LT3012 250mA, 4V to 80V Low Dropout Micropower Linear Regulator DESCRIPTION FEATURES n n n n n n n n n n n n n Wide Input Voltage Range: 4V to 80V Low Quiescent Current: 40μA 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 Packages APPLICATIONS n n n n The LT®3012 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 (40μA operating and 1μA in shutdown) makes the LT3012 an ideal choice. Quiescent current is also well controlled in dropout. Other features of the LT3012 include 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 LT3012 regulator is available in the 16-lead TSSOP and 12 pin low profile (0.75mm) (4mm × 3mm) DFN packages with an exposed pad for enhanced thermal handling capability. Low Current High Voltage Regulators Regulator for Battery-Powered Systems Telecom Applications Automotive Applications L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 5V Supply with Shutdown Dropout Voltage 400 VIN 5.4V TO 80V LT3012 1μF VOUT 5V 250mA OUT SHDN GND 750k 3.3μF ADJ 249k 3012 TA01 VSHDN <0.3V >2.0V OUTPUT OFF ON 350 DROPOUT VOLTAGE (mV) IN 300 250 200 150 100 50 0 0 50 100 150 200 OUTPUT CURRENT (mA) 250 3012 TA02 3012fd 1 LT3012 ABSOLUTE MAXIMUM RATINGS (Note 1) IN Pin Voltage .........................................................±80V OUT Pin Voltage ......................................................±60V IN to OUT Differential Voltage .................................±80V ADJ Pin Voltage ........................................................±7V SHDN Pin Input Voltage ..........................................±80V 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) LT3012E ............................................. –40°C to 125°C LT3012HFE......................................... –40°C to 140°C Lead Temperature (FE16 Soldering, 10 sec) ......... 300°C PIN CONFIGURATION TOP VIEW TOP VIEW GND 1 16 GND NC 1 12 NC NC 2 15 NC OUT 2 11 IN OUT 3 14 IN OUT 3 10 IN OUT 4 ADJ 4 9 NC ADJ 5 GND 5 8 SHDN GND 6 11 SHDN NC 7 10 NC GND 8 9 NC 13 6 7 NC 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 17 13 IN 12 NC 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 INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3012EDE#PBF LT3012EDE#TRPBF 3012 12-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C LT3012EFE#PBF LT3012EFE#TRPBF 3012EFE 16-Lead Plastic TSSOP –40°C to 125°C LT3012HFE#PBF LT3012HFE#TRPBF 3012HFE 16-Lead Plastic TSSOP –40°C to 140°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3012EDE LT3012EDE#TR 3012 12-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C LT3012EFE LT3012EFE#TR 3012EFE 16-Lead Plastic TSSOP –40°C to 125°C LT3012HFE LT3012HFE#TR 3012HFE 16-Lead Plastic TSSOP –40°C to 140°C Consult LTC Marketing for parts specified with wider operating temperature ranges. 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/ 3012fd 2 LT3012 ELECTRICAL CHARACTERISTICS (LT3012E) The l denotes the specifications which apply over the –40°C to 125°C operating temperature range, otherwise specifications are at TJ = 25°C. PARAMETER CONDITIONS MIN TYP 4 4.75 V 1.225 1.2 1.24 1.24 1.255 1.28 V V l Minimum Input Voltage ILOAD = 250mA ADJ Pin Voltage (Notes 2, 3) VIN = 4V, ILOAD = 1mA 4.75V < VIN < 80V, 1mA < ILOAD < 250mA l Line Regulation ΔVIN = 4V to 80V, ILOAD = 1mA (Note 2) l Load Regulation (Note 2) VIN = 4.75V, ΔILOAD = 1mA to 250mA VIN = 4.75V, ΔILOAD = 1mA to 250mA l Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) ILOAD = 10mA ILOAD = 10mA l ILOAD = 50mA ILOAD = 50mA l ILOAD = 250mA ILOAD = 250mA l l MAX UNITS 0.1 5 mV 7 12 25 mV mV 160 230 300 mV mV 250 340 420 mV mV 400 490 620 mV mV 40 3 10 100 μA mA mA GND Pin Current VIN = 4.75V (Notes 4, 6) ILOAD = 0mA ILOAD = 100mA ILOAD = 250mA Output Voltage Noise COUT = 10μF, ILOAD = 250mA, BW = 10Hz to 100kHz 100 ADJ Pin Bias Current (Note 7) 30 100 nA Shutdown Threshold VOUT = Off to On VOUT = On to Off 1.3 0.8 2 V V 0.3 0.1 2 1 μA μA 1 5 μA SHDN Pin Current (Note 8) VSHDN = 0V VSHDN = 6V Quiescent Current in Shutdown VIN = 6V, VSHDN = 0V Ripple Rejection VIN = 7V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 250mA Current Limit VIN = 7V, VOUT = 0V VIN = 4.75V, ΔVOUT = –0.1V (Note 2) Reverse Output Current (Note 9) l l l 0.3 65 l 18 μVRMS 75 dB 400 mA mA 250 VOUT = 1.24V, VIN < 1.24V (Note 2) 12 25 μA ELECTRICAL CHARACTERISTICS (LT3012H) The l denotes the specifications which apply over the –40°C to 140°C operating temperature range, otherwise specifications are at TJ = 25°C. PARAMETER CONDITIONS Minimum Input Voltage ILOAD = 200mA l ADJ Pin Voltage (Notes 2, 3) VIN = 4V, ILOAD = 1mA 4.75V < VIN < 80V, 1mA < ILOAD < 200mA l Line Regulation ΔVIN = 4V to 80V, ILOAD = 1mA (Note 2) l Load Regulation (Note 2) VIN = 4.75V, ΔILOAD = 1mA to 200mA VIN = 4.75V, ΔILOAD = 1mA to 200mA l Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) ILOAD = 10mA ILOAD = 10mA l ILOAD = 50mA ILOAD = 50mA l ILOAD = 200mA ILOAD = 200mA l GND Pin Current VIN = 4.75V (Notes 4, 6) ILOAD = 0mA ILOAD = 100mA ILOAD = 200mA MIN l l 1.225 1.2 TYP MAX UNITS 4 4.75 V 1.24 1.24 1.255 1.28 V V 0.1 5 mV 6 12 30 mV mV 160 230 320 mV mV 250 340 450 mV mV 360 490 630 mV mV 40 3 7 110 μA mA mA 18 3012fd 3 LT3012 ELECTRICAL CHARACTERISTICS (LT3012H) The l denotes the specifications which apply over the –40°C to 140°C operating temperature range, otherwise specifications are at TJ = 25°C. PARAMETER CONDITIONS Output Voltage Noise COUT = 10μF, ILOAD = 200mA, BW = 10Hz to 100kHz 100 ADJ Pin Bias Current (Note 7) 30 100 nA Shutdown Threshold VOUT = Off to On VOUT = On to Off 1.3 0.8 2 V V 0.3 0.1 2 1 μA μA 1 5 μA SHDN Pin Current (Note 8) MIN l l VSHDN = 0V VSHDN = 6V Quiescent Current in Shutdown VIN = 6V, VSHDN = 0V Ripple Rejection VIN = 7V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 200mA Current Limit VIN = 7V, VOUT = 0V VIN = 4.75V, ΔVOUT = –0.1V (Note 2) Reverse Output Current (Note 9) 0.3 VOUT = 1.24V, VIN < 1.24V (Note 2) 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 LT3012 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 LT3012 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). 65 l TYP MAX UNITS μVRMS 75 dB 400 mA mA 200 12 25 μA 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: 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 LT3012E 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 LT3012H is tested to the LT3012H 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 (LT3012E) or 140°C (LT3012H) when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. 