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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8 500mA, Low Voltage, Very Low Dropout Linear Regulator
FEATURES

DESCRIPTIO
VIN Range: 0.9V to 10V Dropout Voltage: 160mV Typical Output Current: 500mA Adjustable Output (VREF = VOUT(MIN) = 200mV) Fixed Output Voltages: 1.2V, 1.5V, 1.8V Stable with Low ESR, Ceramic Output Capacitors (3.3F Minimum) 0.2% Load Regulation from 0mA to 500mA Quiescent Current: 120A (Typ) 3A Typical Quiescent Current in Shutdown Current Limit Protection Reverse-Battery Protection No Reverse Current Thermal Limiting with Hysteresis 16-Pin DFN (5mm x 5mm) and 8-Lead SO Packages
The LT(R)3021 is a very low dropout voltage (VLDOTM) linear regulator that operates from input supplies down to 0.9V. This device supplies 500mA of output current with a typical dropout voltage of 160mV. The LT3021 is ideal for low input voltage to low output voltage applications, providing comparable electrical efficiency to that of a switching regulator. The LT3021 regulator optimizes stability and transient response with low ESR, ceramic output capacitors as small as 3.3F. Other LT3021 features include 0.05% typical line regulation and 0.2% typical load regulation. In shutdown, quiescent current typically drops to 3A. Internal protection circuitry includes reverse-battery protection, current limiting, thermal limiting with hysteresis, and reverse-current protection. The LT3021 is available as an adjustable output device with an output range down to the 200mV reference. Three fixed output voltages, 1.2V, 1.5V and 1.8V, are also available. The LT3021 regulator is available in the low profile (0.75mm) 16-pin (5mm x 5mm) DFN package with exposed pad and the 8-lead SO package.
, LTC and LT 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.
APPLICATIO S

Low Current Regulators Battery-Powered Systems Cellular Phones Pagers Wireless Modems
TYPICAL APPLICATIO
VIN 1.8V 3.3F
1.8V to 1.5V, 500mA VLDO Regulator
VOUT 1.5V 500mA
MINIMUM INPUT VOLTAGE (V)
1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
IL = 500mA
IN
OUT LT3021-1.5 3.3F
SHDN
SENSE
GND
3021 TA01
0 -50
-25
U
Minimum Input Voltage
0 25 50 75 TEMPERATURE (C) 100 125
3021 TA02
U
U
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
ABSOLUTE AXI U RATI GS
IN Pin Voltage ........................................................ 10V OUT Pin Voltage .................................................... 10V Input-to-Output Differential Voltage ....................... 10V ADJ/SENSE Pin Voltage ........................................ 10V SHDN Pin Voltage ................................................. 10V Output Short-Circut Duration .......................... Indefinite
PACKAGE/ORDER I FOR ATIO
TOP VIEW NC NC OUT OUT NC NC ADJ AGND 1 2 3 4 5 6 7 8 17 16 NC 15 NC 14 IN 13 NC 12 IN 11 NC 10 PGND 9 SHDN NC NC OUT OUT NC NC SENSE AGND 1 2 3 4 5 6 7 8
TOP VIEW 16 NC 15 NC 14 IN 17 13 NC 12 IN 11 NC 10 PGND 9 SHDN
LT3021-ADJ DH PACKAGE 16-LEAD (5mm x 5mm) PLASTIC DFN
LT3021-FIXED DH PACKAGE 16-LEAD (5mm x 5mm) PLASTIC DFN
TJMAX = 125C, JA = 35C/ W*, JC = 3C/ W** TJMAX = 125C, JA = 35C/ W*, JC = 3C/ W** EXPOSED PAD IS GND (PIN 17) CONNECT TO PINS 8, 10 EXPOSED PAD IS GND (PIN 17) CONNECT TO PINS 8, 10 *SEE THE APPLICATIONS INFORMATION SECTION *SEE THE APPLICATIONS INFORMATION SECTION **MEASURED JUNCTION TO PIN 17 **MEASURED JUNCTION TO PIN 17
TOP VIEW NC 1 OUT 2 ADJ 3 AGND 4 8 7 6 5 IN NC PGND SHDN NC 1 OUT 2 SENSE 3 AGND 4
TOP VIEW 8 7 6 5 IN NC PGND SHDN
LT3021-ADJ S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 125C/ W*, JC = 40C/ W** *SEE THE APPLICATIONS INFORMATION SECTION **MEASURED JUNCTION TO PIN 6
LT3021-FIXED S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 125C/ W*, JC = 40C/ W** *SEE THE APPLICATIONS INFORMATION SECTION **MEASURED JUNCTION TO PIN 6
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult factory for parts specified with wider operating temperature ranges.
2
U
U
W
WW
U
W
(Note 1)
Operating Junction Temperature Range (Notes 2, 3) .......................................... - 40C to 125C Storage Temperature Range DH .................................................... - 65C to 125C S8 ..................................................... - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LT3021EDH
DH PART MARKING 3021
ORDER PART NUMBER LT3021EDH-1.2 LT3021EDH-1.5 LT3021EDH-1.8 ORDER PART NUMBER LT3021ES8
DH PART MARKING 302112 302115 302118 S8 PART MARKING 3021
ORDER PART NUMBER LT3021ES8-1.2 LT3021ES8-1.5 LT3021ES8-1.8
S8 PART MARKING 302112 302115 302118
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are TJ = 25C.
