LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 500mA Micropower VLDO Linear Regulators DESCRIPTION FEATURES n n n n n n n n n n n n n n n Wide Input Voltage Range: 0.9V to 5.5V Stable with Ceramic Capacitors Very Low Dropout: 85mV at 500mA Adjustable Output Range: 0.4V to 3.6V (LTC3025-1) Fixed Output: 1.2V(LTC3025-2), 1.5V(LTC3025-3), 1.8V(LTC3025-4) ±2% Voltage Accuracy over Temperature, Supply and Load Low Noise: 80μVRMS (10Hz to 100kHz) BIAS Voltage Range: 2.5V to 5.5V Fast Transient Recovery Shutdown Disconnects Load from VIN and VBIAS Low Operating Current: IIN = 4μA, IBIAS = 50μA Typ Low Shutdown Current: IIN = 1μA, IBIAS = 0.01μA Typ Output Current Limit Thermal Overload Protection Available in 6-Lead (2mm × 2mm) DFN Package APPLICATIONS n n n n n n n Low Power Handheld Devices Low Voltage Logic Supplies DSP Power Supplies Cellular Phones Portable Electronic Equipment Handheld Medical Instruments Post Regulator for Switching Supply Noise Rejection The LTC®3025-X is a micropower, VLDO™ (very low dropout) linear regulator which operates from input voltages as low as 0.9V. The device is capable of supplying 500mA of output current with a typical dropout voltage of only 85mV. A BIAS supply is required to run the internal reference and LDO circuitry while output current comes directly from the IN supply for high efficiency regulation. The LTC3025-1 features an adjustable output with a low 0.4V reference while the LTC3025-2, LTC3025-3, and LTC3025-4 have fixed 1.2V, 1.5V and 1.8V output voltages respectively. The LTC3025-X’s low quiescent current makes it an ideal choice for use in battery-powered systems. For 3-cell NiMH and single cell Li-Ion applications, the BIAS voltage can be supplied directly from the battery while the input can come from a high efficiency buck regulator, providing a high efficiency, low noise output. Other features include high output voltage accuracy, excellent transient response, stability with ultralow ESR ceramic capacitors as small as 1μF, short-circuit and thermal overload protection and output current limiting. The LTC3025-X is available in a tiny, low profile (0.75mm) 6-lead DFN (2mm × 2mm) package. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. VLDO is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 7224204, 7218082. TYPICAL APPLICATION 1.2V Output Voltage from 1.5V Input Supply 1MHz VIN Supply Rejection 50 1.5V HIGH EFFICIENCY 1.5V DC/DC BUCK 0.1μF OUT 1μF LTC3025-2 IN SHDN 45 COUT = 10μF 40 SENSE 0.1μF OFF ON VOUT = 1.2V IOUT ≤ 500mA GND 30251234 TA01 REJECTION (dB) BIAS Li-Ion OR 3-CELL NiMH 35 COUT = 1μF 30 25 20 15 10 5 BIAS = 3.6V VOUT = 1.2V 0 1.2 1.4 1.6 IOUT = 100mA IOUT = 300mA 1.8 2.0 VIN (V) 2.2 2.4 2.6 30251234fc 30251234 TA01b 1 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Notes 1, 2) VBIAS, VIN to GND......................................... –0.3V to 6V SHDN to GND............................................... –0.3V to 6V SENSE, ADJ to GND ..................................... –0.3V to 6V VOUT ........................................–0.3V to VIN + 0.3V or 6V Operating Junction Temperature Range (Note 3).................................................. –40°C to 125°C Storage Temperature Range................... –65°C to 125°C Output Short-Circuit Duration .......................... Indefinite TOP VIEW 6 SHDN BIAS 1 GND 2 7 5 ADJ/SENSE* IN 3 4 OUT DC6 PACKAGE 6-LEAD (2mm × 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 102°C/W, θJC = 20°C/W EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB *ADJ FOR LTC3025-1, SENSE FOR LTC3025-2, LTC3025-3, LTC3025-4 ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3025EDC-1#PBF LTC3025EDC-1#TRPBF LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-1#PBF LTC3025IDC-1#TRPBF LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025EDC-2#PBF LTC3025EDC-2#TRPBF LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-2#PBF LTC3025IDC-2#TRPBF LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025EDC-3#PBF LTC3025EDC-3#TRPBF LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-3#PBF LTC3025IDC-3#TRPBF LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025EDC-4#PBF LTC3025EDC-4#TRPBF LDPQ 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-4#PBF LTC3025IDC-4#TRPBF LDPQ 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3025EDC-1 LTC3025EDC-1#TR LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-1 LTC3025IDC-1#TR LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025EDC-2 LTC3025EDC-2#TR LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-2 LTC3025IDC-2#TR LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025EDC-3 LTC3025EDC-3#TR LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-3 LTC3025IDC-3#TR LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025EDC-4 LTC3025EDC-4#TR LDPQ 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C LTC3025IDC-4 LTC3025IDC-4#TR LDPQ 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.5V, VBIAS = 3.6V, COUT = 1μF, CIN = 0.1μF, CBIAS = 0.1μF (all capacitors ceramic) unless otherwise noted. PARAMETER VIN Operating Voltage (Note 4) CONDITIONS MIN TYP MAX UNITS LTC3025-1 l 0.9 5.5 V LTC3025-2 l 1.4 5.5 V LTC3025-3 l 1.7 5.5 V LTC3025-4 l 2.0 5.5 V 30251234fc 2 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.5V, VBIAS = 3.6V, COUT = 1μF, CIN = 0.1μF, CBIAS = 0.1μF (all capacitors ceramic) unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS VBIAS Operating Voltage (Note 4) LTC3025-1 l 2.5 5.5 V LTC3025-2 l 2.7 5.5 V LTC3025-3 l 3.0 5.5 V LTC3025-4 l 3.3 5.5 V l 2.2 2.5 V VIN Operating Current IOUT = 10μA, VOUT = 1.2V, LTC3025-1 l 4 10 μA VIN Operating Current IOUT = 0μA, LTC3025-2/LTC3025-3/LTC3025-4 l 4 10 μA VBIAS Operating Current IOUT = 10μA, VOUT = 1.2V, LTC3025-1 l 50 80 μA VBIAS Operating Current IOUT = 0μA, LTC3025-2/LTC3025-3/LTC3025-4 l 50 80 μA VIN Shutdown Current VSHDN = 0V 1 5 μA VBIAS Shutdown Current VSHDN = 0V 0.01 1 μA VADJ Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, VOUT = 1.2V, 1.5V ≤ VIN ≤ 5V, LTC3025-1 1mA ≤ IOUT ≤ 500mA, VOUT = 1.2V, 1.5V ≤ VIN ≤ 5V, LTC3025-1 l 0.395 0.392 0.4 0.4 0.405 0.408 V V VSENSE Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, 1.5V ≤ VIN ≤ 5V, LTC3025-2 1mA ≤ IOUT ≤ 500mA, 1.5V ≤ VIN ≤ 5V, LTC3025-2 l 1.185 1.176 1.2 1.2 1.215 1.224 V V VSENSE Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, 1.7V ≤ VIN ≤ 5V, LTC3025-3 1mA ≤ IOUT ≤ 500mA, 1.7V ≤ VIN ≤ 5V, LTC3025-3 l 1.481 1.470 1.5 1.5 1.519 1.530 V V VSENSE Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, 2.0V ≤ VIN ≤ 5V, LTC3025-4 1mA ≤ IOUT ≤ 500mA, 2.0V ≤ VIN ≤ 5V, LTC3025-4 l 1.777 1.764 1.8 1.8 1.823 1.836 V V IADJ ADJ Input Current VADJ = 0.45V, LTC3025-1 –50 0 50 nA VBIAS Undervoltage Lockout OUT Load Regulation (Referred to ADJ Pin) ΔIOUT = 1mA to 500mA, LTC3025-1 –0.35 mV OUT Load Regulation ΔIOUT = 1mA to 500mA, LTC3025-2 ΔIOUT = 1mA to 500mA, LTC3025-3 ΔIOUT = 1mA to 500mA, LTC3025-4 –1 –1.3 –1.5 mV mV mV VIN Line Regulation (Referred to ADJ Pin) VIN = 1.5V to 5V, VBIAS = 3.6V, VOUT = 1.2V, IOUT = 1mA, LTC3025-1 0.07 mV VIN Line Regulation VIN = 1.5V to 5V, VBIAS = 3.6V, IOUT = 1mA, LTC3025-2 VIN = 1.8V to 5V, VBIAS = 3.6V, IOUT = 1mA, LTC3025-3 VIN = 2.1V to 5V, VBIAS = 3.6V, IOUT = 1mA, LTC3025-4 0.21 0.26 0.32 