3012fd 4 LT3012 TYPICAL PERFORMANCE CHARACTERISTICS Typical Dropout Voltage Guaranteed Dropout Voltage 600 400 TJ = 25°C 300 200 100 0 = TEST POINTS TJ ≤ 125°C 500 500 400 DROPOUT VOLTAGE (mV) TJ = 125°C TJ ≤ 25°C 300 200 100 150 200 OUTPUT CURRENT (mA) 0 250 Quiescent Current 50 150 100 200 OUTPUT CURRENT (mA) 50 40 30 20 IL = 1mA 0 1.250 1.245 1.240 1.235 1.230 VSHDN = VIN 50 40 30 20 VSHDN = GND 25 50 75 100 125 150 TEMPERATURE (°C) 1.220 –50 –25 0 0 25 50 75 100 125 150 TEMPERATURE (°C) Quiescent Current TJ = 25°C 225 RL = ∞ VOUT = 1.24V 200 GND PIN CURRENT (mA) VSHDN = VIN 100 75 VSHDN = GND 2 RL = 49.6Ω IL = 25mA* 0.8 RL = 124Ω IL = 10mA* 0.6 0.4 RL = 1.24k IL = 1mA* 0.2 20 30 40 50 60 INPUT VOLTAGE (V) 70 80 3012 G07 0 0 1 2 9 10 TJ = 25°C, *FOR VOUT = 1.24V 9 8 RL = 4.96Ω IL = 250mA* 7 6 5 RL = 12.4Ω IL = 100mA* 4 3 1 10 8 2 25 0 3 4 5 6 7 INPUT VOLTAGE (V) GND Pin Current 10 TJ = 25°C *FOR VOUT = 1.24V 1.0 150 1 3012 G06 GND Pin Current 1.2 175 0 3012 G05 250 50 60 10 3012 G04 125 25 50 75 100 125 150 TEMPERATURE (°C) TJ = 25°C RL = ∞ VOUT = 1.24V 70 VSHDN = GND 0 –50 –25 0 Quiescent Current 80 1.225 10 IL = 1mA 3012 G03 QUIESCENT CURRENT (μA) ADJ PIN VOLTAGE (V) QUIESCENT CURRENT (μA) VSHDN = VIN IL = 10mA 0 –50 –25 250 1.255 60 IL = 50mA 200 ADJ Pin Voltage 1.260 VIN = 6V 90 RL = ∞ I =0 80 L 0 300 3012 G02 100 70 IL = 100mA 400 0 50 0 IL = 250mA 100 100 3012 G01 QUIESCENT CURRENT(μA) Dropout Voltage 600 GND PIN CURRENT (mA) DROPOUT VOLTAGE (mV) 500 GUARANTEED DROPOUT VOLTAGE (mV) 600 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 3012 G08 0 RL = 24.8Ω, IL = 50mA* 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 3012 G09 3012fd 5 LT3012 TYPICAL PERFORMANCE CHARACTERISTICS SHDN Pin Threshold GND Pin Current vs ILOAD 10 TJ = 25°C CURRENT FLOWS 0.5 OUT OF SHDN PIN 1.8 7 6 5 4 3 2 1.6 OFF-TO-ON 1.4 1.2 1.0 ON-TO-OFF 0.8 0.6 0.4 0.4 0.3 0.2 0.1 0.2 1 50 0 100 150 200 LOAD CURRENT (mA) 0 0 –50 –25 250 0 0 25 50 75 100 125 150 TEMPERATURE (°C) 3012 G10 SHDN Pin Current Current Limit 1000 VOUT = 0V 0.3 0.2 0.1 100 800 CURRENT LIMIT (mA) ADJ PIN BIAS CURRENT (nA) 900 0.4 3.0 3012 G12 ADJ Pin Bias Current 120 VIN = 6V VSHDN = 0V 0.5 CURRENT FLOWS OUT OF SHDN PIN 1.0 2.0 1.5 2.5 SHDN PIN VOLTAGE (V) 0.5 3012 G11 0.6 SHDN PIN CURRENT (μA) SHDN PIN CURRENT (μA) SHDN PIN THRESHOLD (V) GND PIN CURRENT (mA) VIN = 4.75V 9 TJ = 25°C = 1.24V V 8 OUT 0 SHDN Pin Current 0.6 2.0 80 60 40 TJ = 25°C 700 600 TJ = 125°C 500 400 300 200 20 100 0 –50 –25 0 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 0 Current Limit 300 200 VIN = 7V VOUT = 0V 0 –50 –25 TJ = 25°C 180 VIN = 0V VOUT = VADJ 160 140 120 100 CURRENT FLOWS 80 INTO OUTPUT PIN 60 ADJ PIN CLAMP (SEE APPLICATIONS INFORMATION) 40 REVERSE OUTPUT CURRENT (μA) REVERSE OUTPUT CURRENT (μA) CURRENT LIMIT (mA) 400 20 30 40 50 60 INPUT VOLTAGE (V) 70 80 Reverse Output Current 120 200 500 10 3012 G15 Reverse Output Current 700 600 0 3012 G14 3012 G13 100 0 25 50 75 100 125 150 TEMPERATURE (°C) VIN = 0V VOUT = VADJ = 1.24V 100 80 60 40 20 20 0 25 50 75 100 125 150 TEMPERATURE (°C) 3012 G16 0 0 1 2 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 9 10 3012 G17 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3012 G18 3012fd 6 LT3012 TYPICAL PERFORMANCE CHARACTERISTICS Input Ripple Rejection Input Ripple Rejection 100 RIPPLE REJECTION (dB) 80 76 72 68 VIN = 4.75V + 0.5VP-P RIPPLE AT f = 120Hz IL = 250mA VOUT = 1.24V 60 0 25 50 75 100 125 150 TEMPERATURE (°C) 70 60 50 COUT = 10μF 40 30 20 COUT = 3.3μF 10 10 100 1k 10k FREQUENCY (Hz) OUTPUT NOISE SPECTRAL DENSITY (μV/√Hz) –4 –6 –8 –10 –12 –14 –16 –18 0 2.5 2.0 1.5 1.0 0 –50 –25 1M 0 25 50 75 100 125 150 TEMPERATURE (°C) 3012 G21 Output Noise Spectral Density ΔIL = 1mA TO 250mA –20 –50 –25 3.0 3012 G20 Load Regulation –2 3.5 0.5 100k 3012 G19 0 ILOAD = 250mA 