PARAMETER Minimum Input Voltage (Notes 5,14) ADJ Pin Voltage (Notes 4, 5) Regulated Output Voltage (Note 4) CONDITIONS ILOAD = 500mA, TJ > 0C ILOAD = 500mA, TJ < 0C VIN = 1.5V, ILOAD = 1mA 1.15V < VIN < 10V, 1mA < ILOAD < 500mA LT3021-1.2 LT3021-1.5 LT3021-1.8 Line Regulation (Note 6) LT3021 LT3021-1.2 LT3021-1.5 LT3021-1.8 LT3021 LT3021-1.2 LT3021-1.5 LT3021-1.8 ILOAD = 10mA ILOAD = 10mA ILOAD = 500mA ILOAD = 500mA GND Pin Current VIN = VOUT(NOMINAL) + 0.4V (Notes 8, 12) Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 10) Quiescent Current in Shutdown Ripple Rejection (Note 6) ILOAD = 0mA ILOAD = 10mA ILOAD = 100mA ILOAD = 500mA COUT = 4.7F, ILOAD = 500mA, BW = 10Hz to 100kHz, VOUT = 1.2V VADJ = 0.2V, VIN = 1.2V (Notes 6, 9) VOUT = Off to On VOUT = On to Off VSHDN = 0V, VIN = 10V VSHDN = 10V, VIN = 10V VIN = 6V, VSHDN= 0V LT3021 LT3021-1.2 LT3021-1.5 LT3021-1.8 VIN - VOUT = 1V, VRIP = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 500mA VIN - VOUT = 1V, VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 500mA VIN - VOUT = 1V, VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 500mA VIN - VOUT = 1V, VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 500mA

MIN
TYP 0.9 0.9
MAX 1.05 1.10 204 206 1.224 1.236 1.530 1.545 1.836 1.854 +1.75 10.5 13 15.8 2 6 7.5 9 75 110 190 285 250
UNITS V V mV mV V V V V V V mV mV mV mV mV mV mV mV mV mV mV mV A A mA mA VRMS nA V V A A A dB dB dB dB
196 193 1.176 1.157 1.470 1.447 1.764 1.737 -1.75 -10.5 -13 -15.8 -2 -6 -7.5 -9
200 200 1.200 1.200 1.500 1.500 1.800 1.800 0 0 0 0 0.4 1 1.5 2 45
VIN = 1.5V, ILOAD = 1mA 1.5V < VIN < 10V, 1mA < ILOAD < 500mA VIN = 1.8V, ILOAD = 1mA 1.8V < VIN < 10V, 1mA < ILOAD < 500mA VIN = 2.1V, ILOAD = 1mA 2.1V < VIN < 10V, 1mA < ILOAD < 500mA VIN = 1.15V to 10V, ILOAD = 1mA VIN = 1.5V to 10V, ILOAD = 1mA VIN = 1.8V to 10V, ILOAD = 1mA VIN = 2.1V to 10V, ILOAD = 1mA VIN = 1.15V, ILOAD = 1mA to 500mA VIN = 1.5V, ILOAD = 1mA to 500mA VIN = 1.8V, ILOAD = 1mA to 500mA VIN = 2.1V, ILOAD = 1mA to 500mA
Load Regulation (Note 6)
Dropout Voltage (Notes 7, 12)
155

110 920 2.25 6.20 300 20 0.25 0.61 0.61 3 3 70 60 58 56
10 50 0.9 1 9.5 9
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are TJ = 25C.
PARAMETER Current Limit (Note 12) Input Reverse Leakage Current Reverse Output Current (Notes 11, 13) CONDITIONS VIN = 10V, VOUT = 0V VIN = VOUT(NOMINAL) + 0.5V, VOUT = -5% VIN = -10V, VOUT = 0V LT3021 LT3021-1.2 LT3021-1.5 LT3021-1.8 VOUT = 1.2V, VIN = 0V VOUT = 1.2V, VIN = 0V VOUT = 1.5V, VIN = 0V VOUT = 1.8V, VIN = 0V
MIN 550
TYP 1.8 1 0.5 10 10 10
MAX
UNITS A mA
20 5 15 15 15
A A A A A
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT3021 regulators are tested and specified under pulse load conditions such that TJ TA. The LT3021 is 100% production tested at TA = 25C. Performance at -40C and 125C is assured by design, characterization and correlation with statistical process controls. Note 3: 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 4: Maximum junction temperature limits operating conditions. The regulated output voltage specification does not apply for all possible combinations of input voltage and output current. Limit the output current range if operating at maximum input voltage. Limit the input voltage range if operating at maximum output current. Note 5: Typically the LT3021 supplies 500mA output current with a 1V input supply. The guranteed minimum input voltage for 500mA output current is 1.10V. Note 6: The LT3021 is tested and specified for these conditions with an external resistor divider (20k and 30.1k) setting VOUT to 0.5V. The external resistor divider adds 10A of output load current. The line regulation and load regulation specifications refer to the change in the 0.2V reference voltage, not the 0.5V output voltage. Specifications for fixed output voltage devices are referred to the output voltage.
