LT1121CS8-5#TRPBF

LT1121/LT1121-3.3/LT1121-5 Micropower Low Dropout Regulators with Shutdown FEATURES DESCRIPTION 0.4V Dropout Voltage n 150mA Output Current n 30µA Quiescent Current n No Protection Diodes Needed n Adjustable Output from 3.75V to 30V n 3.3V and 5V Fixed Output Voltages n Controlled Quiescent Current in Dropout n Shutdown n 16µA Quiescent Current in Shutdown n Stable with 0.33µF Output Capacitor n Reverse Battery Protection n No Reverse Current with Input Low n Thermal Limiting n Available in the 8-Lead SO, 8-Lead PDIP, 3-Lead SOT-23 and 3-Lead TO-92 Packages The LT®1121/LT1121-3.3/LT1121-5 are micropower low dropout regulators with shutdown. These devices are capable of supplying 150mA of output current with a dropout voltage of 0.4V. Designed for use in battery-powered systems, the low quiescent current, 30µA operating and 16µA in shutdown, makes them an ideal choice. The quiescent current is well-controlled; it does not rise in dropout as it does with many other low dropout PNP regulators. n APPLICATIONS Low Current Regulator Regulator for Battery-Powered Systems n Post Regulator for Switching Supplies n n Other features of the LT1121/LT1121-3.3/LT1121-5 include the ability to operate with very small output capacitors. They are stable with only 0.33µF on the output while most older devices require between 1µF and 100µF for stability. Small ceramic capacitors can be used, enhancing manufacturability. Also the input may be connected to ground or a reverse voltage without reverse current flow from output to input. This makes the LT1121 series ideal for backup power situations where the output is held high and the input is at ground or reversed. Under these conditions only 16µA will flow from the output pin to ground. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 5V Battery-Powered Supply with Shutdown Dropout Voltage 0.5 IN OUT 1 LT1121-3.3 5V 5 + SHDN GND 3 VSHDN (PIN 5) OUTPUT 2.8 ON NC ON 3.3VOUT 150mA 1μF SOLID TANTALUM 0.4 DROPOUT VOLTAGE (V) 8 0.3 0.2 0.1 LT1121 • TA01 0 0 20 40 60 80 100 120 140 160 OUTPUT CURRENT (mA) LT1121 • TA02 1121fg 1 LT1121/LT1121-3.3/LT1121-5 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Voltage LT1121............................................................... ± 30V LT1121HV................................................ +36V, – 30V Output Pin Reverse Current .................................. 10mA Adjust Pin Current ................................................. 10mA Shutdown Pin Input Voltage (Note 2)........... 6.5V, – 0.6V Shutdown Pin Input Current (Note 2) ................... 20mA Output Short-Circuit Duration ........................ Indefinite Operating Junction Temperature Range (Note 3) LT1121C-X............................................. 0°C to 125°C LT1121I-X ......................................... – 40°C to 125°C Storage Temperature Range...................– 65°C to 150°C Lead Temperature (Soldering, 10 sec).................... 300°C PIN CONFIGURATION TOP VIEW OUT 1 8 IN NC/ADJ* 2 7 NC** GND 3 6 NC** NC 4 5 SHDN N8 PACKAGE 8-LEAD PDIP S8 PACKAGE 8-LEAD PLASTIC SO * PIN 2 = NC FOR LT1121-3.3/LT1121-5 = ADJ FOR LT1121 ** PINS 6 AND 7 ARE FLOATING (NO INTERNAL CONNECTION) ON THE STANDARD S8 PACKAGE. PINS 6 AND 7 CONNECTED TO GROUND ON THE A VERSION OF THE LT1121 (S8 ONLY). CONNECTING PINS 6 AND 7 TO THE GROUND PLANE WILL REDUCE THERMAL RESISTANCE. SEE THERMAL RESISTANCE TABLES IN THE APPLICATIONS INFORMATION SECTION. TJMAX = 150°C, θJA = 120°C/W (N8, S8) TJMAX = 150°C, θJA = 70°C/W (AS8) BOTTOM VIEW FRONT VIEW TAB IS GND 3 OUTPUT 2 GND 1 VIN IN GND OUT ST PACKAGE 3-LEAD PLASTIC SOT-223 Z PACKAGE 3-LEAD PLASTIC TO-92 TJMAX = 150°C, θJA = 50°C/W TJMAX = 150°C, θJA = 150°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT1121CN8#PBF