LT1303/LT1303-5
Micropower High Efficiency
DC/DC Converters with
Low-Battery Detector
Adjustable and Fixed 5V
FEATURES
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DESCRIPTION
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 120µA from
the battery and the shutdown pin further reduces current
to 10µA. 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
5V at 200mA from a 2V Input
Supply Voltage As Low As 1.8V
Up to 88% Efficiency
120
µ
A Quiescent Current
Low-Battery Detector
Low V
CESAT
Switch: 170mV at 1A Typ
Uses Inexpensive Surface Mount Inductors
8-Lead PDIP or SO Package
APPLICATIONS
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EL Panel Drivers
2-Cell and 3-Cell to 5V Conversion
Palmtop Computers
Portable Instruments
Bar-Code Scanners
PDAs
Wireless Systems
TYPICAL APPLICATION
L1
22µH
316k
1%
1N5817
90
80
V
IN
LBI
SW
SENSE
LT1303-5
100k
LBO
PGND
100µF
EFFICIENCY (%)
+
2 CELLS
100µF
V
OUT
, 5V
200mA
LOW BATTERY
GOES LOW AT
V
BAT
= 2.2V
412k
1%
SHUTDOWN
SHDN
GND
70
60
50
40
+
L1 = SUMDIA CD54-220
LT1303 TA02
30
Figure 1. 2-Cell to 5V DC/DC Converter with Low-Battery Detect
U
U
U
5V Output Efficiency
V
IN
= 4V
V
IN
= 2V
V
IN
= 2.5V
V
IN
= 3V
0.1
1
10
100
1000
LT1303 TA01
LOAD CURRENT (mA)
1
LT1303/LT1303-5
ABSOLUTE
MAXIMUM
RATINGS
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 INFORMATION
TOP VIEW
GND 1
LBO 2
SHDN 3
FB (SENSE)* 4
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
*FIXED VERSION
T
JMAX
= 100°C,
θ
JA
= 130°C/W (N8)
T
JMAX
= 100°C,
θ
JA
= 150°C/W (S8)
8
7
6
5
PGND
SW
V
IN
LBI
ORDER PART
NUMBER
LT1303CN8
LT1303CS8
LT1303CN8-5
LT1303CS8-5
S8 PART MARKING
1303
13035
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
V
IN
PARAMETER
Quiescent Current
Input Voltage Range
T
A
= 25°C, V
IN
= 2.0V, unless otherwise noted.
MIN
q
q
q
CONDITIONS
V
SHDN
= 0.5V, V
SEL
= 5V, V
SENSE
= 5.5V
V
SHDN
= 1.8V
DC
t
ON
V
CESAT
Feedback Voltage
Output Sense Voltage
Comparator Hysteresis
Output Hysteresis
Feedback Pin Bias Current
Oscillator Frequency
Oscillator TC
Maximum Duty Cycle
Switch On Time
Output Line Regulation
Switch Saturation Voltage
Switch Leakage Current
Peak Switch Current
LBI Trip Voltage
LBI Input Bias Current
LBO Output Low
LBO Leakage Current
Shutdown Pin High
Shutdown Pin Low
Shutdown Pin Bias Current
LT1303
LT1303-5
LT1303 (Note 1)
LT1303-5 (Note 1)
LT1303, V
FB
= 1V
Current Limit Not Asserted
q
q
q
q
q
1.8
2.0
1.22
4.8
TYP
120
7
1.55
1.24
5.0
6
22
7
155
0.2
86
5.6
0.06
130
0.1
1.0
0.9
1.24
7
0.11
0.1
MAX
200
15
120
q
1.26
5.2
12.5
50
20
185
95
0.15
200
10
1.25
1.15
1.27
20
0.4
5
0.5
20
1
75
Current Limit Not Asserted
1.8V < V
IN
< 6V
I
SW
= 700mA
V
SW
= 5V, Switch Off
V
IN
= 2V
V
IN
= 5V
V
LBI
= 1V
I
LOAD
= 100µA
V
LBI
= 1.3V, V
LBO
= 5V
q
q
q
q
q
q
q
q
q
0.75
0.65
1.21
V
SHDNH
V
SHDNL
I
SHDN
1.8
8.0
3.0
0.1
V
SHDN
= 5V
V
SHDN
= 2V
V
SHDN
= 0V
q
q
q
UNITS
µA
µA
V
V
V
V
mV
mV
nA
kHz
%/°C
%
µs
%/V
mV
µA
A
A
V
nA
V
µA
V
V
µA
µA
µA
The
q
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
U
W
U
U
W W
W
LT1303/LT1303-5
TYPICAL PERFORMANCE CHARACTERISTICS
V
CESAT
vs Switch Current
250
225
200
175
150
125
