Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsVoltage RegulatorsLT1521CST-5#PBF

LT1521/LT1521-3

LT1521-3.3/LT1521-5

1521335fb

The LT

1521/LT1521-3/LT1521-3.3/LT1521-5 are low

dropout regulators with micropower quiescent current

and shutdown. These devices are capable of supplying

300mA of output current with a dropout voltage of 0.5V.

Designed for use in battery-powered systems, the low

quiescent current, 12µA operating and 6µA in

shutdown, makes them an ideal choice. The quiescent

current is well controlled; it does not rise in dropout as it

does with many other low dropout PNP regulators.

Other features of the LT1521/LT1521-3/LT1521-3.3/

LT1521-5 include the ability to operate with very small

output capacitors. They are stable with only 1.5µF on the

output while most older devices require between 10µF and

100µF for stability. Small ceramic capacitors can be used,

enhancing manufacturability. Also, the input may be con-

nected to voltages lower than the output voltage, including

negative voltages, without reverse current flow from out-

put to input. This makes the LT1521 series ideal for backup

power situations where the output is held high and the

input is low or reversed. Under these conditions only 5µA

will flow from the output pin to ground.

300mA Low Dropout

Regulators with Micropower

Quiescent Current and Shutdown

5V Battery-Powered Supply with Shutdown

Dropout Voltage

■

Dropout Voltage: 0.5V

■

Output Current: 300mA

■

Quiescent Current: 12

■

No Protection Diodes Needed

■

Adjustable Output from 3.8V to 20V

■

Fixed Output Voltages: 3V, 3.3V, 5V

■

Controlled Quiescent Current in Dropout

■

Shutdown I

= 6µA

■

Reverse Battery Protection

■

No Reverse Current

■

Thermal Limiting

OUTPUT CURRENT (mA)

DROPOUT VOLTAGE (V)

0.1

0.2

0.3

0.4

0.6

100 150 200

LT1521 • TA02

250 300

0.5

6V 1.5µF1µF

300mA

SHDN

(PIN 5) OUTPUT

<0.25 OFF

>2.80 ON

NC ON

LT1521-5

GND

SHDN

OUT

SENSE

LT1521 • TA01

, LTC and LT are registered trademarks of Linear Technology Corporation.

■

Low Current Regulator

■

Regulator for Battery-Powered Systems

■

Post Regulator for Switching Supplies

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

Summary of content (16 pages)

