LT3011IDDTR

FEATURES n n n n n n n n n n n n n n LT3011 50mA, 3V to 80V Low Dropout Micropower Linear Regulator with PWRGD DESCRIPTION The LT®3011 is a high voltage, micropower, low dropout linear regulator. The device is capable of supplying 50mA of output current with a dropout voltage of 300mV. Designed for use in battery-powered high voltage systems, the low quiescent current (46μA operating and 1μA in shutdown) is well controlled in dropout, making the LT3011 an ideal choice. The LT3011 includes a PWRGD flag to indicate output regulation. The delay between regulated output level and flag indication is programmable with a single capacitor. The LT3011 also has the ability to operate with very small output capacitors; it is stable with only 1μF on the output. Small ceramic capacitors can be used without the addition of any series resistance (ESR) as is common with other regulators. Internal protection circuitry includes reversebattery protection, current limiting, thermal limiting, and reverse current protection. The LT3011 features an adjustable output with a 1.24V reference voltage. The device is available in the thermally enhanced 12-lead MSOP and the low profile (0.75mm) 10-pin (3mm × 3mm) DFN package, both providing excellent thermal characteristics. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Wide Input Voltage Range: 3V to 80V Low Quiescent Current: 46μA Low Dropout Voltage: 300mV Output Current: 50mA PWRGD Flag with Programmable Delay No Protection Diodes Needed Adjustable Output from 1.24V to 60V 1μA Quiescent Current in Shutdown Stable with 1μF Output Capacitor Stable with Ceramic, Tantalum, and Aluminum Capacitors Reverse-Battery Protection No Reverse Current Flow from Output to Input Thermal Limiting Thermally Enhanced 12-Lead MSOP and 10-Pin (3mm × 3mm) DFN Packages APPLICATIONS n n n n Low Current High Voltage Regulators Regulator for Battery-Powered Systems Telecom Applications Automotive Applications TYPICAL APPLICATION 5V Supply with Shutdown IN VIN 3V TO 80V 1μF 1.6M OUT LT3011 ADJ CT 249k VOUT 5V 50mA 1μF 350 300 DROPOUT VOLTAGE (mV) 250 200 150 100 50 0 0 10 Dropout Voltage 750k SHDN PWRGD GND POWER GOOD 1000pF VSHDN 2.0V OUTPUT OFF ON 3011 TA01 20 30 40 OUTPUT CURRENT (mA) 50 3011 TA02 3011f 1 LT3011 ABSOLUTE MAXIMUM RATINGS (Note 1) IN Pin Voltage .........................................................±80V OUT Pin Voltage ......................................................±60V Input-to-Output Differential Voltage ........................±80V ADJ Pin Voltage ........................................................±7V SHDN Pin Voltage ...................................................±80V CT Pin Voltage .................................................. 7V, –0.5V PWRGD Pin Voltage ....................................... 80V, –0.5V Output Short-Circuit Duration .......................... Indefinite Storage Temperature Range................... –65°C to 150°C Operating Junction Temperature (Notes 3, 10, 11) LT3011E, LT3011I .............................. –40°C to 125°C LT3011H ............................................ –40°C to 150°C Lead Temperature (Soldering, 10 sec) MSE Package Only ............................................ 