LT1529 LT1529-3.3/LT1529-5 3A Low Dropout Regulators with Micropower Quiescent Current and Shutdown DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Dropout Voltage: 0.6V at IOUT = 3A Output Current: 3A Quiescent Current: 50µA No Protection Diodes Needed Adjustable Output from 3.8V to 14V 3.3V and 5V Fixed Output Voltages Controlled Quiescent Current in Dropout Shutdown IQ = 16µA Stable with 3.3µF Output Capacitor Reverse Battery Protection No Reverse Current Thermal Limiting The LT ®1529/LT1529-3.3/LT1529-5 are 3A low dropout regulators with micropower quiescent current and shutdown. The devices are capable of supplying 3A of output current with a dropout voltage of 0.6V. Designed for use in battery-powered systems, the low quiescent current, 50µA operating and 16µA in shutdown, make them an ideal choice. The quiescent current is well controlled; it does not rise in dropout as it does with many other low dropout PNP regulators. Other features of the LT1529 /LT1529-3.3/LT1529-5 include the ability to operate with small output capacitors. They are 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, enhancing manufacturabiltiy. Also the input may be connected to voltages lower than the output voltage, including negative voltages, without reverse current flow from output to input. This makes the LT1529/LT1529-3.3/LT1529-5 ideal for backup power situations where the output is held high and the input is at ground or reversed. Under these conditions, only 16µA will flow from the OUTPUT pin to ground. The devices are available in 5-lead TO-220 and 5-lead DD packages. U APPLICATIO S ■ ■ ■ ■ High Efficiency Regulator Regulator for Battery-Powered Systems Post Regulator for Switching Supplies 5V to 3.3V Logic Regulator , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO Dropout Voltage 0.6 5V Supply with Shutdown VIN > 5.5V VIN OUTPUT 1 + LT1529-5 4 SHDN SENSE 2 3.3µF SOLID TANT GND 3 5V 3A DROPOUT VOLTAGE (V) 5 0.5 0.4 0.3 0.2 0.1 VSHDN (PIN 4) < 0.25 > 2.8 NC OUTPUT OFF ON ON 0 LT1529 • TA01 0 0.5 1.0 1.5 2.0 OUTPUT CURRENT (A) 2.5 3.0 LT1529 • TA02 1 LT1529 LT1529-3.3/LT1529-5 W W W AXI U U ABSOLUTE RATI GS (Note 1) Input Voltage ...................................................... ±15V* OUTPUT Pin Reverse Current .............................. 10mA SENSE Pin Current .............................................. 10mA ADJ Pin Current ................................................... 10mA SHDN Pin Input Voltage (Note 2) .............. 6.5V, – 0.6V SHDN Pin Input Current (Note 2) .......................... 5mA Output Short-Circuit Duration ......................... Indefinite Storage Temperature Range ................ – 65°C to 150°C Operating Junction Temperature Range Commercial .......................................... 0°C to 125°C Industrial ......................................... – 45°C to 125°C Lead Temperature (Soldering, 10 sec).................. 300°C *For applications requiring input voltage ratings greater than 15V, contact the factory. W U U PACKAGE/ORDER I FOR ATIO FRONT VIEW 5 4 3 2 1 TAB IS GND VIN SHDN GND SENSE/ADJ* OUTPUT Q PACKAGE 5-LEAD PLASTIC DD PAK *PIN 2 = SENSE FOR LT1529-3.3/LT1529-5 = ADJ FOR LT1529 ORDER PART NUMBER LT1529CQ LT1529CQ-3.3 LT1529CQ-5 LT1529IQ LT1529IQ-3.3 LT1529IQ-5 TJMAX = 125°C, θJA ≈ 30°C/ W FRONT VIEW 5 4 3 2 1 TAB IS GND VIN SHDN GND SENSE/ADJ* OUTPUT T PACKAGE 5-LEAD PLASTIC TO-220 *PIN 2 = SENSE FOR LT1529-3.3/LT1529-5 = ADJ FOR LT1529 ORDER PART NUMBER LT1529CT LT1529CT-3.3 LT1529CT-5 LT1529IT LT1529IT-3.3 LT1529IT-5 TJMAX = 125°C, θJA ≈ 50°C/ W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3) PARAMETER CONDITIONS Regulated Output Voltage (Note 