LT3013EDE

LT3013 250mA, 4V to 80V Low Dropout Micropower Linear Regulator with PWRGD FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION The LT®3013 is a high voltage, micropower low dropout linear regulator. The device is capable of supplying 250mA of output current with a dropout voltage of 400mV. Designed for use in battery-powered or high voltage systems, the low quiescent current (65μA operating and 1μA in shutdown) makes the LT3013 an ideal choice. Quiescent current is also well controlled in dropout. Other features of the LT3013 include a PWRGD flag to indicate output regulation. The delay between regulated output level and flag indication is programmable with a single capacitor. The LT3013 also has the ability to operate with very small output capacitors. The regulator is stable with only 3.3μF on the output while most older devices require between 10μF and 100μF for stability. Small ceramic capacitors can be used without any need for series resistance (ESR) as is common with other regulators. Internal protection circuitry includes reverse-battery protection, current limiting, thermal limiting and reverse current protection. The device is available with an adjustable output with a 1.24V reference voltage. The LT3013 regulator is available in the thermally enhanced 16-lead TSSOP and the low profile (0.75mm), 12-pin (4mm × 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: 4V to 80V Low Quiescent Current: 65μA Low Dropout Voltage: 400mV Output Current: 250mA No Protection Diodes Needed Adjustable Output from 1.24V to 60V 1μA Quiescent Current in Shutdown Stable with 3.3μF Output Capacitor Stable with Aluminum, Tantalum or Ceramic Capacitors Reverse-Battery Protection No Reverse Current Flow from Output to Input Thermal Limiting Thermally Enhanced 16-Lead TSSOP and 12-Pin (4mm × 3mm) DFN Package APPLICATIONS ■ ■ ■ ■ Low Current High Voltage Regulators Regulator for Battery-Powered Systems Telecom Applications Automotive Applications TYPICAL APPLICATION 5V Supply with Shutdown DROPOUT VOLTAGE (mV) IN VIN 5.4V TO 80V 1µF 1.6M OUT LT3013 ADJ CT 249k 3013 TA01 Dropout Voltage 400 350 300 250 200 150 100 50 0 0 50 100 150 200 OUTPUT CURRENT (mA) 250 3013 TA02 750k VOUT 5V 250mA 3.3µF SHDN PWRGD GND VSHDN 2.0V OUTPUT OFF ON 1000pF 3013fc 1 LT3013 ABSOLUTE MAXIMUM RATINGS (Note 1) IN Pin Voltage .........................................................±80V OUT Pin Voltage ......................................................±60V IN to OUT Differential Voltage .................................±80V ADJ Pin Voltage ....................................................... ±7V ⎯S⎯H⎯D⎯N Pin Input Voltage ..........................................±80V CT Pin Voltage .................................................7V, –0.5V PWRGD Pin Voltage .......................................80V, –0.5V Output Short-Circuit Duration .......................... Indefinite Storage Temperature Range TSSOP Package ................................. –65°C to 150°C DFN Package...................................... –65°C to 125°C Operating Junction Temperature Range (Notes 3, 10, 11) LT3013E............................................. –40°C to 125°C LT3013HFE ........................................ –40°C to 140°C Lead Temperature (FE16 Soldering, 10 sec) ......... 