FEATURES
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LT1308A/LT1308B
High Current, Micropower
Single Cell, 600kHz
DC/DC Converters
DESCRIPTION
The LT
®
1308A/LT1308B are micropower, fixed frequency
step-up DC/DC converters that operate over a 1V to 10V
input voltage range. They are improved versions of the
LT1308 and are recommended for use in new designs.
The LT1308A features automatic shifting to power sav-
ing Burst Mode operation at light loads and consumes
just 140μA at no load. The LT1308B features continuous
switching at light loads and operates at a quiescent cur-
rent of 2.5mA. Both devices consume less than 1μA in
shutdown.
Low-battery detector accuracy is significantly tighter than
the LT1308. The 200mV reference is specified at ± 2%
at room and ±3% over temperature. The shutdown pin
enables the device when it is tied to a 1V or higher source
and does not need to be tied to V
IN
as on the LT1308. An
internal V
C
clamp results in improved transient response
and the switch voltage rating has been increased to 36V,
enabling higher output voltage applications.
The LT1308A/LT1308B are available in the 8-lead SO and
the 14-lead TSSOP packages.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
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5V at 1A from a Single Li-Ion Cell
5V at 800mA in SEPIC Mode from Four NiCd Cells
Fixed Frequency Operation: 600kHz
Boost Converter Outputs up to 34V
Starts into Heavy Loads
Automatic Burst Mode™ Operation at
Light Load (LT1308A)
Continuous Switching at Light Loads (LT1308B)
Low V
CESAT
Switch: 300mV at 2A
Pin-for-Pin Upgrade Compatible with LT1308
Lower Quiescent Current in Shutdown: 1μA (Max)
Improved Accuracy Low-Battery Detector
Reference: 200mV ± 2%
Available in 8-Lead SO and 14-Lead TSSOP Packages
APPLICATIONS
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GSM/CDMA Phones
Digital Cameras
LCD Bias Supplies
Answer-Back Pagers
GPS Receivers
Battery Backup Supplies
Handheld Computers
TYPICAL APPLICATION
L1
4.7μH
D1
5V
1A
SW
EFFICIENCY (%)
LBO
LT1308B
SHDN
V
C
47k
100pF
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
L1: MURATA LQH6C4R7
*R1: 887k FOR V
OUT
= 12V
FB
GND
R2
100k
R1*
309k
95
90
85
80
75
70
65
60
55
50
1308A/B F01a
Converter Efficiency
V
IN
= 3.6V
V
IN
= 4.2V
+
Li-Ion
CELL
V
IN
C1
47μF
SHUTDOWN
LBI
+
V
IN
= 2.5V
V
IN
= 1.5V
C2
220μF
1
10
100
LOAD CURRENT (mA)
1000
1308A/B F01b
Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
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LT1308A/LT1308B
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
,
SHDN,
LBO Voltage........................................... 10V
SW Voltage .............................................. –0.4V to 36V
FB Voltage ......................................................... V
IN
+ 1V
V
C
Voltage ................................................................. 2V
LBI Voltage ................................................. –0.1V to 1V
Current into FB Pin............................................... ±1mA
Operating Temperature Range
Commercial............................................. 0°C to 70°C
Extended Commerial (Note 2) ............ –40°C to 85°C
Industrial ........................................... –40°C to 85°C
Storage Temperature Range.................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................. 300°C
PIN CONFIGURATION
TOP VIEW
V
C
TOP VIEW
V
C
1
FB 2
SHDN
3
GND 4
8
7
6
5
LBO
LBI
V
IN
SW
FB
SHDN
GND
GND
GND
GND
1
2
3
4
5
6
7
14 LBO
13 LBI
12 V
IN
11 V
IN
10 SW
9
8
SW
SW
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 190°C/W
F PACKAGE
14-LEAD PLASTIC TSSOP
(NOTE 6)
T
JMAX
= 125°C,
θ
JA
= 80°C/W
OBSOLETE, FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
ORDER INFORMATION
LEAD FREE FINISH
LT1308ACS8#PBF
LT1308AIS8#PBF
LT1308BCS8#PBF
LT1308BIS8#PBF
LT1308ACF#PBF
LT1308BCF#PBF
LEAD BASED FINISH
LT1308ACS8
LT1308AIS8
LT1308BCS8
LT1308BIS8
LT1308ACF
LT1308BCF
TAPE AND REEL
LT1308ACS8#TRPBF
LT1308AIS8#TRPBF
LT1308BCS8#TRPBF
LT1308BIS8#TRPBF
LT1308ACF#TRPBF
LT1308BCF#TRPBF
TAPE AND REEL
LT1308ACS8#TR
LT1308AIS8#TR
LT1308BCS8#TR
LT1308BIS8#TR
LT1308ACF#TR
LT1308BCF#TR
PART MARKING
1308A
1308AI
1308B
1308BI
LT1308ACF
LT1308BCF
PART MARKING
1308A
1308AI
1308B
1308BI
LT1308ACF
LT1308BCF
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
14-Lead Plastic TSSOP
14-Lead Plastic TSSOP
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
14-Lead Plastic TSSOP
14-Lead Plastic TSSOP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to:
http://www.linear.com/packaging/
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LT1308A/LT1308B
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
PARAMETER
Quiescent Current
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. Commercial Grade 0°C to 70°C. V
IN
= 1.1V, V
SHDN
= V
IN
, unless otherwise noted.
