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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 500mA Micropower VLDO Linear Regulators FeaTures
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DescripTion
The LTC(R)3025-X is a micropower, VLDOTM (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 1F 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 x 2mm) package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 7224204, 7218082.
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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: 80VRMS (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 = 4A, IBIAS = 50A Typ Low Shutdown Current: IIN = 1A, IBIAS = 0.01A Typ Output Current Limit Thermal Overload Protection Available in 6-Lead (2mm x 2mm) DFN Package
applicaTions
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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
Typical applicaTion
1.2V Output Voltage from 1.5V Input Supply
BIAS Li-Ion OR 3-CELL NiMH 1.5V HIGH EFFICIENCY 1.5V DC/DC BUCK 0.1F IN 0.1F OFF ON SHDN GND
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1MHz VIN Supply Rejection
50 45 VOUT = 1.2V IOUT 500mA REJECTION (dB) COUT = 10F COUT = 1F
OUT 1F
40 35 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
LTC3025-2 SENSE
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 absoluTe MaxiMuM raTings
(Notes 1, 2)
pin conFiguraTion
TOP VIEW BIAS 1 GND 2 IN 3 7 6 SHDN 5 ADJ/SENSE* 4 OUT
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).................................................. -40C to 125C Storage Temperature Range................... -65C to 125C Output Short-Circuit Duration .......................... Indefinite
DC6 PACKAGE 6-LEAD (2mm x 2mm) PLASTIC DFN TJMAX = 125C, JA = 102C/W, JC = 20C/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 LTC3025EDC-1#PBF LTC3025IDC-1#PBF LTC3025EDC-2#PBF LTC3025IDC-2#PBF LTC3025EDC-3#PBF LTC3025IDC-3#PBF LTC3025EDC-4#PBF LTC3025IDC-4#PBF LEAD BASED FINISH LTC3025EDC-1 LTC3025IDC-1 LTC3025EDC-2 LTC3025IDC-2 LTC3025EDC-3 LTC3025IDC-3 LTC3025EDC-4 LTC3025IDC-4 TAPE AND REEL LTC3025EDC-1#TRPBF LTC3025IDC-1#TRPBF LTC3025EDC-2#TRPBF LTC3025IDC-2#TRPBF LTC3025EDC-3#TRPBF LTC3025IDC-3#TRPBF LTC3025EDC-4#TRPBF LTC3025IDC-4#TRPBF TAPE AND REEL LTC3025EDC-1#TR LTC3025IDC-1#TR LTC3025EDC-2#TR LTC3025IDC-2#TR LTC3025EDC-3#TR LTC3025IDC-3#TR LTC3025EDC-4#TR LTC3025IDC-4#TR PART MARKING* LDDW LDDW LDMK LDMK LDQS LDQS LDPQ LDPQ PART MARKING* LDDW LDDW LDMK LDMK LDQS LDQS LDPQ LDPQ PACKAGE DESCRIPTION 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN PACKAGE DESCRIPTION 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) Plastic DFN TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C
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/
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 elecTrical characTerisTics