Note 7: Dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a specified output current. In dropout the output voltage equals: (VIN - VDROPOUT). Note 8: GND pin current is tested with VIN = VOUT(NOMINAL) + 0.4V and a current source load. GND pin current will increase in dropout. See GND pin current curves in the Typical Performance Characteristics section. Note 9: Adjust pin bias current flows out of the ADJ pin. Note 10: Shutdown pin current flows into the SHDN pin. Note 11: Reverse output current is tested with IN grounded and OUT forced to the rated output voltage. This current flows into the OUT pin and out of the GND pin. For fixed voltage devices this includes the current in the output resistor divider. Note 12: The LT3021 is tested and specified for these conditions with an external resistor divider (20k and 100k) setting VOUT to 1.2V. The external resistor divider adds 10A of load current. Note 13: Reverse current is higher for the case of (rated_output) < VOUT < VIN, because the no-load recovery circuitry is active in this region and is trying to restore the output voltage to its nominal value. Note 14: Minimum input voltage is the minimum voltage required by the control circuit to regulate the output voltage and supply the full 500mA rated current. This specification is tested at VOUT = 0.5V. At higher output voltages the minimum input voltage required for regulation will be equal to the regulated output voltage VOUT plus the dropout voltage.
TYPICAL PERFOR A CE CHARACTERISTICS
Dropout Voltage
250 225 DROPOUT VOLTAGE (mV) 200 175 150 125 100 75 50 25 0 0 100 200 300 400 OUTPUT CURRENT (mA) 500
3021 G01
DROPOUT VOLTAGE (mV)
200 175 150 125 100 75 50 25 0 -50 -25 0 25 50 75 TEMPERATURE (C) IL = 50mA IL = 10mA IL = 1mA 100 125 IL = 100mA IL = 250mA
MINIMUM INPUT VOLTAGE (V)
TJ = 125C
TJ = 25C
4
UW
Dropout Voltage
250 225 VOUT = 1.2V IL = 500mA 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3
Minimum Input Voltage
IL = 500mA
0.2 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
3021 G02
3021 G16
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8 TYPICAL PERFOR A CE CHARACTERISTICS
ADJ Pin Voltage
206 204 ADJ PIN VOLTAGE (mV) 202 200 198 196 194 -50
ADJ PIN BIAS CURRENT (nA)
QUIESCENT CURRENT (A)
-25
0 25 50 75 TEMPERATURE (C)
Output Voltage
1.23 1.22
OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V)
ILOAD = 1mA
1.21 1.20 1.19 1.18 1.17 -50 -25
1.51 1.50 1.49 1.48 1.47 -50 -25
OUTPUT VOLTAGE (V)
50 25 75 0 TEMPERATURE (C)
Quiescent Current
3.0 VOUT = 1.2V IL = 0 2.5 TJ = 25C
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (mA)
2.0 1.5 VSHDN = VIN 1.0 VSHDN = 0V 0.5 0
0
1
2
34567 INPUT VOLTAGE (V)
UW
100
3021 G04
ADJ Pin Bias Current
25 250
Quiescent Current
VIN = 6V 225 VOUT = 1.2V IL = 0 200 175 150 125 100 75 50 25 VSHDN = 0V -25 0 25 50 75 TEMPERATURE (C) 100 125 VSHDN = VIN
20
15
10
5
125
0 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
0 -50
3021 G11
3021 G05
Output Voltage
1.53 1.52 ILOAD = 1mA 1.83 1.82 1.81 1.80 1.79 1.78
Output Voltage
ILOAD = 1mA
100
125
50 25 75 0 TEMPERATURE (C)
100
125
1.77 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
3021 G28
3021 G23
3021 G22
Quiescent Current
3.0 VOUT = 1.5V IL = 0 2.5 TJ = 25C 2.0 1.5 VSHDN = VIN 1.0 VSHDN = 0V 0.5 0 3.0
Quiescent Current
VOUT = 1.8V IL = 0 2.5 TJ = 25C 2.0 1.5 VSHDN = VIN 1.0 VSHDN = 0V 0.5 0
8
9
10
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
3021 G03
3021 G26
3021 G27
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8 TYPICAL PERFOR A CE CHARACTERISTICS
GND Pin Current
8 7
GND PIN CURRENT (mA)
RL = 2.4 IL = 500mA
VOUT = 1.2V TJ = 25C
GND PIN CURRENT (mA)
6 5 4 3 2 1 RL = 1.2k, IL = 1mA 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 RL = 12 IL = 100mA RL = 4.8 IL = 250mA
GND PIN CURRENT (mA)
RL = 24 IL = 50mA RL = 120 IL = 10mA
GND Pin Current vs ILOAD
10 9
SHDN PIN THRESHOLD (V)
VSHDN = 10V
GND PIN CURRENT (mA)
8 7 6 5 4 3 2 1 0 0 100 200 300 400 LOAD CURRENT (mA) 500