CONDITIONS
Not Switching, LT1308A
Switching, LT1308B
V
SHDN
= 0V (LT1308A/LT1308B)
l
MIN
TYP
140
2.5
0.01
MAX
240
4
1
1.24
80
0.4
0.2
1
UNITS
μA
mA
μA
V
nA
%/V
%/V
V
μmhos
V/V
V
FB
I
B
Feedback Voltage
FB Pin Bias Current
Reference Line Regulation
Minimum Input Voltage
(Note 3)
1.1V ≤ V
IN
≤ 2V
2V ≤ V
IN
≤ 10V
∆I
= 5μA
V
IN
= 1.2V
Duty Cycle = 30% (Note 4)
I
SW
= 2A (25°C, 0°C), V
IN
= 1.5V
I
SW
= 2A (70°C), V
IN
= 1.5V
V
IN
= 2.5V, Circuit of Figure 1
V
SHDN
= 1.1V
V
SHDN
= 6V
V
SHDN
= 0V
1.20
1.22
27
0.03
0.01
0.92
60
100
l
l
g
m
A
V
f
OSC
Error Amp Transconductance
Error Amp Voltage Gain
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
Switch V
CESAT
Burst Mode Operation Switch Current Limit
(LT1308A)
Shutdown Pin Current
l
l
500
82
2
600
90
3
290
330
400
700
4.5
350
400
kHz
%
A
mV
mV
mA
l
l
l
l
2
20
0.01
196
194
200
200
0.1
0.01
33
3000
5
35
0.1
204
206
0.25
0.1
100
10
μA
μA
μA
mV
mV
V
μA
nA
V/V
μA
LBI Threshold Voltage
LBO Output Low
LBO Leakage Current
LBI Input Bias Current (Note 5)
Low-Battery Detector Gain
Switch Leakage Current
V
SW
= 5V
I
SINK
= 50μA
V
LBI
= 250mV, V
LBO
= 5V
V
LBI
= 150mV
l
l
l
0.01
The
l
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
Industrial Grade –40°C to 85°C. V
IN
= 1.2V, V
SHDN
= V
IN
, unless otherwise noted.
SYMBOL
I
Q
PARAMETER
Quiescent Current
CONDITIONS
Not Switching, LT1308A
Switching, LT1308B
V
SHDN
= 0V (LT1308A/LT1308B)
(Note 3)
1.1V ≤ V
IN
≤ 2V
2V ≤ V
IN
≤ 10V
∆I
= 5μA
l
l
l
l
l
l
l
MIN
TYP
140
2.5
0.01
MAX
240
4
1
1.25
80
0.4
0.2
1
UNITS
μA
mA
μA
V
nA
%/V
%/V
V
μmhos
V/V
V
FB
I
B
Feedback Voltage
FB Pin Bias Current
Reference Line Regulation
Minimum Input Voltage
1.19
1.22
27
0.05
0.01
0.92
60
100
g
m
A
V
Error Amp Transconductance
Error Amp Voltage Gain
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LT1308A/LT1308B
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. Industrial Grade –40°C to 85°C. V
IN
= 1.2V, V
SHDN
= V
IN
, unless otherwise noted.
