LT1761 Series 100mA, Low Noise, LDO Micropower Regulators in TSOT-23 FEATURES DESCRIPTION n The LT®1761 series are micropower, low noise, low dropout regulators. With an external 0.01μF bypass capacitor, output noise drops to 20μVRMS over a 10Hz to 100kHz bandwidth. Designed for use in battery-powered systems, the low 20μA quiescent current makes them an ideal choice. In shutdown, quiescent current drops to less than 0.1μA. The devices are capable of operating over an input voltage from 1.8V to 20V, and can supply 100mA of output current with a dropout voltage of 300mV. Quiescent current is well controlled, not rising in dropout as it does with many other regulators. n n n n n n n n n n n n n n Low Noise: 20μVRMS (10Hz to 100kHz) Low Quiescent Current: 20μA Wide Input Voltage Range: 1.8V to 20V Output Current: 100mA Very Low Shutdown Current: <0.1μA Low Dropout Voltage: 300mV at 100mA Fixed Output Voltages: 1.2V, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V Adjustable Output from 1.22V to 20V Stable with 1μF Output Capacitor Stable with Aluminum, Tantalum or Ceramic Capacitors Reverse-Battery Protected No Reverse Current No Protection Diodes Needed Overcurrent and Overtemperature Protected Available in Tiny 5-Lead TSOT-23 Package APPLICATIONS n n n n n Cellular Phones Pagers Battery-Powered Systems Frequency Synthesizers Wireless Modems The LT1761 regulators are stable with output capacitors as low as 1μF. Small ceramic capacitors can be used without the series resistance required by other regulators. Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. The device is available in fixed output voltages of 1.2V, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V and 5V, and as an adjustable device with a 1.22V reference voltage. The LT1761 regulators are available in the 5-lead TSOT-23 package. L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 10Hz to 100kHz Output Noise 5V Low Noise Regulator VIN 5.4V TO 20V IN 1μF OUT LT1761-5 SHDN BYP 0.01μF + 5V AT100mA 20μVRMS NOISE 10μF VOUT 100μV/DIV 20μVRMS 1761 TA01 GND 1761 TA01b 1761sff 1 LT1761 Series ABSOLUTE MAXIMUM RATINGS (Note 1) IN Pin Voltage .........................................................±20V OUT Pin Voltage ......................................................±20V Input to Output Differential Voltage .........................±20V ADJ Pin Voltage ...................................................... ±7V BYP Pin Voltage .....................................................±0.6V SHDN Pin Voltage ................................................. ±20V Output Short-Circuit Duration ........................ Indefinite Operating Junction Temperature Range E, I Grade (Note 2) ............................. –40°C to 125°C MP Grade (Note 2) ............................. –55°C to 125°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C PIN CONFIGURATION LT1761-BYP LT1761-SD TOP VIEW IN 1 5 OUT GND 2 BYP 3 LT1761-X TOP VIEW IN 1 5 OUT IN 1 GND 2 4 ADJ SHDN 3 TOP VIEW 5 OUT GND 2 SHDN 3 4 ADJ 4 BYP S5 PACKAGE 5-LEAD PLASTIC TSOT-23 S5 PACKAGE 5-LEAD PLASTIC TSOT-23 S5 PACKAGE 5-LEAD PLASTIC TSOT-23 TJMAX = 150°C, θJA = 250°C/W SEE APPLICATIONS INFORMATION SECTION TJMAX = 150°C, θJA = 250°C/W SEE APPLICATIONS INFORMATION SECTION TJMAX = 150°C, θJA = 250°C/W SEE APPLICATIONS INFORMATION SECTION ORDER INFORMATION LEAD FREE FINISH LT1761ES5-BYP#PBF LT1761IS5-BYP#PBF LT1761ES5-SD#PBF LT1761IS5-SD#PBF LT1761ES5-1.2#PBF LT1761IS5-1.2#PBF LT1761ES5-1.5#PBF LT1761IS5-1.5#PBF LT1761ES5-1.8#PBF LT1761IS5-1.8#PBF LT1761MPS5-1.8#PBF LT1761ES5-2#PBF LT1761IS5-2#PBF LT1761ES5-2.5#PBF LT1761IS5-2.5#PBF LT1761ES5-2.8#PBF LT1761IS5-2.8#PBF LT1761ES5-3#PBF LT1761IS5-3#PBF LT1761ES5-3.3#PBF LT1761IS5-3.3#PBF LT1761MPS5-3.3#PBF TAPE AND REEL LT1761ES5-BYP#TRPBF LT1761IS5-BYP#TRPBF LT1761ES5-SD#TRPBF LT1761IS5-SD#TRPBF LT1761ES5-1.2#TRPBF LT1761IS5-1.2#TRPBF LT1761ES5-1.5#TRPBF LT1761IS5-1.5#TRPBF LT1761ES5-1.8#TRPBF LT1761IS5-1.8#TRPBF LT1761MPS5-1.8#TRPBF LT1761ES5-2#TRPBF LT1761IS5-2#TRPBF LT1761ES5-2.5#TRPBF LT1761IS5-2.5#TRPBF LT1761ES5-2.8#TRPBF LT1761IS5-2.8#TRPBF LT1761ES5-3#TRPBF LT1761IS5-3#TRPBF LT1761ES5-3.3#TRPBF LT1761IS5-3.3#TRPBF LT1761MPS5-3.3#TRPBF PART MARKING * LTGC LTGC LTGH LTGH LTCDS LTCDS LTMT LTMT LTJM LTJM LTDCH LTJE LTJE LTGD LTGD LTLB LTLB LTGE LTGE LTGF LTGF LTGF PACKAGE DESCRIPTION 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 5-Lead Plastic TSOT-23 TEMPERATURE RANGE –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –55°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 125°C –55°C to 125°C 1761sff 2 LT1761 Series ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING * PACKAGE DESCRIPTION TEMPERATURE RANGE LT1761ES5-5#PBF LT1761ES5-5#TRPBF LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-5#PBF LT1761IS5-5#TRPBF LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761MPS5-5#PBF LT1761MPS5-5#TRPBF LTGG 5-Lead Plastic TSOT-23 –55°C to 125°C LEAD BASED FINISH TAPE AND REEL PART MARKING * PACKAGE DESCRIPTION TEMPERATURE RANGE LT1761ES5-BYP LT1761ES5-BYP#TR LTGC 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-BYP LT1761IS5-BYP#TR LTGC 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-SD LT1761ES5-SD#TR LTGH 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-SD LT1761IS5-SD#TR LTGH 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-1.2 LT1761ES5-1.2#TR LTCDS 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-1.2 LT1761IS5-1.2#TR LTCDS 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-1.5 LT1761ES5-1.5#TR LTMT 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-1.5 LT1761IS5-1.5#TR LTMT 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-1.8 LT1761ES5-1.8#TR LTJM 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-1.8 LT1761IS5-1.8#TR LTJM 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761MPS5-1.8 LT1761MPS5-1.8#TR LTDCH 5-Lead Plastic TSOT-23 –55°C to 125°C LT1761ES5-2 LT1761ES5-2#TR LTJE 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-2 LT1761IS5-2#TR LTJE 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-2.5 LT1761ES5-2.5#TR LTGD 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-2.5 LT1761IS5-2.5#TR LTGD 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-2.8 LT1761ES5-2.8#TR LTLB 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-2.8 LT1761IS5-2.8#TR LTLB 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-3 LT1761ES5-3#TR LTGE 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-3 LT1761IS5-3#TR LTGE 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761ES5-3.3 LT1761ES5-3.3#TR LTGF 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-3.3 LT1761IS5-3.3#TR LTGF 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761MPS5-3.3 LT1761MPS5-3.3#TR LTGF 5-Lead Plastic TSOT-23 –55°C to 125°C LT1761ES5-5 LT1761ES5-5#TR LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761IS5-5 LT1761IS5-5#TR LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C LT1761MPS5-5 LT1761MPS5-5#TR LTGG 5-Lead Plastic TSOT-23 –55°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. 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/ 1761sff 3 LT1761 Series ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) PARAMETER CONDITIONS Minimum Input Voltage (Notes 3, 11) ILOAD = 100mA MIN TYP MAX 1.8 2.3 V Regulated Output Voltage (Note 4) LT1761-1.2 VIN = 2V, ILOAD = 1mA 2.3V < VIN < 20V, 1mA < ILOAD < 50mA 2.3V < VIN < 20V, 1mA < ILOAD < 100mA l l 1.185 1.170 1.150 1.2 1.2 1.2 1.215 1.230 1.240 V V V LT1761-1.5 VIN = 2V, ILOAD = 1mA 2.5V < VIN < 20V, 1mA < ILOAD < 50mA 2.5V < VIN < 20V, 1mA < ILOAD < 100mA l l 1.478 1.457 1.436 1.5 1.5 1.5 1.522 1.538 1.555 V V V LT1761-1.8 VIN = 2.3V, ILOAD = 1mA 2.8V < VIN < 20V, 1mA < ILOAD < 50mA 2.8V < VIN < 20V, 1mA < ILOAD < 100mA l l 1.775 1.750 1.725 1.8 1.8 1.8 1.825 1.845 1.860 V V V LT1761-2 VIN = 2.5V, ILOAD = 1mA 3V < VIN < 20V, 1mA < ILOAD < 50mA 3V < VIN < 20V, 1mA < ILOAD < 100mA l l 1.970 1.945 1.920 2 2 2 2.030 2.045 2.060 V V V LT1761-2.5 VIN = 3V, ILOAD = 1mA 3.5V < VIN < 20V, 1mA < ILOAD < 50mA 3.5V < VIN < 20V, 1mA < ILOAD < 100mA l l 2.465 2.435 2.415 2.5 2.5 2.5 2.535 2.565 2.575 V V V LT1761-2.8 VIN = 3.3V, ILOAD = 1mA 3.8V < VIN < 20V, 1mA < ILOAD < 50mA 3.8V < VIN < 20V, 1mA < ILOAD < 100mA l l 2.762 2.732 2.706 2.8 2.8 2.8 2.838 2.868 2.884 V V V LT1761-3 VIN = 3.5V, ILOAD = 1mA 4V < VIN < 20V, 1mA < ILOAD < 50mA 4V < VIN < 20V, 1mA < ILOAD < 100mA l l 2.960 2.930 2.900 3 3 3 3.040 3.070 3.090 V V V LT1761-3.3 VIN = 3.8V, ILOAD = 1mA 4.3V < VIN < 20V, 1mA < ILOAD < 50mA 4.3V < VIN < 20V, 1mA < ILOAD < 100mA l l 3.250 3.230 3.190 3.3 3.3 3.3 3.350 3.370 3.400 V V V LT1761-5 VIN = 5.5V, ILOAD = 1mA 6V < VIN < 20V, 1mA < ILOAD < 50mA 6V < VIN < 20V, 1mA < ILOAD < 100mA l l 4.935 4.900 4.850 5 5 5 5.065 5.100 5.120 V V V ADJ Pin Voltage (Note 3, 4) LT1761 VIN = 2V, ILOAD = 1mA 2.3V < VIN < 20V, 1mA < ILOAD < 50mA 2.3V < VIN < 20V, 1mA < ILOAD < 100mA l l 1.205 1.190 1.170 1.220 1.220 1.220 1.235 1.250 1.260 V V V Line Regulation LT1761-1.2 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 LT1761-5 LT1761 (Note 3) ΔVIN = 2V to 20V, ILOAD = 1mA ΔVIN = 2V to 20V, ILOAD = 1mA ΔVIN = 2.3V to 20V, ILOAD = 1mA ΔVIN = 2.5V to 20V, ILOAD = 1mA ΔVIN = 3V to 20V, ILOAD = 1mA ΔVIN = 3.3V to 20V, ILOAD = 1mA ΔVIN = 3.5V to 20V, ILOAD = 1mA ΔVIN = 3.8V to 20V, ILOAD = 1mA ΔVIN = 5.5V to 20V, ILOAD = 1mA ΔVIN = 2V to 20V, ILOAD = 1mA l l l l l l l l l l 1 1 1 1 1 1 1 1 1 1 10 10 10 10 10 10 10 10 10 10 l UNITS mV mV mV mV mV mV mV mV mV mV 1761sff 4 LT1761 Series ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) PARAMETER CONDITIONS Load Regulation LT1761-1.2 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 LT1761-5 LT1761 (Note 3) Dropout Voltage VIN = VOUT(NOMINAL) (Notes 5, 6, 11) MIN VIN = 2.3V, ΔILOAD = 1mA to 50mA VIN = 2.3V, ΔILOAD = 1mA to 50mA VIN = 2.3V, ΔILOAD = 1mA to 100mA VIN = 2.3V, ΔILOAD = 1mA to 100mA VIN = 2.5V, ΔILOAD = 1mA to 50mA VIN = 2.5V, ΔILOAD = 1mA to 50mA VIN = 2.5V, ΔILOAD = 1mA to 100mA VIN = 2.5V, ΔILOAD = 1mA to 100mA VIN = 2.8V, ΔILOAD = 1mA to 50mA VIN = 2.8V, ΔILOAD = 1mA to 50mA VIN = 2.8V, ΔILOAD = 1mA to 100mA VIN = 2.8V, ΔILOAD = 1mA to 100mA VIN = 3V, ΔILOAD = 1mA to 50mA VIN = 3V, ΔILOAD = 1mA to 50mA VIN = 3V, ΔILOAD = 1mA to 100mA VIN = 3V, ΔILOAD = 1mA to 100mA VIN = 3.5V, ΔILOAD = 1mA to 50mA VIN = 3.5V, ΔILOAD = 1mA to 50mA VIN = 3.5V, ΔILOAD = 1mA to 100mA VIN = 3.5V, ΔILOAD = 1mA to 100mA VIN = 3.8V, ΔILOAD = 1mA to 50mA VIN = 3.8V, ΔILOAD = 1mA to 50mA VIN = 3.8V, ΔILOAD = 1mA to 100mA VIN = 3.8V, ΔILOAD = 1mA to 100mA VIN = 4V, ΔILOAD = 1mA to 50mA VIN = 4V, ΔILOAD = 1mA to 50mA VIN = 4V, ΔILOAD = 1mA to 100mA VIN = 4V, ΔILOAD = 1mA to 100mA VIN = 4.3V, ΔILOAD = 1mA to 50mA VIN = 4.3V, ΔILOAD = 1mA to 50mA VIN = 4.3V, ΔILOAD = 1mA to 100mA VIN = 4.3V, ΔILOAD = 1mA to 100mA VIN = 6V, ΔILOAD = 1mA to 50mA VIN = 6V, ΔILOAD = 1mA to 50mA VIN = 6V, ΔILOAD = 1mA to 100mA VIN = 6V, ΔILOAD = 1mA to 100mA VIN = 2.3V, ΔILOAD = 1mA to 50mA VIN = 2.3V, ΔILOAD = 1mA to 50mA VIN = 2.3V, ΔILOAD = 1mA to 100mA VIN = 2.3V, ΔILOAD = 1mA to 100mA l l l l l l l l l l l l l l l l l l l l ILOAD = 1mA ILOAD = 1mA l ILOAD = 10mA ILOAD = 10mA l ILOAD = 50mA ILOAD = 50mA l ILOAD = 100mA ILOAD = 100mA TYP MAX 1 6 12 12 50 mV mV mV mV 20 35 30 55 mV mV mV mV 20 35 30 60 mV mV mV mV 20 35 35 65 mV mV mV mV 20 35 40 80 mV mV mV mV 20 38 40 86 mV mV mV mV 20 40 40 90 mV mV mV mV 20 40 40 100 mV mV mV mV 30 60 65 150 mV mV mV mV 6 12 12 50 mV mV mV mV 1 10 14 10 15 10 15 10 20 10 20 10 20 10 20 15 25 1 1 UNITS 0.10 0.15 0.19 V V 0.17 0.22 0.29 V V 0.24 0.28 0.38 V V 0.30 0.35 0.45 V V 1761sff 5 LT1761 Series ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) PARAMETER CONDITIONS GND Pin Current VIN = VOUT(NOMINAL) (Notes 5, 7) ILOAD = 0mA ILOAD = 1mA ILOAD = 10mA ILOAD = 50mA ILOAD = 100mA MIN Output Voltage Noise COUT = 10μF, CBYP = 0.01μF, ILOAD = 100mA, BW = 10Hz to 100kHz ADJ Pin Bias Current (Notes 3, 8) Shutdown Threshold VOUT = Off to On VOUT = On to Off l l SHDN Pin Current (Note 9) VSHDN = 0V VSHDN = 20V l l Quiescent Current in Shutdown VIN = 6V, VSHDN = 0V Ripple Rejection (Note 3) VIN – VOUT = 1.5V (Avg), VRIPPLE = 0.5VP-P , fRIPPLE = 120Hz, ILOAD = 50mA Current Limit VIN = 7V, VOUT = 0V VIN = VOUT(NOMINAL) + 1V or 2.3V (Note 12), ΔVOUT = –5% l Input Reverse Leakage Current VIN = –20V, VOUT = 0V l Reverse Output Current (Note 10) LT1761-1.2 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 LT1761-5 LT1761 (Note 3) l l l l l VOUT = 1.2V, VIN < 1.2V VOUT = 1.5V, VIN < 1.5V VOUT = 1.8V, VIN < 1.8V VOUT = 2V, VIN < 2V VOUT = 2.5V, VIN < 2.5V VOUT = 2.8V, VIN < 2.8V VOUT = 3V, VIN < 3V VOUT = 3.3V, VIN < 3.3V VOUT = 5V, VIN < 5V VOUT = 1.22V, VIN < 1.22V 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 LT1761 regulators are tested and specified under pulse load conditions such that TJ ≈ TA. The LT1761E is 100% production tested at TA = 25°C. Performance at –40°C and 125°C is assured by design, characterization and correlation with statistical process controls. The LT1761I is guaranteed over the full –40°C to 125°C operating junction temperature range. The LT1761MP is 100% tested and guaranteed over the –55°C to 125°C operating junction temperature range. Note 3: The LT1761 (adjustable versions) are tested and specified for these conditions with the ADJ pin connected to the OUT pin. 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. Note 5: To satisfy requirements for minimum input voltage, the LT1761 (adjustable version) is tested and specified for these conditions with an external resistor divider (two 250k resistors) for an output voltage of 2.44V. The external resistor divider will add a 5μA DC load on the output. TYP MAX UNITS 20 55 230 1 2.2 45 100 400 2 4 μA μA μA mA mA 20 0.25 55 μVRMS 30 100 nA 0.8 0.65 2 V V 0 1 0.5 3 μA μA 0.01 0.1 μA 65 dB 200 mA mA 110 10 10 10 10 10 10 10 10 10 5 1 mA 20 20 20 20 20 20 20 20 20 10 μA μA μA μA μA μA μA μA μA μA Note 6: Dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a specified output current. In dropout, the output voltage will be equal to: VIN – VDROPOUT . Note 7: GND pin current is tested with VIN = VOUT(NOMINAL) or VIN = 2.3V (whichever is greater) and a current source load. This means the device is tested while operating in its dropout region or at the minimum input voltage specification. This is the worst-case GND pin current. The GND pin current will decrease slightly at higher input voltages. Note 8: ADJ pin bias current flows into the ADJ pin. Note 9: SHDN pin current flows into the SHDN pin. Note 10: Reverse output current is tested with the IN pin grounded and the OUT pin forced to the rated output voltage. This current flows into the OUT pin and out the GND pin. Note 11: For the LT1761, LT1761-1.2, LT1761-1.5, LT1761-1.8 and LT1761-2 dropout voltage will be limited by the minimum input voltage specification under some output voltage/load conditions. See the curve of Minimum Input Voltage in the Typical Performance Characteristics. Note 12: To satisfy requirements for minimum input voltage, current limit is tested at VIN = VOUT(NOMINAL) + 1V or VIN = 2.3V, whichever is greater. 1761sff 6 LT1761 Series TYPICAL PERFORMANCE CHARACTERISTICS Guaranteed Dropout Voltage 500 450 450 350 TJ = 125°C 300 250 TJ = 25°C 200 150 = TEST POINTS 450 400 TJ ≤ 125°C 350 300 TJ ≤ 25°C 250 200 150 350 250 150 50 50 50 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) 1.220 OUTPUT VOLTAGE (V) 25 VSHDN = VIN 20 15 10 1.528 IL = 1mA 1.215 1.521 1.210 1.514 1.205 1.200 1.195 1.190 1.185 5 0 –50 VSHDN = 0V –25 0 25 50 75 100 125 1.180 –50 –25 0 25 50 75 1.507 1.500 1.493 1.486 100 125 1.472 –50 2.04 2.54 IL = 1mA 2.02 2.52 1.78 1.77 OUTPUT VOLTAGE (V) 1.82 OUTPUT VOLTAGE (V) 2.53 1.79 2.01 2.00 1.99 1.98 1.97 –25 0 25 50 75 100 125 TEMPERATURE (°C) 75 1.96 –50 100 125 IL = 1mA 2.51 2.50 2.49 2.48 2.47 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G06 50 LT1761-2.5 Output Voltage 2.03 1.80 25 1761 G51 LT1761-2 Output Voltage 1.81 0 TEMPERATURE (°C) 1.83 1.76 –50 –25 1761 G05 1761 G03 IL = 1mA 125 IL = 1mA TEMPERATURE (°C) LT1761-1.8 Output Voltage 100 1.479 TEMPERATURE (°C) 1.84 50 25 0 75 TEMPERATURE (°C) LT1761-1.5 Output Voltage OUTPUT VOLTAGE (V) VIN = 6V RL = ∞ (250k FOR LT1761-BYP, -SD) IL = 0 (5μA FOR