4.0 0 10 COUT = 3.3μF ILOAD = 250mA 1 0.1 0.01 25 50 75 100 125 150 TEMPERATURE (°C) 10 100 1k 10k FREQUENCY (Hz) 100k 3012 G23 3012 G22 10Hz to 100kHz Output Noise Transient Response OUTPUT VOLTAGE DEVIATION (V) 0.15 VOUT 100μV/DIV COUT = 10μF IL = 250mA VOUT = 1.24V 1ms/DIV 3012 G24 LOAD CURRENT (mA) –50 –25 LOAD REGULATION (mV) RIPPLE REJECTION (dB) 4.5 80 84 64 VIN = 4.75V + 50mVRMS RIPPLE ILOAD = 250mA 90 88 Minimum Input Voltage 5.0 MINIMUM INPUT VOLTAGE (V) 92 0.10 0.05 0 –0.05 VIN = 6V VOUT = 5V CIN = 3.3μF CERAMIC COUT = 3.3μF CERAMIC ΔILOAD = 100mA TO 200mA –0.10 –0.15 300 200 100 0 0 100 300 200 TIME (μs) 400 500 3012 G25 3012fd 7 LT3012 PIN FUNCTIONS (DFN Package/TSSOP Package) NC (Pins 1, 6, 7, 9, 12)/(Pins 2, 7, 10, 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. SHDN (Pin 8)/(Pin 11): Shutdown. The SHDN pin is used to put the LT3012 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 to VIN. 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 LT3012 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 LT3012 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT3012 and no reverse voltage will appear at the load. The device will protect both itself and the load. APPLICATIONS INFORMATION The LT3012 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 (40μA) drops to 1μA in shutdown. In addition to the low quiescent current, the LT3012 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 LT3012 acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The LT3012 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. 3012fd 8 LT3012 APPLICATIONS INFORMATION IN VIN VOUT OUT LT3012 R2 + ADJ 3012 F01 R1 GND VOUT = 1.24V 1 + R2 + (IADJ)(R2) R1 VADJ = 1.24V IADJ = 30nA AT 25°C OUTPUT RANGE = 1.24V TO 60V Figure 1. Adjustable Operation 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 LT3012 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 LT3012 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 20 improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT3012, 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 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. 40 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF 20 X5R CHANGE IN VALUE (%) CHANGE IN VALUE (%) 0 –20 –40 –60 Y5V –80 –100 0 X5R –20 –40 Y5V –60 –80 0 2 4 8 6 10 12 DC BIAS VOLTAGE (V) 14 16 3012 F02 Figure 2. Ceramic Capacitor DC Bias Characteristics BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF –100 50 25 75 –50 –25 0 TEMPERATURE (°C) 100 125 3012 F03 Figure 3. Ceramic Capacitor Temperature Characteristics 3012fd 9 LT3012 APPLICATIONS INFORMATION Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. Current Limit and Safe Operating Area Protection Like many IC power regulators, the LT3012 has safe operating area protection. The safe operating area protection decreases the current limit as the input voltage increases and keeps the power transistor in a safe operating region. The protection is designed to provide some output current at all values of input voltage up to the device breakdown (see curve of Current Limit vs Input Voltage in the Typical Performance Characteristics). The LT3012 is limited for operating conditions by maximum junction temperature. While 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. Device specifications will not apply for all possible combinations of input voltage and output current. Operating the LT3012 beyond the maximum junction temperature rating may impair the life of the device. Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature of (125°C for LT3012E, or 140°C for LT3012HFE). 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 GND pin current can be found by examining the GND Pin Current curves in the Typical Performance Characteristics. Power dissipation will be equal to the sum of the two components listed above. The LT3012 has internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions the maximum junction temperature rating of 125°C (E-Grade) or 140°C (H-Grade)must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. For surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Copper board stiffeners and plated through-holes can also be used to spread the heat generated by power devices. The following tables list 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. DFN Measured Thermal Resistance COPPER AREA TOPSIDE BOARD AREA THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 2500 sq mm 2500 sq mm 40°C/W 1000 sq mm 2500 sq mm 45°C/W 225 sq mm 2500 sq mm 50°C/W 100 sq mm 2500 sq mm 62°C/W Table 2. TSSOP Measured Thermal Resistance COPPER AREA TOPSIDE BOARD AREA THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 2500 sq mm 2500 sq mm 40°C/W 1000 sq mm 2500 sq mm 45°C/W 225 sq mm 2500 sq mm 50°C/W 100 sq mm 2500 sq mm 62°C/W The thermal resistance junction-to-case (θJC), measured at the exposed pad on the back of the die, is 16°C/W. Continuous operation at large input/output voltage differentials and maximum load current is not practical due to thermal limitations. Transient operation at high input/output differentials is possible. The approximate thermal time constant for a 2500sq mm 3/32" FR-4 board with maximum topside and backside area for one ounce copper is 3 seconds. This time constant will increase as more thermal mass is added (i.e., vias, larger board, and other components). 3012fd 10 LT3012 APPLICATIONS INFORMATION For an application with transient high power peaks, average power dissipation can be used for junction temperature calculations as long as the pulse period is significantly less than the thermal time constant of the device and board. Calculating Junction Temperature Example 1: Given an output voltage of 5V, an input voltage range of 24V to 30V, 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: P3(72V in, 5mA load) = 5mA • (72V – 5V) + (200μA • 72V) = 0.35W P4(72V in, 50mA load) = 50mA • (72V – 5V) + (1mA • 72V) = 3.42W Operation at the different power levels is as follows: 76% operation at P1, 19% for P2, 4% for P3, and 1% for P4. PEFF = 76%(0.23W) + 19%(2.20W) + 4%(0.35W) + 1%(3.42W) = 0.64W With a thermal resistance in the range of 40°C/W to 62°C/W, this translates to a junction temperature rise above ambient of 26°C to 38°C. IOUT(MAX) = 50mA High Temperature Operation VIN(MAX) = 30V Care must be taken when designing LT3012 applications to operate at high ambient temperatures. The LT3012 works at elevated temperatures but erratic operation can occur due to unforeseen variations in external components. Some tantalum capacitors are available for high temperature operation, but ESR is often several ohms; capacitor ESR above 3Ω is unsuitable for use with the LT3012. Ceramic capacitor manufacturers (Murata, AVX, TDK, and Vishay Vitramon at this writing) now offer ceramic capacitors that are rated to 150°C using an X8R dielectric. Device instability