300°C PIN CONFIGURATION TOP VIEW OUT ADJ GND NC PWRGD 1 2 3 4 5 11 10 IN 9 NC 8 SHDN 7 NC 6 CT NC OUT ADJ GND NC PWRGD 1 2 3 4 5 6 TOP VIEW 12 11 10 9 8 7 NC IN NC SHDN NC CT 13 DD PACKAGE 10-LEAD (3mm 3mm) PLASTIC DFN MSE PACKAGE 12-LEAD PLASTIC MSOP TJMAX = 150°C, θJA = 43°C/W, θJC = 16°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB TJMAX = 150°C, θJA = 40°C/W, θJC = 16°C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH LT3011EDD#PBF LT3011IDD#PBF LT3011EMSE#PBF LT3011HMSE#PBF LT3011IMSE#PBF LEAD BASED FINISH LT3011EDD LT3011IDD LT3011EMSE LT3011HMSE LT3011IMSE TAPE AND REEL LT3011EDD#TRPBF LT3011IDD#TRPBF LT3011EMSE#TRPBF LT3011HMSE#TRPBF LT3011IMSE#TRPBF TAPE AND REEL LT3011EDD#TR LT3011IDD#TR LT3011EMSE#TR LT3011HMSE#TR LT3011IMSE#TR PART MARKING* LDKQ LDKQ 3011 3011 3011 PART MARKING* LDKQ LDKQ 3011 3011 3011 PACKAGE DESCRIPTION 10-Lead (3mm × 3mm) Plastic DFN 10-Lead (3mm × 3mm) Plastic DFN 12-Lead Plastic MSOP 12-Lead Plastic MSOP 12-Lead Plastic MSOP PACKAGE DESCRIPTION 10-Lead (3mm × 3mm) Plastic DFN 10-Lead (3mm × 3mm) Plastic DFN 12-Lead Plastic MSOP 12-Lead Plastic MSOP 12-Lead Plastic MSOP TEMPERATURE RANGE –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 150°C –40°C to 125°C TEMPERATURE RANGE –40°C to 125°C –40°C to 125°C –40°C to 125°C –40°C to 150°C –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. 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/ 3011f 2 LT3011 ELECTRICAL CHARACTERISTICS PARAMETER Minimum Input Voltage ADJ Pin Voltage (Notes 2, 3) Line Regulation (Note 2) Load Regulation (Note 2) Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) CONDITIONS ILOAD = 50mA VIN = 3V, ILOAD = 1mA 4V < VIN < 80V, 1mA < ILOAD < 50mA ΔVIN = 3V to 80V, ILOAD = 1mA VIN = 4V, ΔILOAD = 1mA to 50mA VIN = 4V, ΔILOAD = 1mA to 50mA ILOAD = 1mA ILOAD = 1mA ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA GND Pin Current VIN = VOUT(NOMINAL) (Notes 4, 6) Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 8) Quiescent Current in Shutdown PWRGD Trip Point PWRGD Trip Point Hysteresis PWRGD Output Low Voltage CT Pin Charging Current CT Pin Voltage Differential Ripple Rejection Current Limit Input Reverse Leakage Current Reverse Output Current (Note 9) VCT(PWRGD High) – VCT(PWRGD Low) VIN = 7V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 50mA VIN = 7V, VOUT = 0V VIN = 4V, ΔVOUT = –0.1V (Note 2) VIN = –80V, VOUT = 0V VOUT = 1.24V, VIN < 1.24V (Note 2) l l l l l l l l l l l l l (LT3011E, LT3011I) The l denotes the specifications which apply over the –40°C to 125°C operating temperature range, otherwise specifications are TJ = 25°C. MIN 1.228 1.215 TYP 2.8 1.24 1.24 1 6 100 200 300 46 105 410 1.9 100 30 l l MAX 4 1.252 1.265 12 15 25 150 190 260 350 370 550 90 200 700 3.3 100 2 2 0.5 5 94 250 6 UNITS V V V mV mV mV mV mV mV mV mV mV μA μA μA mA μVRMS nA V V μA μA μA % % mV μA V dB mA mA ILOAD = 0mA ILOAD = 1mA ILOAD = 10mA ILOAD = 50mA COUT = 10μF ILOAD = 50mA, BW = 10Hz to 100kHz, VOUT = 1.24V , (Note 7 ) VOUT = Off to On VOUT = On to Off VSHDN = 0V VSHDN = 6V VIN = 6V, VSHDN = 0V % of Nominal Output Voltage, Output Rising % of Nominal Output Voltage IPWRGD = 50μA 0.3 1.3 1.1 0.5 0.1 1 l l l 85 90 1.1 140 3 1.67 65 60 85 140 6 8 15 mA μA ELECTRICAL CHARACTERISTICS PARAMETER Minimum Input Voltage ADJ Pin Voltage (Notes 2, 3) Line Regulation (Note 2) Load Regulation (Note 2) CONDITIONS ILOAD = 50mA (LT3011H) The l denotes the specifications which apply over the –40°C to 150°C operating temperature range, otherwise specifications are TJ = 25°C. MIN l l l l TYP 2.8 1.24 1.24 1 6 MAX 4 1.252 1.265 12 15 25 UNITS V V V mV mV mV VIN = 3V, ILOAD = 1mA 4V < VIN < 80V, 1mA < ILOAD < 50mA ΔVIN = 3V to 80V, ILOAD = 1mA VIN = 4V, ΔILOAD = 1mA to 50mA VIN = 4V, ΔILOAD = 1mA to 50mA 1.228 1.215 3011f 3 LT3011 ELECTRICAL CHARACTERISTICS PARAMETER Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) CONDITIONS ILOAD = 1mA ILOAD = 1mA ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA GND Pin Current VIN = VOUT(NOMINAL) (Notes 