LT1761-BYP, -SD) 30 –25 1761 G01.1 LT1761-1.2 Output Voltage Quiescent Current 35 IL = 1mA 1761 G01 1761 G00 40 IL = 10mA 0 –50 0 0 IL = 50mA 200 100 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) IL = 100mA 300 100 0 QUIESCENT CURRENT (μA) 400 100 0 OUTPUT VOLTAGE (V) Dropout Voltage 500 DROPOUT VOLTAGE (mV) 400 DROPOUT VOLTAGE (mV) DROPOUT VOLTAGE (mV) Typical Dropout Voltage 500 2.46 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G07 1761 G08 1761sff 7 LT1761 Series TYPICAL PERFORMANCE CHARACTERISTICS LT1761-2.8 Output Voltage 3.060 IL = 1mA LT1761-3.3 Output Voltage 3.360 IL = 1mA 3.045 3.345 2.82 3.030 3.330 2.81 2.80 2.79 2.78 2.77 OUTPUT VOLTAGE (V) 2.83 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 2.84 LT1761-3 Output Voltage 3.015 3.000 2.985 2.970 2.955 2.76 –50 0 –25 25 50 75 100 0 –25 TEMPERATURE (°C) 25 50 75 100 3.270 125 3.240 –50 1.235 5.04 1.230 5.00 4.98 4.96 4.94 0 25 50 75 100 125 1.225 1.220 1.215 1.210 0 –25 25 50 75 100 100 75 50 VSHDN = VIN 75 50 3 4 5 6 7 INPUT VOLTAGE (V) VSHDN = VIN VSHDN = 0V 0 1 2 8 10 1761 G53 8 200 TJ = 25°C 175 RL = ∞ 150 125 100 75 50 VSHDN = VIN 1 2 10 3 4 5 6 7 INPUT VOLTAGE (V) 8 150 125 100 75 50 VSHDN = VIN 25 VSHDN = 0V 0 9 LT1761-2 Quiescent Current TJ = 25°C 175 RL = ∞ 0 9 3 4 5 6 7 INPUT VOLTAGE (V) 1761 G10b 200 25 VSHDN = 0V 2 100 0 125 QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) 125 1 125 LT1761-1.8 Quiescent Current TJ = 25°C 175 RL = ∞ 0 150 1761 G10 200 0 175 TEMPERATURE (°C) 1761 G12 25 200 25 1.200 –50 LT1761-1.5 Quiescent Current 125 100 TJ = 25°C 225 RL = ∞ IL = 1mA TEMPERATURE (°C) 150 75 LT1761-1.2 Quiescent Current 1.205 –25 50 1761 G11 QUIESCENT CURRENT (μA) 5.06 5.02 25 250 1.240 IL = 1mA 4.92 –50 0 –25 TEMPERATURE (°C) LT1761-BYP, LT1761-SD ADJ Pin Voltage ADJ PIN VOLTAGE (V) OUTPUT VOLTAGE (V) 3.285 1761 G09 LT1761-5 Output Voltage QUIESCENT CURRENT (μA) 3.300 TEMPERATURE (°C) 1761 G52 5.08 3.315 3.255 2.940 –50 125 IL = 1mA VSHDN = 0V 0 9 10 1761 G18 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 1761 G19 1761sff 8 LT1761 Series TYPICAL PERFORMANCE CHARACTERISTICS LT1761-2.5 Quiescent Current LT1761-2.8 Quiescent Current 200 200 125 100 75 50 VSHDN = VIN 25 3 4 5 6 7 INPUT VOLTAGE (V) 125 100 75 50 VSHDN = VIN 0 9 8 0 10 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 9 8 100 75 50 VSHDN = VIN 9 125 100 75 50 VSHDN = VIN 1 2 3 4 5 6 7 INPUT VOLTAGE (V) RL = 12Ω IL = 100mA* 1.50 1.25 RL = 24Ω IL = 50mA* 1.00 0.75 RL = 1.2k IL = 1mA* 0.50 0.25 RL = 120Ω IL = 10mA* 1 2 VSHDN = 0V 9 8 0 10 3 4 5 6 7 INPUT VOLTAGE (V) 8 1.75 RL = 15Ω IL = 100mA* 1.50 1.25 RL = 30Ω IL = 50mA* 1.00 0.75 RL = 1.5k IL = 1mA* 0.25 9 10 1761 G17b 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V) 1761 G17 LT1761-1.8 GND Pin Current 2.00 0.50 0 0 10 5 2.50 TJ = 25°C *FOR VOUT = 1.5V 2.25 GND PIN CURRENT (mA) GND PIN CURRENT (mA) 2.50 10 15 1761 G16 TJ = 25°C *FOR VOUT = 1.2V 9 8 VSHDN = VIN 20 LT1761-1.5 GND Pin Current 2.00 3 4 5 6 7 INPUT VOLTAGE (V) TJ = 25°C RL = 250k IL = 5μA VSHDN = 0V 0 10 LT1761-1.2 GND Pin Current 2.25 2 1761 G14 25 1761 G15 2.50 1 LT1761-BYP, LT1761-SD Quiescent Current 150 0 8 VSHDN = 0V 30 25 VSHDN = 0V 3 4 5 6 7 INPUT VOLTAGE (V) VSHDN = VIN 0 QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) 125 1.75 10 TJ = 25°C 175 RL = ∞ 150 2 50 0 200 TJ = 25°C 175 RL = ∞ 1 75 LT1761-5 Quiescent Current 200 0 100 1761 G54 LT1761-3.3 Quiescent Current 0 125 25 1761 G13 25 150 VSHDN = 0V TJ = 25°C *FOR VOUT = 1.8V 2.25 GND PIN CURRENT (mA) 2 150 25 VSHDN = 0V 0 TJ = 25°C 175 RL = ∞ QUIESCENT CURRENT (μA) 150 1 200 TJ = 25°C 175 RL = ∞ QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) TJ = 25°C 175 RL = ∞ 0 LT1761-3 Quiescent Current 2.00 1.75 RL = 18Ω IL = 100mA* 1.50 1.25 RL = 36Ω IL = 50mA* 1.00 0.75 RL = 1.8k IL = 1mA* 0.50 RL = 150Ω IL = 10mA* 0.25 0 RL = 180Ω IL = 10mA* 0 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 1761 G55 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 1761 G02 1761sff 9 LT1761 Series TYPICAL PERFORMANCE CHARACTERISTICS LT1761-2.5 GND Pin Current 2.50 2.25 2.00 RL = 20Ω IL = 100mA* 1.75 1.50 1.25 RL = 40Ω IL = 50mA* 1.00 0.75 RL = 2k IL = 1mA* 0.50 0.25 RL = 25Ω IL = 100mA 2.00 1.75 1.50 1.25 RL = 50Ω IL = 50mA* 1.00 0.75 RL = 2.5k IL = 1mA* 0.50 RL = 200Ω IL = 10mA* 0.25 0 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 2.00 RL = 30Ω IL = 100mA* 1.25 RL = 60Ω IL = 50mA* 0.75 RL = 3k IL = 1mA* 0.50 0.25 8 9 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 1.75 1.50 1.25 RL = 66Ω IL = 50mA* 1.00 0.75 RL = 3.3k IL = 1mA* 10 2.50 2.50 1.25 RL = 24.4Ω IL = 50mA* 1.00 0.75 RL = 1.22k IL = 1mA* 0.50 0.25 RL = 122Ω IL = 10mA* 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 1.50 1.25 8 0.75 10 1761 G24 RL = 5k IL = 1mA* RL = 500Ω IL = 10mA* 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 1761 G23 SHDN Pin Threshold (On to Off) 1.0 0.9 2.00 1.75 1.50 1.25 1.00 0.75 0.25 9 RL = 100Ω IL = 50mA* 1.00 10 0.50 0 10 RL = 50Ω IL = 100mA 1.75 0.25 SHDN PIN THRESHOLD (V) 1.50 9 2.00 0.50 VIN = VOUT(NOMINAL) + 1V 2.25 GND PIN CURRENT (mA) 1.75 8 TJ = 25°C *FOR VOUT = 5V 2.25 GND Pin Current vs ILOAD RL = 12.2Ω IL = 100mA* 3 4 5 6 7 INPUT VOLTAGE (V) 1761 G22 TJ = 25°C *FOR VOUT = 1.22V 2.00 2 0 0 LT1761-BYP, LT1761-SD GND Pin Current 2.25 1 1761 G56 RL = 330Ω IL = 10mA* 1761 G21 2.50 RL = 280Ω IL = 10mA* LT1761-5 GND Pin Current RL = 33Ω IL = 100mA* 0.25 9 RL = 2.8k IL = 1mA* 0 0 1 0.75 10 2.00 0.50 RL = 300Ω IL = 10mA* 0 0 RL = 56Ω IL = 50mA* 1.00 0.25 TJ = 25°C *FOR VOUT = 3.3V 2.25 GND PIN CURRENT (mA) GND PIN CURRENT (mA) 2.50 TJ = 25°C *FOR VOUT = 3V 1.00 1.25 LT1761-3.3 GND Pin Current 2.25 1.50 1.50 1761 G20 LT1761-3 GND Pin Current 2.50 RL = 28Ω IL = 100mA 1.75 0 0 1761 G04 1.75 2.00 0.50 RL = 250Ω IL = 10mA* GND PIN CURRENT (mA) 1 TJ = 25°C *FOR VOUT = 2.8V 2.25 0 0 GND PIN CURRENT (mA) 2.50 TJ = 25°C *FOR VOUT = 2.5V 2.25 GND PIN CURRENT (mA) GND PIN CURRENT (mA) 2.50 TJ = 25°C *FOR VOUT = 2V LT1761-2.8 GND Pin Current GND PIN CURRENT (mA) LT1761-2 GND Pin Current IL = 1mA 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) 1761 G25 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1761 G26 1761sff 10 LT1761 Series TYPICAL PERFORMANCE CHARACTERISTICS SHDN Pin Input Current 1.0 0.9 0.9 IL = 100mA 0.8 0.7 0.6 IL = 1mA 0.5 0.4 0.3 0.2 SHDN Pin Input Current 1.4 SHDN PIN INPUT CURRENT (μA) 1.0 SHDN PIN INPUT CURRENT (μA) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.1 0 –50 0 50 25 0 75 TEMPERATURE (°C) –25 100 125 0 1 2 3 4 5 6 7 8 SHDN PIN VOLTAGE (V) 9 ADJ Pin Bias Current 350 60 50 40 30 20 10 50 25 0 75 TEMPERATURE (oC) 100 300 300 250 200 150 100 50 0 1 4 3 2 5 INPUT VOLTAGE (V) 1 2 REVERSE OUTPUT CURRENT (μA) REVERSE OUTPUT CURRENT (μA) 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 9 200 150 100 1761 G33 –25 50 25 0 75 TEMPERATURE (°C) 100 Input Ripple Rejection LT1761-BYP,-SD 7.5 70 LT1761-BYP 60 LT1761-5 LT1761-1.2,-1.5,-1.8,-2, -2.5,-2.8,-3,-3.3,-5 IL = 100mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE CBYP = 0 50 COUT = 10μF 40 30 20 5.0 0 –50 125 1761 G32 80 VIN = 0V 22.5 VOUT = 1.22V (LT1761-BYP, -SD) VOUT = 1.2V (LT1761-1.2) 20.0 VOUT = 1.5V (LT1761-1.5) VOUT = 1.8V (LT1761-1.8) 17.5 VOUT = 2V (LT1761-2) VOUT = 2.5V (LT1761-2.5) 15.0 VOUT = 2.8V (LT1761-2.8) VOUT = 3V (LT1761-3) 12.5 VOUT = 3.3V (LT1761-3.3) VOUT = 5V (LT1761-5) 10.0 2.5 10 125 250 Reverse Output Current LT1761-5 100 VIN = 7V VOUT = 0V 0 –50 7 6 25.0 LT1761-3.3 50 25 0 75 TEMPERATURE (°C) 1761 G31 Reverse Output Current TJ = 25°C LT1761-BYP LT1761-SD 90 VIN = 0V CURRENT FLOWS 80 INTO OUTPUT PIN LT1761-1.2 70 VOUT = VADJ (LT1761-BYP, -SD) 60 LT1761-1.5 LT1761-1.8 50 LT1761-2 LT1761-2.5 40 LT1761-2.8 30 LT1761-3 20 –25 50 0 125 100 0 0.2 Current Limit 1761 G30 0 0.4 350 CURRENT LIMIT (mA) SHORT-CIRCUIT CURRENT (mA) ADJ PIN BIAS CURRENT (nA) 70 10 0.6 1761 G29 VOUT = 0V TJ = 25°C 90 –25 0.8 Current Limit 100 0 –50 1.0 1761 G28 1761 G27 80 VSHDN = 20V 1.2 0 –50 10 RIPPLE REJECTION (dB) SHDN PIN THRESHOLD (V) SHDN Pin Threshold (Off to On) COUT = 1μF 10 0 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1761 G34 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1761 G35 1761sff 11 LT1761 Series TYPICAL PERFORMANCE CHARACTERISTICS LT1761-5 Input Ripple Rejection 80 80 CBYP = 0.01μF 70 CBYP = 1000pF RIPPLE REJECTION (dB) 60 50 CBYP = 100pF 40 30 20 IL = 100mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE COUT = 10μF 10 100 60 50 40 30 20 VIN = VOUT (NOMINAL) + 1V + 0.5VP-P RIPPLE AT f = 120Hz IL = 50mA 10 0 –50 0 10 2.5 100k 1k 10k FREQUENCY (Hz) 1M MINIMUM INPUT VOLTAGE (V) 70 RIPPLE REJECTION (dB) LT1761-BYP, LT1761-SD Minimum Input Voltage Input Ripple Rejection 0 –25 50 25 75 100 IL = 100mA 1.5 IL = 50mA 1.0 0.5 0 –50 125 50 25 0 75 TEMPERATURE (°C) –25 TEMPERATURE (°C) 1761 G36 1761 G37 Load Regulation ΔIL = 1mA to 50mA 100 125 1761 G38 Load Regulation ΔIL = 1mA to 100mA 0 LT1761-BYP, -SD, -1.2 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 –5 –10 –15 –20 –25 –30 LT1761-5 LOAD REGULATION (mV) 0 LOAD REGULATION (mV) 2.0 –10 LT1761-BYP, -SD, -1.2 –20 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 –30 –40 –50 –60 –70 LT1761-5 –80 –35 –90 –25 0 25 50 75 100 TEMPERATURE (°C) –100 –50 125 1761 G39 OUTPUT NOISE SPECTRAL DENSITY (μV/√Hz) OUTPUT NOISE SPECTRAL DENSITY (μV/√Hz) LT1761-3.3 LT1761-2.8,-3 LT1761-2.5 LT1761-5 1 LT1761-BYP, -SD, 1.2 LT1761-1.5 LT1761-1.8 0.1 LT1761-2 COUT = 10μF CBYP = 0 IL = 100mA 1k 10k FREQUENCY (Hz) 25 75 50 100k 1761 G41 100 125 1761 G40 RMS Output Noise vs Bypass Capacitor Output Noise Spectral Density 10 100 0 TEMPERATURE (°C) Output Noise Spectral Density 0.01 10 –25 10 140 LT1761-5 120 LT1761-5 CBYP = 1000pF 1 CBYP = 100pF LT1761-BYP 0.1 CBYP = 0.01μF LT1761-3.3 COUT = 10μF IL = 100mA f = 10Hz TO 100kHz LT1761-3 100 LT1761-2.8 LT1761-2.5 80 60 40 LT1761-1.8, -2 20 COUT = 10μF IL = 100mA 0.01 10 OUTPUT NOISE (μVRMS) –40 –50 LT1761-1.5 LT1761-BYP, -1.2 0 100 1k 10k FREQUENCY (Hz) 100k 10 100 1k CBYP (pF) 10k 1761 G43 1761 G42 1761sff 12 LT1761 Series TYPICAL PERFORMANCE CHARACTERISTICS LT1761-5 10Hz to 100kHz Output Noise CBYP = 0pF RMS Output Noise vs Load Current (10Hz to 100kHz) LT1761-5 10Hz to 100kHz Output Noise CBYP = 100pF 160 COUT = 10μF CBYP = 0 CBYP = 0.01μF LT1761-5 120 VOUT 100μV/DIV VOUT 100μV/DIV 100 80 LT1761-BYP 60 40 LT1761-5 20 COUT = 10μF IL = 100mA LT1761-BYP 10 0.1 1 LOAD CURRENT (mA) 1761 G45 1ms/DIV COUT = 10μF IL = 100mA 1ms/DIV 1761 G46 100 1761 G44 LT1761-5 10Hz to 100kHz Output Noise CBYP = 1000pF LT1761-5 10Hz to 100kHz Output Noise CBYP = 0.01μF VOUT 100μV/DIV VOUT 100μV/DIV COUT = 10μF IL = 100mA 1761 G46 1ms/DIV COUT = 10μF IL = 100mA VIN = 6V CIN = 10μF COUT = 10μF 0.2 0.1 0 –0.1 LOAD CURRENT (mA) –0.2 100 50 0 0 400 800 1200 TIME (μs) 1600 1761 G48 1ms/DIV LT1761-5 Transient Response