LT1761ES5-2.8

LT1761 Series 100mA, Low Noise, LDO Micropower Regulators in SOT-23 FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO 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 SOT-23 Package APPLICATIO S ■ ■ ■ ■ ■ Cellular Phones Pagers Battery-Powered Systems Frequency Synthesizers Wireless Modems 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. 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 SOT-23 package. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO 10Hz to 100kHz Output Noise 5V Low Noise Regulator IN 1μF OUT LT1761-5 SHDN GND BYP 1761 TA01 VIN 5.4V TO 20V 0.01μF + 5V AT100mA 20μVRMS NOISE 10μF VOUT 100μV/DIV U 20μVRMS 1761 G48 U U 1761sfc 1 LT1761 Series ABSOLUTE AXI U RATI GS 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 PACKAGE/ORDER I FOR ATIO TOP VIEW IN 1 GND 2 BYP 3 4 ADJ 5 OUT IN 1 GND 2 SHDN 3 S5 PACKAGE 5-LEAD PLASTIC SOT-23 TJMAX = 150°C, θJA = 250°C/ W SEE THE APPLICATIONS INFORMATION SECTION. S5 PACKAGE 5-LEAD PLASTIC SOT-23 TJMAX = 150°C, θJA = 250°C/ W SEE THE APPLICATIONS INFORMATION SECTION. ORDER PART NUMBER LT1761ES5-BYP S5 PART MARKING LTGC ORDER PART NUMBER LT1761ES5-SD Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. 2 U U W WW U W (Note 1) Output Short-Circuit Duration ......................... Indefinite Operating Junction Temperature Range E 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 TOP VIEW 5 OUT IN 1 GND 2 4 ADJ SHDN 3 TOP VIEW 5 OUT 4 BYP S5 PACKAGE 5-LEAD PLASTIC SOT-23 TJMAX = 150°C, θJA = 250°C/ W SEE THE APPLICATIONS INFORMATION SECTION. S5 PART MARKING LTGH ORDER PART NUMBER LT1761ES5-1.2 LT1761ES5-1.5 LT1761ES5-1.8 LT1761MPS5-1.8 LT1761ES5-2 LT1761ES5-2.5 LT1761ES5-2.8 LT1761ES5-3 LT1761ES5-3.3 LT1761ES5-5 S5 PART MARKING LTCDS LTMT LTJM LTDCH LTJE LTGD LTLB LTGE LTGF LTGG 1761sfc LT1761 Series ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2) PARAMETER Regulated Output Voltage (Note 4) CONDITIONS ● MIN VIN = 2V, ILOAD = 1mA 2.3V < VIN < 20V, 1mA < ILOAD < 50mA 2.3V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 2V, ILOAD = 1mA 2.5V < VIN < 20V, 1mA < ILOAD < 50mA 2.5V < VIN < 20V, 1mA < ILOAD < 50mA VIN = 2.3V, ILOAD = 1mA 2.8V < VIN < 20V, 1mA < ILOAD < 50mA 2.8V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 2.5V, ILOAD = 1mA 3V < VIN < 20V, 1mA < ILOAD < 50mA 3V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 3V, ILOAD = 1mA 3.5V < VIN < 20V, 1mA < ILOAD < 50mA 3.5V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 3.3V, ILOAD = 1mA 3.8V < VIN < 20V, 1mA < ILOAD < 50mA 3.8V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 3.5V, ILOAD = 1mA 4V < VIN < 20V, 1mA < ILOAD < 50mA 4V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 3.8V, ILOAD = 1mA 4.3V < VIN < 20V, 1mA < ILOAD < 50mA 4.3V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 5.5V, ILOAD = 1mA 6V < VIN < 20V, 1mA < ILOAD < 50mA 6V < VIN < 20V, 1mA < ILOAD < 100mA VIN = 2V, ILOAD = 1mA 2.3V < VIN < 20V, 1mA < ILOAD < 50mA 2.3V < VIN < 20V, 1mA < ILOAD < 100mA 1.185 1.170 1.150 1.478 1.457 1.436 1.775 1.750 1.725 1.970 1.945 1.920 2.465 2.435 2.415 2.762 2.732 2.706 2.960 2.930 2.900 3.250 3.230 3.190 4.935 4.900 4.850 1.205 1.190 1.170 TYP 1.8 1.2 1.2 1.2 1.5 1.5 1.5 1.8 1.8 1.8 2 2 2 2.5 2.5 2.5 2.8 2.8 2.8 3 3 3 3.3 3.3 3.3 5 5 5 1.220 1.220 1.220 1 1 1 1 1 1 1 1 1 1 MAX 