PARAMETER VIN Operating Voltage (Note 4) CONDITIONS LTC3025-1 LTC3025-2 LTC3025-3 LTC3025-4 VBIAS Operating Voltage (Note 4) LTC3025-1 LTC3025-2 LTC3025-3 LTC3025-4 VBIAS Undervoltage Lockout VIN Operating Current VIN Operating Current VBIAS Operating Current VBIAS Operating Current VIN Shutdown Current VBIAS Shutdown Current VADJ Regulation Voltage (Note 5) VSENSE Regulation Voltage (Note 5) VSENSE Regulation Voltage (Note 5) VSENSE Regulation Voltage (Note 5) IADJ ADJ Input Current OUT Load Regulation IOUT = 10A, VOUT = 1.2V, LTC3025-1 IOUT = 0A, LTC3025-2/LTC3025-3/LTC3025-4 IOUT = 10A, VOUT = 1.2V, LTC3025-1 IOUT = 0A, LTC3025-2/LTC3025-3/LTC3025-4 VSHDN = 0V VSHDN = 0V 1mA IOUT 500mA, VOUT = 1.2V, 1.5V VIN 5V, LTC3025-1 1mA IOUT 500mA, VOUT = 1.2V, 1.5V VIN 5V, LTC3025-1 1mA IOUT 500mA, 1.5V VIN 5V, LTC3025-2 1mA IOUT 500mA, 1.5V VIN 5V, LTC3025-2 1mA IOUT 500mA, 1.7V VIN 5V, LTC3025-3 1mA IOUT 500mA, 1.7V VIN 5V, LTC3025-3 1mA IOUT 500mA, 2.0V VIN 5V, LTC3025-4 1mA IOUT 500mA, 2.0V VIN 5V, LTC3025-4 VADJ = 0.45V, LTC3025-1 IOUT = 1mA to 500mA, LTC3025-2 IOUT = 1mA to 500mA, LTC3025-3 IOUT = 1mA to 500mA, LTC3025-4 VIN = 1.5V to 5V, VBIAS = 3.6V, VOUT = 1.2V, IOUT = 1mA, LTC3025-1 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 VIN = 1.5V, VBIAS = 2.7V to 5V, VOUT = 1.2V, IOUT = 1mA, LTC3025-1 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 VBIAS = 3V, VIN = 1.5V, IOUT = 500mA, VADJ = 0.37V(LTC3025-1), VSENSE = 1.15V(LTC3025-2) VBIAS = 3.1V, VIN = 1.7V, IOUT = 500mA, VSENSE = 1.45V(LTC3025-3) VBIAS = 3.4V, VIN = 2.0V, IOUT = 500mA, VSENSE = 1.75V(LTC3025-4) LTC3025-1
l l l l l l l l l l l l l l l l l l l l l l
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.5V, VBIAS = 3.6V, COUT = 1F CIN = 0.1F CBIAS = 0.1F , , (all capacitors ceramic) unless otherwise noted. (Note 3)
MIN 0.9 1.4 1.7 2.0 2.5 2.7 3.0 3.3 2.2 4 4 50 50 1 0.01 0.395 0.392 1.185 1.176 1.481 1.470 1.777 1.764 -50 0.4 0.4 1.2 1.2 1.5 1.5 1.8 1.8 0 -0.35 -1 -1.3 -1.5 0.07 0.21 0.26 0.32 4.5 4.5 4.5 4.5 85 90
l
TYP
MAX 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 2.5 10 10 80 80 5 1 0.405 0.408 1.215 1.224 1.519 1.530 1.823 1.836 50
UNITS V V V V V V V V V A A A A A A V V V V V V V V nA mV mV mV mV mV mV mV mV
OUT Load Regulation (Referred to ADJ Pin) IOUT = 1mA to 500mA, LTC3025-1
VIN Line Regulation (Referred to ADJ Pin) VIN Line Regulation VBIAS Line Regulation VBIAS Line Regulation VIN to VOUT Dropout Voltage (Notes 4, 6) VIN to VOUT Dropout Voltage (Notes 4, 6) VIN to VOUT Dropout Voltage (Notes 4, 6) VBIAS to VOUT Dropout Voltage (Note 4)
16.5 16.5 16.5 16.5 120 170 130 185 130 185 1.5
mV mV mV mV mV mV mV mV mV mV V
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l l
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.5V, VBIAS = 3.6V, COUT = 1F CIN = 0.1F CBIAS = 0.1F , , (all capacitors ceramic) unless otherwise noted. (Note 3)
PARAMETER IOUT Continuous Output Current IOUT Current Limit en Output Voltage Noise VIH SHDN Input High Voltage VIL SHDN Input Low Voltage IIH SHDN Input High Current IL SHDN Input Low Current SHDN = 1.2V SHDN = 0V VADJ = 0V(LTC3025-1), VSENSE = 0V(LTC3025-2/LTC3025-3/LTC3025-4) f = 10Hz to 100kHz, IOUT = 300mA
l l
elecTrical characTerisTics
CONDITIONS
MIN
l
TYP 1130 80
MAX
UNITS mA mA VRMS V
500
0.9 0.3 -1 -1 1 1
V A A
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 125C 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 0C and 125C. Specifications over the -40C to 125C 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 -40C to 125C operating junction temperature range.
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.