CBYP = 0.01μF OUTPUT VOLTAGE DEVIATION (V) LT1761-5 Transient Response CBYP = 0pF OUTPUT VOLTAGE DEVIATION (V) 0 0.01 LOAD CURRENT (mA) OUTPUT NOISE (μVRMS) 140 2000 1761 G49 VIN = 6V CIN = 10μF COUT = 10μF 0.04 0.02 0 –0.02 –0.04 100 50 0 0 20 40 60 80 100 120 140 160 180 200 TIME (μs) 1761 G50 1761sff 13 LT1761 Series PIN FUNCTIONS IN (Pin 1): Input. Power is supplied to the device through the IN pin. A bypass capacitor is required on this pin 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 advisable to include a bypass capacitor in battery-powered circuits. A bypass capacitor in the range of 1μF to 10μF is sufficient. The LT1761 regulators are designed to withstand reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reverse input, which can happen if a battery is plugged in backwards, the device will act as if there is a diode in series with its input. There will be no reverse current flow into the regulator and no reverse voltage will appear at the load. The device will protect both itself and the load. GND (Pin 2): Ground. SHDN (Pin 3, Fixed/-SD Devices): Shutdown. The SHDN pin is used to put the LT1761 regulators into a low power shutdown state. The output will be off when the SHDN pin is pulled low. The SHDN pin can be driven either by 5V logic or open-collector logic with a pull-up resistor. The pull-up resistor is required to supply the pull-up current of the open-collector gate, normally several microamperes, and the SHDN pin current, typically 1μA. If unused, the SHDN pin must be connected to VIN. The device will not function if the SHDN pin is not connected. For the LT1761-BYP, the SHDN pin is internally connected to VIN. BYP (Pins 3/4, Fixed/-BYP Devices): Bypass. The BYP pin is used to bypass the reference of the LT1761 regulators to achieve low noise performance from the regulator. The BYP pin is clamped internally to ±0.6V (one VBE) from ground. A small capacitor from the output to this pin will bypass the reference to lower the output voltage noise. A maximum value of 0.01μF can be used for reducing output voltage noise to a typical 20μVRMS over a 10Hz to 100kHz bandwidth. If not used, this pin must be left unconnected. ADJ (Pin 4, Adjustable Devices Only): Adjust Pin. For the adjustable LT1761, this is the input to the error amplifier. This pin is internally clamped to ±7V. It has a bias current of 30nA which flows into the pin (see curve of ADJ Pin Bias Current vs Temperature in the Typical Performance Characteristics section). The ADJ pin voltage is 1.22V referenced to ground and the output voltage range is 1.22V to 20V. OUT (Pin 5): Output. The output supplies power to the load. A minimum output capacitor of 1μF is required to prevent oscillations. Larger output capacitors will be required for applications with large transient loads to limit peak voltage transients. See the Applications Information section for more information on output capacitance and reverse output characteristics. 1761sff 14 LT1761 Series APPLICATIONS INFORMATION The LT1761 series are 100mA low dropout regulators with micropower quiescent current and shutdown. The devices are capable of supplying 100mA at a dropout voltage of 300mV. Output voltage noise can be lowered to 20μVRMS over a 10Hz to 100kHz bandwidth with the addition of a 0.01μF reference bypass capacitor. Additionally, the reference bypass capacitor will improve transient response of the regulator, lowering the settling time for transient load conditions. The low operating quiescent current (20μA) drops to less than 1μA in shutdown. In addition to the low quiescent current, the LT1761 regulators incorporate several protection features which make them ideal for use in battery-powered systems. The devices are protected against both reverse input 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 LT1761-X acts like it has a diode in series with its output and prevents reverse current flow. Additionally, in dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 20V and still allow the device to start and operate. Adjustable Operation The adjustable version of the LT1761 has an output voltage range of 1.22V to 20V. The output voltage is set by the ratio of two external resistors as shown in Figure 1. The device servos the output to maintain the ADJ pin voltage at 1.22V referenced to ground. The current in R1 is then equal to 1.22V/R1 and the current in R2 is the current in R1 plus the ADJ pin bias current. The ADJ pin bias current, 30nA at 25°C, flows through R2 into the ADJ pin. The output voltage can be calculated using the formula in Figure 1. The value of R1 should be no greater than 250k to minimize errors in the output voltage caused by the OUT IN VIN + R2 LT1761 ADJ pin bias current. Note that in shutdown the output is turned off and the divider current will be zero. Curves of ADJ Pin Voltage vs Temperature and ADJ Pin Bias Current vs Temperature appear in the Typical Performance Characteristics. The adjustable device is tested and specified with the ADJ pin tied to the OUT pin for an output voltage of 1.22V. Specifications for output voltages greater than 1.22V will be proportional to the ratio of the desired output voltage to 1.22V: VOUT/1.22V. For example, load regulation for an output current change of 1mA to 100mA is –1mV typical at VOUT = 1.22V. At VOUT = 12V, load regulation is: (12V/1.22V)(–1mV) = –9.8mV Bypass Capacitance and Low Noise Performance The LT1761 