1
LT1303/LT1303-5
Micropower High Efficiency
DC/DC Converters with
Low-Battery Detector
Adjustable and Fixed 5V
FEATURES
s
5V at 200mA from a 2V Input
s
Supply Voltage As Low As 1.8V
s
Up to 88% Efficiency
s
120
A Quiescent Current
s
Low-Battery Detector
s
Low V
CESAT
Switch: 170mV at 1A Typ
s
Uses Inexpensive Surface Mount Inductors
s
8-Lead PDIP or SO Package
DESCRIPTIO
N
U
s
EL Panel Drivers
s
2-Cell and 3-Cell to 5V Conversion
s
Palmtop Computers
s
Portable Instruments
s
Bar-Code Scanners
s
PDAs
s
Wireless Systems
APPLICATIO
N
S
U
TYPICAL APPLICATIO
N
U
The LT
1303/LT1303-5 are micropower step-up high
efficiency DC/DC converters using Burst Mode
TM
opera-
tion. They are ideal for use in small, low-voltage battery-
operated systems. The LT1303-5 accepts an input voltage
between 1.8V and 5V and converts it to a regulated 5V. The
LT1303 is an adjustable version that can supply an output
voltage up to 25V. Quiescent current is only 120
A from
the battery and the shutdown pin further reduces current
to 10
A. The low-battery detector provides an open-
collector output that goes low when the input voltage
drops below a preset level. The on-chip NPN power switch
has a low 170mV saturation voltage at a switch current
of 1A. The LT1303/LT1303-5 are available in 8-lead PDIP
or SO packages, easing board space requirements.
For higher output current, please see the LT1305 or
LT1302.
LOAD CURRENT (mA)
0.1
30
EFFICIENCY (%)
70
80
90
1
100
10
1000
LT1303 TA01
60
50
40
V
IN
= 2V
V
IN
= 4V
V
IN
= 2.5V
V
IN
= 3V
5V Output Efficiency
V
IN
SW
GND
PGND
SENSE
LBI
LBO
SHDN
LT1303-5
+
+
100k
100
F
SHUTDOWN
412k
1%
100
F
2 CELLS
316k
1%
L1
22
H
1N5817
V
OUT
, 5V
200mA
LOW BATTERY
GOES LOW AT
V
BAT
= 2.2V
L1 = SUMDIA CD54-220
LT1303 TA02
Figure 1. 2-Cell to 5V DC/DC Converter with Low-Battery Detect
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
2
LT1303/LT1303-5
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Q
Quiescent Current
V
SHDN
= 0.5V, V
SEL
= 5V, V
SENSE
= 5.5V
q
120
200
A
V
SHDN
= 1.8V
q
7
15
A
V
IN
Input Voltage Range
1.8
1.55
V
q
2.0
V
Feedback Voltage
LT1303
q
1.22
1.24
1.26
V
Output Sense Voltage
LT1303-5
q
4.8
5.0
5.2
V
Comparator Hysteresis
LT1303 (Note 1)
q
6
12.5
mV
Output Hysteresis
LT1303-5 (Note 1)
q
22
50
mV
Feedback Pin Bias Current
LT1303, V
FB
= 1V
q
7
20
nA
Oscillator Frequency
Current Limit Not Asserted
120
155
185
kHz
Oscillator TC
0.2
%/
C
DC
Maximum Duty Cycle
q
75
86
95
%
t
ON
Switch On Time
Current Limit Not Asserted
5.6
s
Output Line Regulation
1.8V < V
IN
< 6V
q
0.06
0.15
%/V
V
CESAT
Switch Saturation Voltage
I
SW
= 700mA
q
130
200
mV
Switch Leakage Current
V
SW
= 5V, Switch Off
q
0.1
10
A
Peak Switch Current
V
IN
= 2V
q
0.75
1.0
1.25
A
V
IN
= 5V
0.65
0.9
1.15
A
LBI Trip Voltage
q
1.21
1.24
1.27
V
LBI Input Bias Current
V
LBI
= 1V
q
7
20
nA
LBO Output Low
I
LOAD
= 100
A
q
0.11
0.4
V
LBO Leakage Current
V
LBI
= 1.3V, V
LBO
= 5V
q
0.1
5
A
V
SHDNH
Shutdown Pin High
q
1.8
V
V
SHDNL
Shutdown Pin Low
0.5
V
I
SHDN
Shutdown Pin Bias Current
V
SHDN
= 5V
q
8.0
20
A
V
SHDN
= 2V
q
3.0
A
V
SHDN
= 0V
q
0.1
1
A
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
V
IN
Voltage .............................................................. 10V
SW1 Voltage ............................................................ 25V
Sense Voltage (LT1303-5) ....................................... 20V
FB Voltage (LT1303) ................................................ 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
Lead Temperature (Soldering, 10 sec).................. 300
C
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
T
A
= 25
C, V
IN
= 2.0V, unless otherwise noted.