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 Typical perForMance characTerisTics
VIN to VOUT Dropout Voltage vs IOUT
120 100 DROPOUT VOLTAGE (mV) 80 60 40 20 0 TA = -40C VBIAS = 2.8V VIN = 1.4V TA = 125C TA = 25C IBIAS (A) 500 450 400 350 125C 25C -40C IBIAS (A) 300 250 200 150 100 50 0 50 100 150 200 250 300 350 400 450 500 IOUT (mA)
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(TA = 25C unless otherwise noted)
Operating BIAS Current vs Output Current
80
BIAS No Load Operating Current
VIN = 1.5V 70 VOUT = 1.2V 60 50 40 30 20 10 125C -40C 25C
0 0.01
0.1
1
10 IOUT (mA)
100
1000
0 2.5
3
3.5
4.5 4 VBIAS (V)
5
5.5
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VIN No Load Operating Current
14 12 10 IIN (A) 8 6 4 2 0 0.5 1.5 2.5 3.5 4.5 5.5 VBIAS = 5V VOUT = 0.8V 7 6 125C 85C 25C -40C IIN (A) 5 4 3 2 1
VIN Shutdown Current
VBIAS = 5V 405 404 403 ADJUST VOLTAGE (mV) 402 401 400 399 398 397 396 1.5 2.5 3.5 4.5 5.5 -40C
Adjust Voltage vs Temperature
VBIAS = 3.6V VIN = 1.5V IOUT = 10A
25C 85C
0 0.5
395 -50
-25
VIN (V)
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VIN (V)
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50 25 0 75 TEMPERATURE (C)
100
125
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SHDN Threshold vs Temperature
1000 900 800 SHDN THRESHOLD (mV) 700 600 500 400 300 200 100 0 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125 VBIAS = 2.5V VBIAS = 5V CURRENT LIMIT (mA) 1600 1400 1200 1000 800 600 400 200 0
Current Limit vs VIN Voltage
VIN AC 100mV/DIV
Burst Mode DC/DC Buck Ripple Rejection
VOUT AC 10mV/DIV
0
1
2
3 VIN (V)
4
5
6
VIN = 1.8V VOUT = 1.5V COUT = 1F IOUT = 50mA
10s/DIV
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 Typical perForMance characTerisTics
VIN Ripple Rejection vs Frequency
70 60 50 40 30 20 10 VBIAS = 3.6V VIN = 1.5V VOUT = 1.2V IOUT = 100mA 1k 10k 100k 1M 10M FREQUENCY (Hz)
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(TA = 25C unless otherwise noted)
BIAS Ripple Rejection vs Frequency
70 50 45 COUT = 10F REJECTION (dB) 40 35 30 25 20 15 10 60 50 40 30 20 10 COUT = 1F VBIAS = 3.6V VIN = 1.5V VOUT = 1.2V IOUT = 100mA 1k 10k 100k 1M 10M FREQUENCY (Hz)
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3MHz VIN Supply Rejection
COUT = 10F COUT = 1F
COUT = 10F
REJECTION (dB)
REJECTION (dB)
COUT = 1F
0 100
0 100
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
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Transient Response
0.300
IOUT 250mA 10mA
VIN to VOUT Dropout Voltage vs VIN (25C) LTC3025-1
BIAS = 2.7V
0.300 0.275 0.250 0.225 DROPOUT (V) 0.200 0.175 0.150 0.125 0.100 0.075 0.050 0.025 0
VIN to VOUT Dropout Voltage vs VIN (90C) LTC3025-1
0.275 0.250 0.225 DROPOUT (V) 0.200 0.175 0.150 0.125 0.100 0.075
VIN = 1.5V VOUT = 1.2V VBIAS = 3.6V COUT = 1F 100s/DIV
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BIAS = 3V
BIAS = 3.3V
VOUT AC 10mV/DIV
BIAS = 3.8V BIAS = 5V VADJ = 0.385 IOUT = 500mA TA = 25C 1 1.5 2 3 2.5 VIN (V) 3.5 4 4.5
BIAS = 3.8V BIAS = 5V BIAS = 3.3V VADJ = 0.385 BIAS = 3V IOUT = 500mA BIAS = 2.7V TA = 90C 1 1.5 2 3 2.5 VIN (V) 3.5 4 4.5
0.050 0.025 0
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 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 0.01F to 0.1F 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 0.1F to 1F 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 1F 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 10A 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. GND (Exposed Pad Pin 7): Ground and Heat Sink. Must be soldered to PCB ground plane or large pad for optimal thermal performance.