300°C PACKAGE/ORDER INFORMATION TOP VIEW TOP VIEW NC OUT OUT ADJ GND PWRGD 1 2 3 13 4 5 6 9 8 7 NC SHDN CT 12 NC 11 IN 10 IN GND NC OUT OUT ADJ GND PWRGD GND DE PACKAGE 12-LEAD (4mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 40°C/W, θJC = 16°C/W EXPOSED PAD (PIN 13) IS GND MUST BE SOLDERED TO PCB 1 2 3 4 5 6 7 8 17 16 GND 15 NC 14 IN 13 IN 12 NC 11 SHDN 10 CT 9 GND FE PACKAGE 16-LEAD PLASTIC TSSOP TJMAX = 140°C, θJA = 40°C/W, θJC = 16°C/W EXPOSED PAD (PIN 17) IS GND MUST BE SOLDERED TO PCB ORDER PART NUMBER LT3013EDE DE PART MARKING 3013 ORDER PART NUMBER LT3013EFE LT3013HFE FE PART MARKING* 3013EFE 3013HFE 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. *The temperature grade is identified by a label on the shipping container. 3013fc 2 LT3013 ELECTRICAL CHARACTERISTICS PARAMETER Minimum Input Voltage ADJ Pin Voltage (Notes 2,3) Line Regulation Load Regulation (Note 2) Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) CONDITIONS ILOAD = 250mA VIN = 4V, ILOAD = 1mA 4.75V < VIN < 80V, 1mA < ILOAD < 250mA ΔVIN = 4V to 80V, ILOAD = 1mA (Note 2) VIN = 4.75V, ΔILOAD = 1mA to 250mA VIN = 4.75V, ΔILOAD = 1mA to 250mA ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 250mA ILOAD = 250mA GND Pin Current VIN = 4.75V (Notes 4, 6) Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold ⎯S⎯H⎯D⎯N 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 Reverse Output Current (Note 9) VCT(PWRGD High) – VCT(PWRGD Low) VIN = 7V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 250mA VIN = 7V, VOUT = 0V VIN = 4.75V, ΔVOUT = –0.1V (Note 2) VOUT = 1.24V, VIN < 1.24V (Note 2) ● ● ● ● ● ● ● ● ● ● (LT3013E) The ● denotes the specifications which apply over the –40°C to 125°C operating temperature range, otherwise specifications are at TJ = 25°C. MIN 1.225 1.2 TYP 4 1.24 1.24 0.1 7 160 250 400 65 3 10 100 30 ● ● MAX 4.75 1.255 1.28 5 12 25 230 300 340 420 490 620 120 18 100 2 2 1 5 94 250 6 UNITS V V V mV mV mV mV mV mV mV mV mV μA mA mA μVRMS nA V V μA μA μA % % mV μA V dB ILOAD = 0mA ILOAD = 100mA ILOAD = 250mA COUT = 10μF, ILOAD = 250mA, BW = 10Hz to 100kHz (Note 7 ) VOUT = Off to On VOUT = On to Off V⎯S⎯H⎯D⎯N = 0V V⎯S⎯H⎯D⎯N = 6V VIN = 6V, V⎯S⎯H⎯D⎯N = 0V % of Nominal Output Voltage, Output Rising % of Nominal Output Voltage IPWRGD = 50μA 0.3 1.3 0.8 0.3 0.1 1 ● ● 85 90 1.1 140 3.0 1.6 65 250 75 400 12 25 μA ELECTRICAL CHARACTERISTICS PARAMETER Minimum Input Voltage ADJ Pin Voltage (Notes 2,3) Line Regulation Load Regulation (Note 2) CONDITIONS ILOAD = 200mA (LT3013H) The ● denotes the specifications which apply over the –40°C to 140°C operating temperature range, otherwise specifications are at TJ = 25°C. MIN ● ● ● ● TYP 4 1.24 1.24 0.1 6 MAX 4.75 1.255 1.28 5 12 30 UNITS V V V mV mV mV VIN = 4V, ILOAD = 1mA 4.75V < VIN < 80V, 1mA < ILOAD < 200mA ΔVIN = 4V to 80V, ILOAD = 1mA (Note 2) VIN = 4.75V, ΔILOAD = 1mA to 200mA VIN = 4.75V, ΔILOAD = 1mA to 200mA 1.225 1.2 3013fc 3 LT3013 ELECTRICAL CHARACTERISTICS PARAMETER Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) CONDITIONS ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 200mA ILOAD = 200mA GND Pin Current VIN = 4.75V (Notes 4, 6) Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold ⎯S⎯H⎯D⎯N 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 Reverse Output Current (Note 9) VCT(PWRGD High) – VCT(PWRGD Low) VIN = 7V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 200mA VIN = 7V, VOUT = 0V VIN = 4.75V, ΔVOUT = –0.1V (Note 2) VOUT = 1.24V, VIN < 1.24V (Note 2) ● ● ● ● ● ● (LT3013H) The ● denotes the specifications which apply over the –40°C to 140°C operating temperature range, otherwise specifications are at TJ = 25°C. MIN TYP 160 250 360 65 3 7 100 30 ● ● MAX 230 320 340 450 490 630 130 18 100 2 2 1 5 95 250 6 UNITS mV mV mV mV mV mV μA mA mA μVRMS nA V V μA μA μA % % mV μA V dB mA mA ILOAD = 0mA ILOAD = 100mA ILOAD = 200mA COUT = 10μF, ILOAD = 200mA, BW = 10Hz to 100kHz (Note 7) VOUT = Off to On VOUT = On to Off V⎯S⎯H⎯D⎯N = 0V V⎯S⎯H⎯D⎯N = 6V VIN = 6V, V⎯S⎯H⎯D⎯N = 0V % of Nominal Output Voltage, Output Rising % of Nominal Output Voltage IPWRGD = 50μA 0.3 1.3 0.8 0.3 0.1 1 ● ● 85 90 1.1 140 3.0 1.6 65 200 75 400 12 25 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 LT3013 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 LT3013 is tested and specified for these conditions with an external resistor divider (249k bottom, 649k top) for an output voltage of 4.5V. 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 = 4.75V 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: ⎯S⎯H⎯D⎯N pin current flows out of the ⎯S⎯H⎯D⎯N 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 LT3013E is guaranteed to meet performance specifications from 0°C to 125°C operating junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3013H is tested to the LT3013H Electrical Characteristics table at 140°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 (LT3013E) or 140°C (LT3013H) when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. 3013fc 4 LT3013 TYPICAL PERFORMANCE CHARACTERISTICS Typical Dropout Voltage 600 500 DROPOUT VOLTAGE (mV) 400 300 200 100 0 TJ = 25°C TJ = 125°C GUARANTEED DROPOUT VOLTAGE (mV) 600 500 DROPOUT VOLTAGE (mV) 400 300 200 100 0 0 50 150 100 200 OUTPUT CURRENT (mA) 250 3013 G02 Guaranteed Dropout Voltage = TEST POINTS 600 TJ ≤ 125°C 500 400 300 200 100 Dropout Voltage IL = 250mA IL = 100mA TJ ≤ 25°C IL = 50mA IL = 10mA IL = 1mA 0 50 100 150 200 OUTPUT CURRENT (mA) 250 3013 G01 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G03 Quiescent Current 120 VIN = 6V RL = ∞ 100 IL = 0 QUIESCENT CURRENT (µA) 80 60 40 20 VSHDN = GND 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G04 ADJ Pin Voltage 1.260 1.255 ADJ PIN VOLTAGE (V) IL = 1mA VSHDN = VIN 1.250 1.245 1.240 1.235 1.230 1.225 1.220 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G05 0 3013fc 5 LT3013 TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Current 80 70 QUIESCENT CURRENT (µA) 60 50 40 30 20 10 VSHDN = GND 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 TJ = 25°C RL = ∞ QUIESCENT CURRENT (µA) VSHDN = VIN 250 Quiescent Current TJ = 25°C 225 RL = ∞ VOUT = 1.24V 200 175 150 125 100 75 50 25 0 0 10 20 30 40 50 60 INPUT VOLTAGE (V) 70 80 0 VSHDN = GND VSHDN = VIN GND PIN CURRENT (mA) 1.2 1.0 0.8 0.6 0.4 0.2 GND Pin Current TJ = 25°C *FOR VOUT = 1.24V RL = 49.6Ω IL = 25mA* RL = 124Ω IL = 10mA* RL = 1.24k IL = 1mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 3013 G06 3013 G06b 3013 G07 GND Pin Current 10 9 8 GND PIN CURRENT (mA) 7 6 5 4 3 2 1 0 0 1 2 RL = 24.8Ω, IL = 50mA* 34567 INPUT VOLTAGE (V) 8 9 10 RL = 12.4Ω IL = 100mA* GND PIN CURRENT (mA) RL = 4.96Ω IL = 250mA* TJ = 25°C, *FOR VOUT = 1.24V 10 GND Pin Current vs ILOAD VIN = 4.75V 9 TJ = 25°C 8 7 6 5 4 3 2 1 0 0 50 100 150 200 LOAD CURRENT (mA) 250 3013 G09 3013 G08 3013fc 6 LT3013 TYPICAL PERFORMANCE CHARACTERISTICS ⎯S⎯H⎯D⎯N Pin Threshold 2.0 1.8 SHDN PIN THRESHOLD (V) 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) 3013 G10 ⎯SH⎯D⎯N Pin Current ⎯ 0.6 TJ = 25°C CURRENT FLOWS 0.5 OUT OF SHDN PIN 0.6 ⎯S⎯H⎯D⎯N Pin Current VIN = 6V VSHDN = 0V 0.5 CURRENT FLOWS