LT1121CN8#TRPBF LT1121CN8 8-Lead Plastic PDIP 0°C to 125°C LT1121CN8-3.3#PBF LT1121CN8-3.3#TRPBF LT1121CN8-3.3 8-Lead Plastic PDIP 0°C to 125°C LT1121CN8-5#PBF LT1121CN8-5#TRPBF LT1121CN8-5 8-Lead Plastic PDIP 0°C to 125°C LT1121IN8#PBF LT1121IN8#TRPBF LT1121IN8 8-Lead Plastic PDIP –40°C to 125°C LT1121IN8-3.3#PBF LT1121IN8-3.3#TRPBF LT1121IN8-3.3 8-Lead Plastic PDIP –40°C to 125°C LT1121IN8-5#PBF LT1121IN8-5#TRPBF LT1121IN8-5 8-Lead Plastic PDIP –40°C to 125°C LT1121CS8#PBF LT1121CS8#TRPBF 1121 8-Lead Plastic S0 0°C to 125°C LT1121CS8-3.3#PBF LT1121CS8-3.3#TRPBF 11213 8-Lead Plastic S0 0°C to 125°C LT1121CS8-5#PBF LT1121CS8-5#TRPBF 11215 8-Lead Plastic S0 0°C to 125°C LT1121HVCS8#PBF LT1121HVCS8#TRPBF 1121HV 8-Lead Plastic S0 –40°C to 125°C LT1121IS8#PBF LT1121IS8#TRPBF 1121I 8-Lead Plastic S0 –40°C to 125°C LT1121IS8-3.3#PBF LT1121IS8-3.3#TRPBF 121I3 8-Lead Plastic S0 –40°C to 125°C LT1121IS8-5#PBF LT1121IS8-5#TRPBF 121I5 8-Lead Plastic S0 –40°C to 125°C LT1121HVIS8#PBF LT1121HVIS8#TRPBF 121HVI 8-Lead Plastic S0 –40°C to 125°C LT1121ACS8#PBF LT1121ACS8#TRPBF 1121A 8-Lead Plastic S0 0°C to 125°C LT1121ACS8-3.3#PBF LT1121ACS8-3.3#TRPBF 1121A3 8-Lead Plastic S0 0°C to 125°C LT1121ACS8-5#PBF LT1121ACS8-5#TRPBF 1121A5 8-Lead Plastic S0 0°C to 125°C 1121fg 2 LT1121/LT1121-3.3/LT1121-5 ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT1121AHVCS8#PBF LT1121AHVCS8#TRPBF 121AHV 8-Lead Plastic S0 0°C to 125°C LT1121AIS8#PBF LT1121AIS8#TRPBF 121AI 8-Lead Plastic S0 –40°C to 125°C LT1121AIS8-3.3#PBF LT1121AIS8-3.3#TRPBF 121AI3 8-Lead Plastic S0 –40°C to 125°C LT1121AIS8-5#PBF LT1121AIS8-5#TRPBF 121AI5 8-Lead Plastic S0 –40°C to 125°C LT1121AHVIS8#PBF LT1121AHVIS8#TRPBF 21AHVI 8-Lead Plastic S0 –40°C to 125°C LT1121CST-3.3#PBF LT1121CST-3.3#TRPBF 11213 3-Lead Plastic SOT-223 0°C to 125°C LT1121IST-3.3#PBF LT1121IST-3.3#TRPBF 121I3 3-Lead Plastic SOT-223 –40°C to 125°C LT1121CST-5#PBF LT1121CST-5#TRPBF 11215 3-Lead Plastic SOT-223 0°C to 125°C LT1121IST-5#PBF LT1121IST-5#TRPBF 1121I5 3-Lead Plastic SOT-223 –40°C to 125°C LT1121CZ3-3#PBF LT1121CZ3-3#TRPBF LT1121CZ3-3 3-Lead Plastic TO-92 0°C to 125°C LT1121IZ3-3#PBF LT1121IZ3-3#TRPBF LT1121IZ3-3 3-Lead Plastic TO-92 –40°C to 125°C LT1121CZ-5#PBF LT1121CZ-5#TRPBF LT1121CZ-5 3-Lead Plastic TO-92 0°C to 125°C LT1121IZ-5#PBF LT1121IZ-5#TRPBF LT1121IZ-5 3-Lead Plastic TO-92 –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on nonstandard lead based finish parts. 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/ ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS Regulated Output Voltage (Note 4) LT1121-3.3 LT1121-5 LT1121 (Note 5) Line Regulation Load Regulation Dropout Voltage (Note 6) MIN TYP MAX UNITS VIN = 3.8V, IOUT = 1mA, TJ = 25ºC 4.3V < VIN < 20V, 1mA < IOUT < 150mA l 3.25 3.2 3.3 3.3 3.35 3.4 V V VIN = 5.5V, IOUT = 1mA, TJ = 25ºC 6V < VIN < 20V, 1mA < IOUT < 150mA l 4.925 4.85 5 5 5.075 5.15 V V VIN = 4.3V, IOUT = 1mA, TJ = 25ºC 4.8V < VIN < 20V, 1mA < IOUT < 150mA l 3.695 3.64 3.75 3.75 3.805 3.86 V V 1.5 1.5 1.5 10 10 10 mV mV mV –12 –20 –17 –28 –12 –18 –25 –40 –35 –50 –25 –40 mV mV mV mV mV mV 0.13 0.16 0.25 V V 0.3 0.35 0.5 V V 0.37 0.45 0.6 V V 0.42 0.55 0.7 V V LT1121-3.3 ΔVIN = 4.8V TO 20V, IOUT = 1mA LT1121-5 ΔVIN = 5.5V TO 20V, IOUT = 1mA LT1121 (Note 5) ΔVIN = 4.3V TO 20V, IOUT = 1mA LT1121-3.3 ΔILOAD = 1mA to 150mA, TJ = 25ºC ΔILOAD = 1mA to 150mA LT1121-5 ΔILOAD = 1mA to 150mA, TJ = 25ºC ΔILOAD = 1mA to 150mA LT1121 (Note 5) ΔILOAD = 1mA to 150mA, TJ = 25ºC ΔILOAD = 1mA to 150mA l l l l l l ILOAD = 1mA, TJ = 25ºC ILOAD = 1mA l ILOAD = 50mA, TJ = 25ºC ILOAD = 50mA l ILOAD = 100mA, TJ = 25ºC ILOAD = 100mA l ILOAD = 150mA, TJ = 25ºC ILOAD = 150mA l 1121fg 3 LT1121/LT1121-3.3/LT1121-5 