3021 G07
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125
SHDN PIN INPUT CURRENT (A)
SHDN Pin Input Current
5
SHDN PIN INPUT CURRENT (A)
VSHDN = 10V
4
CURRENT LIMIT (A)
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
VIN = 10V
REVERSE OUTPUT CURRENT (A)
3
2
1
0 -50
-25
0 25 50 75 TEMPERATURE (C)
6
UW
3021 G06
GND Pin Current
8 7 6 5 4 3 2 1 0 0 1 RL = 15 IL = 100mA RL = 1.5k, IL = 1mA 2 34567 INPUT VOLTAGE (V) 8 9 10 RL = 6 IL = 250mA RL = 30 IL = 50mA RL = 150 IL = 10mA RL = 3 IL = 500mA VOUT = 1.5V TJ = 25C 9 8 7 6 5 4 3 2 1 0
GND Pin Current
VOUT = 1.8V TJ = 25C RL = 3.6 IL = 500mA
RL = 7.2 IL = 250mA RL = 36 IL = 50mA RL = 180 IL = 10mA RL = 18 IL = 100mA RL = 1.8k, IL = 1mA 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
3021 G24
3021 G25
SHDN Pin Threshold
1.0 0.9 IL = 1mA 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0
SHDN Pin Input Current
0
1
2
345678 SHDN PIN VOLTAGE (V)
9
10
3021 G08
3021 G09
Current Limit
2.0 1.8 VOUT = 0V 500
Reverse Output Current
VIN = 0V 450 VOUT = 1.2V 400 350 300 250 200 150 100 50
VIN = 1.7V
100
125
0 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
0 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
3021 G10
3021 G12
3021 G13
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8 TYPICAL PERFOR A CE CHARACTERISTICS
Input Ripple Rejection
70
INPUT RIPPLE REJECTION (dB)
INPUT RIPPLE REJECTION (dB)
60 50 40 30 20 10 VIN = 1.5V + 50mVRMS RIPPLE VOUT = 0.5V I = 500mA 0L 10 1k 10k 100 FREQUENCY (Hz) COUT = 4.7F COUT = 22F
70 60 50 40 30 20 VIN = 1.5V + 0.5VP-P RIPPLE AT 120Hz 10 VOUT = 0.5V IL = 500mA 0 0 25 50 75 100 -50 -25 TEMPERATURE (C)
LOAD REGULATION (mV)
No-Load Recovery Threshold
OUTPUT NOISE SPECTRAL DENSITY (V/Hz)
18 16
OUTPUT SINK CURRENT (mA)
14 12 10 8 6 4 2 0 0 5 10 15 OUTPUT OVERSHOOT (%) 20
3021 G20
RMS Output Noise vs Load Current (10Hz to 100kHz)
300 250
OUTPUT NOISE (VRMS)
VOUT = 1.2V COUT = 4.7F
VOUT 50mV/DIV
200 150 100 50 0 0.01
IOUT 500mA/DIV
0.1 1 10 LOAD CURRENT (mA)
UW
100k 1M
3021 G14
Input Ripple Rejection
100 90 80
2.5 2.0 1.5 1.0 0.5 0 -0.5
Load Regulation IL = 1mA to 500mA
125
-1.0 V = 1.15V IN -1.5 VOUT = 0.5V *LOAD REGULATION NUMBER REFERS -2.0 TO CHANGE IN THE 200mV REFERENCE VOLTAGE -2.5 0 25 50 75 100 -50 -25 TEMPERATURE (C)
125
3021 G15
3021 G17
Output Noise Spectral Density
10 VOUT = 1.2V IL = 500mA COUT = 4.7F
1
0.1
0.01 10
100
1k 10k FREQUENCY (Hz)
100k
1M
3021 G18
Transient Response
100
3021 G19
50s/DIV IOUT = 50mA TO 500mA VIN = 1.5V VOUT = 1.2V COUT = 22F
3021 G21
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
PI FU CTIO S
OUT (Pins 3, 4/Pin 2): These pins supply power to the load. Use a minimum output capacitor of 3.3F to prevent oscillations. Applications with large load transients require larger output capacitors to limit peak voltage transients. See the Applications Information section for more information on output capacitance and reverse output characteristics. SENSE (Pin 7/Pin 3, Fixed Voltage Device Only): This pin is the sense point for the internal resistor divider. It should be tied directly to the OUT pins (1, 2) for best results. ADJ (Pin 7/Pin 3): This pin is the inverting terminal to the error amplifier. Its typical input bias current of 20nA flows out of the pin (see curve of ADJ Pin Bias Current vs Temperature in the Typical Performance Characteristics). The ADJ pin reference voltage is 200mV (referred to GND). AGND (Pin 8/Pin 4): Ground. PGND (Pins 10, 17/Pin 6): Ground. SHDN (Pin 9/Pin 5): The SHDN pin puts the LT3021 into a low power state. Pulling the SHDN pin low turns the output off. Drive the SHDN pin with either logic or an open collector/drain device with a pull-up resistor. The pull-up
BLOCK DIAGRA
SHDN (9/5)
SHUTDOWN
200mV BIAS CURRENT AND REFERENCE GENERATOR 212mV
-
NO-LOAD RECOVERY Q2 R2
NOTE: FOR LT3021 ADJUST PIN (7/3) IS CONNECTED TO THE ADJUST PIN, R1 AND R2 ARE EXTERNAL. FOR LT3021-1.X PIN (7/3) IS CONNECTED TO THE OUTPUT SENSE PIN, R1 AND R2 ARE INTERNAL.