4) LT1529-3.3 MIN TYP MAX UNITS ● 3.250 3.200 3.300 3.300 3.350 3.400 V V VIN = 5.5V, IOUT = 1mA, TJ = 25°C 6V < VIN < 15V, 1mA < IOUT < 3A ● 4.925 4.850 5.000 5.000 5.075 5.150 V V VIN = 4.3V, IOUT = 1mA, TJ = 25°C 4.8V < VIN < 15V, 1mA < IOUT < 3A ● 3.695 3.640 3.750 3.750 3.805 3.860 V V LT1529-3.3 ∆VIN = 3.8V to 15V, IOUT = 1mA ● 1.5 10 mV LT1529-5 ∆VIN = 5.5V to 15V, IOUT = 1mA ∆VIN = 4.3V to 15V, IOUT = 1mA ● 1.5 10 mV LT1529-5 LT1529 (Note 5) Line Regulation LT1529 (Note 5) Load Regulation LT1529-3.3 LT1529-5 LT1529 (Note 5) Dropout Voltage (Note 6) 2 VIN = 3.8V, IOUT = 1mA, TJ = 25°C 4.3V < VIN < 15V, 1mA < IOUT < 3A ● 1.5 10 mV ∆ILOAD = 1mA to 3A, VIN = 4.3V, TJ = 25°C ∆ILOAD = 1mA to 3A, VIN = 4.3V ● 5 12 20 30 mV mV ∆ILOAD = 1mA to 3A, VIN = 6V, TJ = 25°C ∆ILOAD = 1mA to 3A, VIN = 6V ● 5 12 20 30 mV mV ∆ILOAD = 1mA to 3A, VIN = 4.8V, TJ = 25°C ∆ILOAD = 1mA to 3A, VIN = 4.8V ● 5 12 20 30 mV mV 110 180 250 mV mV 200 300 400 mV mV ILOAD = 10mA, TJ = 25°C ILOAD = 10mA ● ILOAD = 100mA, TJ = 25°C ILOAD = 100mA ● LT1529 LT1529-3.3/LT1529-5 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3) PARAMETER Dropout Voltage (Note 6) GND Pin Current (Note 7) ADJ Pin Bias Current (Notes 5, 9) Shutdown Threshold SHDN Pin Current (Note 10) Quiescent Current in Shutdown (Note 11) Ripple Rejection Current Limit Input Reverse Leakage Current Reverse Output Current (Note 12) CONDITIONS ILOAD = 700mA, TJ = 25°C ILOAD = 700mA ILOAD = 1.5A, TJ = 25°C ILOAD = 1.5A ILOAD = 3A, TJ = 25°C ILOAD = 3A ILOAD = 0mA, TJ = 25°C ILOAD = 0mA, TJ = 125°C (Note 8) ILOAD = 100mA, TJ = 25°C ILOAD = 100mA, TJ = 125°C (Note 8) ILOAD = 700mA ILOAD = 1.5A ILOAD = 3A TJ = 25°C VOUT = Off to On VOUT = On to Off VSHDN = 0V VIN = VOUT (Nominal) + 1V, VSHDN = 0V VIN – VOUT = 1V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 1.5A VIN – VOUT = 7V, TJ = 25°C VIN = VOUT (Nominal) + 1.5V, ∆VOUT = – 0.1V VIN = – 15V, VOUT = 0V LT1529-3.3 VOUT = 3.3V, VIN = 0V LT1529-5 VOUT = 5V, VIN = 0V LT1529 (Note 6) VOUT = 3.8V, VIN = 0V Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The SHDN pin input voltage rating is required for a low impedance source. Internal protection devices connected to the SHDN pin will turn on and clamp the pin to approximately 7V or – 0.6V. This range allows the use of 5V logic devices to drive the pin directly. For high impedance sources or logic running on supply voltages greater than 5.5V, the maximum current driven into the SHDN pin must be limited to less than 5mA. Note 3: The device is tested under pulse load conditions such that TJ = TA. Note 4: Operating conditions are limited by maximum junction temperature. The regulated output voltage specification will not apply for all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range must be limited. When operating at maximum output current the input voltage range must be limited. Note 5: The LT1529 is tested and specified with the ADJ pin connected to the OUTPUT pin. Note 6: Dropout voltage is the minimum input/output voltage required to maintain regulation at the specified output current. In dropout the output voltage will be equal to (VIN – VDROPOUT). MIN TYP 320 ● 430 ● 600 ● ● ● ● ● ● 0.25 ● ● ● 50 400 0.6 1.0 5.5 20 80 150 1.20 0.75 4.5 15 MAX 430 550 550 700 750 950 100 1.0 12 40 160 300 2.8 10 30 UNITS mV mV mV mV mV mV µA µA mA mA mA mA mA nA V V µA µA 50 62 dB 3.2 5 4.7 A A mA µA µA µA 1.0 ● 16 16 16 Note 7: GND pin current is tested with VIN = VOUT (nominal) and a current source load. This means that the device is tested while operating in its dropout region. This is the worst-case GND pin current. The GND pin current will decrease slightly at higher input voltages. Note 