LT1308A/LT1308B
High Current, Micropower
Single Cell, 600kHz
DC/DC Converters
DESCRIPTION
FEATURES
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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 VCESAT 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
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 saving 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 current 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 VIN as on the LT1308. An
internal VC 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.
TYPICAL APPLICATION
L1
4.7μH
Li-Ion
CELL
VIN
C1
47μF
SHUTDOWN
95
D1
5V
1A
LBO
LT1308B
SHDN
VC
R1*
309k
FB
GND
47k
VIN = 4.2V
85
SW
LBI
VIN = 3.6V
90
+
C2
220μF
R2
100k
EFFICIENCY (%)
+
Converter Efficiency
80
VIN = 2.5V
VIN = 1.5V
75
70
65
60
100pF
55
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
L1: MURATA LQH6C4R7
*R1: 887k FOR VOUT = 12V
50
1308A/B F01a
Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
1
10
100
LOAD CURRENT (mA)
1000
1308A/B F01b
1308abfb
1