mV mV mV VBIAS Line Regulation VIN = 1.5V, VBIAS = 2.7V to 5V, VOUT = 1.2V, IOUT = 1mA, LTC3025-1 l 4.5 16.5 mV VBIAS Line Regulation VIN = 1.5V, VBIAS = 2.7V to 5V, IOUT = 1mA, LTC3025-2 VIN = 1.8V, VBIAS = 3.0V to 5V, IOUT = 1mA, LTC3025-3 VIN = 2.1V, VBIAS = 3.3V to 5V, IOUT = 1mA, LTC3025-4 l l l 4.5 4.5 4.5 16.5 16.5 16.5 mV mV mV VIN to VOUT Dropout Voltage (Notes 4, 6) VBIAS = 2.8V, VIN = 1.5V, IOUT = 500mA, VADJ = 0.37V(LTC3025-1), VSENSE = 1.15V(LTC3025-2) l 85 120 170 mV mV VIN to VOUT Dropout Voltage (Notes 4, 6) VBIAS = 3.1V, VIN = 1.7V, IOUT = 500mA, VSENSE = 1.45V(LTC3025-3) l 90 130 185 mV mV VIN to VOUT Dropout Voltage (Notes 4, 6) VBIAS = 3.4V, VIN = 2.0V, IOUT = 500mA, VSENSE = 1.75V(LTC3025-4) l 90 130 185 mV mV VBIAS to VOUT Dropout Voltage (Note 4) LTC3025-1 l 1.5 V l IOUT Continuous Output Current IOUT Current Limit VADJ = 0V(LTC3025-1), VSENSE = 0V(LTC3025-2/LTC3025-3/LTC3025-4) en Output Voltage Noise f = 10Hz to 100kHz, IOUT = 300mA 500 mA 1130 80 mA μVRMS 30251234fc 3 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.5V, VBIAS = 3.6V, COUT = 1μF, CIN = 0.1μF, CBIAS = 0.1μF (all capacitors ceramic) unless otherwise noted. PARAMETER CONDITIONS MIN VIH SHDN Input High Voltage l VIL SHDN Input Low Voltage l TYP MAX UNITS 0.9 V 0.3 V IIH SHDN Input High Current SHDN = 1.2V –1 1 μA IL SHDN Input Low Current SHDN = 0V –1 1 μA Note 4: For the LTC3025-1, a regulated output voltage will only be available when the minimum IN and BIAS operating voltages as well as the IN to OUT and BIAS to OUT dropout voltages are all satisfied. For the LTC3025-2/LTC3025-3/LTC3025-4 the minimum IN operating voltage assumes IOUT = 500mA. For correct regulation at IOUT < 500mA the minimum IN operating voltage decreases to the maximum VSENSE Regulation Voltage as IOUT decreases to 0mA (i.e. VINMIN = 1.312V at IOUT = 250mA for the LTC3025-2). Note 5: 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 6: Dropout voltage is 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 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: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 3: The LTC3025-X regulators are tested and specified under pulse load conditions such that TJ ≈ TA. The LTC3025E-X are guaranteed to meet performance specifications from 0°C and 125°C. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC3025I-X are guaranteed to meet performance specifications over the full –40°C to 125°C operating junction temperature range. TYPICAL PERFORMANCE CHARACTERISTICS VIN to VOUT Dropout Voltage vs IOUT VIN = 1.5V 70 VOUT = 1.2V 400 60 350 TA = 25°C IBIAS (μA) 60 TA = –40°C 40 80 450 TA = 125°C 80 BIAS No Load Operating Current 500 VBIAS = 2.8V VIN = 1.4V 100 DROPOUT VOLTAGE (mV) Operating BIAS Current vs Output Current 300 125°C 250 25°C –40°C 200 0 50 100 150 200 250 300 350 400 450 500 IOUT (mA) 30251234 G01 –40°C 40 25°C 30 20 10 50 0 125°C 50 150 100 20 IBIAS (μA) 120 (TA = 25°C unless otherwise noted) 0 0.01 0.1 1 10 IOUT (mA) 100 1000 30251234 G02 0 2.5 3 3.5 4.5 4 VBIAS (V) 5 5.5 30251234 G03 30251234fc 4 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 TYPICAL PERFORMANCE CHARACTERISTICS VIN Shutdown Current VIN No Load Operating Current 10 IIN (μA) VBIAS = 5V 404 6 5 125°C 8 85°C 6 403 ADJUST VOLTAGE (mV) 12 Adjust Voltage vs Temperature 405 7 VBIAS = 5V VOUT = 0.8V 25°C –40°C 4 IIN (μA) 14 (TA = 25°C unless otherwise noted) 3 25°C –40°C 4 2 2 1 0 0.5 0 0.5 2.5 3.5 4.5 5.5 1.5 2.5 3.5 399 398 –25 VIN (V) 1000 1600 900 1400 CURRENT LIMIT (mA) 800 VBIAS = 5V VBIAS = 2.5V 400 300 100 125 30251234 G06 Burst Mode DC/DC Buck Ripple Rejection Current Limit vs