PAGE 1
LT1521/LT1521-3 LT1521-3.3/LT1521-5 300mA Low Dropout Regulators with Micropower Quiescent Current and Shutdown U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT ®1521/LT1521-3/LT1521-3.3/LT1521-5 are low dropout regulators with micropower quiescent current and shutdown. These devices are capable of supplying 300mA of output current with a dropout voltage of 0.5V. Designed for use in battery-powered systems, the low quiescent current, 12µA operating and 6µA in shutdown, makes them an ideal choice.
PAGE 2
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U W W W ABSOLUTE MAXIMUM RATINGS (Note 1) Input Voltage ...................................................... ± 20V* Output Pin Reverse Current .................................. 10mA Adjust Pin Current ................................................ 10mA Shutdown Pin Input Voltage (Note 1) .......... 6.5V, – 0.6V Shutdown Pin Input Current (Note 1) ..................... 5mA Output Short-Circuit Duration ..........................
PAGE 3
LT1521/LT1521-3 LT1521-3.3/LT1521-5 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
PAGE 4
LT1521/LT1521-3 LT1521-3.3/LT1521-5 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER Input Reverse Leakage Current Reverse Output Current (Note 11) CONDITIONS VIN = – 20V, VOUT = 0V LT1521-3 VOUT = 3V, VIN < 3V, TJ = 25°C LT1521-3.3 VOUT = 3.3V, VIN < 3.3V, TJ = 25°C LT1521-5 VOUT = 5V, VIN < 5V, TJ = 25°C LT1521 (Note 5) VOUT = 3.8V, VIN < 3.
PAGE 5
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U W TYPICAL PERFORMANCE CHARACTERISTICS LT1521-3 Output Voltage LT1521-3.3 Output Voltage 3.38 3.36 3.04 3.34 OUTPUT VOLTAGE (V) 3.06 3.02 3.00 2.98 2.96 5.08 IOUT = 1mA 5.06 OUTPUT VOLTAGE (V) 3.08 3.32 3.30 3.28 3.26 3.24 2.94 2.92 –50 –25 0 50 75 25 TEMPERATURE (°C) 100 3.22 –50 125 75 50 25 TEMPERATURE (°C) –25 3.75 3.73 3.71 30 25 20 15 0 100 VSHDN = OPEN 10 3.
PAGE 6
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U W TYPICAL PERFORMANCE CHARACTERISTICS LT1521-3 Ground Pin Current LT1521-3.3 Ground Pin Current 8 8 1000 GROUND PIN CURRENT (µA) 6 RLOAD = 10Ω ILOAD = 300mA* 5 4 RLOAD = 20Ω ILOAD = 150mA* 3 2 RLOAD = 30Ω ILOAD = 100mA* 1 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 800 600 RLOAD = 132Ω ILOAD = 25mA* 500 400 RLOAD = 330Ω ILOAD = 10mA* 300 200 0 10 RLOAD = 3.
PAGE 7
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U W TYPICAL PERFORMANCE CHARACTERISTICS Shutdown Pin Threshold (Off-to-On) 3.0 25 SHUTDOWN PIN CURRENT (µA) ILOAD = 300mA 1.6 1.4 1.2 ILOAD = 1mA 1.0 0.8 0.6 0.4 SHUTDOWN PIN INPUT CURRENT (mA) VSHDN = 0V 1.8 SHUTDOWN PIN THRESHOLD (V) Shutdown Pin Input Current Shutdown Pin Current 2.0 2.5 2.0 1.5 1.0 0.5 0.
PAGE 8
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U W TYPICAL PERFORMANCE CHARACTERISTICS Load Regulation Ripple Rejection 0 100 ILOAD = 150mA VIN = 6V + 50mVRMS RIPPLE 90 –5 LOAD REGULATION (mV) RIPPLE REJECTION (dB) 80 70 60 COUT = 33µF SOLID TANTALUM 50 40 30 20 COUT = 3.3µF SOLID TANTALUM 10 0 10 100 1k 10k FREQUENCY (Hz) 100k ∆ILOAD = 1mA TO 300mA –10 LT1521-5 LT1521-3 –15 LT1521* –25 –30 –35 VIN = VOUT (NOMINAL + 1V) *VADJ = VOUT –40 –50 –25 1M LT1521-3.
PAGE 9
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U U U PIN FUNCTIONS 5 + VIN IN OUT 1 RP LT1521 4 SHDN SENSE + 2 LOAD GND 3 RP LT1521 • F01 Figure 1. Kelvin Sense Connection ADJ (Pin 2): For adjustable LT1521, the adjust pin is the input to the error amplifier. This pin is internally clamped to 6V and – 0.6V (one VBE). It has a bias current of 50nA which flows into the pin. See Adjust Pin Bias Current vs Temperature in the Typical Performance Characteristics section.
PAGE 10
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U U W U APPLICATIONS INFORMATION IN VOUT OUT + VIN R2 LT1521 SHDN ADJ GND ) ) R1 VOUT = 3.75V 1 + R2 + (IADJ + R2) R1 VADJ = 3.75V IADJ = 50nA AT 25°C OUTPUT RANGE = 3.75V TO 20V LT1521 • F01 Figure 2. Adjustable Operation output is turned off and the divider current will be zero. Curves of Adjust Pin Voltage vs Temperature and Adjust Pin Bias Current vs Temperature appear in the Typical Performance Characteristics.
PAGE 11
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U W U U APPLICATIONS INFORMATION Table 3. SOT-223 Package (Thermal Resistance Junction-to-Tab 20°C/W) COPPER AREA TOPSIDE* BACKSIDE BOARD AREA THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 2500mm2 2500mm2 2500mm2 50°C/W 1000mm2 2500mm2 2500mm2 50°C/W 225mm2 2500mm2 2500mm2 58°C/W 100mm2 2500mm2 2500mm2 64°C/W 1000mm2 1000mm2 1000mm2 57°C/W 0 1000mm2 60°C/W 1000mm2 is required to prevent oscillations.
PAGE 12
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U W U U APPLICATIONS INFORMATION In circuits where a backup battery is required, several different input/output conditions can occur. The output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage or is left open circuit. Current flow back into the output will vary depending on the conditions. Many battery-powered circuits incorporate some form of power management.
PAGE 13
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U U W U APPLICATIONS INFORMATION Table 4.
PAGE 14
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.
PAGE 15
LT1521/LT1521-3 LT1521-3.3/LT1521-5 U PACKAGE DESCRIPTION ST Package 3-Lead Plastic SOT-223 (Reference LTC DWG # 05-08-1630) 0.248 – 0.264 (6.30 – 6.71) 0.114 – 0.124 (2.90 – 3.15) 0.264 – 0.287 (6.70 – 7.30) 0.130 – 0.146 (3.30 – 3.71) 0.033 – 0.041 (0.84 – 1.04) 0.0905 (2.30) NOM 10° – 16° 0.010 – 0.014 (0.25 – 0.36) 10° MAX 0.071 (1.80) MAX 10° – 16° 0.024 – 0.033 (0.60 – 0.84) 0.181 (4.60) NOM 0.012 (0.31) MIN 0.0008 – 0.0040 (0.0203 – 0.
PAGE 16
LT1521/LT1521-3 LT1521-3.3/LT1521-5 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC® 1174 425mA High Efficiency Step-Down Switching Regulator >90% Efficiency, SO-8 Package LT1175 500mA Micropower Low Dropout Negative Linear Regulator Selectable Current Limit LT1120A 125mA Micropower Low Dropout Linear Regulator 20µA Quiescent Current, Includes Comparator LT1304 Micropower Step-Up DC/DC Converter 15µA Quiescent Current, 1.