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS MIN Ground Pin Current (Note 7) ILOAD = 0mA ILOAD = 1mA ILOAD = 10mA ILOAD = 50mA ILOAD = 100mA ILOAD = 150mA Adjust Pin Bias Current (Notes 5, 8) TJ = 25ºC Shutdown Threshold VOUT = Off to On VOUT = On to Off l l Shutdown Pin Current (Note 9) VSHDN = 0V l l l l l l l Quiescent Current in Shutdown (Note 10) VIN = 6V, VSHDN = 0V l Ripple Rejection VIN – VOUT = 1V (Avg), VRIPPLE = 0.5VP-P , fRIPPLE = 120Hz, ILOAD = 0.1A Current Limit VIN – VOUT = 7V, TJ = 25ºC Input Reverse Leakage Current VIN = –20V, VOUT = 0V Reverse Output Current (Note 11) LT1121-3.3 VOUT = 3.3V, VIN = 0V LT1121-5 VOUT = 5V, VIN = 0V LT1121 (Note 5) VOUT = 3.8V, VIN = 0V 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: The shutdown pin input voltage rating is required for a low impedance source. Internal protection devices connected to the shutdown pin will turn on and clamp the pin to approximately 7V or – 0.6V. This range allows the use of 5V logic devices to drive the pin directly. For high impedance sources or logic running on supply voltages greater than 5.5V, the maximum current driven into the shutdown pin must be limited to less than 20mA. Note 3: For junction temperatures greater than 110°C, a minimum load of 1mA is recommended. For TJ > 110°C and IOUT < 1mA, output voltage may increase by 1%. Note 4: Operating conditions are limited by maximum junction temperature. The regulated output voltage specification will not apply for all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range must be limited. When operating at maximum output current the input voltage range must be limited. 0.25 50 TYP MAX UNITS 30 90 350 1.5 4 7 50 120 500 2.5 7 14 µA µA µA mA mA mA 150 300 nA 1.2 0.75 2.8 V V 6 10 µA 16 22 58 200 l 16 16 16 µA dB 500 mA 1 mA 25 25 25 µA µA µA Note 5: The LT1121 (adjustable version) is tested and specified with the adjust pin connected to the output pin. Note 6: Dropout voltage is the minimum input/output voltage required to maintain regulation at the specified output current. In dropout the output voltage will be equal to: (VIN – VDROPOUT). Note 7: Ground pin current is tested with VIN = VOUT (nominal) and a current source load. This means that the device is tested while operating in its dropout region. This is the worst case ground pin current. The ground pin current will decrease slightly at higher input voltages. Note 8: Adjust pin bias current flows into the adjust pin. Note 9: Shutdown pin current at VSHDN = 0V flows out of the shutdown pin. Note 10: Quiescent current in shutdown is equal to the sum total of the shutdown pin current (6µA) and the ground pin current (9µA). Note 11: Reverse output current is tested with the input pin grounded and the output pin forced to the rated output voltage. This current flows into the output pin and out of the ground pin. 1121fg 4 LT1121/LT1121-3.3/LT1121-5 TYPICAL PERFORMANCE CHARACTERISTICS Dropout Voltage 0.6 0.6 TJ ≤ 125°C 0.5 0.4 TJ ≤ 25°C 0.3 0.2 0.1 0 Quiescent Current 50 ILOAD = 150mA ILOAD = 100mA 0.5 0.4 0.3 ILOAD = 50mA 0.2 ILOAD = 1mA 0.1 = TEST POINTS 0 0 –50 40 60 80 100 120 140 160 OUTPUT CURRENT (mA) 20 50 25 0 75 TEMPERATURE (°C) –25 100 1121 G01 VSHDN = OPEN 40 2 3 4 5 6 7 INPUT VOLTAGE (V) 80 VSHDN = OPEN 60 40 20 VSHDN = 0V 1 8 9 0 10 1 0 2 3.32 3.30 3.28 3.26 3.24 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 50 0 75 25 TEMPERATURE (°C) 80 VSHDN = OPEN 60 40 0 10 100 125 1121 G07 VSHDN = 0V 1 0 2 3 4 5 6 7 INPUT VOLTAGE (V) 9 10 1121 G06 3.83 IOUT = 1mA 5.06 3.81 5.04 3.79 5.02 5.00 4.98 4.96 4.92 –50 8 LT1121 Adjust Pin Voltage IOUT = 1mA 3.77 3.75 3.73 3.71 3.69 4.94 –25 125 100 TJ = 25°C RLOAD = ∞ VOUT = VADJ 20 ADJ PIN VOLTAGE (V) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 