ELECTRICAL C
C
HARA TERISTICS
Note 1: Hysteresis specified is DC. Output ripple may be higher if output
capacitance is insufficient or capacitor ESR is excessive.
The
q
denotes specifications which apply over the 0
C to 70
C operating
temperature range.
ORDER PART
NUMBER
LT1303CN8
LT1303CS8
LT1303CN8-5
LT1303CS8-5
S8 PART MARKING
1303
13035
Consult factory for Industrial and Military grade parts.
1
2
3
4
8
7
6
5
TOP VIEW
GND
LBO
SHDN
FB (SENSE)*
PGND
SW
V
IN
LBI
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
*FIXED VERSION
T
JMAX
= 100
C,
JA
= 130
C/W (N8)
T
JMAX
= 100
C,
JA
= 150
C/W (S8)
3
LT1303/LT1303-5
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
SWITCH CURRENT (A)
0.1
V
CESAT
(mV)
150
200
250
225
175
125
75
25
0.8
LT1303 G01
100
50
0
0.2
1.0
0.3
0.5
0.7
0.9
0.4
0.6
1.0
LT1303 FB Voltage
TEMPERATURE (
C)
50
100
V
CESAT
(mV)
120
130
140
150
160
170
25
0
25
50
LT1303 G02
75
180
190
200
110
100
I
SW
= 700mA
LT1303-5 Sense Pin Resistance
to Ground
Low Battery Detect Trip Point
LT1303-5 Sense Voltage
TEMPERATURE (C)
50
700
800
900
25
75
LT1303 GO3
600
500
25
0
50
100
400
300
RESISTANCE (k
)
1000
V
CESAT
vs Switch Current
LBI Pin Bias Current
FB Pin Bias Current
Switch Current Limit
TEMPERATURE (
C)
50
1.200
FEEDBACK VOLTAGE (V)
1.210
1.215
1.220
1.225
1.230
1.235
25
0
25
50
LT1330 G04
75
1.240
1.245
1.250
1.205
100
TEMPERATURE (
C)
50
1.200
LBI VOLTAGE (V)
1.210
1.215
1.220
1.225
1.230
1.235
25
0
25
50
LT1303 G06
75
1.240
1.245
1.250
1.205
100
TEMPERATURE (
C)
50
4.90
SENSE VOLTAGE (V)
4.94
4.96
4.98
5.00
5.02
5.04
25
0
25
50
LT1303 G05
75
5.06
5.08
5.10
4.92
100
TEMPERATURE (
C)
50
0
BIAS CURRENT (nA)
4
6
8
10
12
14
25
0
25
50
LT1303 G07
75
16
18
20
2
100
TEMPERATURE (
C)
50
25
25
75
0.60
SWITCH CURRENT (A)
0.70
0.90
1.00
1.10
50
1.50
LT1303 G09
0.80
0
100
1.20
1.30
1.40
V
IN
= 2V
TEMPERATURE (
C)
50
0
BIAS CURRENT (nA)
4
6
8
10
12
14
25
0
25
50
LT1303 G08
75
16
18
20
2
100
V
CESAT
vs Temperature
4
LT1303/LT1303-5
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Oscillator Frequency
Switch On-Time
Maximum Duty Cycle
TEMPERATURE (
C)
50
2
ON-TIME (
s)
3
4
5
6
8
25
0
25
50
LT1303 G10
75
100
7
TEMPERATURE (
C)
50
100
FREQUENCY (kHz)
120
130
140
150
160
170
25