VIN Voltage 600 50 25 0 75 TEMPERATURE (°C) 30251234 G05 SHDN Threshold vs Temperature SHDN THRESHOLD (mV) 400 395 –50 5.5 4.5 30251234 G04 500 401 396 VIN (V) 700 402 397 85°C 1.5 VBIAS = 3.6V VIN = 1.5V IOUT = 10μA VIN AC 100mV/DIV 1200 1000 800 VOUT AC 10mV/DIV 600 400 200 VIN = 1.8V VOUT = 1.5V COUT = 1μF IOUT = 50mA 200 100 0 –50 0 –25 50 25 0 75 TEMPERATURE (°C) 100 125 0 1 2 4 3 VIN (V) 6 5 30251234 G09 10μs/DIV 30251234 G08 30251234 G07 VIN Ripple Rejection vs Frequency BIAS Ripple Rejection vs Frequency 70 3MHz VIN Supply Rejection 50 70 45 60 50 40 COUT = 1μF 30 20 10 0 100 1k 50 40 30 COUT = 1μF 20 VBIAS = 3.6V VIN = 1.5V VOUT = 1.2V IOUT = 100mA 10 10k 100k 1M 10M FREQUENCY (Hz) COUT = 10μF REJECTION (dB) COUT = 10μF REJECTION (dB) REJECTION (dB) 60 1k 35 COUT = 1μF 30 25 20 10 10k 100k 1M 10M FREQUENCY (Hz) 30251234 G10 COUT = 10μF 15 VBIAS = 3.6V VIN = 1.5V VOUT = 1.2V IOUT = 100mA 0 100 40 30251234 G11 5 VBIAS = 3.6V VOUT = 1.2V 0 1.2 1.4 1.6 IOUT = 100mA IOUT = 300mA 1.8 2.0 VIN (V) 2.2 2.4 2.6 30251234 G12 30251234fc 5 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted) VIN to VOUT Dropout Voltage vs VIN (25°C) LTC3025-1 Transient Response VIN to VOUT Dropout Voltage vs VIN (90°C) LTC3025-1 0.300 0.725 0.250 0.250 0.225 VOUT AC 10mV/DIV 0.175 0.150 BIAS = 3.8V 0.125 0.100 0.075 VIN = 1.5V VOUT = 1.2V VBIAS = 3.6V COUT = 1μF 100μs/DIV 30251234 G13 0.225 BIAS = 3.3V BIAS = 3V 0.200 DROPOUT (V) 10mA DROPOUT (V) IOUT 0.300 BIAS = 2.7V 0.725 250mA BIAS = 5V VADJ = 0.385 IOUT = 500mA TA = 25°C 0.050 0.025 0 1 1.5 2 3 2.5 VIN (V) 3.5 4 4.5 30251234 G14 0.200 0.175 0.150 BIAS = 3.8V 0.125 BIAS = 5V 0.100 0.075 BIAS = 3.3V VADJ = 0.385 BIAS = 3V IOUT = 500mA BIAS = 2.7V TA = 90°C 0.050 0.025 0 1 1.5 2 3 2.5 VIN (V) 3.5 4 4.5 30251234 G15 PIN FUNCTIONS BIAS (Pin 1): BIAS Input Voltage. BIAS provides internal power for LTC3025-X circuitry. The BIAS pin should be locally bypassed to ground if the LTC3025-X is more than a few inches away from another source of bulk capacitance. In general, the output impedance of a battery rises with frequency, so it is usually advisable to include an input bypass capacitor in battery-powered circuits. A capacitor in the range of 0.01μF to 0.1μF is usually sufficient. GND (Pin 2): Ground. Connect to a ground plane. IN (Pin 3): Input Supply Voltage. The output load current is supplied directly from IN. The IN pin should be locally bypassed to ground if the LTC3025-X is more than a few inches away from another source of bulk capacitance. In general, the output impedance of a battery rises with frequency, so it is usually advisable to include an input bypass capacitor when supplying IN from a battery. A capacitor in the range of 0.1μF to 1μF is usually sufficient. OUT (Pin 4): Regulated Output Voltage. The OUT pin supplies power to the load. A minimum ceramic output capacitor of at least 1μF is required to ensure stability. Larger output capacitors may be required for applications with large transient loads to limit peak voltage transients. See the Applications Information section for more information on output capacitance. ADJ (Pin 5) LTC3025-1: Adjust Input. This is the input to the error amplifier. The ADJ pin reference voltage is 0.4V referenced to ground. The output voltage range is 0.4V to 3.6V and is typically set by connecting ADJ to a resistor divider from OUT to GND. See Figure 2. SENSE (Pin 5) LTC3025-2, LTC3025-3, LTC3025-4: Output Sense. The sense is the input to the resistor divider driving the error amplifier. Optimum regulation will be obtained at the point where SENSE is connected to OUT. The SENSE pin bias current is 10μA at the nominal rated output voltage. SHDN (Pin 6): Shutdown Input, Active Low. This pin is used to put the LTC3025-X into shutdown. The SHDN pin current is typically less than 10nA. The SHDN pin cannot be left floating and must be tied to a valid logic level (such as BIAS) if not used. Exposed Pad (Pin 7): Ground and Heat Sink. Must be soldered to PCB ground plane or large pad for optimal thermal performance. 