8: GND pin current will rise at TJ > 75°C. This is due to internal circuitry designed to compensate for leakage currents in the output transistor at high temperatures. This allows quiescent current to be minimized at lower temperatures, yet maintain output regulation at high temperatures with light loads. See quiescent current curve in typical performance characteristics. Note 9: ADJ pin bias current flows into the ADJ pin. Note 10: SHDN pin current at VSHDN = 0V flows out of the SHDN pin. Note 11: Quiescent current in shutdown is equal to the sum total of the SHDN pin current (5µA) and the GND pin current (10µA). Note 12: Reverse output current is tested with the VIN pin grounded and the OUTPUT pin forced to the rated output voltage. This current flows into the OUTPUT pin and out of the GND pin. 3 LT1529 LT1529-3.3/LT1529-5 U W TYPICAL PERFOR A CE CHARACTERISTICS Dropout Voltage 0.8 0.9 0.7 DROPOUT VOLTAGE (V) 0.7 0.6 0.5 0.4 0.3 A: ILOAD = 3A E: ILOAD = 100mA B: ILOAD = 1.5A F: ILOAD = 10mA C: ILOAD = 700mA D: ILOAD = 300mA A 0.6 VIN = 6V RL = ∞ 0.5 B 0.4 C 0.3 D 0.2 E 0.2 0 0.5 2.5 1.5 2.0 1.0 OUTPUT CURRENT (A) 0 – 50 – 25 3.0 0 50 75 25 TEMPERATURE (°C) 100 LT1529-3.3 Quiescent Current QUIESCENT CURRENT (µA) 175 150 VSHDN = OPEN (HIGH) 125 100 75 50 VSHDN = 0V 25 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 9 150 VSHDN = OPEN (HIGH) 125 100 75 50 VSHDN = 0V 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) LT1529 • G04 200 175 150 100 75 50 8 9 0 10 5.050 3.800 ADJ PIN VOLTAGE (V) 3.350 OUTPUT VOLTAGE (V) 3.825 5.025 5.000 4.975 4.950 4.925 75 50 25 TEMPERATURE (°C) 100 125 LT1529 • G07 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 ILOAD = 1mA 5.075 0 2 3.850 3.375 3.200 – 50 – 25 1 LT1529 ADJ Pin Voltage ILOAD = 1mA 3.225 0 LT1529 • G06 5.100 3.250 VSHDN = 0V 25 LT1529 • G05 ILOAD = 1mA 3.275 VSHDN = OPEN (HIGH) 125 LT1529-5 Output Voltage 3.300 ILOAD = 0 RL = ∞ VOUT = VADJ 225 175 LT1529-3.3 Output Voltage 125 LT1529 Quiescent Current 200 0 10 3.325 100 250 25 8 50 25 0 75 TEMPERATURE (°C) LT1529 • G03 ILOAD = 0 RL = ∞ 225 200 4 VSHDN = 0V 0 – 50 – 25 125 250 ILOAD = 0 RL = ∞ 225 QUIESCENT CURRENT (µA) VSHDN = OPEN 50 LT1529-5 Quiescent Current 250 OUTPUT VOLTAGE (V) 100 LT1529 • G02 LT1529 • G01 3.400 150 F = TEST POINT 0 0 200 0.1 0.1 QUIESCENT CURRENT (µA) DROPOUT VOLTAGE (V) 0.8 Quiescent Current 250 QUIESCENT CURRENT (µA) Guaranteed Dropout Voltage 1.0 4.900 –50 –25 3.775 3.750 3.725 3.700 3.675 75 50 25 TEMPERATURE (˚C) 0 100 125 LT1529 • G08 3.650 – 50 – 25 75 50 25 TEMPERATURE (°C) 0 100 125 LT1529 • G09 LT1529 LT1529-3.3/LT1529-5 U W TYPICAL PERFOR A CE CHARACTERISTICS LT1529-5 GND Pin Current LT1529-3.3 GND Pin Current RLOAD = 6.6Ω ILOAD = 500mA* 3.5 3.0 RLOAD = 330Ω ILOAD = 10mA* 2.5 2.0 RLOAD = 11Ω ILOAD = 300mA* 1.5 RLOAD = 33Ω ILOAD = 100mA* 1.0 3.5 2.5 1.5 RLOAD = 50Ω ILOAD = 100mA* 1.0 0.5 0 2 RLOAD = 16.6Ω ILOAD = 300mA* 2.0 0 1 RLOAD = 500Ω ILOAD = 10mA* 3.0 0.5 0 3 4 5 6 7 INPUT VOLTAGE (V) 9 8 10 RLOAD = 10Ω ILOAD = 500mA* 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 100 80 60 50 RLOAD = 4.7Ω ILOAD = 700mA* 40 30 RLOAD = 2.2Ω ILOAD = 1.5A* 20 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 9 8 50 30 0 RLOAD = 3.3Ω ILOAD = 1.5A* TJ = 125°C 40 TJ = – 50°C 30 30 0 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 LT1529 • G16 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 SHDN Pin Threshold (Off-to-On) 2.0 ILOAD = 1mA 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0 – 50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 LT1529 • G17 ILOAD = 3A 1.4 1.2 1.0 ILOAD = 1mA 0.8 0.6 0.2 3.0 RLOAD = 2.5Ω ILOAD = 1.5A* LT1529 • G15 0.4 2.5 RLOAD = 5.3Ω ILOAD = 700mA* 40 0.2 1.5 2.0 1.0 OUTPUT CURRENT (A) RLOAD = 1.25Ω ILOAD = 3A* 50 0.4 0.5 10 60 10 0 9 70 20 0 8 10 1.6 50 3 4 5 6 7 INPUT VOLTAGE (V) LT1529 • G14 1.8 TJ = 25°C 60 2 20 SHDN THRESHOLD (V) 70 1 TJ = 25°C 90 VOUT = VADJ *FOR VOUT = 3.75V 80 RLOAD = 1.7Ω ILOAD = 3A* 2.0 80 0 LT1529 • G12 SHDN Pin Threshold (On-to-Off) VIN = 3.75V (LT1529) VIN = 3.3V (LT1529-3.3) VIN = 5V (LT1529-5) DEVICE IS OPERATING IN DROPOUT RLOAD = 38Ω ILOAD = 100mA* 100 40 10 SHDN THRESHOLD (V) GND PIN CURRENT (mA) 10 RLOAD = 7.1Ω ILOAD = 700mA* 60 GND Pin Current 90 1.5 LT1529 GND Pin Current LT1529 • G13 100 RLOAD = 12.5Ω ILOAD = 300mA* 2.0 0.5 10 0 2.5 1.0 70 20 10 0 TJ = 25°C VOUT = VSENSE *FOR VOUT = 5V 90 GND PIN CURRENT (mA) GND PIN CURRENT (mA) 70 RLOAD = 375Ω ILOAD = 10mA* 3.0 LT1529-5 GND Pin Current TJ = 25°C *FOR VOUT = 3.3V VOUT = VSENSE RLOAD = 1.1Ω ILOAD = 3A* 80 9 RLOAD = 7.5Ω ILOAD = 500mA* LT1529 • G11 LT1529-3.3 GND Pin Current 90 TJ = 25°C 4.5 VOUT = VADJ *FOR VOUT = 4.0 3.75V 3.5 0 0 LT1529 • G10 100 GND PIN CURRENT (mA) GND PIN CURRENT (mA) 4.0 TJ = 25°C 4.5 VOUT = VSENSE *FOR VOUT = 5V 4.0 GND PIN CURRENT (mA) 4.5 5.0 5.0 TJ = 25°C VOUT = VSENSE *FOR VOUT = 3.3V GND PIN CURRENT (mA) 5.0 LT1529 GND Pin Current 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 LT1529 • G18 5 LT1529 LT1529-3.3/LT1529-5 U W TYPICAL PERFOR A CE CHARACTERISTICS SHDN Pin Input Current SHDN Pin Current 10 VSHDN = 0V VADJ = VOUT = 3.75V 450 8 7 6 5 4 3 2 20 ADJ PIN BIAS CURRENT (nA) SHDN PIN INPUT CURRENT (mA) SHDN PIN CURRENT (µA) 9 ADJ Pin Bias Current 500 25 15 10 5 400 350 300 250 200 150 100 50 1 0 – 50 –25 50 25 0 75 TEMPERATURE (°C) 100 0 –50 –25 0 125 0 1 2 7 3 5 6 4 SHDN PIN VOLTAGE (V) LT1529 • G19 8 9 Reverse Output Current Current Limit 6 VIN = 7V VOUT = 0V VOUT = 0V 50 25 5 SHORT-CIRCUIT CURRENT (A) SHORT-CIRCUIT CURRENT (A) 4 3 2 1 0 0 – 50 – 25 50 25 75 0 TEMPERATURE (°C) 100 125 0 1 4 3 5 2 INPUT VOLTAGE (V) Reverse Output Current TJ = 25°C, VIN = 0V VOUT = VSENSE (LT1529-3.3/LT1529-5) VOUT = VADJ (LT1529) CURRENT FLOWS INTO DEVICE 60 60 RIPPLE REJECTION (dB) OUTPUT CURRENT (µA) 70 LT1529 50 40 30 LT1529-3.3 20 0 1 2 1 50 25 75 0 TEMPERATURE (°C) 100 125 LT1529 • G24 Ripple Rejection (VIN – VOUT)AVG = 1V VRIPPLE = 0.5VP-P ILOAD = 1.5A f = 120Hz 58 56 54 52 IOUT = 1.5A VIN = VOUT (NOMINAL) + 1 + 50mVRMS RIPPLE 90 80 70 COUT = 47µF SOLID TANT 60 50 40 COUT = 3.3µF SOLID TANT 30 20 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 9 10 LT1529 • G25 6 2 100 50 LT1529-5 10 3 0 – 50 – 25 7 62 80 4 Ripple Rejection 100 90 5 LT1529 • G23 LT1529 • G22 0 6 RIPPLE REJECTION (dB) OUTPUT CURRENT (µA) 75 125 Current Limit 6 100 100 LT1529 • G21 LT1529 • G20 150 125 50 25 0 75 TEMPERATURE (°C) 48 – 50 – 25 10 0 50 25 75 0 TEMPERATURE (°C) 100 125 LT1529 • G26 10 100 1k 10k FREQUENCY (Hz) 100k LT1529 • G27 LT1529 LT1529-3.3/LT1529-5 U W TYPICAL PERFOR A CE CHARACTERISTICS Load Regulation LT1529-5 Transient Response LT1529-5 Transient Response 5 –10 –15 –20 VIN = VOUT (NOMINAL) + 1V ∆ILOAD = 100mA to 3A VADJ = VOUT –25 – 50 – 25 50 25 75 0 TEMPERATURE (°C) 100 125 0.1 VIN = 6V CIN = 3.3µF TANT COUT = 47µF TANT OUTPUT VOLTAGE DEVIATION (V) LT1529-3.3 LT1529 –5 LOAD CURRENT (A) LOAD REGULATION (mV) 0 0.2 0 – 0.1 – 0.2 3 2 1 0.1 0 – 0.1 – 0.2 3 2 1 0 100 200 300 400 500 600 700 800 900 1000 TIME (µs) LT1529 • G28 VIN = 6V CIN = 10µF TANT COUT = 4.7µF TANT 0.2 LOAD CURRENT (A) OUTPUT VOLTAGE DEVIATION (V) LT1529-5 0 20 40 60 80 100 120 140 160 180 200 TIME (µs) LT1529 • G29 LT1529 • G30 U U U PI FU CTIO S OUTPUT (Pin 1): OUTPUT Pin. The OUTPUT pin supplies power to the load. A minimum output capacitor of 3.3µF is required to