SYMBOL
f
OSC
PARAMETER
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
Switch V
CESAT
Burst Mode Operation Switch Current Limit
(LT1308A)
Shutdown Pin Current
Duty Cycle = 30% (Note 4)
I
SW
= 2A (25°C, – 40°C), V
IN
= 1.5V
I
SW
= 2A (85°C), V
IN
= 1.5V
V
IN
= 2.5V, Circuit of Figure 1
V
SHDN
= 1.1V
V
SHDN
= 6V
V
SHDN
= 0V
l
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
l
l
MIN
500
82
2
TYP
600
90
3
290
330
400
2
20
0.01
MAX
750
4.5
350
400
UNITS
kHz
%
A
mV
mV
mA
5
35
0.1
204
207
0.25
0.1
100
10
μA
μA
μA
mV
mV
V
μA
nA
V/V
μA
LBI Threshold Voltage
LBO Output Low
LBO Leakage Current
LBI Input Bias Current (Note 5)
Low-Battery Detector Gain
Switch Leakage Current
V
SW
= 5V
I
SINK
= 50μA
V
LBI
= 250mV, V
LBO
= 5V
V
LBI
= 150mV
l
l
l
196
193
200
200
0.1
0.01
33
3000
l
0.01
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LT1308ACS8, LT1308ACF LT1308BCS8 and LT1308BCF are
,
designed, characterized and expected to meet the industrial temperature
limits, but are not tested at –40°C and 85°C. I grade devices are
guaranteed over the –40°C to 85°C operating temperature range.
Note 3:
Bias current flows into FB pin.
Note 4:
Switch current limit guaranteed by design and/or correlation to
static tests. Duty cycle affects current limit due to ramp generator (see
Block Diagram).
Note 5:
Bias current flows out of LBI pin.
Note 6:
Connect the four GND pins (Pins 4–7) together at the device.
Similarly, connect the three SW pins (Pins 8–10) together and the two V
IN
pins (Pins 11, 12) together at the device.
TYPICAL PERFORMANCE CHARACTERISTICS
LT1308B
3.3V Output Efficiency
95
90
85
EFFICIENCY (%)
80
75
70
65
60
55
50
1
100
10
LOAD CURRENT (mA)
1000
1308A/B G01
LT1308A
3.3V Output Efficiency
95
95
90
V
IN
= 1.8V
V
IN
= 2.5V
EFFICIENCY (%)
85
80
75
70
65
60
55
50
1
100
10
LOAD CURRENT (mA)
1000
1308A/B G02
LT1308A
5V Output Efficiency
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 1.8V
V
IN
= 2.5V
90
85
EFFICIENCY (%)
80
75
70
65
60
55
50
V
IN
= 1.2V
V
IN
= 1.2V
V
IN
= 1.5V
V
IN
= 2.5V
1
10
100
LOAD CURRENT (mA)
1000
1308A/B G03
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LT1308A/LT1308B
TYPICAL PERFORMANCE CHARACTERISTICS
LT1308B
12V Output Efficiency
90
85
80
EFFICIENCY (%)
75
70
65
60
55
50
1
10
100
LOAD CURRENT (mA)
1000
1308A/B G04
Switch Current Limit vs
Duty Cycle
4.0
500
Switch Saturation Voltage
vs Current
V
IN
= 5V
SWITCH V
CESAT
(mV)
V
IN
= 3.3V
3.5
CURRENT LIMIT (A)
400
85°C
300
25°C
–40°C
3.0
200
2.5
100
2.0
0
0
20
60
40
DUTY CYCLE (%)
80
100
1308 • G05
0
1.0
0.5
1.5
SWITCH CURRENT (A)
2.0
1308 G06
SHDN
Pin Bias Current vs Voltage
50
80
70
SHDN
PIN CURRENT (μA)
40
–40°C
BIAS CURRENT (nA)
60
FB, LBI Bias Current vs
Temperature
203
202
201
LBI
V
REF
(mV)
FB
20
10
197
196
–25
0
25
50
TEMPERATURE (°C)
75
100
1308 • G08
Low Battery Detector Reference
vs Temperature
30
50
40
30
200
199
198
25°C
85°C
20
10
0
0
2
6
8
4
SHDN
PIN VOLTAGE (V)
10
1308 G07
0
–50
195
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1308 • G09
Oscillator Frequency vs
Temperature
800
750
QUIESCENT CURRENT (μA)
700
FREQUENCY (kHz)
650
600
550
500
450
400
–50
–2.5
0
25
50
TEMPERATURE (°C)
75
100
180
170
160
150
140
130
120
110
LT1308A Quiescent Current vs
Temperature
1.25
1.24
1.23
V
FB
(V)
–25
0
25
50
TEMPERATURE (°C)
75
100
1308 • G11
Feedback Pin Voltage vs
Temperature
1.22
1.21
1.20
1.19
1.18
–50
100
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1308 • G12
1308 • G10
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