LT1761ES5-2

LT1761 Series 100mA, Low Noise, LDO Micropower Regulators in SOT-23 FEATURES s s s s s s s s DESCRIPTIO s s s s s s s Tiny 5-Lead SOT-23 Package 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: 1.5V, 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 APPLICATIO S s s s s 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 1.5V, 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. , LTC and LT are registered trademarks of Linear Technology Corporation. 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 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 Consult factory for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2) PARAMETER CONDITIONS q q q q q q q q q Minimum Input Voltage (Notes 3, 11) ILOAD = 100mA Regulated Output Voltage LT1761-1.5 VIN = 2V, ILOAD = 1mA (Note 4) 2.5V < VIN < 20V, 1mA < ILOAD < 50mA 2.5V < VIN < 20V, 1mA < ILOAD < 100mA LT1761-1.8 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 LT1761-2 LT1761-2.5 2 U U W WW U W (Note 1) Output Short-Circut Duration .......................... Indefinite Operating Junction Temperature Range (Note 2) ............................................ – 40°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 LT1761ES5-1.5 LT1761ES5-1.8 LT1761ES5-2 LT1761ES5-2.5 LT1761ES5-2.8 LT1761ES5-3 LT1761ES5-3.3 LT1761ES5-5 S5 PART MARKING LTMT LTJM LTJE LTGD LTLB LTGE LTGF LTGG MIN 1.478 1.457 1.436 1.775 1.750 1.725 1.970 1.945 1.920 2.465 2.435 2.415 TYP 1.8 1.5 1.5 1.5 1.8 1.8 1.8 2 2 2 2.5 2.5 2.5 MAX 2.3 1.522 1.538 1.555 1.825 1.845 1.860 2.030 2.045 2.060 2.535 2.565 2.575 UNITS V V V V V V V V V V V V V LT1761 Series ELECTRICAL CHARACTERISTICS PARAMETER Regulated Output Voltage (Note 4) CONDITIONS LT1761-2.8 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 ∆VIN = 2V to 20V, ILOAD = 1mA ∆VIN = 2.3V to 20V, ILOAD = 1mA ∆VIN = 2.5V to 20V, ILOAD = 1mA ∆VIN = 3V to 20V, ILOAD = 1mA ∆VIN = 3.3V to 20V, ILOAD = 1mA ∆VIN = 3.5V to 20V, ILOAD = 1mA ∆VIN = 3.8V to 20V, ILOAD = 1mA ∆VIN = 5.5V to 20V, ILOAD = 1mA ∆VIN = 2V to 20V, ILOAD = 1mA VIN = 2.5V, ∆ILOAD = 1mA to 50mA VIN = 2.5V, ∆ILOAD = 1mA to 50mA VIN = 2.5V, ∆ILOAD = 1mA to 100mA VIN = 2.5V, ∆ILOAD = 1mA to 100mA VIN = 2.8V, ∆ILOAD = 1mA to 50mA VIN = 2.8V, ∆ILOAD = 1mA to 50mA VIN = 2.8V, ∆ILOAD = 1mA to 100mA VIN = 2.8V, ∆ILOAD = 1mA to 100mA VIN = 3V, ∆ILOAD = 1mA to 50mA VIN = 3V, ∆ILOAD = 1mA to 50mA VIN = 3V, ∆ILOAD = 1mA to 100mA VIN = 3V, ∆ILOAD = 1mA to 100mA VIN = 3.5V, ∆ILOAD = 1mA to 50mA VIN = 3.5V, ∆ILOAD = 1mA to 50mA VIN = 3.5V, ∆ILOAD = 1mA to 100mA VIN = 3.5V, ∆ILOAD = 1mA to 100mA VIN = 3.8V, ∆ILOAD = 1mA to 50mA VIN = 3.8V, ∆ILOAD = 1mA to 50mA VIN = 3.8V, ∆ILOAD = 1mA to 100mA VIN = 3.8V, ∆ILOAD = 1mA to 100mA VIN = 4V, ∆ILOAD = 1mA to 50mA VIN = 4V, ∆ILOAD = 1mA to 50mA VIN = 4V, ∆ILOAD = 1mA to 100mA VIN = 4V, ∆ILOAD = 1mA to 100mA q q q q q q q q q q q q q q q q q q q q The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2) MIN 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 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 10 14 q MAX 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 20 35 30 55 20 35 30 60 20 35 35 65 20 35 40 80 20 38 40 86 20 40 40 90 UNITS 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 mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV LT1761-3 LT1761-3.3 LT1761-5 ADJ Pin Voltage (Note 3, 4) Line Regulation LT1761 LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 LT1761-5 LT1761(Note 3) LT1761-1.5 Load Regulation LT1761-1.8 10 q 15 q LT1761-2 10 q 15 q LT1761-2.5 10 q 20 q LT1761-2.8 10 q 20 q LT1761-3 10 q 20 q 3 LT1761 Series ELECTRICAL CHARACTERISTICS PARAMETER Load Regulation CONDITIONS LT1761-3.3 VIN = 4.3V, ∆ILOAD = 1mA to 50mA VIN = 4.3V, ∆ILOAD = 1mA to 50mA VIN = 4.3V, ∆ILOAD = 1mA to 100mA VIN = 4.3V, ∆ILOAD = 