prevent oscillations. Larger values will be required to optimize transient response for large load current deltas. See the Applications Information section for further information on output capacitance and reverse output characteristics. SENSE (Pin 2): SENSE Pin. For fixed voltage versions of the LT1529 (LT1529-3.3, LT1529-5) the SENSE pin is the input to the error amplifier. Optimum regulation will be obtained at the point where the SENSE pin is connected to the output pin. For most applications the SENSE pin is connected directly to the OUTPUT pin at the regulator. In critical applications small voltage drops caused by the resistance (RP) of PC traces between the regulator and the load, which would normally degrade regulation, may be eliminated by connecting the SENSE pin to the OUTPUT pin at the load as shown in Figure 1 (Kelvin Sense Connection). Note that the voltage drop across the external PC traces will add to the dropout voltage of the regulator. The SENSE pin bias current is 15µA at the nominal regulated output voltage. This pin is internally clamped to – 0.6V (one VBE). ADJ (Pin 2): Adjust Pin. For the LT1529 (adjustable version) the ADJ pin is the input to the error amplifier. This 5 VIN OUTPUT 1 RP LT1529-5 + VIN 4 SHDN SENSE 2 + LOAD GND 3 RP LT1529 • F01 Figure 1. Kelvin Sense Connection pin is internally clamped to 6V and – 0.6V (one VBE). This pin has a bias current of 150nA which flows into the pin. See Bias Current curve in the Typical Performance Characteristics. The ADJ pin reference voltage is equal to 3.75V referenced to ground. SHDN (Pin 4): Shutdown Pin. This pin is used to put the device into shutdown. In shutdown the output of the device is turned off. This pin is active low. The device will be shut down if the SHDN pin is actively pulled low. The SHDN pin current with the pin pulled to ground will be 6µA. The SHDN pin is internally clamped to 7V and – 0.6V (one VBE). This allows the SHDN pin to be driven directly by 5V logic or by open-collector logic with a pull-up resistor. The pull-up resistor is only required to supply the leakage current of the open-collector gate, normally several microamperes. Pull-up current must be limited to a maximum of 5mA. A curve of SHDN pin input current as a 7 LT1529 LT1529-3.3/LT1529-5 U U U PI FU CTIO S function of voltage appears in the Typical Performance Characteristics. If the SHDN pin is not used it can be left open circuit. The device will be active, output on, if the SHDN pin is not connected. VIN (Pin 5): Input Pin. Power is supplied to the device through the VIN pin. The VIN pin should be bypassed to ground 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 U W U UO APPLICATI S I FOR ATIO The LT1529 is a 3A low dropout regulator with micropower quiescent current and shutdown capable of supplying 3A of output current at a dropout voltage of 0.6V. The device operates with very low quiescent current (50µA). In shutdown the quiescent current drops to only 16µA. In addition to the low quiescent current the LT1529 incorporates several protection features which make it ideal for use in battery-powered systems. The device is protected against reverse input voltages. In battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the LT1529 acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The adjustable version of the LT1529 has an output voltage range of 3.75V to 14V. The output voltage is set by the ratio of two external resistors as shown in Figure 2. The device servos the output voltage to maintain the voltage at the ADJ pin at 3.75V. The current in R1 is then equal to 3.75V/R1. The current in R2 is equal to the sum of the current in R1 and the