2.3 1.215 1.230 1.240 1.522 1.538 1.555 1.825 1.845 1.860 2.030 2.045 2.060 2.535 2.565 2.575 2.838 2.868 2.884 3.040 3.070 3.090 3.350 3.370 3.400 5.065 5.100 5.120 1.235 1.250 1.260 10 10 10 10 10 10 10 10 10 10 UNITS V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V mV mV mV mV mV mV mV mV mV mV Minimum Input Voltage (Notes 3, 11) ILOAD = 100mA LT1761-1.2 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 LT1761-5 ADJ Pin Voltage (Note 3, 4) Line Regulation LT1761 LT1761-1.2 ΔVIN = 2V to 20V, ILOAD = 1mA LT1761-1.5 ΔVIN = 2V to 20V, ILOAD = 1mA LT1761-1.8 ΔVIN = 2.3V to 20V, ILOAD = 1mA LT1761-2 ΔVIN = 2.5V to 20V, ILOAD = 1mA LT1761-2.5 ΔVIN = 3V to 20V, ILOAD = 1mA LT1761-2.8 ΔVIN = 3.3V to 20V, ILOAD = 1mA LT1761-3 ΔVIN = 3.5V to 20V, ILOAD = 1mA LT1761-3.3 ΔVIN = 3.8V to 20V, ILOAD = 1mA LT1761-5 ΔVIN = 5.5V to 20V, ILOAD = 1mA LT1761 (Note 3) ΔVIN = 2V to 20V, ILOAD = 1mA 1761sfc 3 LT1761 Series ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2) PARAMETER Load Regulation CONDITIONS LT1761-1.2 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 50mA VIN = 2.5V, ΔILOAD = 1mA to 50mA 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 ● MIN TYP 1 1 MAX 6 12 12 50 20 35 30 55 20 35 30 60 20 35 35 65 20 35 40 80 20 38 40 86 20 40 40 90 20 40 40 100 30 60 65 150 6 12 12 50 0.15 0.19 0.22 0.29 0.28 0.38 0.35 0.45 UNITS mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV V V V V V V V V ● LT1761-1.5 10 ● 14 ● LT1761-1.8 10 ● 15 ● LT1761-2 10 ● 15 ● LT1761-2.5 10 ● 20 ● LT1761-2.8 10 ● 20 ● LT1761-3 10 ● 20 ● LT1761-3.3 10 ● 20 ● LT1761-5 15 ● 25 ● LT1761 (Note 3) 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 Dropout Voltage VIN = VOUT(NOMINAL) (Notes 5, 6, 11) ILOAD = 1mA ILOAD = 1mA ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 100mA ILOAD = 100mA 1 ● 1 ● 0.10 ● 0.17 ● 0.24 ● 0.30 ● 1761sfc 4 LT1761 Series ELECTRICAL CHARACTERISTICS PARAMETER GND Pin Current VIN = VOUT(NOMINAL) (Notes 5, 7) CONDITIONS ILOAD = 0mA ILOAD = 1mA ILOAD = 10mA ILOAD = 50mA ILOAD = 100mA The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2) MIN ● ● ● ● ● TYP 20 55 230 1 2.2 20 30 MAX 45 100 400 2 4 100 2 0.5 3 0.1 UNITS μA μA μA mA mA μVRMS nA V V μA μA μA dB mA mA Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 9) Quiescent Current in Shutdown Ripple Rejection (Note 3) Current Limit Input Reverse Leakage Current Reverse Output Current (Note 10) COUT = 10μF, CBYP = 0.01μF, ILOAD = 100mA, BW = 10Hz to 100kHz (Notes 3, 8) VOUT = Off to On VOUT = On to Off VSHDN = 0V VSHDN = 20V VIN = 6V, VSHDN = 0V VIN – VOUT = 1.5V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 50mA VIN = 7V, VOUT = 0V VIN = VOUT(NOMINAL) + 1V or 2.3V (Note 12), ΔVOUT = – 5% VIN = – 20V, VOUT = 0V LT1761-1.2 VOUT = 1.2V, VIN < 1.2V LT1761-1.5 VOUT = 1.5V, VIN < 1.5V LT1761-1.8 VOUT = 1.8V, VIN < 1.8V LT1761-2 VOUT = 2V, VIN < 2V LT1761-2.5 VOUT = 2.5V, VIN < 2.5V LT1761-2.8 VOUT = 2.8V, VIN < 2.8V LT1761-3 VOUT = 3V, VIN < 3V LT1761-3.3 VOUT = 3.3V, VIN < 3.3V LT1761-5 VOUT = 5V, VIN < 5V LT1761 (Note 3) VOUT = 1.22V, VIN < 1.22V ● ● ● ● ● ● 0.25 0.8 0.65 0 1 0.01 55 65 200 110 1 10 10 10 10 10 10 10 10 10 5 20 20 20 20 20 20 20 20 20 10 mA μA μA μA μA μA μA μA μA μA μA 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 LT1761MP is 100% tested and guaranteed over the – 55°C to 125°C 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. 