1mA to 100mA VIN = 6V, ∆ILOAD = 1mA to 50mA VIN = 6V, ∆ILOAD = 1mA to 50mA VIN = 6V, ∆ILOAD = 1mA to 100mA VIN = 6V, ∆ILOAD = 1mA to 100mA q The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2) MIN TYP 10 20 q MAX 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 45 100 400 2 4 100 2 0.5 3 0.1 UNITS mV mV mV mV mV mV mV mV mV mV mV mV V V V V V V V V µA µA µA mA mA µVRMS nA V V µA µA µA dB mA mA LT1761-5 15 q 25 q LT1761 (Note 3) VIN = 2.3V, ∆ILOAD = 1mA to 50mA VIN = 2.3V, ∆ILOAD = 1mA to 50mA VIN = 2.3V, ∆ILOAD = 1mA to 100mA VIN = 2.3V, ∆ILOAD = 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 GND Pin Current VIN = VOUT(NOMINAL) (Notes 5, 7) ILOAD = 0mA ILOAD = 1mA ILOAD = 10mA ILOAD = 50mA ILOAD = 100mA 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, ∆VOUT = – 5% VIN = – 20V, VOUT = 0V 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 1 q 1 q 0.10 q 0.17 q 0.24 q 0.30 q q q q q q 20 55 230 1 2.2 20 30 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) q q q q 0.25 0.8 0.65 0 1 0.01 55 65 200 q q 110 1 10 10 10 10 10 10 10 10 5 20 20 20 20 20 20 20 20 10 mA µA µA µA µA µA µA µA µA µA Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1761 regulators are tested and specified under pulse load conditions such that TJ ≈ TA. The LT1761 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. Note 3: The LT1761 (adjustable versions) are tested and specified for these conditions with the ADJ pin connected to the OUT pin. 4 LT1761 Series ELECTRICAL CHARACTERISTICS 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, LT1761-1.5, 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. 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 VIN = 6V RL = ∞ (250k FOR LT1761-BYP, -SD) IL = 0 (5µA FOR LT1761-BYP, -SD) 1.528 1.521 QUIESCENT CURRENT (µA) OUTPUT VOLTAGE (V) 25 VSHDN = VIN 20 15 10 5 0 –50 –25 VSHDN = 0V 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G03 1.507 1.500 1.493 1.486 1.479 1.472 –50 –25 0 25 50 75 100 125 OUTPUT VOLTAGE (V) 30 UW Guaranteed Dropout Voltage 500 450 400 Dropout Voltage 500 450 400 350 300 250 200 150 100 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 LT1761-1.5 Output Voltage 1.84 IL = 1mA 1.83 1.82 1.81 1.80 1.79 1.78 1.77 1.514 LT1761-1.8 Output Voltage IL = 1mA 1.76 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G51 TEMPERATURE (°C) 1761 G06 5 LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS LT1761-2 Output Voltage 2.04 IL = 1mA 2.03 2.53 2.02 2.01 2.00 1.99 1.98 1.97 1.96 –50 –25 0 25 50 75 100 125 2.52 2.51 2.50 1.49 1.48 1.47 1.46 –50 –25 0 25 50 75 100 125 2.54 IL = 1mA 2.83 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) TEMPERATURE (°C) 1761 G07 LT1761-3 Output Voltage 3.060 IL = 1mA 3.045 3.345 3.030 3.015 3.000 2.985 2.970 2.955 2.940 –50 –25 0 25 50 75 100 125 3.360 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) TEMPERATURE (°C) 1761 G09 LT1761-BYP, LT1761-SD ADJ Pin Voltage 1.240 1.235 ADJ PIN VOLTAGE (V) IL = 1mA QUIESCENT CURRENT (µA) 1.230 1.225 1.220 1.215 1.210 1.205 1.200 –50 –25 0 25 50 75 100 125 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 10 QUIESCENT CURRENT (µA) TEMPERATURE (°C) 1761 G10 6 UW LT1761-2.5 Output Voltage 2.84 LT1761-2.8 Output Voltage IL = 1mA 2.82 2.81 2.80 2.79 2.78 2.77 2.76 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G08 TEMPERATURE (°C) 1761 G52 LT1761-3.3 Output Voltage 5.08 IL = 1mA 5.06 5.04 5.02 5.00 4.98 4.96 4.94 0 25 50 75 125 3.330 3.315 3.300 3.285 3.270 3.255 3.240 –50 –25 100 LT1761-5 Output Voltage IL = 1mA 4.92 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1761 G11 TEMPERATURE (°C) 1761 G12 LT1761-1.5 Quiescent Current 200 175 TJ = 25°C RL = ∞ 200 175 150 125 100 75 50 25 0 LT1761-1.8 Quiescent Current TJ = 25°C RL = ∞ VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 