block DiagraM
LTC3025-1 BIAS BIAS LTC3025-2, LTC3025-3, LTC3025-4 1 1
6
SHDN
REFERENCE SHDN 0.4V
SOFT-START
IN
+ -
6A
3
6
SHDN
REFERENCE SHDN 0.4V
SOFT-START
IN
+ -
6A
3
2
GND
OUT ADJ
4 5
2
GND R1 40k R2 80k (LTC3025-2) 110k (LTC3025-3) 140k (LTC3025-4)
OUT SENSE
4 5
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 applicaTions inForMaTion
Operation (Refer to Block Diagram) 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 1F 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. 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 = 4A, IBIAS = 50A drop to IIN = 1A, IBIAS = 0.01A 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 0mA
Adjustable Output Voltage (LTC3025-1) 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 in R1 should be at least 8A, 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. The LTC3025-1 operates at a relatively high gain of -0.7V/ 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. 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.
OUT VOUT = 0.4V 1 + R2 R1 COUT R1
IOUT
VOUT AC 20mV/DIV
R2 ADJ
()
VIN = 1.5V VOUT = 1.2V VBIAS = 3.6V COUT = 1F
100s/DIV
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GND
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Figure 2. Programming the LTC3025-1
Figure 1. LTC3025-X Transient Response
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 applicaTions inForMaTion
Output Capacitance and Transient Response 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 1F with an ESR of 0.05 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. 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 1F Y5V capacitor can lose as much as 75% of its initial 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 0.4F or instability , or degraded performance may occur.
CHANGE IN VALUE (%) 20 0 -20 -40 -60 -80 -100 BOTH CAPACITORS ARE 1F, 10V, 0603 CASE SIZE X5R
Y5V
0
2
6 4 DC BIAS VOLTAGE (V)
8
10
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Figure 3. Ceramic Capacitor DC Bias Characteristics
20 0 CHANGE IN VALUE (%) X5R -20 -40 -60 -80 Y5V
BOTH CAPACITORS ARE 1F, 10V, 0603 CASE SIZE -100 -50 0 25 50 -25 TEMPERATURE (C)
75
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Figure 4. Ceramic Capacitor Temperature Characteristics
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 applicaTions inForMaTion
Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature (125C). 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 500A 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 125C 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 x 2mm DFN package is specified as having a junction-to-ambient thermal resistance of 102C/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 60C/W. Calculating Junction Temperature 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 50C, what will the maximum junction temperature be? The power dissipated by the device will be equal to: IOUT(MAX) (VIN(MAX) - VOUT) where: 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 102C/W, the junction temperature rise above ambient will be approximately equal to: 0.18W(102C/W) = 18.4C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJ = 50C + 18.4C = 68.4C 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 150C. It will re enable the LDO once the junction temperature drops back to approximately 140C. The LTC3025-X will cycle in and out of thermal shutdown without latch-up or damage until the overstress condition is removed. Long term overstress (TJ > 125C) should be avoided as it can degrade the performance or shorten the life of the part.
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 applicaTions inForMaTion
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 600s. There is a short 700s 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.
ON OFF 1.2V
VOUT Start-Up and Supply Sequencing During power-up, the output shutdown circuitry is not active below VIN of about 0.65V DC (typical). As a result, the output voltage can drift up during power-up due to leakage current (<1 mA typical) from VIN to VOUT . At 0.9V input, the shutdown circuitry is active and the output is actively held off. This usually causes no circuit problems and is similar to 3-terminal regulators such as the LT3080, LT1086 and LT317 which have no ground pin and can have the output rise under some conditions. A slowly rising VIN with the part enabled may result in non-monotonic ramping of VOUT due to LDO circuitry becoming active at VIN of about 0.65V (typical) as well. With fast rising inputs (>1V/ms) or with sufficient resistive load on VOUT , output voltage rise during power-up is reduced or eliminated. Such conditions also reduce or eliminate non-monotonic initial power-up with the part enabled. If VBIAS is sequenced up before VIN, the leakage current from VIN to VOUT may increase until the shutdown circuitry is active at a VIN of about 0.65V typical. Thus, to minimize VOUT rise during start-up, sequence up VIN before VBIAS. At VIN = 0.9V, the output is actively held off in shutdown or it is actively held on when enabled under all conditions.