OUT OF SHDN PIN 0.4 0.3 0.2 0.1 0 –50 –25 OFF-TO-ON SHDN PIN CURRENT (µA) 0.4 0.3 0.2 0.1 0 0 0.5 1.5 2.5 1.0 2.0 SHDN PIN VOLTAGE (V) 3.0 3013 G11 ON-TO-OFF SHDN PIN CURRENT (µA) 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G12 ADJ Pin Bias Current PWRGD TRIP POINT (% OF OUTPUT VOLTAGE) 120 100 80 60 40 20 0 –50 –25 95 94 93 92 91 90 89 88 87 86 PWRGD Trip Point ADJ PIN BIAS CURRENT (nA) OUTPUT RISING OUTPUT FALLING 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G13 85 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G25 3013fc 7 LT3013 TYPICAL PERFORMANCE CHARACTERISTICS PWRGD Output Low Voltage 200 PWRGD OUTPUT LOW VOLTAGE (mV) 180 160 140 120 100 80 60 40 20 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G26 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) 3013 G27 CT Comparator Thresholds 2.0 CT COMPARATOR THRESHOLDS (V) 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 –50 –25 0 VCT (LOW) 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G28 IPWRGD = 50µA PWRGD TRIPPED HIGH VCT (HIGH) Current Limit 1000 900 800 CURRENT LIMIT (mA) 700 600 500 400 300 200 100 0 0 10 20 30 40 50 60 INPUT VOLTAGE (V) 70 80 100 TJ = 125°C CURRENT LIMIT (mA) TJ = 25°C 500 400 300 200 VOUT = 0V 700 600 Current Limit 0 –50 –25 VIN = 7V VOUT = 0V 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G15 3013 G14 3013fc 8 LT3013 TYPICAL PERFORMANCE CHARACTERISTICS Reverse Output Current 200 REVERSE OUTPUT CURRENT (µA) REVERSE OUTPUT CURRENT (µA) TJ = 25°C 180 VIN = 0V VOUT = VADJ 160 140 120 100 80 60 40 20 0 0 1 2 345678 OUTPUT VOLTAGE (V) 9 10 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G17 Reverse Output Current 120 100 80 60 40 20 RIPPLE REJECTION (dB) VIN = 0V VOUT = VADJ = 1.24V 92 88 84 80 76 72 68 64 60 Input Ripple Rejection CURRENT FLOWS INTO OUTPUT PIN ADJ PIN CLAMP (SEE APPLICATIONS INFORMATION) VIN = 4.75V + 0.5VP-P RIPPLE AT f = 120Hz IL = 250mA VOUT = 1.24V –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G18 3013 G16 Input Ripple Rejection 100 VIN = 4.75V + 50mVRMS RIPPLE 90 ILOAD = 250mA 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M 3013 G19 Minimum Input Voltage 5.0 4.5 MINIMUM INPUT VOLTAGE (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G20 ILOAD = 250mA COUT = 10µF COUT = 3.3µF 3013fc 9 LT3013 TYPICAL PERFORMANCE CHARACTERISTICS Load Regulation –2 LOAD REGULATION (mV) –4 –6 –8 –10 –12 –14 –16 –18 –20 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3013 G21 Output Noise Spectral Density OUTPUT NOISE SPECTRAL DENSITY (µV/√Hz) 10 COUT = 3.3µF ILOAD = 250mA 0 ∆IL = 1mA TO 250mA 1 0.1 0.01 10 100 1k 10k FREQUENCY (Hz) 100k 3013 G22 10Hz to 100kHz Output Noise OUTPUT VOLTAGE DEVIATION (V) Transient Response 0.15 0.10 0.05 0 –0.05 –0.10 –0.15 300 200 100 0 0 100 300 200 TIME (µs) 400 500 3013 G24 VOUT 100µV/DIV COUT = 10µF IL = 250mA VOUT = 1.24V 1ms/DIV 3013 G23 LOAD CURRENT (mA) VIN = 6V VOUT = 5V CIN = 3.3µF CERAMIC COUT = 3.3µF CERAMIC ∆ILOAD = 100mA TO 200mA 3013fc 10 LT3013 PIN FUNCTIONS (DFN Package)/(TSSOP Package) NC (Pins 1, 9, 12)/(Pins 2, 12, 15): No Connect. These pins have no internal connection; connecting NC pins to a copper area for heat dissipation provides a small improvement in thermal performance. OUT (Pins 2, 3)/(Pins 3, 4): Output. The output supplies power to the load. A minimum output capacitor of 3.3μF 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. ADJ (Pin 4)/(Pin 5): 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 