1761 G53 1761 G18 LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS LT1761-2 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 Quiescent Current 200 175 TJ = 25°C RL = ∞ 200 175 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-BYP, LT1761-SD Quiescent Current 30 25 QUIESCENT CURRENT (µA) TJ = 25°C RL = 250k IL = 5µA GND PIN CURRENT (mA) 20 15 10 5 VSHDN = VIN 1.75 1.50 1.25 1.00 0.75 0.50 RL = 15Ω IL = 100mA* RL = 30Ω IL = 50mA* RL = 1.5k IL = 1mA* RL = 150Ω IL = 10mA* 8 9 10 GND PIN CURRENT (mA) VSHDN = 0V 0 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V) 1761 G17 UW 1761 G14 LT1761-2.5 Quiescent Current 200 175 150 125 100 75 50 25 0 LT1761-2.8 Quiescent Current TJ = 25°C RL = ∞ VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 1761 G19 1761 G13 1761 G54 LT1761-3.3 Quiescent Current 200 TJ = 25°C RL = ∞ 175 150 125 100 75 50 25 0 LT1761-5 Quiescent Current TJ = 25°C RL = ∞ VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 1761 G15 1761 G16 LT1761-1.5 GND Pin Current 2.50 2.25 2.00 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 0 1 2 34567 INPUT VOLTAGE (V) 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 0.25 0 0 1 2 34567 INPUT VOLTAGE (V) 1761 G55 1761 G02 7 LT1761 Series TYPICAL PERFOR A CE CHARACTERISTICS LT1761-2 GND Pin Current 2.50 2.25 TJ = 25°C *FOR VOUT = 2V GND PIN CURRENT (mA) 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) 8 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 0 75 25 TEMPERATURE (°C) 100 125 IL = 1mA VIN = VOUT(NOMINAL) + 1V 1761 G26 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 0 75 25 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 0 75 25 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 90 VIN = 0V CURRENT FLOWS 80 INTO OUTPUT PIN 70 VOUT = VADJ (LT1761-BYP, -SD) 60 LT1761-1.5 LT1761-1.8 50 LT1761-2 40 LT1761-2.5 LT1761-2.8 30 LT1761-3 20 10 0 0 1 2 LT1761-5 LT1761-BYP LT1761-SD RIPPLE REJECTION (dB) LT1761-3.3 345678 OUTPUT VOLTAGE (V) 9 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 = 1.5V (LT1761-1.5) 20.0 VOUT = 1.8V (LT1761-1.8) V = 2V (LT1761-2) 17.5 VOUT = 2.5V (LT1761-2.5) OUT VOUT = 2.8V (LT1761-2.8) 15.0 VOUT = 3V (LT1761-3) 12.5 VOUT = 3.3V (LT1761-3.3) VOUT = 5V (LT1761-5) 10.0 7.5 5.0 2.5 0 –50 –25 LT1761-1.5,-1.8,-2, -2.5,-2.8,-3,-3.3,-5 50 0 75 25 TEMPERATURE (°C) 100 125 LT1761-BYP,-SD Input Ripple Rejection 80 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1761 G35 LT1761-BYP LT1761-5 IL = 100mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE CBYP = 0 COUT = 10µF COUT = 1µF 1761 G33 1761 G34 9 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 ∆IL = 1mA to 50mA 0 –5 LT1761-BYP, -SD LT1761-1.5 LT1761-1.8 LT1761-2 LT1761-2.5 LT1761-2.8 LT1761-3 LT1761-3.3 0 –10 LOAD REGULATION (mV) LOAD REGULATION (mV) –10 –15 –20 –25 – 30 –35 –40 –50 –25 0 25 50 75 100 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 0.1 COUT = 10µF CBYP = 0 IL = 100mA 0.01 10 100 1k 10k FREQUENCY (Hz) 100k 1761 G41 OUTPUT NOISE (µVRMS) LT1761-1.5 LT1761-1.8 LT1761-2 10 UW Input Ripple Rejection 80 70 2.0 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 TEMPERATURE (°C) 1761 G37 LT1761-BYP, LT1761-SD Minimum Input Voltage 2.5 IL = 100mA 1.5 IL = 50mA 1.0 0.5 0 –50 –25 0 –50 –25 50 0 75 25 TEMPERATURE (°C) 100 125 1761 G38 Load Regulation ∆IL = 1mA to 100mA LT1761-BYP, -SD 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 CBYP = 1000pF CBYP = 100pF 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 1k 10k 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 UW 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 COUT = 10µF IL = 100mA 1ms/DIV 1761 G46 LT1761-5 10Hz to 100kHz Output Noise CBYP = 0.01µF VOUT 100µV/DIV 1ms/DIV 1761 G47 COUT = 10µF IL = 100mA 1ms/DIV 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 11 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. 