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. 1761sfc 5 LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS Typical Dropout Voltage 500 450 DROPOUT VOLTAGE (mV) DROPOUT VOLTAGE (mV) 350 300 250 200 150 100 50 0 0 TJ = 125°C 350 300 250 200 150 100 50 0 TJ ≤ 125°C TJ ≤ 25°C DROPOUT VOLTAGE (mV) 400 TJ = 25°C 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) 1761 G00 Quiescent Current 40 35 QUIESCENT CURRENT (μA) VIN = 6V RL = ∞ (250k FOR LT1761-BYP, -SD) IL = 0 (5μA FOR LT1761-BYP, -SD) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 30 25 VSHDN = VIN 20 15 10 5 0 –50 –25 VSHDN = 0V 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G03 LT1761-1.8 Output Voltage 1.84 IL = 1mA 1.83 OUTPUT VOLTAGE (V) 1.81 1.80 1.79 1.78 1.77 1.76 –50 –25 0 25 50 75 100 125 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 1.82 TEMPERATURE (°C) 1761 G06 6 UW Guaranteed Dropout Voltage 500 450 400 500 Dropout Voltage 450 400 350 300 250 200 150 100 50 IL = 50mA IL = 10mA IL = 1mA IL = 100mA = TEST POINTS 0 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) 1761 G01 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1761 G01.1 LT1761-1.2 Output Voltage 1.220 1.215 1.210 1.205 1.200 1.195 1.190 1.185 1.180 –50 –25 0 25 50 75 100 125 IL = 1mA 1.528 1.521 1.514 1.507 1.500 1.493 1.486 1.479 LT1761-1.5 Output Voltage IL = 1mA 1.472 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G05 TEMPERATURE (°C) 1761 G51 LT1761-2 Output Voltage 2.04 IL = 1mA 2.03 2.02 2.01 2.00 1.99 1.98 1.97 1.96 –50 –25 0 25 50 75 100 125 LT1761-2.5 Output Voltage 2.54 IL = 1mA 2.53 2.52 2.51 2.50 2.49 2.48 2.47 2.46 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G07 TEMPERATURE (°C) 1761 G08 1761sfc LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS LT1761-2.8 Output Voltage 2.84 IL = 1mA 2.83 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 2.81 2.80 2.79 2.78 2.77 2.76 –50 –25 0 25 50 75 100 125 OUTPUT VOLTAGE (V) 2.82 TEMPERATURE (°C) 1761 G52 LT1761-5 Output Voltage 5.08 IL = 1mA 5.06 OUTPUT VOLTAGE (V) ADJ PIN VOLTAGE (V) 5.04 5.02 5.00 4.98 4.96 4.94 4.92 –50 –25 0 25 50 75 100 125 1.230 1.225 1.220 1.215 1.210 1.205 1.200 –50 –25 0 25 50 75 100 125 QUIESCENT CURRENT (μA) TEMPERATURE (°C) 1761 G12 LT1761-1.5 Quiescent Current 200 175 QUIESCENT CURRENT (μA) 200 TJ = 25°C RL = ∞ QUIESCENT CURRENT (μA) 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 150 125 100 75 50 25 0 VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 QUIESCENT CURRENT (μA) UW LT1761-3 Output Voltage 3.060 IL = 1mA 3.045 3.030 3.015 3.000 2.985 2.970 2.955 2.940 –50 –25 0 25 50 75 100 125 3.345 3.330 3.315 3.300 3.285 3.270 3.255 3.360 LT1761-3.3 Output Voltage IL = 1mA 3.240 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G09 TEMPERATURE (°C) 1761 G11 LT1761-BYP, LT1761-SD ADJ Pin Voltage 1.240 1.235 IL = 1mA 250 225 200 175 150 125 100 75 50 25 0 LT1761-1.2 Quiescent Current TJ = 25°C RL = ∞ VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 TEMPERATURE (°C) 1761 G10 1761 G10b LT1761-1.8 Quiescent Current 200 TJ = 25°C RL = ∞ 175 150 125 100 75 50 25 0 175 LT1761-2 Quiescent Current TJ = 25°C RL = ∞ VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 10 1761 G53 1761 G18 1761 G19 1761sfc 7 LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS LT1761-2.5 Quiescent Current 200 175 TJ = 25°C RL = ∞ 200 175 TJ = 25°C RL = ∞ QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 10 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 10 QUIESCENT CURRENT (μA) LT1761-3.3 Quiescent Current 200 175 QUIESCENT CURRENT (μA) 200 TJ = 25°C RL = ∞ QUIESCENT CURRENT (μA) 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 10 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 QUIESCENT CURRENT (μA) LT1761-1.2 GND Pin Current 2.50 2.25 GND PIN CURRENT (mA) TJ = 25°C *FOR VOUT = 1.2V 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 0 1 2 GND PIN CURRENT (mA) GND PIN CURRENT (mA) 2.00 RL = 12Ω IL = 100mA* RL = 24Ω IL = 50mA* RL = 1.2k IL = 1mA* RL = 120Ω IL = 10mA* 8 9 10 34567 INPUT VOLTAGE (V) 8 UW 1761 G13 LT1761-2.8 Quiescent Current 200 175 150 125 100 75 50 25 0 LT1761-3 Quiescent Current TJ = 25°C RL = ∞ VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 1761 G54 1761 G14 LT1761-5 Quiescent Current 30 TJ = 25°C RL = ∞ 175 LT1761-BYP, LT1761-SD Quiescent Current TJ = 25°C RL = 250k IL = 5μA VSHDN = VIN 25 20 15 10 5 VSHDN = 0V 0 10 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V) 1761 G17 1761 G15 1761 G16 LT1761-1.5 GND Pin Current 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 RL = 1.5k IL = 1mA* RL = 150Ω IL = 10mA* RL = 30Ω IL = 50mA* RL = 15Ω IL = 100mA* TJ = 25°C *FOR VOUT = 1.5V 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 LT1761-1.8 GND Pin Current TJ = 25°C *FOR VOUT = 1.8V RL = 18Ω IL = 100mA* RL = 36Ω IL = 50mA* RL = 1.8k IL = 1mA* RL = 180Ω IL = 10mA* 8 9 10 0 1 2 34567 INPUT VOLTAGE (V) 1761 G17b 1761 G55 1761 G02 1761sfc LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS LT1761-2 GND Pin Current 2.50 2.25 GND PIN CURRENT (mA) TJ = 25°C *FOR VOUT = 2V GND PIN CURRENT (mA) 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 0 1 2 RL = 20Ω IL = 100mA* 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 GND PIN CURRENT (mA) 2.00 RL = 40Ω IL = 50mA* RL = 2k IL = 1mA* RL = 200Ω IL = 10mA* 8 9 10 34567 INPUT VOLTAGE (V) LT1761-3 GND Pin Current 2.50 2.25 GND PIN CURRENT (mA) TJ = 25°C *FOR VOUT = 3V GND PIN CURRENT (mA) 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 0 1 2 RL = 30Ω IL = 100mA* RL = 60Ω IL = 50mA* RL = 3k IL = 1mA* RL = 300Ω IL = 10mA* 8 9 10 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 0 1 2 GND PIN CURRENT (mA) 2.00 34567 INPUT VOLTAGE (V) LT1761-BYP, LT1761-SD GND Pin Current 2.50 2.25 GND PIN CURRENT (mA) TJ = 25°C *FOR VOUT = 1.22V SHDN PIN THRESHOLD (V) GND PIN CURRENT (mA) 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 0 1 2 RL = 12.2Ω IL = 100mA* RL = 24.4Ω IL = 50mA* RL = 1.22k IL = 1mA* RL = 122Ω IL = 10mA* 8 9 10 34567 INPUT VOLTAGE (V) UW 1761 G04 1761 G21 1761 G24 LT1761-2.5 GND Pin Current 2.50 2.25 2.00 RL = 25Ω IL = 100mA TJ = 25°C *FOR VOUT = 2.5V 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 LT1761-2.8 GND Pin Current TJ = 25°C *FOR VOUT = 2.8V RL = 28Ω IL = 100mA RL = 50Ω IL = 50mA* RL = 2.5k IL = 1mA* RL = 250Ω IL = 10mA* 8 9 10 RL = 56Ω IL = 50mA* RL = 2.8k IL = 1mA* RL = 280Ω IL = 10mA* 8 9 10 0 1 2 34567 INPUT VOLTAGE (V) 0 1 2 34567 INPUT VOLTAGE (V) 1761 G20 1761 G56 LT1761-3.3 GND Pin Current 2.50 2.25 2.00 RL = 33Ω IL = 100mA* RL = 66Ω IL = 50mA* RL = 3.3k IL = 