will occur if output capacitor value and ESR are outside design limits at elevated temperature and operating DC voltage bias (see information on capacitor characteristics under Output Capacitance and Transient Response). Check each passive component for absolute value and voltage ratings over the operating temperature range. IGND at (IOUT = 50mA, VIN = 30V) = 1mA So: P = 50mA • (30V – 5V) + (1mA • 30V) = 1.28W The thermal resistance will be in the range of 40°C/W to 62°C/W depending on the copper area. So the junction temperature rise above ambient will be approximately equal to: 1.31W • 50°C/W = 65.5°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 + 65.5°C = 115.5°C Example 2: Given an output voltage of 5V, an input voltage of 48V that rises to 72V for 5ms(max) out of every 100ms, and a 5mA load that steps to 50mA for 50ms out of every 250ms, what is the junction temperature rise above ambient? Using a 500ms period (well under the time constant of the board), power dissipation is as follows: P1(48V in, 5mA load) = 5mA • (48V – 5V) + (200μA • 48V) = 0.23W Leakages in capacitors or from solder flux left after insuficient board cleaning adversely affects low quiescent current operation. The output voltage resistor divider should use a maximum bottom resistor value of 124k to compensate for high temperature leakage, setting divider current to 10μA. Consider junction temperature increase due to power dissipation in both the junction and nearby components to ensure maximum specifications are not violated for the device or external components. P2(48V in, 50mA load) = 50mA • (48V – 5V) + (1mA • 48V) = 2.20W 3012fd 11 LT3012 APPLICATIONS INFORMATION The LT3012 incorporates several protection features which make it 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 device is protected against reverse-input voltages, and reverse voltages from output to input. Like many IC power regulators, the LT3012 has safe operating area protection. The safe area protection decreases the current limit as input voltage increases and keeps the power transistor inside a safe operating region for all values of input voltage. The protection is designed to provide some output current at all values of input voltage up to the device breakdown. The SOA protection circuitry for the LT3012 uses a current generated when the input voltage exceeds 25V to decrease current limit. This current shows up as additional quiescent current for input voltages above 25V. This increase in quiescent current occurs both in normal operation and in shutdown (see curve of Quiescent Current in the Typical Performance Characteristics). 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 (LT3012E) or 140°C (LT3012HFE). The input of the device will withstand reverse voltages of 80V. 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 ADJ pin of the 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. If the input is powered by a voltage source, pulling the ADJ pin below the reference voltage will cause the device to current limit. This will cause the output to go to a unregulated high voltage. Pulling the ADJ pin above the reference voltage will turn off all output current. 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 1.24V reference when the output is forced to 60V. 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 53V difference between the OUT and ADJ pins divided by the 5mA maximum current into the ADJ pin yields a minimum top resistor value of 10.6k. 