBATT SUPPLY CURRENT (μA) SUPPLY CURRENT (μA) 3.5 VBATT = VLOGIC = 3V 3.0 VTH.A = 1.5V 2.5 Threshold Voltage vs Threshold Adjust Voltage VTH.A = 0V 2.0 1.5 1.0 THRESHOLD VOLTAGE (V) 3.5 Quiescent Supply Current vs Temperature 2.5 VTH.A = 1.5V 2.0 1.5 1.0 3.0 0.5 0.5 0 –50 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 SUPPLY VOLTAGE (V) –30 –10 10 30 50 TEMPERATURE (°C) 70 2.5 90 0 1998 G02 1998 G01 Available Hysteresis vs Threshold Voltage 1998 G03 Threshold Voltage Error vs Temperature 750 Input Current vs Temperature 1.0 10000 0.7 250 0.6 0.5 0.4 VTH.A = 1V THRESHOLD = 3V 0.3 0.2 VTH.A SHORTED TO GROUND, THRESHOLD = 2.5V INPUT CURRENT VTH.A, VH.A (pA) VTH.A SET BY 1% EXTERNAL R, THRESHOLD = 3V 0.8 % ERROR AVAILABLE HYSTERESIS (mV) 0.9 500 1.5 0.5 1.0 THRESHOLD ADJUST VOLTAGE (V) VIN = 1.5V 1000 VIN = 1V 100 VIN = 0.5V 10 1 0.1 0 2.5 3.25 2.75 3.0 LOW BATTERY THRESHOLD VOLTAGE (V) 1998 G04 0 –45 –25 35 15 55 –5 TEMPERATURE (°C) 75 95 1998 G05 0.1 35 45 55 65 75 85 95 105 115 125 TEMPERATURE (°C) 1998 G06 1998fa 4 LTC1998 TYPICAL PERFORMANCE CHARACTERISTICS Output Low Voltage vs Load Current Output High Voltage vs Load Current OUTPUT VOLTAGE (V) TA = 25°C VLOGIC = VBATT = 3V TA = 85°C 0.4 TA = 25°C 0.2 TA = –40°C 0 120 TA = 85°C TA = 25°C TA = –40°C –50 –100 TA = –40°C TA = 25°C –150 TA = 85°C –200 TA = 25°C VLOGIC = VBATT –250 0 1 2 3 4 OUTPUT SINK CURRENT (mA) 5 1998 G07 100 CURRENT (mA) OUTPUT VOLTAGE RELATIVE TO VBATT (mV) 0.6 Output Short-Circuit Current vs Supply Voltage 1 80 60 2 3 4 OUTPUT SOURCE CURRENT (mA) 5 1998 G08 SOURCE CURRENT, BATTLO SHORTED TO GND 40 20 BATT = 3V BATT = 5V TA = 25°C VBATT = VLOGIC SINK CURRENT, BATTLO SHORTED TO VLOGIC 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 SUPPLY VOLTAGE (V) 1998 G09 1998fa 5 LTC1998 PIN FUNCTIONS BATT (Pin 1): Battery Voltage to be monitored. Supply current is also drawn from this pin. Board layout should connect this pin to the battery(+) terminal, through a trace that does not conduct load current. GND (Pin 2): Ground should be connected to the battery (–) terminal through a trace that does not conduct load return current. VTH.A (Pin 3): Threshold Adjust Pin. Adjusts the low battery threshold voltage, VBATT.Th = 2.5V + (VTH.A/2). VTH.A can be supplied by a voltage source or a resistor divider. VH.A (Pin 4): Hysteresis Adjust. Hysteresis threshold voltage VTH2 = 2.5V + (VH.A/2). VH.A can be supplied by a voltage source or resistor divider. VH.A must always be programmed to a higher potential than VTH.A. Hysteresis voltage, VHYST = VTH2 – VBATT.Th. VLOGIC (Pin 5): Positive Supply Voltage for Output Driver. This voltage can be driven from an external logic supply or tied to BATT. BATTLO (Pin 6): Output of Comparator. Low for BATT < VBATT.Th (low battery threshold voltage). Output state guaranteed for VBATT ≥ 1.5V. 1998fa 6 LTC1998 QUICK DESIGN GUIDE The LTC1998 is a low battery warning indicator and is especially designed for monitoring the voltage of single-cell Lithium-Ion batteries. The LTC1998 compares its supply pin (BATT) to an accurate internal reference; if the battery voltage falls below the programmed low battery threshold voltage of the LTC1998, the battery low pin (BATTLO) will change state, from high to low, to indicate a low battery condition. The low battery threshold voltage is programmed via the voltage threshold adjust pin (VTH.A). A hysteresis adjust pin (VH.A) will add hysteresis to the programmed value of the low battery threshold voltage. Typical Application Table 1: Design Equations for R1, R2, R3, Figure 1 Choose desired values for: • VBATT.Th: Low Battery Threshold Voltage • VHYST: Hysteresis Voltage • IR: Max Allowable Resistor Current Solve: 4.2V RTOTAL = R1 + R2 + R3 = IR Example 1: A system using a 4.2V (fully charged) LithiumIon battery requires a low battery threshold of 2.7V, 100mV hysteresis and can allow up to 4.2μA maximum resistor current. RTOTAL = 1MΩ, R1 = 786k, R2 = 66k and R3 = 148k Choose standard 1% values. R1 = 787k, R2 = 66.5k, R3 = 147k 1.5V TO 4.2V + Li-Ion How to Calculate the External Resistor Values R1 1% REGULATOR 0.1μF 4 R2 1% 1 BATT 5 VH.A VLOGIC LTC1998 3 R3 1% VLOGIC μP 6 VTH.A BATTLO GND 2 1998 F01 Figure 1. Low Battery Threshold Detector with Hysteresis ⎛ ⎞ 5V R1 = RTOTAL • ⎜ – 1⎟ ⎝ VBATT .Th + VHYST ⎠ ⎛ 5V ⎞ R2 = RTOTAL • ⎜ – 1⎟ – R1 ⎝ VBATT .Th ⎠ R3 = RTOTAL – R1 – R2 1998fa 7 LTC1998 APPLICATIONS INFORMATION LOW BATTERY THRESHOLD VOLTAGE AND HYSTERESIS ADJUST Low Battery Threshold Voltage Adjustment, Pin 3 The low battery threshold voltage is the battery voltage which will trip the (BATTLO) pin high to low. It should be adjusted via the threshold adjust pin (VTH.A). This is a high input impedance pin that senses an externally applied voltage and programs the low battery threshold voltage (VBATT.Th). The VTH.A pin is designed to accommodate voltages from 0V to 1.5V with respect to ground. This allows the low battery threshold voltage to be set to any voltage between 2.5V and 3.25V, that is: VBATT .Th = 2.5V + (VTH.A ) 2 For instance, if the applied voltage at pin 3, VTH.A, is 1V the LTC1998 will indicate a low battery condition when the battery voltage pin (BATT) falls below 3V. The voltage at the threshold adjust pin (VTH.A) can be set with any voltage source. This pin allows a continuous time adjustment, that is, the low battery threshold voltage may be changed at any time. The high input impedance of the VTH.A pin allows the use of a high valued resistive divider (to minimize current drain) from the battery to set the battery low threshold voltage, Figure 2. + 1 BATT Li-Ion R1 3 R2 The simple calculations of resistor values R1 and R2 are illustrated below. Set a value for R1 + R2. This value will affect the max amount of current drawn from the battery when fully charged. For instance if R1 + R2 = 1M the resistive divider will draw 4.1μA when the battery voltage is 4.1V. Set the desired value of VBATT.Th (this value should be between 2.5V and 3.25V) that is the value of the battery voltage that will trip the internal circuitry of the LTC1998 and change the state of the battery low pin (BATTLO). ⎛ 5V ⎞ Solve for R1= (R1+ R2) ⎜ – 1⎟ ⎝ VBATT.Th ⎠ Example: A Lithium-Ion battery is monitored and a battery low signal should be issued when it discharges to 2.85V, that is, VBATT.Th = 2.85V; if (R1 + R2) = 1M, then R1 = 754.38k and R2 = 245.62k. Choose the closest 1% value