1mA* RL = 330Ω IL = 10mA* 8 9 10 TJ = 25°C *FOR VOUT = 3.3V 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 34567 INPUT VOLTAGE (V) LT1761-5 GND Pin Current TJ = 25°C *FOR VOUT = 5V RL = 50Ω IL = 100mA RL = 100Ω IL = 50mA* RL = 5k IL = 1mA* RL = 500Ω IL = 10mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 1761 G22 1761 G23 GND Pin Current vs ILOAD 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 0 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) 1761 G25 SHDN Pin Threshold (On-to-Off) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 IL = 1mA VIN = VOUT(NOMINAL) + 1V 1761 G26 1761sfc 9 LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS SHDN Pin Threshold (Off-to-On) 1.0 0.9 IL = 100mA SHDN PIN INPUT CURRENT (μA) SHDN PIN THRESHOLD (V) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 –50 –25 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 SHDN PIN INPUT CURRENT (μA) IL = 1mA 50 25 0 75 TEMPERATURE (°C) ADJ Pin Bias Current 100 90 ADJ PIN BIAS CURRENT (nA) 80 70 60 50 40 30 20 10 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 SHORT-CIRCUIT CURRENT (mA) 250 200 150 100 50 0 0 1 4 3 2 5 INPUT VOLTAGE (V) 6 7 1761 G31 CURRENT LIMIT (mA) Reverse Output Current 100 REVERSE OUTPUT CURRENT (μA) REVERSE OUTPUT CURRENT (μA) 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 10 0 0 1 2 LT1761-5 345678 OUTPUT VOLTAGE (V) 9 10 LT1761-3.3 RIPPLE REJECTION (dB) 10 UW 100 1761 G27 1761 G30 SHDN Pin Input Current 1.0 0.9 SHDN Pin Input Current 1.4 VSHDN = 20V 1.2 1.0 0.8 0.6 0.4 0.2 0 –50 –25 125 0 0 1 2 345678 SHDN PIN VOLTAGE (V) 9 10 50 25 0 75 TEMPERATURE (°C) 100 125 1761 G28 1761 G29 Current Limit 350 300 VOUT = 0V TJ = 25°C 350 300 250 200 150 100 50 Current Limit VIN = 7V VOUT = 0V 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1761 G32 Reverse Output Current 25.0 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 Input Ripple Rejection 80 70 60 50 40 30 20 10 0 10 100 COUT = 1μF COUT = 10μF LT1761-BYP LT1761-5 IL = 100mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE CBYP = 0 7.5 5.0 2.5 0 –50 –25 LT1761-BYP,-SD LT1761-1.2,-1.5,-1.8,-2, -2.5,-2.8,-3,-3.3,-5 50 25 0 75 TEMPERATURE (°C) 100 125 1k 10k FREQUENCY (Hz) 100k 1M 1761 G35 1761 G33 1761 G34 1761sfc LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS LT1761-5 Input Ripple Rejection 80 70 RIPPLE REJECTION (dB) CBYP = 0.01μF CBYP = 1000pF RIPPLE REJECTION (dB) MINIMUM INPUT VOLTAGE (V) 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1761 G36 CBYP = 100pF IL = 100mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE COUT = 10μF Load Regulation ΔIL = 1mA to 50mA 0 –5 LT1761-BYP, -SD, -1.2 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 0 –10 LOAD REGULATION (mV) –10 –15 –20 –25 – 30 –35 –40 –50 –25 0 25 50 75 100 LOAD REGULATION (mV) TEMPERATURE (°C) 1761 G39 Output Noise Spectral Density OUTPUT NOISE SPECTRAL DENSITY (μV/√Hz) OUTPUT NOISE SPECTRAL DENSITY (μV/√Hz) 10 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 0.01 10 100 1k 10k FREQUENCY (Hz) 100k 1761 G41 CBYP = 1000pF CBYP = 100pF OUTPUT NOISE (μVRMS) UW Input Ripple Rejection 80 70 LT1761-BYP, LT1761-SD Minimum Input Voltage 2.5 2.0 IL = 100mA 1.5 IL = 50mA 1.0 60 50 40 30 20 10 VIN = VOUT (NOMINAL) + 1V + 0.5VP-P RIPPLE AT f = 120Hz IL = 50mA 0 25 50 75 100 125 0.5 0 –50 –25 0 –50 –25 TEMPERATURE (°C) 1761 G37 50 25 0 75 TEMPERATURE (°C) 100 125 1761 G38 Load Regulation ΔIL = 1mA to 100mA LT1761-BYP, -SD, -1.2 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 –20 –30 –40 –50 –60 –70 –80 –90 LT1761-5 LT1761-5 125 –100 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G40 Output Noise Spectral Density 10 RMS Output Noise vs Bypass Capacitor 140 LT1761-5 120 LT1761-3.3 LT1761-3 LT1761-2.8 LT1761-2.5 COUT = 10μF IL = 100mA f = 10Hz TO 100kHz LT1761-5 1 100 80 60 40 LT1761-BYP 0.1 CBYP = 0.01μF COUT = 10μF IL = 100mA 0.01 10 100 1k 10k FREQUENCY (Hz) 100k 1761 G42 LT1761-1.8, -2 20 0 10 100 CBYP (pF) 1761 G43 LT1761-1.5 LT1761-BYP, -1.2 1k 10k 1761sfc 11 LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS RMS Output Noise vs Load Current (10Hz to 11kHz) 160 140 OUTPUT NOISE (μVRMS) 120 100 80 60 40 20 0 0.01 LT1761-5 LT1761-BYP 10 0.1 1 LOAD CURRENT (mA) 100 1761 G44 COUT = 10μF CBYP = 0 CBYP = 0.01μF LT1761-5 VOUT 100μV/DIV LT1761-BYP VOUT 100μV/DIV LT1761-5 10Hz to 100kHz Output Noise CBYP = 1000pF VOUT 100μV/DIV COUT = 10μF IL = 100mA LT1761-5 Transient Response CBYP = 0 OUTPUT VOLTAGE DEVIATION (V) OUTPUT VOLTAGE DEVIATION (V) 0.2 0.1 0 –0.1 –0.2 LOAD CURRENT (mA) LOAD CURRENT (mA) 100 50 0 0 400 800 1200 TIME (μs) 1600 2000 1761 G49 12 UW 1ms/DIV LT1761-5 10Hz to 100kHz Output Noise CBYP = 0 LT1761-5 10Hz to 100kHz Output Noise CBYP = 100pF COUT = 10μF IL = 100mA 1ms/DIV 1761 G45 1ms/DIV COUT = 10μF IL = 100mA 1761 G46 LT1761-5 10Hz to 100kHz Output Noise CBYP = 0.01μF VOUT 100μV/DIV 1ms/DIV 1761 G47 COUT = 10μF IL = 100mA 1761 G48 LT1761-5 Transient Response CBYP = 0.01μF 0.04 0.02 0 –0.02 –0.04 VIN = 6V CIN = 10μF COUT = 10μF VIN = 6V CIN = 10μF COUT = 10μF 100 50 0 0 20 40 60 80 100 120 140 160 180 200 TIME (μs) 1761 G50 1761sfc LT1761 Series PI FU CTIO S 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. U U U 1761sfc 13 LT1761 Series APPLICATIO S I FOR ATIO 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 ADJ IN VIN LT1761 ADJ GND Figure 1. Adjustable Operation 1761sfc 14 U 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 VOUT 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 inversely proportional to the size of the bypass capacitor, slowing to 15ms with a 0.01μF bypass capacitor and 10μF output capacitor. OUT VOUT W UU + R2 ⎛ R2 ⎞ VOUT = 1.22V ⎜ 1 + ⎟ + IADJ R2 ⎝ R1⎠ VADJ = 1.22V IADJ = 30nA AT 25°C ( )( ) R1 1761 F01 OUTPUT RANGE = 1.22V TO 20V LT1761 Series APPLICATIO S I FOR ATIO Output Capacitance and Transient Response 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 4.0 3.5 3.0 STABLE REGION 2.5 ESR (Ω) 2.0 1.5 1.0 0.5 0 1 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (μF) 1761 F02 CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP > 3300pF Figure 2. Stability 20 0 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF X5R CHANGE IN VALUE (%) CHANGE IN VALUE (%) –20 –40 –60 Y5V –80 –100 0 2 4 8 6 10 12 DC BIAS VOLTAGE (V) 14 16 1761 F03 Figure 3. Ceramic Capacitor DC Bias Characteristics U 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. 40 20 0 –20 –40 –60 –80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF 50 25 75 0 TEMPERATURE (°C) 100 125 1761 F04 W UU X5R Y5V –100 –50 –25 Figure 4. Ceramic Capacitor Temperature Characteristics 1761sfc 15 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. 