4, 6) Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 8) Quiescent Current in Shutdown PWRGD Trip Point PWRGD Trip Point Hysteresis PWRGD Output Low Voltage CT Pin Charging Current CT Pin Voltage Differential Ripple Rejection Current Limit Input Reverse Leakage Current Reverse Output Current (Note 9) VCT(PWRGD High) – VCT(PWRGD Low) VIN = 7V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 50mA VIN = 7V, VOUT = 0V VIN = 4V, ΔVOUT = –0.1V (Note 2) VIN = –80V, VOUT = 0V VOUT = 1.24V, VIN < 1.24V (Note 2) l l l l l l l l l (LT3011H) The l denotes the specifications which apply over the –40°C to 150°C operating temperature range, otherwise specifications are at TJ = 25°C. MIN TYP 100 200 300 46 105 410 1.9 100 30 l l MAX 150 220 260 380 370 575 125 225 750 3.5 100 2 2 0.5 5 95 250 6 UNITS mV mV mV mV mV mV μA μA μA mA μVRMS nA V V μA μA μA % % mV μA V dB mA mA ILOAD = 0mA ILOAD = 1mA ILOAD = 10mA ILOAD = 50mA COUT = 10μF ILOAD = 50mA, BW = 10Hz to 100kHz, VOUT = 1.24V , (Note 7) VOUT = Off to On VOUT = On to Off VSHDN = 0V VSHDN = 6V VIN = 6V, VSHDN = 0V % of Nominal Output Voltage, Output Rising % of Nominal Output Voltage IPWRGD = 50μA 0.3 1.3 1.1 0.5 0.1 1 l l l 85 90 1.1 140 3 1.67 65 60 85 140 6 8 15 mA 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 LT3011 is tested and specified for these conditions with the ADJ pin connected to the OUT pin. Note 3: 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 4: To satisfy requirements for minimum input voltage, the LT3011 is tested and specified for these conditions with an external resistor divider (249k bottom, 409k top) for an output voltage of 3.3V. The external resistor divider will add a 5μA DC load on the output. Note 5: 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 6: GND pin current is tested with VIN = VOUT(NOMINAL) and a current source load. This means the device is tested while operating close to its dropout region. This is the worst-case GND pin current. The GND pin current will decrease slightly at higher input voltages. Note 7: ADJ pin bias current flows into the ADJ pin. Note 8: SHDN pin current flows out of the SHDN pin. Note 9: 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 10: The LT3011 regulators are tested and specified under pulse load conditions such that TJ ≅ TA. The LT3011E regulators are 100% tested at TA = 25°C. Performance of the LT3011E over the full –40°C to 125°C operating junction temperature range is assured by design, characterization and correlation with statistical process controls. The LT3011I regulators are guaranteed over the full –40°C to 125°C operating junction temperature range. The LT3011H is tested to the LT3011H Electrical Characteristics table at 150°C operating junction temperature. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125°C. Note 11: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C (LT3011E/LT3011I) or 150°C (LT3011H) when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. 3011f 4 LT3011 TYPICAL PERFORMANCE CHARACTERISTICS Dropout Voltage 400 350 TJ DROPOUT VOLTAGE (mV) 300 250 200 150 100 50 0 0 10 20 30 40 50 3011 G01 TJ = 25°C, unless otherwise noted. Guaranteed Dropout Voltage 600 = TEST POINTS 400 350 DROPOUT VOLTAGE (mV) 300 250 500 DROPOUT VOLTAGE (mV) 400 300 TJ 200 100 0 0 5 10 15 20 25 30 35 40 45 50 OUTPUT CURRENT (mA) 3011 G02 Dropout Voltage IL = 50mA 125 C 25 C TJ TJ 125 C IL = 10mA 200 150 100 50 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G03 25 C IL = 1mA OUTPUT CURRENT (mA) Quiescent Current 80 70 QUIESCENT CURRENT (μA) 60 50 40 30 20 10 0 –50 –25 VSHDN = GND 