0
25
50
LT1303 G11
75
180
190
200
110
100
TEMPERATURE (
C)
50
50
DUTY CYCLE (%)
60
65
70
75
80
85
25
0
25
50
LT1303 G12
75
90
95
100
55
100
Quiescent Current
Quiescent Current
Switch Current Limit
TEMPERATURE (
C)
50
100
QUIESCENT CURRENT (
A)
120
130
140
150
160
170
25
0
25
50
LT1303 G13
75
180
190
200
110
100
SWITCH OFF
V
IN
= 2V
INPUT VOLTAGE (V)
0
SWITCH CURRENT (mA)
1000
1100
1200
8
LT1303 G15
900
800
700
2
4
6
10
L = 33
H
V
L
= 3V
INPUT VOLTAGE (V)
0
QUIESCENT CURRENT (
A)
300
400
500
8
LT1303 G14
200
100
0
2
4
6
10
T
A
= 25
C
SWITCH OFF
200
s/DIV
Transient Response
Figure 1 Circuit
V
IN
= 2V
V
OUT
= 5V
LT1303 G16
200mA
0mA
V
OUT
100mV/DIV
AC COUPLED
I
LOAD
R
PULL-UP
= 47k
Low Battery Detector Transient
Response
LT1303 G18
5
s/DIV
V
LBO
2V/DIV
V
TRIP
+10mV
V
TRIP
10mV
LT1303 G17
500
s/DIV
5V
Shutdown Pin Response
R
LOAD
= 100
V
IN
= 2V
V
OUT
= 5V
C
OUT
= 100
F
V
OUT
1V/DIV
V
SHDN
5V/DIV
V
LBI
5
LT1303/LT1303-5
PI
N
FU
N
CTIO
N
S
U
U
U
GND (Pin 1): Signal Ground. Tie to PGND under the
package.
LBO (Pin 2): Open-Collector Output of Low-Battery Com-
parator. Can sink 100
A. Disabled when device is in
shutdown.
SHDN (Pin 3): Shutdown. Pull high to shut down the
device. Ground for normal operation.
FB/Sense (Pin 4): On 1303 (adjustable) this pin connects
to the main comparator C1 input. On LT1303-5 this pin
connects to the resistor string that sets output voltage
at 5V.
LBI (Pin 5): Low-Battery Comparator Input. When voltage
on this pin below 1.24V, LBO is low.
V
IN
(Pin 6): Supply Pin. Must be bypassed with a large
value electrolytic to ground. Keep bypass within 0.2" of the
device.
SW (Pin 7): Switch Pin. Connect inductor and diode here.
Keep layout short and direct to minimize radio frequency
interference.
PGND (Pin 8): Power ground. Tie to signal ground (pin1)
under the package. Bypass capacitor from V
IN
should be
tied directly to PGND within 0.2" of the device.
W
I
D AGRA
BLOCK
S
Figure 2. LT1303 Block Digram
+
+
+
6
7
8
3
2
5
1
4
+
+
C1
C2
L1
D1
V
IN
V
IN
R1
3
Q2
1
Q1
160
SHUTDOWN
LBO
LBI
GND
PGND
SW
R1
R2
C3
C2
C1
FB
OFF
OSCILLATOR
A3
DRIVER
CURRENT
COMPARATOR
HYSTERETIC
COMPARATOR
REFERENCE
1.24V
18mV
LT1303 BD01
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