regulators may be used with the addition of a bypass capacitor from OUT to the BYP pin to lower output voltage noise. A good quality low leakage capacitor is recommended. This capacitor will bypass the reference of the regulator, providing a low frequency noise pole. The noise pole provided by this bypass capacitor will lower the output voltage noise to as low as 20μVRMS with the addition of a 0.01μF bypass capacitor. Using a bypass capacitor has the added benefit of improving transient response. With no bypass capacitor and a 10μF output capacitor, a 10mA to 100mA load step will settle to within 1% of its final value in less than 100μs. With the addition of a 0.01μF bypass capacitor, the output will stay within 1% for a 10mA to 100mA load step (see LT1761-5 Transient Response in Typical Performance Characteristics section). However, regulator start-up time is proportional to the size of the bypass capacitor, slowing to 15ms with a 0.01μF bypass capacitor and 10μF output capacitor. VOUT ¥ R2 ´ VOUT 122V ¦ 1 µ § R1¶ IADJ R2 VADJ 122V ADJ GND R1 IADJ 30nA AT 25oC OUTPUT RANGE = 1.22V TO 20V 1761 F01 Figure 1. Adjustable Operation 1761sff 15 LT1761 Series APPLICATIONS INFORMATION The LT1761 regulators are designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. A minimum output capacitor of 1μF with an ESR of 3Ω or less is recommended to prevent oscillations. The LT1761-X is a micropower device and output transient response will be a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT1761-X, will increase the effective output capacitor value. With larger capacitors used to bypass the reference (for low noise operation), larger values of output capacitors are needed. For 100pF of bypass capacitance, 2.2μF of output capacitor is recommended. With a 330pF bypass capacitor or larger, a 3.3μF output capacitor is recommended. The shaded region of Figure 2 defines the region over which the LT1761 regulators are stable. The minimum ESR needed is defined by the amount of bypass capacitance used, while the maximum ESR is 3Ω. Extra consideration must be given to the use of ceramic capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are specified with EIA temperature characteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but they tend to have strong voltage and temperature coefficients as shown in Figures 3 and 4. When used with a 5V regulator, a 16V 10μF Y5V capacitor can exhibit an effective value as low as 1μF to 2μF for the DC bias voltage applied and over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available in higher values. Care still must be exercised when using X5R and X7R capacitors; the X5R and X7R codes only specify operating temperature range and maximum capacitance change over temperature. Capacitance change due to DC bias with X5R and X7R capacitors is better than Y5V and Z5U capacitors, but can still be significant enough to drop capacitor values below appropriate levels. Capacitor DC bias characteristics tend to improve as component case size increases, but expected capacitance at operating voltage should be verified. 20 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF 0 CHANGE IN VALUE (%) Output Capacitance and Transient Response X5R –20 –40 –60 Y5V –80 –100 0 2 4 14 8 6 10 12 DC BIAS VOLTAGE (V) 16 1761 F03 Figure 3. Ceramic Capacitor DC Bias Characteristics 4.0 40 3.5 20 STABLE REGION ESR (Ω) 2.5 2.0 CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP > 3300pF 1.5 1.0 0.5 CHANGE IN VALUE (%) 3.0 –20 –40 1 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (μF) 1761 F02 Figure 2. Stability Y5V –60 –80 0 X5R 0 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF –100 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1761 F04 Figure 4. Ceramic Capacitor Temperature Characteristics 1761sff 16 LT1761 Series APPLICATIONS INFORMATION Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. The resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced Figure 5’s trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise. The ground pin current can be found by examining the GND Pin Current curves in the Typical Performance Characteristics section. Power dissipation will be equal to the sum of the two components listed above. The LT1761 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal 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. For surface mount devices, heat sinking 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. The following table lists thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with one ounce copper. VOUT 500μV/DIV Table 1. Measured Thermal Resistance LT1761-5 COUT = 10μF CBYP = 0.01μF ILOAD = 100mA 100ms/DIV 1761 F05 Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature (125°C). The power dissipated by the device will be made up of two components: 1. Output current multiplied by the input/output voltage differential: (IOUT)(VIN – VOUT), and COPPER AREA THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) TOPSIDE* BACKSIDE 2500mm2 2500mm2 2500mm2 125°C/W 1000mm2 2500mm2 2500mm2 125°C/W 225mm2 2500mm2 2500mm2 130°C/W 100mm2 2500mm2 2500mm2 135°C/W 50mm2 2500mm2 2500mm2 150°C/W *Device is mounted on topside. Calculating Junction Temperature Example: Given an output voltage of 3.3V, an input voltage range of 4V to 6V, an output current range of 0mA to 50mA 2. GND pin current multiplied by the input voltage: (IGND)(VIN). 