100
75
50
25
0
0.1 1.0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
SWITCH CURRENT (A)
LT1303 G01
160
150
140
130
120
110
100
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
RESISTANCE (kΩ)
V
CESAT
(mV)
V
CESAT
(mV)
LT1303 FB Voltage
1.250
1.245
1.240
FEEDBACK VOLTAGE (V)
SENSE VOLTAGE (V)
1.230
1.225
1.220
1.215
1.210
1.205
1.200
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
5.02
5.00
4.98
4.96
4.94
4.92
4.90
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
LBI VOLTAGE (V)
1.235
LBI Pin Bias Current
20
18
16
BIAS CURRENT (nA)
14
12
10
8
6
4
2
0
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
14
12
10
8
6
4
2
0
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
SWITCH CURRENT (A)
BIAS CURRENT (nA)
U W
LT1303 G07
V
CESAT
vs Temperature
200
190
180
170
800
700
600
500
400
LT1303-5 Sense Pin Resistance
to Ground
1000
900
I
SW
= 700mA
300
–50
–25
50
25
0
TEMPERATURE (˚C)
75
100
LT1303 G02
LT1303 GO3
LT1303-5 Sense Voltage
5.10
5.08
5.06
5.04
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
1.205
Low Battery Detect Trip Point
1.200
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
LT1330 G04
LT1303 G05
LT1303 G06
FB Pin Bias Current
20
18
16
1.50
1.40
1.30
1.20
1.10
1.00
0.90
0.80
0.70
Switch Current Limit
V
IN
= 2V
0.60
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
LT1303 G08
LT1303 G09
3
LT1303/LT1303-5
TYPICAL PERFORMANCE CHARACTERISTICS
Switch On-Time
8
7
6
5
4
3
2
–50
FREQUENCY (kHz)
200
190
180
160
150
140
130
120
110
DUTY CYCLE (%)
–25
25
50
0
TEMPERATURE (°C)
75
100
ON-TIME (µs)
–25
0
25
50
TEMPERATURE (°C)
Quiescent Current
200
190
QUIESCENT CURRENT (µA)
SWITCH OFF
V
IN
= 2V
QUIESCENT CURRENT (µA)
170
160
150
140
130
120
110
100
–50
300
SWITCH CURRENT (mA)
180
–25
25
50
0
TEMPERATURE (°C)
Transient Response
Figure 1 Circuit
V
OUT
100mV/DIV
AC COUPLED
5V
V
OUT
1V/DIV
I
LOAD
200mA
0mA
200µs/DIV
V
IN
= 2V
V
OUT
= 5V
4
U W
75
Oscillator Frequency
100
95
90
85
80
75
70
65
60
55
Maximum Duty Cycle
170
100
100
–50
50
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
LT1303 G10
LT1303 G11
LT1303 G12
Quiescent Current
500
T
A
= 25°C
SWITCH OFF
400
1100
1200
Switch Current Limit
L = 33µH
V
L
= 3V
1000
200
900
100
800
0
75
100
0
2
6
4
INPUT VOLTAGE (V)
8
10
LT1303 G14
700
0
2
6
4
INPUT VOLTAGE (V)
8
10
LT1303 G15
LT1303 G13
Shutdown Pin Response
V
LBO
2V/DIV
Low Battery Detector Transient
Response
V
SHDN
5V/DIV
LT1303 G16
V
LBI
500µs/DIV
R
LOAD
= 100Ω
V
IN
= 2V
V
OUT
= 5V
C
OUT
= 100µF
V
TRIP
+10mV
V
TRIP
–10mV
5µs/DIV
R
PULL-UP
= 47k
LT1303 G18
LT1303 G17
LT1303/LT1303-5
PIN FUNCTIONS
GND (Pin 1):
Signal Ground. Tie to PGND under the
package.
LBO (Pin 2):
Open-Collector Output of Low-Battery Com-
parator. Can sink 100µA. 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.
BLOCK DIAGRA S
V
IN
+
C1
6
C2
4
FB
–
C1
OFF
OSCILLATOR
A3
DRIVER
Q2
1×
Q1
160×
R2
REFERENCE
1.24V
+
–
C3
+
GND
1
5
LBI
2
LBO
SHUTDOWN
3
8
PGND
Figure 2. LT1303 Block Digram
–
R1
HYSTERETIC
COMPARATOR
+
W
U
U
U
L1
V
IN
SW
D1
+
C2
7
CURRENT
COMPARATOR
18mV
R1
3Ω
LT1303 BD01
5
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