Linear Technology LT1305 Datasheet

LT1305

Micropower High Power

DC/DC Converter with

Low-Battery Detector

EATU

F

■

5V at 400mA from 2V Input

■

Supply Voltage As Low As 1.8V

■

120µA Quiescent Current

■

Low-Battery Detector

■

Low V

■

Uses Inexpensive Surface Mount Inductors

■

8-Lead SO Package

PPLICATI

A

■

2-Cell and 3-Cell to 5V Conversion

■

EL Panel Drivers

■

Portable Instruments

S

RE

Switch: 310mV at 2A Typ

CESAT

U

O

S

A

PPLICATITYPICAL

O

U

DUESCRIPTIO

The LT®1305 is a micropower step-up DC/DC converter
that uses Burst ModeTM operation. Similar to the LT1303,
the LT1305 features a 2A internal low-loss switch and can
deliver up to four times the output power of the LT1303.

Quiescent current is only 120µA and the Shutdown pin
further reduces current to 10µA. A low-battery detector
provides an open-collector output that goes low when the
input voltage drops below a preset level. The LT1305 is
available in an 8-pin SO, easing board space requirements.

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

Burst Mode is a trademark of Linear Technology Corporation

2-Cell and 3-Cell to 5V/400mA DC/DC Converter

with Low-Battery Detect

316k
1%

2 TO 3
CELLS

C1, C2: AVX TPSE227010R0100
D1: MOTOROLA MBRS130LT3
L1: COILCRAFT D03316-103

+

C1
220µF

412k
1%

SHUTDOWN

L1

10µH

V

IN

LBI

LT1305

SHDN

GND PGND

SW

LBO

Efficiency

D1

LOW BATTERY

100k

301k

100k
1%

1%

C2

220µF

FB

GOES LOW AT

= 2.2V

V

BAT

V



OUT

5V
400mA

+

LT1305 • TA03

90

80

EFFICIENCY (%)

70

60

1

VIN = 4.00V

VIN = 3.00V

= 2.00V

V

IN

VIN = 2.50V

10 100 1000

LOAD CURRENT (mA)

LT1305 • TA02

1

LT1305

WU

U

PACKAGE

/

O

RDER I FOR ATIO

W

O

A

LUTEXI T

S

VIN Voltage .............................................................. 10V

SW1 Voltage ............................................................ 25V

FB Voltage ............................................................... 10V

Shutdown Voltage ................................................... 10V

LBO Voltage............................................................. 10V

LBI Voltage .............................................................. 10V

Maximum Power Dissipation ............................. 500mW

Operating Temperature Range ..................... 0°C to 70°C

Storage Temperature Range ................. –65°C to 150°C

A

WUW

ARB

U
G

I

S

GND

LBO

SHDN

1

2

3

FB

4

T

JMAX

TOP VIEW

S8 PACKAGE

8-LEAD PLASTIC SO

= 100°C, θJA = 80°C/ W

ORDER PART

NUMBER

PGND

8

SW

7

V



6

IN

LBI

5

LT1305CS8

S8 PART MARKING

1305

Lead Temperature (Soldering, 10 sec)..................300°C

Consult factory for Industrial and Military grade parts.

LECTRICAL C CHARA TERIST

E

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

Q

VINInput Voltage Range 1.8 1.55 V

DC Maximum Duty Cycle ● 75 86 95 %
t

ON

V

CESAT

V

SHDNH

V

SHDNL

I

SHDN

Quiescent Current V

Feedback Voltage ● 1.22 1.24 1.26 V
Comparator Hysteresis ● 6 12.5 mV
Feedback Pin Bias Current VFB = 1V ● 720 nA
Oscillator Frequency Current Limit Not Asserted 120 155 185 kHz
Oscillator TC 0.2 %/°C

Switch On Time Current Limit Not Asserted 5.6 µs
Output Line Regulation 1.8V < VIN < 6V ● 0.06 0.15 %/V
Switch Saturation Voltage ISW = 1A ● 140 280 mV
Switch Leakage Current VSW = 5V, Switch Off ● 0.1 10 µA
Peak Switch Current VIN = 2V 1.35 2 2.35 A

LBI Trip Voltage (Note 2) ● 1.21 1.24 1.27 V
LBI Input Bias Current V
LBO Output Low I
LBO Leakage Current V
Shutdown Pin High ● 1.8 V
Shutdown Pin Low 0.5 V
Shutdown Pin Bias Current V

ICS

TA = 25°C, VIN = 2.0V, unless otherwise noted.

= 0.5V, VFB = 2V ● 120 200 µA

SHDN

V

= 1.8V ● 715 µA

SHDN

● 2.0 V

● 1.20 2.50 A

VIN = 5V 1.15 2.15 A

= 1V ● 720 nA

LBI

= 100µA ● 0.11 0.4 V

LOAD

= 1.3V, V

LBI

= 5V ● 8.0 20 µA

SHDN

= 2V ● 3.0 µA

V

SHDN

= 0V ● 0.1 1 µA

V

SHDN

= 5V ● 0.1 5 µA

LBO

The ● denotes specifications which apply over the 0°C to 70°C operating
temperature range.

Note 1: Hysteresis specified is DC. Output ripple may be higher if output
capacitance is insufficient or capacitor ESR is excessive.

2

Note 2: Low-battery detector comparator is inoperative when device is in
shutdown.

W

TEMPERATURE (˚C)

–50



1.8

2.0

2.2

25 75

LT1305 • G06

1.6

1.4

–25 0

50 100

1.2

1.0

PEAK SWITCH CURRENT (A)

2.4

TEMPERATURE (°C)

–50

1.200

FEEDBACK VOLTAGE (V)

1.210

1.215

1.220

1.225

1.230

1.235

–25

0

25 50

LT1305 • G09

75

1.240

1.245

1.250

1.205

100

U

TYPICAL PERFORMANCE CHARACTERISTICS

LT1305

Switch On Time

8

7

6

5

ON TIME (µs)

4

3

2

–50

–25

02550

TEMPERATURE (°C)

75 100

LT1305 • G01

Oscillator Frequency

200
190
180
170

160
150
140

FREQUENCY (kHz)

130
120
110
100

–50

–25

Quiescent Current Quiescent Current

QUIESCENT CURRENT (µA)

500

400

300

200

100

0

TA = 25°C
SWITCH OFF

0

2

200
190
180
170

160
150
140
130

QUIESCENT CURRENT (µA)

120
110
100

SWITCH OFF
V

IN

–50

= 2V

–25

TEMPERATURE (°C)

0

25 50

75

LT1305 • G04

100

25 50

0

TEMPERATURE (°C)

6

4

INPUT VOLTAGE (V)

75

LT1305 • G02

8

LT1305 • G05

100

10

Maximum Duty Cycle

100

95
90
85

80
75
70

DUTY CYCLE (%)

65
60
55
50

–50

–25

TEMPERATURE (°C)

Current Limit

0

25 50

75

LT1305 • G03

100

LBI Pin Bias Current FB Pin Bias Current

20
18
16
14

12
10

8

BIAS CURRENT (nA)

6
4
2
0

–50

–25

25 50

0

TEMPERATURE (°C)

75

LT1305 • G07

100

20
18
16
14

12
10

8

BIAS CURRENT (nA)

6
4
2
0

–50

–25

25 50

0

TEMPERATURE (°C)

75

LT1305 • G08

FB Voltage

100

3