ADJ pin bias current. The ADJ pin bias current, 150nA at 25°C, flows through R2 into the ADJ pin. The output voltage can be calculated according to the formula in Figure 2. The value of R1 should be less than 400k to minimize errors in the output voltage caused by the ADJ pin bias current. Note that in shutdown the output is turned off and the divider current will be zero. Curves of ADJ Pin Voltage vs Temperature and ADJ Pin 8 include a bypass capacitor in battery-powered circuits. A bypass capacitor in the range of 1µF to 10µF is sufficient. The LT1529 is designed to withstand reverse voltages on the VIN pin with respect to ground and OUTPUT pin. In the case of a reversed input, which can happen if a battery is plugged in backwards, the LT1529 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT1529 and no reverse voltage will appear at the load. The device will protect both itself and the load. 5 VIN VIN OUTPUT 1 LT1529 4 SHDN SENSE GND R2 + VOUT 2 R1 3 ( ) LT1529 • F02 VOUT = 3.75V 1 + R2 + (IADJ × R2) R1 VADJ = 3.75V IADJ = 150nA AT 25°C OUTPUT RANGE = 3.3V TO 14V Figure 2. Adjustable Operation Bias Current vs Temperature appear in the Typical Performance Characteristics. The reference voltage at the ADJ pin has a positive temperature coefficient of approximately 15ppm/°C. The ADJ pin bias current has a negative temperature coefficient. These effects will tend to cancel each other. The adjustable device is specified with the ADJ pin tied to the OUTPUT pin. This sets the output voltage to 3.75V. Specifications for output voltage greater than 3.75V will be proportional to the ratio of the desired output voltage to 3.75V (VOUT/3.75V). For example: load regulation for an output current change of 1mA to 3A is – 0.5mV typical at VOUT = 3.75V. At VOUT = 12V, load regulation would be: 12V ( – 0.5 mV) = ( –1.6mV ) 3.75V LT1529 LT1529-3.3/LT1529-5 U W U UO APPLICATI S I FOR ATIO Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature (125°C). The power dissipated by the device will be made up of two components: 1. Output current multiplied by the input/output voltage differential: IOUT • (VIN – VOUT), and 2. Ground 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. tance. The thermal resistance for each application will be affected by thermal interactions with other components as well as board size and shape. Some experimentation will be necessary to determine the actual value. Table 1. Q Package, 5-Lead DD COPPER AREA TOPSIDE* BACKSIDE THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 2500 sq. mm 25°C/W 125 sq. mm 2500 sq. mm 33°C/W 2500 sq. mm 23°C/W * Device is mounted on topside. T Package, 5-Lead TO-220 Thermal Resistance (Junction-to-Case) = 2.5°C/W The LT1529 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal load conditions the maximum junction temperature rating of 125°C must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. Calculating Junction Temperature For surface mount devices heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Experiments have shown that the heat spreading copper layer does not need to be electrically connected to the tab of the device. The PC material can be very effective at transmitting heat between the pad area, attached to the tab of the device, and a ground or power plane layer either inside or on the opposite side of the board. Although the actual thermal resistance of the PC material is high, the length/area ratio of the thermal resistor between layers is small. Copper board stiffeners and plated through-holes can also be used to spread the heat generated by power devices. where, IOUT(MAX) = 500mA VIN(MAX) = 5.5V IGND at (IOUT = 500mA, VIN = 5.5V) = 3.6mA