SHDN
VOUT 200mV/DIV
0V TA = 25C VIN = 1.5V VBIAS = 3.6V COUT = 1F RLOAD = 4 500s/DIV
30251234 F05
Figure 5. Output Start-Up and Shutdown
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 package DescripTion
(Reference LTC DWG # 05-08-1703 Rev B)
DC Package 6-Lead Plastic DFN (2mm x 2mm)
0.70 0.05 2.55 0.05 1.15 0.05 0.61 0.05 (2 SIDES)
PACKAGE OUTLINE
0.25 0.05 0.50 BSC 1.42 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.125 TYP 0.56 0.05 (2 SIDES) 2.00 0.10 (4 SIDES) 0.40 0.10 4 6
PIN 1 BAR TOP MARK (SEE NOTE 6)
PIN 1 NOTCH R = 0.20 OR 0.25 x 45 CHAMFER R = 0.05 TYP 3
(DC6) DFN REV B 1309
1
0.200 REF
0.75 0.05
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
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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.
LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 revision hisTory
REV E DATE 07/10 DESCRIPTION Added (Note 3) notation to "The l denotes" statement in Electrical Characteristics section Updated Pin 7 in Pin Functions Added "VOUT Start-Up and Supply Sequencing" section Updated Related Parts section F 04/11 Updated y-axis on graphs G14 and G15
(Revision history begins at Rev E)
PAGE NUMBER 3, 4 7 11 14 6
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LTC3025-1/LTC3025-2/ LTC3025-3/LTC3025-4 Typical applicaTion
High Efficiency 1.5V Step-Down Converter with Efficient 1.2V VLDO Output
OFF ON 0.1F VIN 2.7V TO 5.5V 4 CIN** 4.7F CER 1 VIN SW 3 2.2H* 3 IN 1 BIAS OUT 4 80.6k 1F VOUT = 1.2V IOUT 500mA
LTC3025-1 ADJ
5
LTC3406-1.5 RUN VOUT GND 5
VOUT 1.5V 600mA
6
SHDN
GND
2
40.2k
COUT 10F *MURATA LQH32CN2R2M33 CER **TAIYO YUDEN JMK212BJ475MG TAIYO YUDEN JMK316BJ106ML
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Efficiency vs Output Current
100 90 EFFICIENCY (%) 80 70 60 50 40 0.1 VIN = 3.6V LTC3406-1.5 VOUT = 1.5V
LTC3025-1 VOUT = 1.2V
1 10 100 OUTPUT CURRENT (mA)
1000
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relaTeD parTs
PART NUMBER LT1761 LT1762 LTC1844 LT1962 LT1964 LT3020 LTC3025 LTC3026 DESCRIPTION 100mA, Low Noise Micropower, LDO 150mA, Low Noise Micropower LDO 150mA, Very Low Dropout LDO 300mA, Low Noise Micropower LDO 200mA, Low Noise Micropower, Negative LDO 100mA, Low Voltage, VLDO 300mA Micropower VLDO Linear Regulator 1.5A, Low Input Voltage VLDO Regulator COMMENTS VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 20A, ISD < 1A, VOUT = Adj, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V, ThinSOTTM Package. Low Noise < 20VRMSP-P, Stable with 1F Ceramic Capacitors VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 25A, ISD < 1A, VOUT = Adj, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20VRMSP-P VIN: 1.6V to 6.5V, VOUT(MIN) = 1.25V, VDO = 0.08V, IQ = 40A, ISD < 1A, VOUT = Adj, 1.5V, 1.8V, 2.5V, 2.8V, 3.3V, ThinSOT Package. Low Noise < 30VRMSP-P, Stable with 1F Ceramic Capacitors VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.27V, IQ = 30A, ISD < 1A, VOUT = 1.5, 1.8V, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20VRMSP-P VIN: -0.9V to -20V, VOUT(MIN) = -1.21V, VDO = 0.34V, IQ = 30A, ISD < 3A, VOUT = Adj, -5V, ThinSOT Package. Low Noise < 30VRMSP-P, Stable with Ceramic Capacitors VIN: 0.9V to 10V, VOUT(MIN) = 0.20V, VDO = 0.15V, IQ = 120A, ISD < 3A, VOUT = Adj, DFN, MS8 Package 45mV Dropout Voltage, Low Noise: 80VRMS, VIN: 0.9V to 5.5V, Low IQ = 54A, 2mm x 2mm 6-Lead DFN Package VIN: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V Rail), VDO = 0.1V, IQ = 950A, Stable with 10F Ceramic Capacitors, DFN-10 and MSOP-10 Packages
30251234ff LT 0411 REV F * PRINTED IN USA
14 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2007

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