8
+
-
W
U
U
U
(DH Package/S8 Package)
resistor supplies the pull-up current to the open collector/ drain logic, normally several microamperes, and the SHDN pin current, typically 2.5A. If unused, connect the SHDN pin to VIN. The LT3021 does not function if the SHDN pin is not connected. IN (Pins 12, 14/Pin 8): These pins supply power to the device. The LT3021 requires a bypass capacitor at IN if it is more than six inches away from the main input filter capacitor. The output impedance of a battery rises with frequency, so include a bypass capacitor in battery-powered circuits. A bypass capacitor in the range of 3.3F to 10F suffices. The LT3021 withstands reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reversed input, which occurs if a battery is plugged in backwards, the LT3021 acts as if a diode is in series with its input. No reverse current flows into the LT3021 and no reverse voltage appears at the load. The device protects itself and the load. EXPOSED PAD (Pin 17, DH16 Package Only): Ground. Solder Pin 17 to the PCB ground. Connect directly to Pins 5, 8, 10 for best performance. NC (Pins 1, 2, 5, 6, 11, 15, 16/Pins 1, 7)
(DH Package/S8 Package)
IN (12, 14/8) THERMAL SHUTDOWN R3 D1 Q3 CURRENT GAIN Q1
ERROR AMP
D2
OUT (3,4/2) OUT SENSE (7/3)
+
25k
ADJ (7/3)
FIXED VOUT 1.2V 1.5V 1.8V
R1 R1 R2 GND (8,10,17/4,6)
3021 BD
20k 100k 20k 130k 20k 160k
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
APPLICATIO S I FOR ATIO
The LT3021 is a very low dropout linear regulator capable of 1V input supply operation. Devices supply 500mA of output current and dropout voltage is typically 155mV. Quiescent current is typically 120A and drops to 3A in shutdown. The LT3021 incorporates several protection features, making it ideal for use in battery-powered systems. The device protects itself against reverse-input and reverse-output voltages. In battery backup applications where the output is held up by a backup battery when the input is pulled to ground, the LT3021 acts as if a diode is in series with its output which prevents reverse current flow. In dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 10V without affecting startup or normal operation. Adjustable Operation The LT3021's output voltage range is 0.2V to 9.5V. Figure 1 shows that the output voltage is set by the ratio of two external resistors. The device regulates the output to maintain the ADJ pin voltage at 200mV referenced to ground. The current in R1 equals 200mV/R1 and the current in R2 is the current in R1 minus the ADJ pin bias current. The ADJ pin bias current of 20nA flows out of the pin. Use the formula in Figure 1 to calculate output voltage. An R1 value of 20k sets the resistor divider current to 10A. Note that in shutdown the output is turned off and the divider current is zero. Curves of ADJ Pin Voltage vs Temperature and ADJ Pin Bias Current vs Temperature appear in the Typical Performance Characteristics section.
IN VIN LT3021 SHDN GND ADJ R1
3021 F01
OUT R2
+
VOUT
VOUT = 200mV 1 + R2 - IADJ (R2) R1 VADJ = 200mV IADJ = 20nA AT 25C OUTPUT RANGE = 0.2V TO 9.5V
()
Figure 1. Adjustable Operation
Specifications for output voltages greater than 200mV are proportional to the ratio of desired output voltage to 200mV; (VOUT/200mV). For example, load regulation for an output current change of 1mA to 500mA is typically
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0.4mV at VADJ = 200mV. At VOUT = 1.5V, load regulation is: (1.5V/200mV) * (0.4mV) = 3mV Output Capacitance and Transient Response The LT3021's design is stable with a wide range of output capacitors, but is optimized for low ESR ceramic capacitors. The output capacitor's ESR affects stability, most notably with small value capacitors. Use a minimum output capacitor of 3.3F with an ESR of 0.2 or less to prevent oscillations. The LT3021 is a low voltage device, and output load transient response is a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. For output capacitor values greater than 22F a small feedforward capacitor with a value of 300pF across the upper divider resistor (R2 in Figure 1) is required. Under extremely low output current conditions (ILOAD < 30A) a low frequency small signal oscillation (200Hz/8mVP-P at 1.2V output) can occur. A minimum load of 100A is recommended to prevent this instability. Give extra consideration to the use of ceramic capacitors. Manufacturers make ceramic capacitors with a variety of dielectrics, each with a different behavior across temperature and applied voltage. The most common dielectrics are Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics provide high C-V products in a small package at low cost, but exhibit strong voltage and temperature coefficients. The X5R and X7R dielectrics yield highly stable characterisitics and are more suitable for use as the output capacitor at fractionally increased cost. The X5R and X7R dielectrics both exhibit excellent voltage coefficient characteristics. The X7R type works over a larger temperature range and exhibits better temperature stability whereas X5R is less expensive and is available in higher values. Figures 2 and 3 show voltage coefficient and temperature coefficient comparisons between Y5V and X5R material. Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor, the stress can be induced by vibrations in the system or thermal transients. The resulting voltages produced can cause appreciable amounts
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
APPLICATIO S I FOR ATIO
20 0 CHANGE IN VALUE (%) X5R -20 -40 -60 Y5V -80 -100 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F
0
2
4
8 6 10 12 DC BIAS VOLTAGE (V)
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16
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Figure 2. Ceramic Capacitor DC Bias Characteristics
40 20
CHANGE IN VALUE (%)
0 -20 -40 -60 -80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F 50 25 75 0 TEMPERATURE (C) Y5V
X5R
-100 -50 -25
100
125
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Figure 3. Ceramic Capacitor Temperature Characteristics
of noise. A ceramic capacitor produced Figure 4's trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise. No-Load/Light-Load Recovery A transient load step occurs when the output current changes from its maximum level to zero current or a very small load current. The output voltage responds by overshooting until the regulator lowers the amount of current it delivers to the new level. The regulator loop response time and the amount of output capacitance control the amount of overshoot. Once the regulator has decreased its output current, the current provided by the resistor divider (which sets VOUT) is the only current remaining to discharge the output capacitor from the level to which it overshot. The amount of time it takes for the output voltage to recover easily extends to milliseconds with microamperes of divider current and a few microfarads of output capacitance.