The following tables list thermal resistances for each package. For the TO-220 package, thermal resistance is given for junction-to-case only since this package is usually mounted to a heat sink. Measured values of thermal resistance for several different copper areas are listed for the DD package. All measurements were taken in still air on 3/32" FR-4 board with 1-oz copper. This data can be used as a rough guideline in estimating thermal resis- Example: Given an output voltage of 3.3V, an input voltage range of 4.5V to 5.5V, an output current range of 0mA to 500mA, 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)) so, P = 500mA • (5.5V – 3.3V) + (3.6mA • 5.5V) = 1.12W If we use a DD package, then the thermal resistance will be in the range of 23°C/W to 33°C/W depending on copper area. So the junction temperature rise above ambient will be approximately equal to: 1.12W • 28°C/W = 31.4°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 + 31.4°C = 81.4°C Output Capacitance and Transient Performance The LT1529 is designed to be stable with a wide range of output capacitors. The minimum recommended value is 3.3µF with an ESR of 2Ω or less. The LT1529 is a 9 LT1529 LT1529-3.3/LT1529-5 U W U UO APPLICATI S I FOR ATIO micropower device and output transient response will be a function of output capacitance. See the Transient Response curves in the Typical Performance Characteristics. Larger values of output capacitance will decrease the peak deviations and provide improved output transient response for larter load current deltas. Bypass capacitors, used to decouple individual components powered by the LT1529, will increase the effective value of the output capacitor. Protection Features The LT1529 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. 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. OUTPUT pin of an adjustable device, or the SENSE pin of a fixed voltage device, is pulled below ground, with the input open or grounded, current must be limited to less than 5mA. 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 vary depending on the conditions. Many battery-powered circuits incorporate some form of power management. The following information will help optimize battery life. Table 2 summarizes the following information. The reverse output current will follow the curve in Figure 3 when the input is pulled to ground. This current flows through the device to ground. The state of the SHDN pin will have no effect on output current when the VIN pin is pulled to ground. 100 TJ = 25°C, VIN = 0V VOUT = VSENSE (LT1529-3.3/LT1529-5) VOUT = VADJ (LT1529) CURRENT FLOWS INTO DEVICE 90 For fixed voltage versions of the device, the SENSE pin is internally clamped to one diode drop below ground. For the adjustable version of the device, the OUTPUT pin is internally clamped at one diode drop below ground. If the OUTPUT CURRENT (µA) 80 The input of the device will withstand reverse voltages of 15V. Current flow into the device will be limited to less than 1mA (typically less than 100µA) and no negative voltage will appear at the output. The device will protect both itself and the load. This provides protection against batteries that can be plugged in backwards. 