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G04 ADJ Pin Voltage 1.250 1.248 ADJ PIN VOLTAGE (V) IL = 1mA QUIESCENT CURRENT (μA) 80 Quiescent Current TJ = 25°C 70 RL = 60 50 40 30 20 10 0 VSHDN = VIN VIN = 6V RL = ∞ IL = 0 VSHDN = VIN 1.246 1.244 1.242 1.240 1.238 1.236 1.234 1.232 1.230 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G05 0 1 2 3 4567 INPUT VOLTAGE (V) 8 9 10 3011 G06 GND Pin Current 2.0 1.8 GND PIN CURRENT (mA) GND PIN CURRENT (mA) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 1 2 RL = 124Ω IL = 10mA* RL = 1.24k, IL = 1mA* 34567 INPUT VOLTAGE (V) 8 9 10 RL = 49.6Ω IL = 25mA* RL = 24.8Ω IL = 50mA* 2.0 GND Pin Current vs IOUT VIN = VOUT(NOMINAL) +1V 1.8 TJ = 25°C SHDN PIN THRESHOLD (V) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5 10 15 20 25 30 35 40 45 50 OUTPUT CURRENT (mA) 3011 G08 SHDN Pin Threshold 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G09 TJ = 25°C *FOR VOUT = 1.24V 3011 G07 3011f 5 LT3011 TYPICAL PERFORMANCE CHARACTERISTICS SHDN Pin Current 0.28 TJ = 25°C CURRENT FLOWS 0.24 OUT OF SHDN PIN SHDN PIN CURRENT (μA) 0.20 0.16 0.12 0.08 0.04 0 0 0.5 1 3.5 4 SHDN PIN VOLTAGE (V) 1.5 2 2.5 3 4.5 3011 G10 TJ = 25°C, unless otherwise noted. SHDN Pin Current 0.6 0.5 SHDN PIN CURRENT (μA) 0.4 0.3 0.2 0.1 0 –50 –25 VSHDN = 0V CURRENT FLOWS OUT OF SHDN PIN ADJ PIN BIAS CURRENT (nA) 120 100 80 60 40 20 ADJ Pin Bias Current 5 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G11 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G12 PWRGD Trip Point PWRGD TRIP POINT (% OF OUTPUT VOLTAGE) 95 PWRGD OUTPUT LOW VOLTAGE (mV) 94 93 92 91 90 89 88 87 86 85 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G13 PWRGD Output Low Voltage 200 180 160 140 120 100 80 60 40 20 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G14 CT Charging Current 4.0 3.5 CT CHARGING CURRENT (μA) 3.0 2.5 2.0 1.5 1.0 0.5 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G15 IPWRGD = 50μA PWRGD TRIPPED HIGH OUTPUT RISING OUTPUT FALLING CT Comparator Threshold 2.0 CT COMPARATOR THRESHOLD (V) 1.8 1.6 CURRENT LIMIT (mA) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 –50 –25 VCT(LOW) 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G16 Current Limit 180 160 140 CURRENT LIMIT (mA) 120 100 80 60 40 20 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 VOUT = 0V TJ = 25°C 200 180 160 140 120 100 80 60 40 20 Current Limit VCT(HIGH) VIN = 7V VOUT = 0V 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G18 3011 G17 3011f 6 LT3011 TYPICAL PERFORMANCE CHARACTERISTICS Reverse Output Current 160 REVERSE OUTPUT CURRENT (μA) ADJ PIN CLAMP (SEE APPLICATIONS INFORMATION) REVERSE OUTPUT CURRENT (μA) 140 120 100 80 60 40 20 0 0 1 2 TJ = 25°C VIN = 0V CURRENT FLOWS INTO OUTPUT PIN VOUT = VADJ 34567 OUTPUT VOLTAGE (V) 8 9 10 3011 G19 TJ = 25°C, unless otherwise noted. Reverse Output Current 80 70 60 50 40 30 20 10 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G20 Input Ripple Rejection 90 VIN = 7V + 0.5VP-P RIPPLE AT f = 120Hz 88 IL = 50mA VOUT = 1.24V 86 RIPPLE REJECTION (dB) 84 82 80 78 76 74 72 70 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G21 VIN = 0V VOUT = VADJ = 1.24V Input Ripple Rejection 100 VIN = 7V + 50mVRMS RIPPLE 90 IL = 50mA, VOUT = 1.24V MINIMUM INPUT VOLTAGE (V) 4.0 3.5 COUT = 10μF CERAMIC Minimum Input Voltage IL = 50mA 0 –2 LOAD REGULATION (mV) –4 –6 –8 –10 Load Regulation ΔIL = 1mA TO 50mA VOUT = 1.24V 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M 3011 G22 3.0 2.5 2.0 1.5 1.0 0.5 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G23 COUT = 1μF CERAMIC –12 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3011 