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1mV/DIV VOUT = 1.3V COUT = 10F ILOAD = 0 1ms/DIV
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Figure 4. Noise Resulting from Tapping on a Ceramic Capacitor
To eliminate this problem, the LT3021 incorporates a no-load or light-load recovery circuit. This circuit is a voltage-controlled current sink that significantly improves the light load transient response time by discharging the output capacitor quickly and then turning off. The current sink turns on when the output voltage exceeds 6% of the nominal output voltage. The current sink level is then proportional to the overdrive above the threshold up to a maximum of approximately 15mA. Consult the curve in the Typical Performance Characteristics for the No-Load Recovery Threshold. If external circuitry forces the output above the no load recovery circuit's threshold, the current sink turns on in an attempt to restore the output voltage to nominal. The current sink remains on until the external circuitry releases the output. However, if the external circuitry pulls the output voltage above the input voltage, or the input falls below the output, the LT3021 turns the current sink off and shuts down the bias current/reference generator circuitry. Thermal Considerations The LT3021's power handling capability is limited by its maximum rated junction temperature of 125C. The power dissipated by the device is comprised of two components: 1. Output current multiplied by the input-to-output voltage differential: (IOUT)(VIN - VOUT) and 2. GND pin current multiplied by the input voltage: (IGND)(VIN). GND pin current is found by examining the GND pin current curves in the Typical Performance Characteristics. Power dissipation is equal to the sum of the two components listed above.
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
APPLICATIO S I FOR ATIO
The LT3021 regulator has internal thermal limiting (with hysteresis) designed to protect the device during overload conditions. For normal continuous conditions, do not exceed the maximum junction temperature rating of 125C. Carefully consider all sources of thermal resistance from junction to ambient including other heat sources mounted in proximity to the LT3021. The underside of the LT3021 DH package has exposed metal (14mm2) from the lead frame to where the die is attached. This allows heat to directly transfer from the die junction to the printed circuit board metal to control maximum operating junction temperature. The dual-in-line pin arrangement allows metal to extend beyond the ends of the package on the topside (component side) of a PCB. Connect this metal to GND on the PCB. The multiple IN and OUT pins of the LT3021 also assist in spreading heat to the PCB. The LT3021 S8 package has pin 4 fused with the lead frame. This also allows heat to transfer from the die to the printed circuit board metal, therefore reducing the thermal resistance. Copper board stiffeners and plated throughholes can also be used to spread the heat generated by power devices. The following tables list thermal resistance for several different board sizes and copper areas for two different packages. Measurements were taken in still air on 3/32" FR-4 board with one ounce copper.
Table 1. Measured Thermal Resistance For DH Package
COPPER AREA TOPSIDE* BACKSIDE 2500mm2 900mm2 225mm 50mm
2
BOARD AREA 2500mm2 2500mm2 2500mm2 2500mm2 2500mm
2
THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 30C/W 35C/W 50C/W 55C/W 65C/W
2500mm2 2500mm2 2500mm 2500mm
2
100mm2
2
2500mm2
2
Table 2. Measured Thermal Resistance For S8 Package
COPPER AREA TOPSIDE* BACKSIDE 2500mm2 1000mm 225mm
2 2
BOARD AREA 2500mm2 2500mm2 2500mm
2
THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 70C/W 70C/W 78C/W 84C/W 96C/W
2500mm2 2500mm 2500mm
2 2
100mm2 50mm2
2500mm2 2500mm2
2500mm2 2500mm2
*Device is mounted on topside.
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Calculating Junction Temperature Example: Given an output voltage of 1.2V, an input voltage range of 1.8V 10%, an output current range of 1mA to 500mA, and a maximum ambient temperature of 70C, what will the maximum junction temperature be for an application using the DH package? The power dissipated by the device is equal to: IOUT(MAX)(VIN(MAX) - VOUT) + IGND(VIN(MAX)) where IOUT(MAX) = 500mA VIN(MAX) = 1.98V IGND at (IOUT = 500mA, VIN = 1.98V) = 10mA so P = 500mA(1.98V - 1.2V) + 10mA(1.98V) = 0.41W The thermal resistance is in the range of 35C/W to 70C/W depending on the copper area. So the junction temperature rise above ambient is approximately equal to: 0.41W(52.5C/W) = 21.5C The maximum junction temperature equals the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 21.5C + 70C = 91.5C Protection Features The LT3021 incorporates several protection features that 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 also protects against reverseinput voltages, reverse-output voltages and reverse output-to-input voltages. Current limit protection and thermal overload protection protect the device against current overload conditions at the output of the device. For normal operation, do not exceed a junction temperature of 125C. The IN pins of the device withstand reverse voltages of 10V. The LT3021 limits current flow to less than 1A and no negative voltage appears at OUT. The device protects both itself and the load against batteries that are plugged in backwards.