70 60 LT1529 50 40 30 LT1529-3.3 20 LT1529-5 10 0 0 1 2 3 4 5 6 7 8 OUTPUT VOLTAGE (V) 9 10 LT1529 • F03 Figure 3. Reverse Output Current Table 2. Fault Conditions VIN PIN SHDN PIN < VOUT (Nominal) Open (High) Forced to VOUT (Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4) < VOUT (Nominal) Grounded Forced to VOUT (Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4) Open Open (High) > 1V Reverse Output Current ≈ 15µA Peak (See Figure 3) Open Grounded > 1V Reverse Output Current ≈ 15µA (See Figure 3) ≤ 0.8V Open (High) ≤ 0V Output Current = 0 ≤ 0.8V Grounded ≤ 0V Output Current = 0 >1.5V Open (High) ≤ 0V Output Current = Short-Circuit Current – 15V < VIN < 15V Grounded ≤0V Output Current = 0 10 OUTPUT/SENSE PINS LT1529 LT1529-3.3/LT1529-5 W U U UO S I FOR ATIO In some applications it may be necessary to leave the input to the LT1529 unconnected when the output is held high. This can happen when the LT1529 is powered from a rectified AC source. If the AC source is removed, then the input of the LT1529 is effectively left floating. The reverse output current also follows the curve in Figure 3 if the VIN pin is left open. The state of the SHDN pin will have no effect on the reverse output current when the VIN pin is floating. will typically drop to less than 2µA (see Figure 4). The state of the SHDN pin will have no effect on the reverse output current when the output is pulled above the input. 5 VOUT = 3.3V (LT1529-3.3) VOUT = 5V (LT1529-5) 4 INPUT CURRENT (µA) APPLICATI When the input of the LT1529 is forced to a voltage below its nominal output voltage and its output is held high, the output current will follow the curve shown in Figure 3 . This can happen if the input of the LT1529 is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or by a second regulator circuit. When the VIN pin is forced below the OUTPUT pin or the OUTPUT pin is pulled above the VIN pin, the input current U PACKAGE DESCRIPTIO LT1529-3.3 LT1529-5 3 2 1 0 0 1 3 2 INPUT VOLTAGE (V) 4 5 LT1529 • F04 Figure 4. Input Current Dimensions in inches (millimeters) unless otherwise noted. Q Package 5-Lead Plastic DD Pak (LTC DWG # 05-08-1461) 0.256 (6.502) 0.060 (1.524) TYP 0.060 (1.524) 0.390 – 0.415 (9.906 – 10.541) 0.165 – 0.180 (4.191 – 4.572) 15° TYP 0.060 (1.524) 0.183 (4.648) 0.059 (1.499) TYP 0.330 – 0.370 (8.382 – 9.398) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK ( +0.008 0.004 –0.004 +0.203 0.102 –0.102 ) 0.095 – 0.115 (2.413 – 2.921) 0.075 (1.905) 0.300 (7.620) 0.045 – 0.055 (1.143 – 1.397) ( +0.012 0.143 –0.020 +0.305 3.632 –0.508 ) 0.057 – 0.077 (1.447 – 1.955) 0.028 – 0.038 (0.711 – 0.965) 0.013 – 0.023 (0.330 – 0.584) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of circuits as described herein will not infringe on existing patent rights. 0.050 ± 0.012 (1.270 ± 0.305) Q(DD5) 0396 11 LT1529 LT1529-3.3/LT1529-5 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. T Package 5-Lead Plastic TO-220 (Standard) (LTC DWG # 05-08-1421) 0.390 – 0.415 (9.906 – 10.541) 0.165 – 0.180 (4.191 – 4.572) 0.147 – 0.155 (3.734 – 3.937) DIA 0.045 – 0.055 (1.143 – 1.397) 0.230 – 0.270 (5.842 – 6.858) 0.460 – 0.500 (11.684 – 12.700) 0.570 – 0.620 (14.478 – 15.748) 0.330 – 0.370 (8.382 – 9.398) 0.620 (15.75) TYP 0.700 – 0.728 (17.78 – 18.491) 0.095 – 0.115 (2.413 – 2.921) 0.152 – 0.202 0.260 – 0.320 (3.861 – 5.131) (6.60 – 8.13) 0.013 – 0.023 (0.330 – 0.584) 0.057 – 0.077 (1.448 – 1.956) 0.028 – 0.038 (0.711 – 0.965) 0.135 – 0.165 (3.429 – 4.191) 0.155 – 0.195 (3.937 – 4.953) T5 (TO-220) 0398 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1120A 125mA Low Dropout Regulator with 20µA IQ Includes 2.5V Reference and Comparator LTC 1174 High Efficiency 425mA Step-Down DC/DC Converter Over 90% Efficiency, Includes Comparator LT1303 Micropower Step-Up DC/DC Converter Includes Comparator, Good for EL Displays LT1376 500kHz 1.25A Step-Down DC/DC Converter Uses Extremely Small External Components LT1521 300µA Low Dropout Regulator with 15µA IQ Lowest IQ Low Dropout Regulator ® 12 Linear Technology Corporation 152935fa LT/TP 0499 2K REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1995