1761sff 17 LT1761 Series APPLICATIONS INFORMATION and a maximum ambient temperature of 50°C, what will the maximum junction temperature be? The power dissipated by the device will be equal to: IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX)) where, IOUT(MAX) = 50mA VIN(MAX) = 6V IGND at (IOUT = 50mA, VIN = 6V) = 1mA So, P = 50mA(6V – 3.3V) + 1mA(6V) = 0.14W The thermal resistance will be in the range of 125°C/W to 150°C/W depending on the copper area. So the junction temperature rise above ambient will be approximately equal to: 0.14W(150°C/W) = 21.2°C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50°C + 21.2°C = 71.2°C Protection Features The LT1761 regulators incorporate several protection features which make them 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 devices are 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 20V. 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 which can be plugged in backward. The output of the LT1761-X can be pulled below ground without damaging the device. If the input is left open circuit or grounded, the output can be pulled below ground by 20V. For fixed voltage versions, the output will act like a large resistor, typically 500k or higher, limiting current flow to typically less than 100μA. For adjustable versions, 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. In this case, grounding the SHDN pin will turn off the device and stop the output from sourcing the short-circuit current. The ADJ pin of the adjustable device can be pulled above or below ground by as much as 7V without damaging the device. If the input is left open circuit or grounded, the ADJ pin will act like an open circuit when pulled below ground and like a large resistor (typically 100k) in series with a diode when pulled above ground. 1761sff 18 LT1761 Series APPLICATIONS INFORMATION In situations where the ADJ pin is connected to a resistor divider that would pull the ADJ pin above its 7V clamp voltage if the output is pulled high, the ADJ pin input current must be limited to less than 5mA. For example, a resistor divider is used to provide a regulated 1.5V output from the 1.22V reference when the output is forced to 20V. The top resistor of the resistor divider must be chosen to limit the current into the ADJ pin to less than 5mA when the ADJ pin is at 7V. The 13V difference between output and ADJ pin divided by the 5mA maximum current into the ADJ pin yields a minimum top resistor value of 2.6k. 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 follow the curve shown in Figure 6. When the IN pin of the LT1761-X is forced below the OUT pin or the OUT pin is pulled above the IN pin, input current will typically drop to less than 2μA. This can happen if the input of the device is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or a second regulator circuit. The state of the SHDN pin will have no effect on the reverse output current when the output is pulled above the input. REVERSE OUTPUT CURRENT (μA) 100 TJ = 25°C LT1761-BYP LT1761-SD 90 VIN = 0V CURRENT FLOWS 80 INTO OUTPUT PIN LT1761-1.2 70 VOUT = VADJ (LT1761-BYP, -SD) 60 LT1761-1.5 LT1761-1.8 50 LT1761-2 LT1761-2.5 40 LT1761-2.8 30 LT1761-3 20 LT1761-3.3 10 LT1761-5 0 0 1 2 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 9 10 1761 F06 Figure 6. Reverse Output Current 1761sff 19 LT1761 Series PACKAGE DESCRIPTION S5 Package 5-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1635) 0.62 MAX 0.95 REF 2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 TYP 5 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) 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 1.90 BSC S5 TSOT-23 0302 REV B 1761sff 20 LT1761 Series REVISION HISTORY (Revision history begins at Rev F) REV DATE DESCRIPTION PAGE NUMBER F 5/10 Added MP-grade 2, 3 Added Typical Application 22 1761sff 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. 21 LT1761 Series TYPICAL APPLICATION Noise Bypassing Provides Soft-Start Startup Time 100 IN VIN 5.4V TO 20V 5V AT 100mA OUT LT1761-5 1μF CBYP 10μF OFF ON STARTUP TIME (ms) BYP SHDN GND 1761 TA02a 10 1 0.1 10 100 1000 10000 CBYP (pF) 1761 TA02b RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1120 125mA Low Dropout Regulator with 20μA IQ Includes 2.5V Reference and Comparator LT1121 150mA Micropower Low Dropout Regulator 30μA IQ, SOT-223 Package LT1129 700mA Micropower Low Dropout Regulator 50μA Quiescent Current LT1175 500mA Negative Low Dropout Micropower Regulator 45μA IQ, 0.26V Dropout Voltage, SOT-223 Package LT1521 300mA Low Dropout Micropower Regulator with Shutdown 15μA IQ, Reverse-Battery Protection LT1529 3A Low Dropout Regulator with 50μA IQ 500mV Dropout Voltage LT1762 Series 150mA, Low Noise, LDO Micropower Regulator 25μA Quiescent Current, 20μVRMS Noise LT1763 Series 500mA, Low Noise, LDO Micropower Regulator 30μA Quiescent Current, 20μVRMS Noise LTC1928 Doubler Charge Pump with Low Noise Linear Regulator Low Output Noise: 60μVRMS (100kHz BW) LT1962 Series 300mA, Low Noise, LDO Micropower Regulator 30μA Quiescent Current, 20μVRMS Noise LT1963 1.5A, Low Noise, Fast Transient Response LDO 40μVRMS, SOT-223 Package LT1764 3A, Low Noise, Fast Transient Response LDO 40μVRMS, 340mV Dropout Voltage LTC3404 High Efficiency Synchronous Step-Down Switching Regulator Burst Mode® Operation, Monolithic, 100% Duty Cycle 1761sff 22 Linear Technology Corporation LT 0510 REV F • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005