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
APPLICATIO S I FOR ATIO
The LT3021 incurs no damage if OUT is pulled below ground. If IN is left open circuit or grounded, OUT can be pulled below ground by 10V. No current flows from the pass transistor connected to OUT. However, current flows in (but is limited by) the resistor divider that sets the output voltage. Current flows from the bottom resistor in the divider and from the ADJ pin's internal clamp through the top resistor in the divider to the external circuitry pulling OUT below ground. If IN is powered by a voltage source, OUT sources current equal to its current limit capability and the LT3021 protects itself by thermal limiting. In this case, grounding SHDN turns off the LT3021 and stops OUT from sourcing current. The LT3021 incurs no damage if the ADJ pin is pulled above or below ground by 10V. If IN is left open circuit or grounded and ADJ is pulled above ground, ADJ acts like a 25k resistor in series with a 1V clamp (one Schottky diode in series with one diode). ADJ acts like a 25k resistor in series with a Schottky diode if pulled below ground. If IN is powered by a voltage source and ADJ is pulled below its reference voltage, the LT3021 attempts to source its current limit capability at OUT. The output voltage increases to VIN - VDROPOUT with VDROPOUT set by whatever load current the LT3021 supports. This condition can potentially damage external circuitry powered by the LT3021 if the output voltage increases to an unregulated high voltage. If IN is powered by a voltage source and ADJ is pulled above its reference voltage, two situations can occur. If ADJ is pulled slightly above its reference voltage, the LT3021 turns off the pass transistor, no output current is sourced and the output voltage decreases to either the voltage at ADJ or less. If ADJ is pulled above its no load recovery threshold, the no load recovery circuitry turns on and attempts to sink current. OUT is actively pulled low and the output voltage clamps at a Schottky diode above ground. Please note that the behavior described above applies to the LT3021 only. If a resistor divider is connected under the same conditions, there will be additional V/R current. 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
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circuit. In the case where the input is grounded, there is less than 1A of reverse output current. If the LT3021 IN pin is forced below the OUT pin or the OUT pin is pulled above the IN pin, input current drops to less than 10A typically. This occurs if the LT3021 input is connected to a discharged (low voltage) battery and either a backup battery or a second regulator circuit holds up the output. The state of the SHDN pin has no effect on the reverse output current if OUT is pulled above IN. Input Capacitance and Stability The LT3021 is designed to be stable with a minimum capacitance of 3.3F placed at the IN pin. Ceramic capacitors with very low ESR may be used. However, in cases where a long wire is used to connect a power supply to the input of the LT3021 (and also from the ground of the LT3021 back to the power supply ground), use of low value input capacitors combined with an output load current of 20mA or greater may result in an unstable application. This is due to the inductance of the wire forming an LC tank circuit with the input capacitor and not a result of the LT3021 being unstable. The self-inductance, or isolated inductance, of a wire is directly proportional to its length. However, the diameter of a wire does not have a major influence on its selfinductance. For example, the self inductance of a 2-AWG isolated wire with a diameter of 0.26 in. is about half the inductance of a 30-AWG wire with a diameter of 0.01 in. One foot of 30-AWG wire has 465nH of self inductance. The overall self-inductance of a wire can be reduced in two ways. One is to divide the current flowing towards the LT3021 between two parallel conductors and flows in the same direction in each. In this case, the farther the wires are placed apart from each other, the more inductance will be reduced, up to a 50% reduction when placed a few inches apart. Splitting the wires basically connects two equal inductors in parallel. However, when placed in close proximity from each other, mutual inductance is added to the overall self inductance of the wires. The most effective way to reduce overall inductance is to place the forward and return-current conductors (the wire for the input and the wire for ground) in very close proximity. Two 30-AWG wires separated by 0.02 in. reduce the overall self-inductance to about one-fifth of a single isolated wire.
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
APPLICATIO S I FOR ATIO
If the LT3021 is powered by a battery mounted in close proximity on the same circuit board, a 3.3F input capacitor is sufficient for stability. However, if the LT3021 is powered by a distant supply, use a larger value input capacitor following the guideline of roughly 1F (in addition to the 3.3F minimum) per 8 inches of wire length. As power supply output impedance may vary, the minimum input capacitance needed to stabilize the application may
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also vary. Extra capacitance may also be placed directly on the output of the power supply; however, this will require an order of magnitude more capacitance as opposed to placing extra capacitance in close proximity to the LT3021. Furthermore, series resistance may be placed between the supply and the input of the LT3021 to stabilize the application; as little as 0.1 to 0.5 will suffice.