of R1 = 750k and R2 = 243k. Calculate the practical value for VBATT.Th as it will be slightly different from 2.85V, due to the use of standard 1% resistor values. VBATT .Th = 5V R1 + R2 = 2.849V R1 + (R1 + R2) The above low battery threshold of 2.849V is guaranteed to within 1% even though 1% resistors are used to program the VTH.A voltage applied to Pin 3. For sake of completeness, the voltage at Pin 3 (VTH.A) can be easily calculated by VTH.A = VBATT.Th (R2/(R1 + R2) = 0.6972V (when VBATTERY = VBATT.Th). VTH.A LTC1998 2 1998 F02 Figure 2. Resistor Divider Sets Threshold 1998fa 8 LTC1998 APPLICATIONS INFORMATION The LTC1998 has an adjustable hysteresis ranging from 10mV to 0.75V. A large hysteresis is useful in the event that a low battery signal at the LTC1998’s BATTLO pin causes the system to shed some battery load, thus inducing system confusion as the partially loaded battery recovers and changes the status of Pin 6 (BATTLO). The 2.5V to 3.25V programming window of low battery threshold voltage includes the hysteresis. If, for instance, the low battery threshold voltage is set to 2.5V, 750mV hysteresis can be added on top of the 2.5V. If the low battery threshold voltage is set to 3.15V, only 100mV hysteresis can be applied. The programming of the hysteresis threshold adjust pin (VH.A) is similar to the programming of the voltage threshold adjust pin (VTH.A) already described in the previous paragraph. Pin 4 effectively adjusts the threshold voltage at which the low battery pin (BATTLO) changes state from low to high. This threshold (VTH2) is defined as: VTH2 (V ) = 2.5V + H.A 2 The actual hysteresis voltage is: It is imperative that the hysteresis threshold adjust voltage at Pin 4 be set to a higher voltage than the low battery threshold adjust voltage at Pin 3, at all times, to avoid oscillation at the BATTLO output pin. The hysteresis threshold adjust pin may be set with a voltage source or with a resistor divider, just as with the low battery threshold adjust pin. Combined Control of Threshold and Hysteresis If a resistor divider is desired, then both threshold adjust dividers can be combined in order to save current. This simple technique also guarantees that the hysteresis threshold adjust voltage at Pin 4 is higher than the voltage at the VTH.A pin, Figure 3. + Li-Ion Hysteresis Adjustment, Pin 4. R1 4 1 BATT VH.A LTC1998 R2 3 VTH.A R3 1998 F03 Figure 3. Combined Resistor Divider VHYST = VTH2 – VBATT.Th 1998fa 9 LTC1998 APPLICATIONS INFORMATION The calculation of the resistor values R1, R2 and R3 is quite straightforward and similar to the procedure outlined in the previous paragraph. VERSATILE OUTPUT DRIVER Choose a value for the sum of R1 + R2 + R3 as well as the values for low battery threshold and hysteresis. The LTC1998 uses a CMOS push-pull output stage to drive the low battery output signal. This output pin (BATTLO) has a separate supply pin, (VLOGIC) that can be used to provide an output voltage rail matching the VDD logic of microprocessors. The VLOGIC pin may be tied to a voltage lower than the voltage at the BATT pin. The VLOGIC pin may also be tied to a voltage higher than VBATT via a series resistor greater than 10k. The