Datasheet

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LT1300

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Up to 220mA Output Current at 5V from 2V Supply

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Supply Voltage as Low as 1.8V

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Up to 88% Efficiency

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Small Inductor –10µH

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120µA Quiescent Current

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Shutdown to 10µA

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Programmable 3.3V or 5V Output

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LIM

Pin Programs Peak Switch Current

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Low V

CESAT

Switch: 170mV at 1A Typical

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Uses Inexpensive Surface Mount Inductors

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8-Lead DIP or SOIC Package

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Palmtop Computers

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Portable Instruments

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Bar-Code Scanners

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DC/DC Converter Module Replacements

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Battery Backup Supplies

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Personal Digital Assistants

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PCMCIA Cards

The LT1300 is a micropower step-up DC/DC converter that

utilizes Burst Mode™ operation. The device can deliver 5V

or 3.3V from a two-cell battery input. It features program-

mable 5V or 3.3V output via a logic-controlled input, no-

load quiescent current of 120µA and a shutdown pin which

reduces supply current to 10µA. The on-chip power switch

has a low 170mV saturation voltage at a switch current of

1A, a four-fold reduction over prior designs. A 155kHz

internal oscillator allows the use of extremely small sur-

face mount inductors and capacitors. Operation is guaran-

teed at 1.8V input. This allows more energy to be extracted

from the battery increasing operating life. The I

LIM

pin can

be used to program peak switch current with a single

resistor allowing the use of less expensive and smaller

inductors and capacitors in lighter load applications. The

LT1300 is available in an 8-lead SOIC package, minimizing

board space requirements. For a 5V/12V Selectable Out-

put Converter see the LT1301. For increased output cur-

rent see the LT1302.

DESCRIPTION

FEATURES

TYPICAL APPLICATIONS N

Micropower High Efficiency

3.3/5V Step-Up DC/DC Converter

APPLICATIONS

Two-Cell to 3.3V/5V Step-Up Converter 5V Output Efficiency

L1 = COILCRAFT DO1608-103

OR SUMIDA CD54-100

C1 = AVX TPSD107M010R0100

OR SANYO OS-CON 16SA100M

D1 =MBRS130LT3

OR 1N5817

C1

100µF



5V/3.3V

OUTPUT

L1

10µH D1

C1

100µF

2×

AA

CELL

LIM

PGND

GND

SENSE

LT1300

SELECT

LT1300 TA1

5V/3.3V

SELECT

SHDN

SHUTDOWN

N/C



LOAD CURRENT (mA)

10 100 500

LT1300 TA2

EFFICIENCY (%)

= 4.0V

= 3.0V

= 2.5V

= 2.0V

Burst Mode is a trademark of Linear Technology Corporation.

Summary of content (8 pages)

PAGE 1
LT1300 Micropower High Efficiency 3.3/5V Step-Up DC/DC Converter U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Up to 220mA Output Current at 5V from 2V Supply Supply Voltage as Low as 1.8V Up to 88% Efficiency Small Inductor –10µH 120µA Quiescent Current Shutdown to 10µA Programmable 3.
PAGE 2
LT1300 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION VIN Voltage .............................................................. 10V SW1 Voltage ............................................................ 20V Sense Voltage .......................................................... 10V SHUTDOWN Voltage................................................ 10V SELECT Voltage ....................................................... 10V ILIM Voltage .........................................
PAGE 3
LT1300 U W TYPICAL PERFORMANCE CHARACTERISTICS Efficiency 170 VOUT = 3.3V L = 10µH 86 165 84 EFFICIENCY (%) 82 VIN = 3V 80 INPUT CURRENT (µA) 160 VIN = 2.5V 78 VIN = 2V 76 74 72 150 145 140 68 125 10 100 LOAD CURRENT (mA) VOUT = 3.3V 135 130 1 70 VOUT = 5V 155 70 66 80 ISHDN + IVIN + ISENSE (µA) 88 Total Quiescent Current in Shutdown No-Load Battery Current 50 40 30 20 10 0 120 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.
PAGE 4
LT1300 U U U PIN FUNCTIONS GND (Pin 1): Signal Ground. Sel (Pin 2): Output Select. When tied to VIN or VOUT converter regulates at 5V. When grounded converter regulates at 3.3V. SHDN (Pin 3): Shutdown. Pull high to effect shutdown. Tie to ground for normal operation. Sense (Pin 4): “Output” Pin. ILIM (Pin 5): Float for 1A switch current limit. Tie to ground for approximately 400mA. A resistor between ILIM and ground sets peak current to some intermediate value (see Figure 5). VIN (Pin 6): Supply Pin.
PAGE 5
LT1300 TEST CIRCUITS Oscillator Test Circuit 5V 2V 100Ω VIN IL SEL 100µF SW fOUT LT1300 SENSE SHDN GND PGND U OPERATION Operation of the LT1300 is best understood by referring to the Block Diagram in Figure 1. When A1’s negative input, related to the Sense pin voltage by the appropriate resistor-divider ratio, is higher that the 1.25V reference voltage, A1’s output is low. A2, A3 and the oscillator are turned off, drawing no current. Only the reference and A1 consume current, typically 120µA.
PAGE 6
LT1300 U W U U APPLICATIONS INFORMATION Output Voltage Selection The LT1300 can be selected to 3.3V or 5V under logic control or fixed at either by tying SELECT to ground or VIN respectively. It is permissible to tie SELECT to a voltage higher than VIN as long as it does not exceed 10V. Efficiency in 3.3V mode will be slightly less that in 5V mode due to the fact that the diode drop is a greater percentage of 3.3V than 5V.
PAGE 7
LT1300 U U W U APPLICATIONS INFORMATION Table 1. Recommended Inductors PART NUMBER DO1608-103 DO3316-223 DO1608-223 CTX10-1 CTX20-1 LQH3C2204K0M00 CD54-100M CDRH62-220M CDRH62-100M GA10-102K VENDOR Coilcraft Coilcraft Coilcraft Coiltronics Coiltronics Murata-Frie Sumida Sumida Sumida Gowanda L (µH) 10 22 22 10 20 22 10 22 10 10 DCR (Ω) 0.11 0.050 0.31 0.038 0.175 0.7 0.11 0.38 0.17 0.038 ILIM PIN Float Float Ground Float Ground Ground Float Ground Float Float EFFICIENCY 2.
PAGE 8
LT1300 U TYPICAL APPLICATIONS N Four-Cell to 5V/3.3V Up-Down Converter L1* 27µH 2.5V ≤ VIN ≤ 8V LCD Contrast Supply C2** 100µF VIN 1.8V TO 6V + 4 N/C 4× AA CELL ILIM + 5V/3.3V SELECT C1** 100µF L2* 27µH VIN 1 7 3 10 8 2 1N5817 SHDN SENSE GND PGND 5V/3.