5.08 3.34 50 25 0 75 TEMPERATURE (°C) –25 100 LT1121-5 Output Voltage IOUT = 1mA 3.22 –50 10 1121 G05 LT1121-3.3 Output Voltage 3.36 VSHDN = 0V 120 VSHDN = 0V 1121 G04 3.38 20 1121 G03 QUIESCENT CURRENT (μA) 80 0 30 0 –50 125 TJ = 25°C RLOAD = ∞ 100 QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) 100 20 VSHDN = OPEN LT1121 Quiescent Current 120 TJ = 25°C RLOAD = ∞ 60 40 LT1121-5 Quiescent Current 120 VIN = 6V RLOAD = ∞ 1121 G02 LT1121-3.3 Quiescent Current 0 QUIESCENT CURRENT (μA) 0.7 DROPOUT VOLTAGE (V) DROPOUT VOLTAGE (V) Guaranteed Dropout Voltage 0.7 –25 50 0 75 25 TEMPERATURE (°C) 100 125 1121 G08 3.67 –50 –25 50 0 75 25 TEMPERATURE (°C) 100 125 1121 G09 1121fg 5 LT1121/LT1121-3.3/LT1121-5 TYPICAL PERFORMANCE CHARACTERISTICS 800 TJ = 25°C RLOAD = 130Ω ILOAD = 25mA* 600 500 RLOAD = 330Ω ILOAD = 10mA* 400 300 *FOR VOUT = 3.3V 200 RLOAD = 3.3k ILOAD = 1mA* 100 0 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 800 RLOAD = 200Ω ILOAD = 25mA* 600 500 RLOAD = 500Ω ILOAD = 10mA* 400 300 *FOR VOUT = 5V 200 RLOAD = 5k ILOAD = 1mA* 100 0 10 2 1 0 3 4 5 6 7 INPUT VOLTAGE (V) 8 1121 G10 10 RLOAD = 22Ω ILOAD = 150mA* 7 6 RLOAD = 33Ω ILOAD = 100mA* 5 4 3 RLOAD = 66Ω ILOAD = 50mA* 2 1 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 RLOAD = 33Ω ILOAD = 150mA* 6 RLOAD = 50Ω ILOAD = 100mA* 5 4 3 RLOAD = 100Ω ILOAD = 50mA* 2 1.8 2 0 0 2 1 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 20 40 60 80 100 120 140 160 OUTPUT CURRENT (mA) 1121 G16 3 4 5 6 7 INPUT VOLTAGE (V) 8 10 RLOAD = 25Ω ILOAD = 150mA* 7 6 5 RLOAD = 38Ω ILOAD = 100mA* 4 3 RLOAD = 75Ω ILOAD = 50mA* 2 *FOR VOUT = 3.75V 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 10 9 1121 G15 Shutdown Pin Threshold (Off-to-On) 2.0 ILOAD = 1mA 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0 –50 9 8 0 10 1.6 ILOAD = 150mA 1.4 1.2 ILOAD = 1mA 1.0 0.8 0.6 0.4 0.2 0.2 0 2 1 *FOR VOUT = 5V SHUTDOWN THRESHOLD (V) 4 SHUTDOWN THRESHOLD (V) GROUND PIN CURRENT (mA) 2.0 TJ = –55°C 1 1121 G12 Shutdown Pin Threshold (On-to-Off) TJ = 25°C 0 1121 G14 14 6 RLOAD = 3.8k ILOAD = 1mA* TJ = 25°C 9 VOUT = VADJ 7 Ground Pin Current TJ = 125°C *FOR VOUT = 3.75V 200 LT1121 Ground Pin Current 1121 G13 8 300 0 10 8 0 10 VIN = 3.3V (LT1121-3.3) VIN = 5V (LT1121-5) 12 V = 3.75V (LT1121) IN DEVICE IS OPERATING 10 IN DROPOUT RLOAD = 380Ω ILOAD = 10mA* 400 10 1 *FOR VOUT = 3.3V 0 500 100 TJ = 25°C 9 GROUND PIN CURRENT (mA) GROUND PIN CURRENT (mA) 8 600 LT1121-5 Ground Pin Current TJ = 25°C 9 9 RLOAD = 150Ω ILOAD = 25mA* 1121 G11 LT1121-3.3 Ground Pin Current 10 TJ = 25°C 700 VOUT = VADJ TJ = 25°C 700 GROUND PIN CURRENT (μA) GROUND PIN CURRENT (μA) 700 LT1121 Ground Pin Current GROUND PIN CURRENT (mA) 800 LT1121-5 Ground Pin Current GROUND PIN CURRENT (μA) LT1121-3.3 Ground Pin Current –25 50 25 0 75 TEMPERATURE (°C) 100 125 1121 G17 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1121 G18 1121fg 6 LT1121/LT1121-3.3/LT1121-5 TYPICAL PERFORMANCE CHARACTERISTICS Shutdown Pin Current SHUTDOWN PIN INPUT CURRENT (mA) SHUTDOWN PIN CURRENT (μA) 8 7 6 5 4 3 2 1 0 –50 50 25 0 75 TEMPERATURE (°C) –25 400 25 VSHDN = 0V 9 100 20 15 10 5 0 125 ADJUST PIN BIAS CURRENT (nA) 10 LT1121 Adjust Pin Bias Current Shutdown Pin Input Current 7 3 8 2 5 6 4 SHUTDOWN PIN VOLTAGE (V) 1 0 1121 G19 Reverse Output Current 15 10 5 100 VOUT = 0V 300 300 250 200 150 100 50 0 1 4 2 5 3 INPUT VOLTAGE (V) 0 0 1 2 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 200 150 100 0 –50 7 6 9 10 1121 G25 –25 50 0 75 25 TEMPERATURE (°C) 100 1121 G24 Ripple Rejection IOUT = 100mA 90 VIN = 6V + 50mVRMS RIPPLE RIPPLE REJECTION (dB) 80 60 58 56 54 50 –50 125 100 COUT = 47μF SOLID TANTALUM 70 60 50 40 30 COUT = 1μF SOLID TANTALUM 20 52 LT1121-5 10 125 250 1121 G23 RIPPLE REJECTION (dB) OUTPUT PIN CURRENT (μA) 20 100 50 VIN = VOUT (NOMINAL) + 1V + 0.5VP-P RIPPLE AT f = 120Hz 62 IOUT = 100mA LT1121-3.3 50 0 75 25 TEMPERATURE (°C) Current Limit Ripple Rejection LT1121 (VOUT = VADJ) –25 1121 G21 64 TJ = 25°C 90 VIN = 0V CURRENT FLOWS 80 INTO OUTPUT PIN 70 30 50 VIN = 7V 350 VOUT = 0V Reverse Output Current 40 100 350 0 125 100 50 150 400 1121 G22 60 200 0 –50 9 CURRENT LIMIT (mA) SHORT-CIRCUIT CURRENT (mA) OUTPUT PIN CURRENT (μA) 20 50 25 0 75 TEMPERATURE (°C) 250 Current Limit 400 VIN = 0V VOUT = 5V (LT1121-5) 25 VOUT = 3.3V (LT1121-3.3) VOUT = 3.8V (LT1121) –25 300 1121 G20 30 0 –50 350 10 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1121 G26 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1121 G27 1121fg 7 LT1121/LT1121-3.3/LT1121-5 TYPICAL PERFORMANCE CHARACTERISTICS LT1121-5 Load Transient Response Load Regulation ΔILOAD = 1mA TO 150mA OUTPUT VOLTAGE DEVIATION (V) LT1121* –10 LT1121-3.3 –15 –20 VIN = 6V 0.2 CIN = 0.1μF = 1μF C 0.1 OUT 0 –0.1 –0.2 VIN = 6V 0.2 CIN = 0.1μF COUT = 3.3μF 0.1 0 –0.1 –0.2 LT1121-5 –30 –35 * ADJ PIN TIED TO OUTPUT PIN –40 –50 –25 50 0 75 25 TEMPERATURE (°C) 100 125 150 100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 TIME (ms) 1121 G28 1121 G29 LOAD CURRENT (mA) –25 LOAD CURRENT (mA) LOAD REGULATION (mV) –5 OUTPUT VOLTAGE DEVIATION (V) 0 LT1121-5 Load Transient Response 150 100 50 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 TIME (ms) 1121 G30 PIN FUNCTIONS Input Pin: Power is supplied to the device through the input pin. The input pin should be bypassed to ground if the device is more than six inches away from the main input filter capacitor. In general the output impedance of a battery rises with frequency so it is usually adviseable to include a bypass capacitor in battery-powered circuits. A bypass capacitor in the range of 0.1µF to 1µF is sufficient. The LT1121 is designed to withstand reverse voltages on the input pin with respect to both ground and the output pin. In the case of a reversed input, which can happen if a battery is plugged in backwards, the LT1121 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT1121 and no reverse voltage will appear at the load. The device will protect both itself and the load. Output Pin: The output pin supplies power to the load. An output capacitor is required to prevent oscillations. See the Applications Information section for recommended value of output capacitance and information on reverse output characteristics. Shutdown Pin: This pin is used to put the device into shutdown. In shutdown the output of the device is turned off. This pin is active low. The device will be shut down if the shutdown pin is pulled low. The shutdown pin current with the pin pulled to ground will be 6µA. The shutdown pin is internally clamped to 7V and – 0.6V (one VBE). This allows the shutdown pin to be driven directly by 5V logic or by open collector logic with a pull-up resistor. The pull-up resistor is only required to supply the leakage current of the open collector gate, normally several microamperes. Pull-up current must be limited to a maximum of 20mA. A curve of shutdown pin input current as a function of voltage appears in the Typical Performance Characteristics. If the shutdown pin is not used it can be left open circuit. The device will be active, output on, if the shutdown pin is not connected. Adjust Pin: For the adjustable LT1121, the adjust pin is the input to the error amplifier. This pin is internally clamped to 6V and –0.6V (one VBE). It has a bias current of 150nA which flows into the pin. See Bias Current curve in the Typical Performance Characteristics. The adjust pin reference voltage is 3.75V referenced to ground. The output voltage range that can be produced