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 12 U W UU U U U 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 LT1761 Series APPLICATIO S I FOR ATIO 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 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 IN VIN OUT VOUT + LT1761 ADJ GND R1 1761 F01 R2  R2  VOUT = 1.22V  1 +  + IADJ R2  R1 VADJ = 1.22V IADJ = 30nA AT 25°C OUTPUT RANGE = 1.22V TO 20V Figure 1. Adjustable Operation 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 Reponse in ESR (Ω) U 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. 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 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 4.0 3.5 3.0 STABLE REGION 2.5 2.0 1.5 1.0 0.5 0 1 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (µF) 1761 F02 W UU ( )( ) CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP > 3300pF Figure 2. Stability 13 LT1761 Series APPLICATIO S I FOR ATIO dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but exhibit strong voltage and temperature coefficients as shown in Figures 3 and 4. When used with a 5V regulator, a 10µF Y5V capacitor can exhibit an effective value as low as 1µF to 2µF 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. 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 20 0 CHANGE IN VALUE (%) BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF X5R –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 40 20 CHANGE IN VALUE (%) 0 –20 –40 –60 –80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF 50 25 75 0 TEMPERATURE (°C) Y5V X5R –100 –50 –25 100 125 1761 F04 Figure 4. Ceramic Capacitor Temperature Characteristics 14 U 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. LT1761-5 COUT = 10µF CBYP = 0.01µF ILOAD = 100mA VOUT 500µV/DIV 100ms/DIV 1761 F05 W UU 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 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 LT1761 Series APPLICATIONS INFORMATION 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 2500mm 225mm 2 BOARD AREA 2500mm2 2500mm2 2500mm 2 THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 125°C/W 125°C/W 130°C/W 135°C/W 150°C/W 2500mm 2500mm 2 1000mm2 2 2500mm2 2 100mm2 50mm2 2500mm2 2500mm2 2500mm2 2500mm2 *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 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 W U 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 from the 1.22V reference when the output is forced to 20V. 15 LT1761 Series 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. 100 TJ = 25°C 90 VIN = 0V CURRENT FLOWS 80 INTO OUTPUT PIN 70 VOUT = VADJ (LT1761-BYP, -SD) 60 LT1761-1.5 LT1761-1.8 50 LT1761-2 40 LT1761-2.5 LT1761-2.8 30 LT1761-3 20 10 0 0 1 2 LT1761-5 345678 OUTPUT VOLTAGE (V) 9 10 LT1761-BYP LT1761-SD REVERSE OUTPUT CURRENT (µA) LT1761-3.3 1761 F06 Figure 6. Reverse Output Current PACKAGE DESCRIPTIO S5 Package 5-Lead Plastic SOT-23 (LTC DWG # 05-08-1633) 0.35 – 0.55 (0.014 – 0.022) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DIMENSIONS ARE INCLUSIVE OF PLATING 3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 4. MOLD FLASH SHALL NOT EXCEED 0.254mm 5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ) 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. 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com U Dimensions in inched (millimeters) unless otherwise noted. 2.60 – 3.00 (0.102 – 0.118) 1.50 – 1.75 (0.059 – 0.069) 0.00 – 0.15 (0.00 – 0.006) 0.90 – 1.45 (0.035 – 0.057) 2.80 – 3.00 (0.110 – 0.118) (NOTE 3) 0.09 – 0.20 (0.004 – 0.008) (NOTE 2) 0.35 – 0.50 0.90 – 1.30 (0.014 – 0.020) (0.035 – 0.051) FIVE PLACES (NOTE 2) 1.90 (0.074) REF 0.95 (0.037) REF S5 SOT-23 0599 1761fa LT/TP 0401 2K REV A • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 1999