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 2. GND pin current multiplied by the input voltage: (IGND)(VIN). 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. Table 1. Measured Thermal Resistance COPPER AREA TOPSIDE* BACKSIDE 2500mm2 1000mm 100mm 50mm 2 LT1761-5 COUT = 10μF CBYP = 0.01μF ILOAD = 100mA VOUT 500μV/DIV Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor 16 U W U U BOARD AREA 2500mm2 2500mm 2500mm 2500mm 2 THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 125°C/W 125°C/W 130°C/W 135°C/W 150°C/W 2500mm2 2500mm 2500mm 2500mm 2 225mm2 2 2 2500mm2 2 2 2500mm2 2 2 *Device is mounted on topside. 100ms/DIV 1761 F05 1761sfc LT1761 Series APPLICATIO S I FOR ATIO 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 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 U 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 500kΩ 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. 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 1761sfc W UU 17 LT1761 Series APPLICATIO S I FOR ATIO 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 100 REVERSE OUTPUT CURRENT (μA) 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 10 0 0 1 2 LT1761-5 345678 OUTPUT VOLTAGE (V) 9 10 LT1761-3.3 Figure 6. Reverse Output Current 18 U 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. 1761 F06 W UU 1761sfc LT1761 Series PACKAGE DESCRIPTIO 0.62 MAX 3.85 MAX 2.62 REF RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.20 BSC 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 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 circuits as described herein will not infringe on existing patent rights. U S5 Package 5-Lead Plastic TSOT-23 (LTC DWG # 05-08-1635) 0.95 REF 2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE 0.30 – 0.45 TYP 5 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.01 – 0.10 1.90 BSC S5 TSOT-23 0302 REV B 1761sfc 19 LT1761 Series RELATED PARTS PART NUMBER LT1120 LT1121 LT1129 LT1175 LT1521 LT1529 LT1762 Series LT1763 Series LTC1928 LT1962 Series LT1963 LT1764 LTC3404 DESCRIPTION 125mA Low Dropout Regulator with 20μA IQ 150mA Micropower Low Dropout Regulator 700mA Micropower Low Dropout Regulator 500mA Negative Low Dropout Micropower Regulator 300mA Low Dropout Micropower Regulator with Shutdown 3A Low Dropout Regulator with 50μA IQ 150mA, Low Noise, LDO Micropower Regulator 500mA, Low Noise, LDO Micropower Regulator Doubler Charge Pump with Low Noise Linear Regulator 300mA, Low Noise, LDO Micropower Regulator 1.5A, Low Noise, Fast Transient Response LDO 3A, Low Noise, Fast Transient Response LDO High Efficiency Synchronous Step-Down Switching Regulator COMMENTS Includes 2.5V Reference and Comparator 30μA IQ, SOT-223 Package 50μA Quiescent Current 45μA IQ, 0.26V Dropout Voltage, SOT-223 Package 15μA IQ, Reverse Battery Protection 500mV Dropout Voltage 25μA Quiescent Current, 20μVRMS Noise 30μA Quiescent Current, 20μVRMS Noise Low Output Noise: 60μVRMS (100kHz BW) 30μA Quiescent Current, 20μVRMS Noise 40μVRMS, SOT-223 Package 40μVRMS, 340mV Dropout Voltage Burst ModeTM Operation, Monolithic, 100% Duty Cycle Burst Mode is a trademark of Linear Technology Corporation. 1761sfc 20 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LT 0507 REV C • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 2005