by this device is 3.75V to 30V. 1121fg 8 LT1121/LT1121-3.3/LT1121-5 APPLICATIONS INFORMATION The LT1121 is a micropower low dropout regulator with shutdown, capable of supplying up to 150mA of output current at a dropout voltage of 0.4V. The device operates with very low quiescent current (30µA). In shutdown the quiescent current drops to only 16µA. In addition to the low quiescent current the LT1121 incorporates several protection features which make it ideal for use in batterypowered systems. The device is protected against both reverse input voltages and reverse output voltages. In battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the LT1121 acts like it has a diode in series with its output and prevents reverse current flow. approximately 15ppm/°C. The adjust pin bias current has a negative temperature coefficient. These effects are small and will tend to cancel each other. Adjustable Operation Thermal Considerations The adjustable version of the LT1121 has an output voltage range of 3.75V to 30V. The output voltage is set by the ratio of two external resistors as shown in Figure 1. The device servos the output voltage to maintain the voltage at the adjust pin at 3.75V. The current in R1 is then equal to 3.75V/R1. The current in R2 is equal to the sum of the current in R1 and the adjust pin bias current. The adjust pin bias current, 150nA at 25°C, flows through R2 into the adjust pin. The output voltage can be calculated according to the formula in Figure 1. The value of R1 should be less than 400k to minimize errors in the output voltage caused by the adjust pin bias current. Note that in shutdown the output is turned off and the divider current will be zero. Curves of Adjust Pin Voltage vs Temperature and Adjust Pin Bias Current vs Temperature appear in the Typical Performance Characteristics. The reference voltage at the adjust pin has a slight positive temperature coefficient of Power handling capability will be limited by maximum rated junction temperature (125°C). Power dissipated by the device will be made up of two components: IN VOUT OUT LT1121 R2 SHDN ADJ + R1 GND 1121 • F01 ( ) VOUT = 3.75V 1 + R2 + IADJ • R2 R1 VADJ = 3.75V IADJ = 150nA AT 25°C OUTPUT RANGE = 3.75V TO 30V ( ) Figure 1. Adjustable Operation The adjustable device is specified with the adjust pin tied to the output pin. This sets the output voltage to 3.75V. Specifications for output voltage greater than 3.75V will be proportional to the ratio of the desired output voltage to 3.75V (VOUT/3.75V). For example: load regulation for an output current change of 1mA to 150mA is –12mV typical at VOUT = 3.75V. At VOUT = 12V, load regulation would be: ⎛ 12V ⎞ ⎜⎝ 3.75V ⎟⎠ • ( –12mV ) = ( –38mV ) 1. Output current multiplied by the input/output voltage differential: IOUT • (VIN – VOUT), and 2. Ground pin current multiplied by the input voltage: IGND • VIN. The ground pin current can be found by examining the Ground Pin Current curves in the Typical Performance Characteristics. Power dissipation will be equal to the sum of the two components listed above. The LT1121 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal load conditions the maximum junction temperature rating of 125°C must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. Heat sinking, for surface mount devices, is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Copper board stiffeners and plated through holes can also be used to spread the heat generated by power devices. Tables 1 through 5 list thermal resistances for each package. Measured values of thermal resistance for several different board sizes and copper areas are listed for each package. All measurements were taken in still air, on 3/32" FR-4 board with 1oz copper. All 1121fg 9 