30251234fc 6 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 BLOCK DIAGRAM LTC3025-1 1 6 LTC3025-2, LTC3025-3, LTC3025-4 BIAS SHDN 1 REFERENCE SHDN 0.4V SOFT-START IN + – 2 3 6 BIAS SHDN REFERENCE SHDN SOFT-START IN + 0.4V – 6μA GND OUT ADJ 4 2 3 6μA OUT GND SENSE 5 R1 40k 4 5 R2 80k (LTC3025-2) 110k (LTC3025-3) 140k (LTC3025-4) 30251234 BD APPLICATIONS INFORMATION Operation (Refer to Block Diagram) Adjustable Output Voltage (LTC3025-1) The LTC3025-X is a micropower, VLDO (very low dropout) linear regulator which operates from input voltages as low as 0.9V. The device provides a highly accurate output that is capable of supplying 500mA of output current with a typical dropout voltage of only 85mV. A single ceramic capacitor as small as 1μF is all that is required for output bypassing. A low reference voltage allows the LTC3025-1 output to be programmed to much lower voltages than available in common LDOs (range of 0.4V to 3. 6V). The LTC3025-2/LTC3025-3/LTC3025-4 have fixed outputs of 1.2V, 1.5V and 1.8V respectively, eliminating the need for an external resistor divider. The output voltage is set by the ratio of two external resistors as shown in Figure 2. The device servos the output to maintain the ADJ pin voltage at 0.4V (referenced to ground). Thus, the current in R1 is equal to 0.4V/R1. For good transient response, stability, and accuracy, the current As shown in the Block Diagram, the BIAS input supplies the internal reference and LDO circuitry while all output current comes directly from the IN input for high efficiency regulation. The low quiescent supply currents IIN = 4μA, IBIAS = 50μA drop to IIN = 1μA, IBIAS = 0.01μA typical in shutdown making the LTC3025-X an ideal choice for use in battery-powered systems. The device includes current limit and thermal overload protection. The fast transient response of the follower output stage overcomes the traditional tradeoff between dropout voltage, quiescent current and load transient response inherent in most LDO regulator architectures. The LTC3025-X also includes overshoot detection circuitry which brings the output back into regulation when going from heavy to light output loads (see Figure 1). 300mA IOUT 0mA VOUT AC 20mV/DIV VIN = 1.5V VOUT = 1.2V VBIAS = 3.6V COUT = 1μF 30251234 F01 100μs/DIV Figure 1. LTC3025-X Transient Response ( ) VOUT = 0.4V 1 + R2 R1 OUT R2 ADJ COUT R1 GND 30251234 F02 Figure 2. Programming the LTC3025-1 30251234fc 7 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 APPLICATIONS INFORMATION in R1 should be at least 8μA, thus the value of R1 should be no greater than 50k. The current in R2 is the current in R1 plus the ADJ pin bias current. Since the ADJ pin bias current is typically <10nA, it can be ignored in the output voltage calculation. The output voltage can be calculated using the formula in Figure 2. Note that in shutdown the output is turned off and the divider current will be zero once COUT is discharged. Output Capacitance and Transient Response The LTC3025-1 operates at a relatively high gain of –0.7μV/mA referred to the ADJ input. Thus a load current change of 1mA to 500mA produces a –0.35mV drop at the ADJ input. To calculate the change referred to the