curve of ADJ Pin Bias Current vs Temperature in the Typical Performance Characteristics). The ADJ pin voltage is 1.24V referenced to ground, and the output voltage range is 1.24V to 60V. GND (Pins 5, 13)/(Pins 1, 6, 8, 9, 16, 17): Ground. The exposed backside of the package 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 5/pin 6 on the PC board. PWRGD (Pin 6)/(Pin 7): Power Good. The PWRGD flag is an open collector flag to indicate that the output voltage has come up to 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 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 1.6V differential. The maximum pull-down current of the PWRGD pin in the low state is 50μA. ⎯S⎯H⎯D⎯N (Pin 8)/(Pin 11): Shutdown. The ⎯S⎯H⎯D⎯N pin is used to put the LT3013 into a low power shutdown state. The output will be off when the ⎯S⎯H⎯D⎯N 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 ⎯S⎯H⎯D⎯N pin must be tied to a logic high or VIN. CT (Pin 7)/(Pin 10): 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 1.6V (see the Applications Information Section). IN (Pins 10, 11)/(Pins 13,14): 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 LT3013 is designed to withstand reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reversed input, which can happen if a battery is plugged in backwards, the LT3013 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT3013 and no reverse voltage will appear at the load. The device will protect both itself and the load. 3013fc 11 LT3013 APPLICATIONS INFORMATION The LT3013 is a 250mA high voltage low dropout regulator with micropower quiescent current and shutdown. The device is capable of supplying 250mA at a dropout voltage of 400mV. The low operating quiescent current (65μA) drops to 1μA in shutdown. In addition to the low quiescent current, the LT3013 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 LT3013 acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The LT3013 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 250mA is –7mV typical at VOUT = 1.24V. At VOUT = 12V, load regulation is: (12V/1.24V) • (–7mV) = –68mV Output Capacitance and Transient Response The LT3013 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 3.3μF with an ESR of 3Ω or less is recommended to prevent oscillations. The LT3013 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 LT3013, will increase the effective output capacitor value. VOUT = 1.24V 1 + R2 + (IADJ)(R2) R1 VADJ = 1.24V IADJ = 30nA AT 25°C OUTPUT RANGE = 1.24V TO 60V IN VIN OUT LT3013 ADJ GND R1 R2 + VOUT 3013 F01 Figure 1. Adjustable Operation 3013fc 12 LT3013 APPLICATIONS INFORMATION 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 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 a 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 • tDELAY C TIME = VCT (HIGH) – VCT (LOW) 20 0 CHANGE IN VALUE (%) 40 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF CHANGE IN VALUE (%) X5R 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, 10µF –100 50 25 75 –50 –25 0 TEMPERATURE (°C) 100 125 3013 F02 3013 F03 Figure 2. Ceramic Capacitor DC Bias Characteristics Figure 3. Ceramic Capacitor Temperature Characteristics 3013fc 13 LT3013 APPLICATIONS INFORMATION Figure 4 shows a block diagram of the PWRGD circuit. At startup, 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 flip-flop 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. During normal operation, an internal glitch filter will ignore short transients (