LT1121/LT1121-3.3/LT1121-5 APPLICATIONS INFORMATION NC leads were connected to the ground plane. Table 1. N8 Package* COPPER AREA Table 5. TO-92 Package THERMAL RESISTANCE Package alone 220ºC/W Package soldered into PC board with plated through holes only 175ºC/W Package soldered into PC board with 1/4 sq. inch of copper trace per lead 145ºC/W 160ºC/W 135ºC/W BOARD AREA THERMAL RESISTANCE JUNCTION TO AMBIENT 2500 sq mm 2500 sq mm 2500 sq mm 80ºC/W 1000 sq mm 2500 sq mm 2500 sq mm 80ºC/W Package soldered into PC board with plated through holes in board, no extra copper trace, and a clip-on type heat sink: Thermalloy type 2224B 225 sq mm 2500 sq mm 2500 sq mm 85ºC/W Aavid type 5754 1000 sq mm 1000 sq mm 1000 sq mm 91ºC/W TOPSIDE BACKSIDE * Device is mounted on topside. Leads are through hole and are soldered to both sides of board. Table 2. S8 Package COPPER AREA BOARD AREA THERMAL RESISTANCE JUNCTION TO AMBIENT 2500 sq mm 2500 sq mm 2500 sq mm 120ºC/W 1000 sq mm 2500 sq mm 2500 sq mm 120ºC/W 225 sq mm 2500 sq mm 2500 sq mm 125ºC/W 100 sq mm 1000 sq mm 1000 sq mm 131ºC/W TOPSIDE* BACKSIDE * Device is mounted on topside. Table 3. AS8 Package* COPPER AREA BOARD AREA THERMAL RESISTANCE JUNCTION TO AMBIENT 2500 sq mm 2500 sq mm 2500 sq mm 60ºC/W 1000 sq mm 2500 sq mm 2500 sq mm 60ºC/W 225 sq mm 2500 sq mm 2500 sq mm 68ºC/W 100 sq mm 2500 sq mm 2500 sq mm 74ºC/W TOPSIDE** BACKSIDE * Pins 3, 6 and 7 are ground. ** Device is mounted on topside. BOARD AREA THERMAL RESISTANCE JUNCTION TO AMBIENT 2500 sq mm 2500 sq mm 2500 sq mm 50ºC/W 1000 sq mm 2500 sq mm 2500 sq mm 50ºC/W 225 sq mm 2500 sq mm 2500 sq mm 58ºC/W 100 sq mm 2500 sq mm 2500 sq mm 64ºC/W 1000 sq mm 2500 sq mm 1000 sq mm 57ºC/W 1000 sq mm 1000 sq mm 60ºC/W TOPSIDE* BACKSIDE 0 * Tab of device attached to topside copper. Example: given an output voltage of 3.3V, an input voltage range of 4.5V to 7V, an output current range of 0mA to 100mA, and a maximum ambient temperature of 50°C, what will the maximum junction temperature be? Power dissipated by the device will be equal to: IOUT MAX • (VIN MAX – VOUT) + (IGND • VIN) where, IOUT MAX = 100mA VIN MAX = 7V IGND at (IOUT = 100mA, VIN = 7V) = 5mA so, P = 100mA • (7V – 3.3V) + (5mA • 7V) = 0.405W If we use an SOT-223 package, then the thermal resistance will be in the range of 50°C/W to 65°C/W depending on copper area. So the junction temperature rise above ambient will be less than or equal to: 0.405W • 60°C/W = 24°C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: Table 4. SOT-223 Package (Thermal Resistance Junction-to-Tab 20ºC/W) COPPER AREA Calculating Junction Temperature TJMAX = 50°C + 24°C = 74°C Output Capacitance and Transient Performance The LT1121 is designed to be stable with a wide range of output capacitors. The minimum recommended value is 1µF with an ESR of 3Ω or less. For applications where space is very limited, capacitors as low as 0.33µF can be used if combined with a small series resistor. Assuming that the ESR of the capacitor is low (ceramic) the suggested series 1121fg 10 LT1121/LT1121-3.3/LT1121-5 APPLICATIONS INFORMATION Table 6. Suggested Series Resistor Values OUTPUT CAPACITANCE SUGGESTED SERIES RESISTOR 0.33µF 2Ω 0.47µF 1Ω 0.68µF 1Ω >1µF None Needed Protection Features The LT1121 incorporates several protection features which make it ideal for use in battery-powered circuits. In addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting, the device is protected against reverse input voltages, reverse output voltages, and reverse voltages from output to input. Current limit protection and thermal overload protection are intended to protect the device against current overload conditions at the output of the device. For normal operation, the junction temperature