output simply multiply by the gain of the feedback network (i. e. ,1 + R2/R1). For example, to program the output for 1.2V choose R2/R1 = 2. In this example, an output current change of 1mA to 500mA produces –0.35mV • (1 + 2) = 1.05mV drop at the output. The LTC3025-X is designed to be stable with a wide range of ceramic output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. A minimum output capacitor of 1μF with an ESR of 0.05Ω or less is recommended to ensure stability. The LTC3025-X is a micropower device and output transient response will be a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. Note that bypass capacitors used to decouple individual components powered by the LTC3025-X will increase the effective output capacitor value. High ESR tantalum and electrolytic capacitors may be used, but a low ESR ceramic capacitor must be in parallel at the output. There is no minimum ESR or maximum capacitor size requirements. Because the ADJ pin is relatively high impedance (depending on the resistor divider used), stray capacitance at this pin should be minimized (<10pF) to prevent phase shift in the error amplifier loop. Additionally, special attention should be given to any stray capacitances that can couple external signals onto the ADJ pin producing undesirable output ripple. For optimum performance connect the ADJ pin to R1 and R2 with a short PCB trace and minimize all other stray capacitance to the ADJ pin. 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 Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but exhibit large voltage and temperature coefficients as shown in Figures 3 and 4. When used with a 2V regulator, a 1μF Y5V capacitor can lose as 20 20 BOTH CAPACITORS ARE 1μF, 10V, 0603 CASE SIZE 0 CHANGE IN VALUE (%) CHANGE IN VALUE (%) 0 X5R –20 –40 Y5V –60 Y5V –40 –60 –80 –80 –100 X5R –20 0 2 6 4 DC BIAS VOLTAGE (V) 8 10 30251234 F03 Figure 3. Ceramic Capacitor DC Bias Characteristics BOTH CAPACITORS ARE 1μF, 10V, 0603 CASE SIZE –100 –50 0 25 50 –25 TEMPERATURE (°C) 75 30251234 F04 Figure 4. Ceramic Capacitor Temperature Characteristics 30251234fc 8 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 APPLICATIONS INFORMATION much as 75% of its intial capacitance over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are usually 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. In all cases, the output capacitance should never drop below 0.4μF, or instability or degraded performance may occur. Calculating Junction Temperature Thermal Considerations where: 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 the output current multiplied by the input/output voltage differential: (IOUT) (VIN – VOUT) Note that the BIAS current is less than 500μA even under heavy loads, so its power consumption can be ignored for thermal calculations. The LTC3025-X has internal thermal limiting designed to protect the device during momentary overload conditions. For continuous normal conditions, the maximum junction temperature rating of 125°C must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. For surface mount devices, heat sinking is accomplished by using the heat-spreading capabilities of the PC board and its copper traces. Copper board stiffeners and plated through holes can also be used to spread the heat generated by power devices. The LTC3025-X 2mm × 2mm DFN package is specified as having a junction-to-ambient thermal resistance of 102°C/W, which assumes a minimal heat spreading copper plane. The actual thermal resistance can be reduced substantially by connecting the package directly to a good heat spreading ground plane. When soldered to 