LT1308A/LT1308B
High Current, Micropower
Single Cell, 600kHz
DC/DC Converters
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DESCRIPTIO
FEATURES
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
LT1308andarerecommendedforuseinnewdesigns.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
switchingatlightloadsandoperatesataquiescentcurrent
of 2.5mA. Both devices consume less than 1μA in
shutdown.
■
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 ModeTM 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)
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.
■
Improved Accuracy Low-Battery Detector
Reference: 200mV ±2%
■
Available in 8-Lead SO and 14-Lead TSSOP Packages
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APPLICATIO S
■
GSM/CDMA Phones
■
Digital Cameras
The LT1308A/LT1308B are available in the 8-lead SO and
the 14-lead TSSOP packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst
Mode is a registered trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners.
■
LCD Bias Supplies
■
Answer-Back Pagers
■
GPS Receivers
■
Battery Backup Supplies
■
Handheld Computers
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TYPICAL APPLICATIO
Converter Efficiency
L1
D1
4.7μH
95
5V
1A
V
= 3.6V
V
= 4.2V
= 2.5V
IN
IN
90
85
80
75
70
65
60
55
50
V
SW
IN
+
C1
47μF
R1*
LBO
LBI
309k
V
LT1308B
IN
+
Li-Ion
CELL
V
= 1.5V
C2
220μF
IN
SHUTDOWN
SHDN
FB
V
GND
C
R2
100k
47k
100pF
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
L1: MURATA LQH6C4R7
*R1: 887k FOR V = 12V
OUT
1308A/B F01a
1
10
100
1000
LOAD CURRENT (mA)
Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
1308A/B F01b
1308abfa
1