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
PACKAGE DESCRIPTIO
5.50 0.05 4.10 0.05 3.45 0.05 (2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP R = 0.20 TYP 9 16 0.40 0.05
PIN 1 TOP MARK (SEE NOTE 6) 8 0.200 REF 0.75 0.05 4.10 0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJJD-1) IN JEDEC PACKAGE OUTLINE MO-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 1 0.25 0.05 0.50 BSC
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DH Package 16-Lead Plastic DFN (5mm x 5mm)
(Reference LTC DWG # 05-08-1709)
0.70 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 4.10 0.05 (2 SIDES) 5.00 0.10 5.00 0.10 3.45 0.10 (2 SIDES) PIN 1 NOTCH
(DH16) DFN 0204
0.00 - 0.05
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8
PACKAGE DESCRIPTIO
.050 BSC
8
.245 MIN
.030 .005 TYP RECOMMENDED SOLDER PAD LAYOUT
.010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 0- 8 TYP
.016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN
INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
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.
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S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.045 .005
.189 - .197 (4.801 - 5.004) NOTE 3 7 6 5
.160 .005
.228 - .244 (5.791 - 6.197)
.150 - .157 (3.810 - 3.988) NOTE 3
1
2
3
4
.053 - .069 (1.346 - 1.752)
.004 - .010 (0.101 - 0.254)
.014 - .019 (0.355 - 0.483) TYP
.050 (1.270) BSC
SO8 0303
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LT3021/LT3021-1.2/ LT3021-1.5/LT3021-1.8 RELATED PARTS
PART NUMBER LT1121/LT1121HV LT1129 LT1761 DESCRIPTION 150mA, Micropower LDOs 700mA, Micropower LDO 100mA, Low Noise Micropower LDO COMMENTS VIN: 4.2V to 30V/36V, VOUT: 3.75V to 30V, VDO = 0.42V, IQ = 30A, ISD = 16A, Reverse-Battery Protection, SOT-223, S8, Z Packages VIN: 4.2V to 30V, VOUT: 3.75V to 30V, VDO = 0.4V, IQ = 50A, ISD = 16A, DD, SOT-223, S8, TO220-5, TSSOP20 Packages VIN: 1.8V to 20V, VOUT: 1.22V to 20V, VDO = 0.3V, IQ = 20A, ISD < 1A, Low Noise: < 20VRMSP-P, Stable with 1F Ceramic Capacitor, ThinSOT Package VIN: 1.8V to 20V, VOUT: 1.22V to 20V, VDO = 0.3V, IQ = 25A, ISD < 1A, Low Noise: <20VRMSP-P, MS8 Package VIN: 1.8V to 20V, VOUT: 1.22V to 20V, VDO = 0.3V, IQ = 30A, ISD < 1A, Low Noise: < 20VRMSP-P, S8 Package VIN: 2.7V to 20V, VOUT: 1.21V to 20V, VDO = 0.34V, IQ = 1mA, ISD < 1A, Low Noise: <40VRMSP-P, "A" Version Stable with Ceramic Capacitors, DD, TO220-5 Packages VIN: 1.6V to 6.5V, VOUT(MIN) = 1.25V, VDO = 0.09V, IQ = 35A, ISD < 1A, Low Noise: < 30VRMS, ThinSOT Package VIN: 1.8V to 20V, VOUT: 1.22V to 20V, VDO = 0.27V, IQ = 30A, ISD < 1A, Low Noise: < 20VRMSP-P, MS8 Package VIN: 2.1V to 20V, VOUT: 1.21V to 20V, VDO = 0.34V, IQ = 1mA, ISD < 1A, Low Noise: < 40VRMSP-P, "A" Version Stable with Ceramic Capacitors, DD, TO220-5, SOT223, S8 Packages VIN: 3V to 80V, VOUT: 1.275V to 60V, VDO = 0.3V, IQ = 30A, ISD < 1A, Low Noise: <100VRMSP-P, Stable with 1F Output Capacitor, Exposed MS8 Package VIN: 0.9V to 10V, VOUT: 0.2V to 5V (min), VDO = 0.15V, IQ = 120A, Noise: <250VRMSP-P, Stable with 2.2F Ceramic Capacitors, DFN-8, MS8 Packages VIN: 0.9V to 5.5V, VOUT: 0.4V to 3.6V (min), VDO = 0.05V, IQ = 54A, Stable with 1F Ceramic Capacitors, DFN-6 Package VIN: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V), VDO = 0.1V, IQ = 950A, Stable with 10F Ceramic Capacitors, 10-Lead MSOP and DFN-10 Packages VIN: 1.1V to 10V, VOUT: 1.21V to 10V, VDO = Set by External MOSFET RDS(ON), 1.4MHz Boost Converter Generates Gate Drive, SSOP16 Package
LT1762 LT1763 LT1764/LT1764A
150mA, Low Noise Micropower LDO 500mA, Low Noise Micropower LDO 3A, Low Noise, Fast Transient Response LDOs
LTC1844 LT1962 LT1963/LT1963A
150mA, Low Noise, Micropower VLDO 300mA, Low Noise Micropower LDO 1.5A, Low Noise, Fast Transient Response LDOs
LT3010
50mA, High Voltage, Micropower LDO
LT3020
100mA, Low Voltage LDO
LTC3025 LTC3026
300mA, Low Voltage Micropower LDO 1.5A, Low Input Voltage VLDO Regulator
LT3150
Low VIN, Fast Transient Response, VLDO Controller
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT/TP 0705 500 * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2005

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