2500mm2 double-sided 1 oz. copper plane, the actual junction-toambient thermal resistance can be less than 60°C/W. Example: Given an output voltage of 1.2V, an input voltage of 1.8V to 3V, an output current range of 0mA to 100mA 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) IOUT(MAX) = 100mA VIN(MAX) = 3V So: P = 100mA(3V – 1.2V) = 0.18W Even under worst-case conditions, the LTC3025-X’s BIAS pin power dissipation is only about 1mW, thus can be ignored. Assuming a junction-to-ambient thermal resistance of 102°C/W, the junction temperature rise above ambient will be approximately equal to: 0.18W(102°C/W) = 18.4°C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJ = 50°C + 18.4°C = 68.4°C Short-Circuit/Thermal Protection The LTC3025-X has built-in short-circuit current limiting as well as overtemperature protection. During short-circuit conditions, internal circuitry automatically limits the output current to approximately 1130mA. At higher temperatures, or in cases where internal power dissipation causes excessive self heating on chip, the thermal shutdown circuitry will shut down the LDO when the junction temperature exceeds approximately 150°C. It will re enable the LDO once the junction temperature drops back to approximately 140°C. The LTC3025-X will cycle in and out of thermal 30251234fc 9 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 APPLICATIONS INFORMATION shutdown without latch-up or damage until the overstress condition is removed. Long term overstress (TJ > 125°C) should be avoided as it can degrade the performance or shorten the life of the part. Soft-Start Operation The LTC3025-X includes a soft-start feature to prevent excessive current flow during start-up. When the LDO is enabled, the soft-start circuitry gradually increases the LDO reference voltage from 0V to 0.4V over a period of about 600μs. There is a short 700μs delay from the time the part is enabled until the LDO output starts to rise. Figure 5 shows the start-up and shutdown output waveform. SHDN ON OFF 1.2V VOUT 200mV/DIV 0V TA = 25°C VIN = 1.5V VBIAS = 3.6V COUT = 1μF RLOAD = 4Ω 500μs/DIV 30251234 F05 Figure 5. Output Start-Up and Shutdown TYPICAL APPLICATION High Efficiency 1.5V Step-Down Converter with Efficient 1.2V VLDO Output OFF ON 1 0.1μF VIN 2.7V TO 5.5V 4 CIN** 4.7μF CER VIN SW 3 LTC3406-1.5 1 RUN VOUT 5 2.2μH* OUT BIAS 4 80.6k LTC3025-1 3 IN ADJ 1μF VOUT = 1.2V IOUT ≤ 500mA 5 40.2k VOUT 1.5V 600mA 6 SHDN GND 30251234 TA02 COUT† 10μF CER GND 2 *MURATA LQH32CN2R2M33 **TAIYO YUDEN JMK212BJ475MG † TAIYO YUDEN JMK316BJ106ML Efficiency vs Output Current 100 VIN = 3.6V EFFICIENCY (%) 90 80 LTC3406-1.5 VOUT = 1.5V LTC3025-1 VOUT = 1.2V 70 60 50 40 0.1 1 10 100 OUTPUT CURRENT (mA) 1000 30251234 TA03 30251234fc 10 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 PACKAGE DESCRIPTION DC Package 6-Lead Plastic DFN (2mm × 2mm) (Reference LTC DWG # 05-08-1703) R = 0.115 TYP 0.56 ± 0.05 (2 SIDES) 0.675 ±0.05 2.50 ±0.05 1.15 ±0.05 0.61 ±0.05 (2 SIDES) PIN 1 BAR PACKAGE TOP MARK OUTLINE (SEE NOTE 6) 0.38 ± 0.05 4 2.00 ±0.10 (4 SIDES) PIN 1 CHAMFER OF EXPOSED PAD 3 0.25 ± 0.05 0.50 BSC 1.42 ±0.05 (2 SIDES) 0.200 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 6 0.75 ±0.05 1 (DC6) DFN 1103 0.25 ± 0.05 0.50 BSC 1.37 ±0.05 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2) 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 30251234fc 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. 