should not exceed 125°C. The input of the device will withstand reverse voltages of 30V. Current flow into the device will be limited to less than 1mA (typically less than 100µA) and no negative voltage will appear at the output. The device will protect both itself and the load. This provides protection against batteries that can be plugged in backwards. For fixed voltage versions of the device, the output can be pulled below ground without damaging the device. If the input is open circuit or grounded the output can be pulled below ground by 20V. The output will act like an open circuit, no current will flow out of the pin. If the input is powered by a voltage source, the output will source the short-circuit current of the device and will protect itself by thermal limiting. For the adjustable version of the device, the output pin is internally clamped at one diode drop below ground. Reverse current for the adjustable device must be limited to 5mA. In circuits where a backup battery is required, several different input/output conditions can occur. The output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage, or is left open circuit. Current flow back into the output will vary depending on the conditions. Many battery-powered circuits incorporate some form of power management. The following information will help optimize battery life. Table 7 summarizes the following information. The reverse output current will follow the curve in Figure 2 when the input pin is pulled to ground. This current flows through the output pin to ground. The state of the shutdown pin will have no effect on output current when the input pin is pulled to ground. In some applications it may be necessary to leave the input to the LT1121 unconnected when the output is held high. This can happen when the LT1121 is powered from a rectified AC source. If the AC source is removed, then the input of the LT1121 is effectively left floating. The reverse output current also follows the curve in Figure 2 if the input pin is left open. The state of the shutdown pin will have no effect on the reverse output current when the input pin is floating. 100 OUTPUT PIN CURRENT (μA) resistor is shown in Table 6. The LT1121 is a micropower device and output transient response will be a function of output capacitance. See the Transient Response curves in the Typical Performance Characteristics. Larger values of output capacitance will decrease the peak deviations and provide improved output transient response. Bypass capacitors, used to decouple individual components powered by the LT1121, will increase the effective value of the output capacitor. TJ = 25°C 90 VIN < VOUT CURRENT FLOWS 80 INTO OUTPUT PIN 70 TO GROUND LT1121 (VOUT = VADJ) 60 50 40 LT1121-3.3 30 20 LT1121-5 10 0 0 1 2 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 9 10 1121• F02 Figure 2. Reverse Output Current 1121fg 11 LT1121/LT1121-3.3/LT1121-5 APPLICATIONS INFORMATION 5 VOUT = 3.3V (LT1121-3.3) VOUT = 5V (LT1121-5) 4 INPUT CURRENT (μA) When the input of the LT1121 is forced to a voltage below its nominal output voltage and its output is held high, the reverse output current will still follow the curve in Figure 2. This condition can occur if the input of the LT1121 is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or by a second regulator circuit. When the input pin is forced below the output pin or the output pin is pulled above the input pin, the input current will typically drop to less than 2µA (see Figure 3). The state of the shutdown pin will have no effect on the reverse output current when the output is pulled above the input. 3 2 1 0 1 0 3 2 INPUT VOLTAGE (V) 4 5 1121 F03 Figure 3. Input Current Table 7. Fault Conditions INPUT PIN SHDN PIN OUTPUT PIN