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 4. The rise in reverse output current above 7V occurs from the breakdown of the 7V clamp on the ADJ pin. With a resistor divider on the regulator output, this current will be reduced depending on the size of the resistor divider. 200 REVERSE OUTPUT CURRENT (μA) Protection Features TJ = 25°C 180 VIN = 0V VOUT = VADJ 160 140 120 100 CURRENT FLOWS 80 INTO OUTPUT PIN ADJ PIN CLAMP (SEE ABOVE) 60 40 20 0 0 1 2 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 9 10 3012 F04 Figure 4. Reverse Output Current When the IN pin of the LT3012 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 LT3012 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. 3012fd 12 LT3012 TYPICAL APPLICATIONS 5V Buck Converter with Low Current Keep Alive Backup D2 D1N914 6 VIN 5.5V* TO 60V 4 C3 4.7μF 100V CERAMIC C2 0.33μF BOOST VIN SW 2 14 SHDN VOUT 5V 1A/250mA D1 10MQ060N LT1766 15 L1† 15μH BIAS SYNC FB GND 10 R1 15.4k 12 R2 4.99k VC + C1 100μF 10V SOLID TANTALUM 1, 8, 9, 16 11 CC 1nF 14 OPERATING CURRENT IN OUT 3 LT3012 11 SHDN LOW HIGH ADJ GND 5 3012 TA03 750k 249k 1 * FOR INPUT VOLTAGES BELOW 7.5V, SOME RESTRICTIONS MAY APPLY † INCREASE L1 TO 30μH FOR LOAD CURRENTS ABOVE 0.6A AND TO 60μH ABOVE 1A Buck Converter Efficiency vs Load Current 100 VOUT = 5V L = 68μH VIN = 10V EFFICIENCY (%) 90 VIN = 42V 80 70 60 50 0 0.25 0.75 1.00 0.50 LOAD CURRENT (A) 1.25 3012 TA04 3012fd 13 LT3012 TYPICAL APPLICATIONS LT3012 Automotive Application VIN 12V (LATER 42V) IN + 1μF NO PROTECTION DIODE NEEDED! OUT LT3012 SHDN 750k 3.3μF ADJ GND LOAD: CLOCK, SECURITY SYSTEM ETC 249k OFF ON LT3012 Telecom Application VIN 48V (72V TRANSIENT) IN 1μF OUT LT3012 SHDN + 750k NO PROTECTION DIODE NEEDED! ADJ GND 3.3μF LOAD: SYSTEM MONITOR ETC – BACKUP BATTERY 249k 3012 TA05 OFF ON Constant Brightness for Indicator LED over Wide Input Voltage Range RETURN IN 1μF OFF ON OUT LT3012 SHDN 3.3μF ADJ GND –48V ILED = 1.24V/RSET –48V CAN VARY FROM –4V TO –80V RSET 3012 TA06 3012fd 14 LT3012 PACKAGE DESCRIPTION DE Package 12-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695) 4.00 ±0.10 (2 SIDES) 7 0.70 ±0.05 3.60 ±0.05 2.20 ±0.05 PIN 1 TOP MARK PACKAGE (NOTE 6) OUTLINE 0.25 ± 0.05 0.40 ± 0.10 12 R = 0.05 TYP 3.30 ±0.05 1.70 ± 0.05 R = 0.115 TYP 0.200 REF 0.50 BSC 3.30 ±0.10 3.00 ±0.10 (2 SIDES) 1.70 ± 0.10 0.75 ±0.05 6 0.25 ± 0.05 1 PIN 1 NOTCH R = 0.20 OR 0.35 × 45° CHAMFER (UE12/DE12) DFN 0806 REV D 0.50 BSC 2.50 REF 2.50 REF BOTTOM VIEW—EXPOSED PAD 0.00 – 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED NOTE: 1. DRAWING PROPOSED TO BE A VARIATION OF VERSION (WGED) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE FE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation BB 4.90 – 5.10* (.193 – .201) 3.58 (.141) 3.58 (.141) 16 1514 13 12 1110 6.60 ±0.10 9 2.94 (.116) 4.50 ±0.10 2.94 6.40 (.116) (.252) BSC SEE NOTE 4 0.45 ±0.05 1.05 ±0.10 0.65 BSC 1 2 3 4 5 6 7 8 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.50 – 0.75 (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE 0.25 REF 1.10 (.0433) MAX 0° – 8° 0.65 (.0256) BSC 0.195 – 0.30 (.0077 – .0118) TYP 0.05 – 0.15 (.002 – .006) FE16 (BB) TSSOP 0204 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3012fd Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 15 LT3012 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1020 125mA, Micropower Regulator and