11 LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT®1129 700mA, Micropower, LDO VIN: 4.2V to 30V, VOUT(MIN) = 3.75V, VDO = 0.40V, IQ = 50μA, ISD < 16μA, VOUT = Adj, 3.3V, 5V, DD, SOT-223, S8, TO-220, TSSOP20 Packages LT1175 500mA, Micropower, Negative LDO VIN: –20V to –4.3V, VOUT(MIN) = –3.8V, VDO = 0.50V, IQ = 45μA, ISD < 10μA, VOUT = Adj, –5V, DD, SOT-223, S8, N8 Packages. Guaranteed Voltage Tolerance and Line/Load Regulation LT1185 3A, Negative LDO VIN: –35V to –4.2V, VOUT(MIN) = –2.40V, VDO = 0.80V, IQ = 2.5mA, ISD < 1μA, VOUT = Adj, TO-220 Package. Accurate Programmable Current Limit, Remote Sense LT1761 100mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 20μA, ISD < 1μA, VOUT = Adj, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V, ThinSOTTM Package. Low Noise < 20μVRMSP-P, Stable with 1μF Ceramic Capacitors LT1762 150mA, Low Noise Micropower LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 25μA, ISD < 1μA, VOUT = Adj, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20μVRMSP-P LT1763 500mA, Low Noise Micropower LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 30μA, ISD < 1μA, VOUT = 1.5, 1.8V, 2.5V, 3V, 3.3V, 5V, S8 Package. Low Noise < 20μVRMSP-P 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, VOUT = 1.8V, 2.5V, 3.3V, DD, TO-220 Packages. Low Noise < 40μVRMSP-P, “A” Version Stable with Ceramic Capacitors LTC1844 150mA, Very Low Dropout LDO VIN: 1.6V to 6.5V, VOUT(MIN) = 1.25V, VDO = 0.08V, IQ = 40μA, ISD < 1μA, VOUT = Adj, 1.5V, 1.8V, 2.5V, 2.8V, 3.3V, ThinSOT Package. Low Noise < 30μVRMSP-P, Stable with 1μF Ceramic Capacitors LT1962 300mA, Low Noise Micropower LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.27V, IQ = 30μA, ISD < 1μA, VOUT = 1.5, 1.8V, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20μVRMSP-P 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, VOUT = 1.5V, 1.8V, 2.5V, 3.3V, DD, SOT-223, S8, TO-220 Packages. Low Noise < 40μVRMSP-P, “A”Version Stable with Ceramic Capacitors LT1964 200mA, Low Noise Micropower, Negative LDO VIN: –0.9V to –20V, VOUT(MIN) = –1.21V, VDO = 0.34V, IQ = 30μA, ISD < 3μA, VOUT = Adj, –5V, ThinSOT Package. Low Noise < 30μVRMSP-P, Stable with Ceramic Capacitors LT1965 1.1A, Low Noise, Low Dropout Linear Regulator 290mV Dropout Voltage, Low Noise: 40μVRMS, VIN: 1.8V to 20V, VOUT: 1.2V to 19.5V, Stable with Ceramic Caps, TO-220, DD, MSOP and 3 × 3 DFN Packages LT3020 100mA, Low Voltage, VLDO VIN: 0.9V to 10V, VOUT(MIN) = 0.20V, VDO = 0.15V, IQ = 120μA, ISD < 3μA, VOUT = Adj, DFN, MS8 Package LT3023 Dual, 2 × 100mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 40μA, ISD < 1μA, VOUT = Adj, DFN, MS Packages. Low Noise < 20μVRMSP-P, Stable with 1μF Ceramic Capacitors LT3024 Dual 100mA/500mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 60μA, ISD < 1μA, VOUT = Adj, DFN, TSSOP Packages. Low Noise < 20μVRMSP-P, Stable with 1μF Ceramic Capacitors LTC3025 300mA Micropower VLDO Linear Regulator 45mV Dropout Voltage, Low Noise: 80μVRMS, VIN: 0.9V to 5.5V, Low IQ = 54μA, 2mm × 2mm 6-Lead DFN Package LTC3026 1.5A, Low Input Voltage VLDO Regulator VIN: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V Rail), VDO = 0.1V, IQ = 950μA, Stable with 10μF Ceramic Capacitors, DFN-10 and MSOP-10 Packages LT3080/LT3080-1 1.1A, Parallelable, Low Noise, Low Dropout Linear Regulator 300mV Dropout Voltage (2-supply operation), Low Noise: 40μVRMS, VIN: 1.2V to 36V, VOUT: 0V to 35.7V, Current-Based Reference with 1-Resistor VOUT Set; Directly Parallelable (No Op Amp Required), Stable with Ceramic Caps, TO-220, SOT-223, MSOP and 3 × 3 DFN Packages; “–1” Version Has Integrated Internal Ballast Resistor ThinSOT is a trademark of Linear Technology Corporation. 30251234fc 12 Linear Technology Corporation LT 1008 REV C • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2007