G24 Output Noise Spectral Density 10 VOUT = 1.24V COUT = 1μF IL = 50mA Output Noise (10Hz to 100kHz) OUTPUT VOLTAGE DEVIATION (V) VOUT = 1.24V COUT = 1μF IL = 50mA WORST-CASE NOISE VOUT 100μV/DIV 0.3 0.2 0.1 0 –0.1 –0.2 LOAD CURRENT (mA) Transient Response OUTPUT NOISE SPECTRAL DENSITY (μV/ Hz) 1 0.1 0.01 1ms/DIV 3011 G26 50 25 0 0.001 10 VIN = 6V VOUT SET FOR 5V CIN = 1μF CERAMIC COUT = 1μF CERAMIC ΔILOAD = 1mA TO 50mA 0 100 200 300 400 500 600 700 800 900 1000 TIME (μs) 3011 G27 100 1k 10k FREQUENCY (Hz) 100k 3011 G25 3011f 7 LT3011 PIN FUNCTIONS (DFN/MSOP) OUT (Pin 1/Pin 2): Output. The output supplies power to the load. A minimum output capacitor of 1μF is required to prevent oscillations. Larger 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. ADJ (Pin 2/Pin 3): Adjust. 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 the curve labeled ADJ Pin Bias Current vs Temperature in the Typical Performance Characteristics section). The ADJ pin voltage is 1.24V referenced to ground, and the output voltage range is 1.24V to 60V. GND (Pins 3, 11/Pins 4, 13): Ground. The exposed backside of the package (Pin 11/Pin 13) is an electrical connection for GND. As such, to ensure optimum device operation and thermal performance, the Exposed Pad must be connected directly to Pin 3/Pin 4 on the PC board. NC (Pins 4, 7, 9/Pins 1, 5, 8, 10, 12): No Connection. These pins have no internal connection. Connecting NC pins to a copper area for heat dissipation provides a small improvement in thermal performance. PWRGD (Pin 5/Pin 6): Power Good. The PWRGD flag is an open-collector flag to indicate that the output voltage has increased above 90% of the nominal output voltage. There is no internal pull-up on this pin; a pull-up resistor must be used. The PWRGD pin will change state from an open-collector pull-down to high impedance after both the output is above 90% of the nominal voltage and the capacitor on the CT pin has charged through a 1.67V differential. The maximum pull-down current of the PWRGD pin in the low state is 50μA. CT (Pin 6/Pin 7): Timing Capacitor. The CT pin allows the use of a small capacitor to delay the timing between the point where the output crosses the PWRGD threshold and the PWRGD flag changes to a high impedance state. Current out of this pin during the charging phase is 3μA. The voltage difference between the PWRGD low and PWRGD high states is 1.67V (see the Applications Information section). SHDN (Pin 8/Pin 9): Shutdown. The SHDN pin is used to put the LT3011 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 only required to supply the pull-up current of the open-collector gate, normally several microamperes. If unused, the SHDN pin must be tied to a logic high or VIN. IN (Pin 10/Pin 11): 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 LT3011 is designed to withstand reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reverse input voltage, which can occur if a battery is plugged in backwards, the LT3011 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT3011 and no reverse voltage will appear at the load. The device will protect both itself and the load. Exposed Pad (Pin 11/Pin 13): Ground. The Exposed Pad must be soldered to the PCB. 3011f 8 LT3011 APPLICATIONS INFORMATION The LT3011 is a 50mA high voltage/low dropout regulator with micropower quiescent current and shutdown. The device is capable of supplying 50mA at a dropout voltage of 300mV. The low operating quiescent current (46μA) drops to 1μA in shutdown. In addition to low quiescent current, the LT3011 incorporates several protection features which make it ideal for use in battery-powered systems. The device is 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 LT3011 acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The LT3011 has an output voltage range of 1.24V to 60V. 