output will then act as an open-drain device. Solve for resistor R1: ⎛ 5V ⎞ R1= (R1+ R2 + R3) ⎜ – 1⎟ ⎝ VTH2 ⎠ Solve for the sum of ⎛ 5V ⎞ (R1+ R2) = (R1+ R2 + R3) ⎜ – 1⎟ ⎝ VBATT.Th ⎠ then solve for R2 and R3. Example: A system needs to detect a low battery voltage of 3V (VBATT.Th = 3V) with 250mV hysteresis (VTH2 = 3.25V). Set the value of the resistor divider (R1 + R2 + R3) = 1M. R1 = 539k, R1 + R2 = 667k, R2 = 128k, R3 = 333k. Choose the closest 1% values, that is 536k, 332k, 127k. Figure 4 graphically shows the function of the LTC1998 as described above. VLOGIC, BATTLO (Pins 5,6) In a given application, if it is possible for BATTLO to be shorted to GND or a supply, a series resistor should be added to limit the short-circuit current to 5mA. 3.25V PROGRAMMED HYSTERESIS THRESHOLD PROGRAMMED LOW BATT THRESHOLD 2.50V HYSTERESIS PROGRAMMABLE THRESHOLD RANGE BATTERY VOLTAGE RECOVERS UNDER REDUCED LOAD BATTERY VOLTAGE VLOGIC BATTLO 1998 F04 Figure 4. LTC1998 Function Plot 1998fa 10 LTC1998 PACKAGE DESCRIPTION S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 3.85 MAX 2.62 REF 1.4 MIN 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.90 BSC S6 TSOT-23 0302 REV B NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 1998fa 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 LTC1998 TYPICAL APPLICATIONS Single Li-Ion Cell Low Battery Detector Backup Battery Switchover Circuit VLOGIC = 1V TO 5V VBATT = 1.5V TO 4.2V REGULATOR 0.1μF R1 1% 1 BATT 5 4 VH.A VLOGIC R2 1% LTC1998 3 R3 1% R1 787k 1% 4 + R2 68.1k 1% 3 Li-Ion Li-Ion + MBRM120 2.5V TO 4.2V μP 6 VTH.A BATTLO GND 2 R3 147k 1% VOUT BAT54C R4 1M 1 BATT 5 VH.A VLOGIC Si2301 Si2301 LTC1998 VTH.A BATTLO GND 2 BAT54C 6 + 3V BACKUP BATTERY 1998 TA01 SWITCHES TO BACKUP BATTERY WHEN PRIMARY FALLS BELOW 2.7V. SWITCHES BACK TO PRIMARY WHEN VOLTAGE RECOVERS TO ≥ 2.8V 1998 TA04 Micropower 2.9V VCC Threshold Detector with 15mV Hysteresis High Accuracy Window Comparator with Dual Hysteresis 3.3V R1 715k 1% 4 R2 9.09k 1% 3 R3 274k 1% 1 VIN BATT 5 VH.A VLOGIC R1 619k 1% 4 LTC1998 VTH.A BATTLO GND 2 6 OUT R2 6.04k 1% 3 LOW THRESHOLD = 2.9V HYSTERESIS = 15mV R3 383k 1% 1998 TA03 Low Battery Load Reduction Circuit R4 909k 1% 4 REGULATOR Li-Ion + R1 787k 1% 4 R2 68.1k 1% 3 R3 147k 1% Si2301 1 BATT 5 VH.A VLOGIC CRITICAL CIRCUITRY R5 6.98k 1% 3 R6 76.8k 1% LTC1998 6 VTH.A BATTLO GND 2 NONCRITICAL CIRCUITRY LOW THRESHOLD = 2.7V HYSTERESIS = 100mV V+ 1 R7 1M BATT 5 VH.A VLOGIC VOUT LTC1998 VTH.A BATTLO GND 2 6 2N7002 VOUT = V+ WHEN 2.6V ≤ VIN ≤ 3.1V 1 BATT 5 NC VH.A VLOGIC LTC1998 VTH.A BATTLO GND 2 6 WINDOW LOW THRESHOLD = 2.6V HYSTERESIS = 10mV WINDOW HIGH THRESHOLD = 3.1V HYSTERESIS = 10mV 1998 TA06 1998 TA05 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1440/LTC1540 Micropower Comparator with 1% Reference 1.182V ±1% Reference, ±10mV (Max) Input Offset LTC1441/LTC1442 Micropower Dual Comparator with 1% Reference 1.182V ±1% Reference (LTC1442) LTC1443/LTC1444/LTC1445 Micropower Quad Comparator with 1% Reference LTC1443 has 1.182V Reference, LTC1444/LTC1445 have 1.221V Reference and Adjustable Hysteresis 1998fa 12 Linear Technology Corporation LT 0108 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 2001