Comparator VIN: 4.5V to 36V, VOUT(MIN) = 2.5V, VDO = 0.4V, IQ = 40μA, ISD = 40μA, Comparator and Reference, Class B Outputs, S16, PDIP14 Packages LT1120/LT1120A 125mA, Micropower Regulator and Comparator VIN: 4.5V to 36V, VOUT(MIN) = 2.5V, VDO = 0.4V, IQ = 40μA, ISD = 10μA, Comparator and Reference, Logic Shutdown, Ref Sources and Sinks 2/4mA, S8, N8 Packages LT1121/LT1121HV 150mA, Micropower, LDO VIN: 4.2V to 30/36V, VOUT(MIN) = 3.75V, VDO = 0.42V, IQ = 30μA, ISD = 16μA, Reverse Battery Protection, SOT-223, S8, Z Packages LT1129 700mA, Micropower, LDO VIN: 4.2V to 30V, VOUT(MIN) = 3.75V, VDO = 0.4V, IQ = 50μA, ISD = 16μA, DD, S0T-223, S8,TO220-5, TSSOP20 Packages LT1676 60V, 440mA (IOUT), 100kHz, High Efficiency Step-Down DC/DC Converter VIN: 7.4V to 60V, VOUT(MIN) = 1.24V, IQ = 3.2mA, ISD = 2.5μA, S8 Package LT1761 100mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.3V, IQ = 20μA, ISD = <1μA, Low Noise < 20μVRMS, Stable with 1μF Ceramic Capacitors, ThinSOT™ Package LT1762 150mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.3V, IQ = 25μA, ISD = <1μA, Low Noise < 20μVRMS, MS8 Package LT1763 500mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.3V, IQ = 30μA, ISD = <1μA, Low Noise < 20μVRMS, S8 Package LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDO VIN: 2.7V to 20V, VOUT(MIN) = 1.21V, VDO = 0.34V, IQ = 1mA, ISD = <1μA, Low Noise < 40μVRMS, “A” Version Stable with Ceramic Capacitors, DD, TO220-5 Packages LT1766 60V, 1.2A (IOUT), 200kHz, High Efficiency Step-Down DC/DC Converter VIN: 5.5V to 60V, VOUT(MIN) = 1.2V, IQ = 2.5mA, ISD = 25μA, TSSOP16/E Package LT1776 40V, 550mA (IOUT), 200kHz, High Efficiency Step-Down DC/DC Converter VIN: 7.4V to 40V, VOUT(MIN) = 1.24V, IQ = 3.2mA, ISD = 30μA, N8, S8 Packages LT1934/LT1934-1 300mA/60mA, (IOUT), Constant Off-Time, High Efficiency Step-Down DC/DC Converter 90% Efficiency, VIN: 3.2V to 34V, VOUT(MIN) = 1.25V, IQ = 14μA, ISD = <1μA, ThinSOT Package LT1956 60V, 1.2A (IOUT), 500kHz, High Efficiency Step-Down DC/DC Converter VIN: 5.5V to 60V, VOUT(MIN) = 1.2V, IQ = 2.5mA, ISD = 25μA, TSSOP16/E Package LT1962 300mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.27V, IQ = 30μA, ISD = <1μA, Low Noise < 20μVRMS, MS8 Package LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDO VIN: 2.1V to 20V, VOUT(MIN) = 1.21V, VDO = 0.34V, IQ = 1mA, ISD = <1μA, Low Noise < 40μVRMS, “A” Version Stable with Ceramic Capacitors, DD, TO220-5, S0T-223, S8 Packages LT1964 200mA, Low Noise Micropower, Negative LDO VIN: –1.9V to –20V, VOUT(MIN) = –1.21V, VDO = 0.34V, IQ = 30μA, ISD = 3μA, Low Noise < 30μVRMS, Stable with Ceramic Capacitors, ThinSOT Package LT3010/LT3010H 50mA, 3V to 80V, Low Noise Micropower LDO VIN: 3V to 8V, VOUT(MIN) = 1.275V, VDO = 0.3V, IQ = 30μA, ISD = 1μA, Low Noise < 100μVRMS, MS8E Package, H Grade = +140°C TJMAX. LT3013/LT3013H 250mA, 4V to 80V, Low Dropout Micropower Linear Regulator with PWRGD VIN: 4V to 80V, VOUT: 1.24V to 60V, VDO = 0.4V, IQ = 65μA, ISD = <1μA, Power Good Feature; TSSOP-16E and 4mm × 3mm DFN-12 Packages, H Grade = +140°C TJMAX. LT3014/HV 20mA, 3V to 80V, Low Dropout Micropower Linear Regulator VIN: 3V to 80V (100V for 2ms, HV version), VOUT: 1.22V to 60V, VDO = 0.35V, IQ = 7μA, ISD = <1μA, ThinSOT and 3mm × 3mm DFN-8 Packages. ThinSOT is a trademark of Linear Technology Corporation. 3012fd 16 Linear Technology Corporation LT 0508 REV D • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005