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 voltage at the adjust pin at 1.24V referenced to ground. The current in R1 is then equal to 1.24V/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 less 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. The adjustable device is tested and specified with the ADJ pin tied to the OUT pin and a 5μA DC load (unless otherwise specified) for an output voltage of 1.24V. Specifications for output voltages greater than 1.24V will be proportional to the ratio of the desired output voltage to 1.24V; (VOUT/1.24V). For example, load regulation for an output current change of 1mA to 50mA is –6mV (typical) at VOUT = 1.24V. At VOUT = 12V, load regulation is: 1 2V • – 6 mV = – 58mV 1 . 24V Output Capacitance and Transient Response The LT3011 is 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 LT3011 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 LT3011, will increase the effective output capacitor value. 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 VOUT = VADJ 1 + R2 + (IADJ)(R2) R1 VADJ = 1.24V IADJ = 30nA AT 25 C OUTPUT RANGE = 1.24V TO 60V IN VIN OUT LT3011 ADJ GND R1 R2 + VOUT 3011 F01 Figure 1. Adjustable Operation 3011f 9 LT3011 APPLICATIONS INFORMATION in a small package, but they tend to have strong voltage and temperature coefficients, as shown in Figures 2 and 3. 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. 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 piezoelectric accelerometer or microphone works. For a ceramic capacitor, the stress can be induced by vibrations in the system or thermal transients. PWRGD Flag and Timing Capacitor Delay The PWRGD flag is used to indicate that the ADJ pin voltage is within 10% of the regulated voltage. The PWRGD pin is an open-collector output, capable of sinking 50μA of current when the ADJ pin voltage is low. There is no internal pull-up on the PWRGD pin; an external pull-up resistor must be used. When the ADJ pin rises to within 10% of its final reference value, a delay timer is started. At the end of this delay, programmed by the value of the capacitor on the CT pin, the PWRGD pin switches to a high impedance and is pulled up to a logic level by an external pull-up resistor. To calculate the capacitor value on the CT pin, use the following formula: ICT • t DELAY C TIME = VCT(HIGH) − VCT (LOW) Figure 4 shows a block diagram of the PWRGD circuit. At start-up, the timing capacitor is discharged and the PWRGD pin will be held low. As the output voltage increases and the ADJ pin crosses the 90% threshold, the JK flipflop is reset, and the 3μA current source begins to charge the timing capacitor. Once the voltage on the CT pin reaches the VCT(HIGH) threshold (approximately 1.7V at 25°C), the capacitor voltage is clamped and the PWRGD pin is set to a high impedance state. 20 0 CHANGE IN VALUE (%) BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10 F CHANGE IN VALUE (%) X5R 40 20 0 X5R –20 –40 –60 –80 Y5V –20 –40 –60 Y5V –80 –100 0 2 4 8 6 10 12 DC BIAS VOLTAGE (V) 14 16 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10 F –100 50 25 75 –50 –25 0 TEMPERATURE ( C) 100 125 3011 F02 3011 F03 Figure 2. Ceramic Capacitor DC Bias Characteristics Figure 3. Ceramic Capacitor Temperature Characteristics 3011f 10 LT3011 APPLICATIONS INFORMATION During normal operation, an internal glitch filter will ignore short transients (