Datasheet

LT1308A/LT1308B
1
1308abfb
TYPICAL APPLICATION
DESCRIPTION
High Current, Micropower
Single Cell, 600kHz
DC/DC Converters
The LT
®
1308A/LT1308B are micropower, fi xed 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 signifi cantly tighter than
the LT1308. The 200mV reference is specifi ed 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.
Converter Effi ciency
FEATURES
APPLICATIONS
n
5V at 1A from a Single Li-Ion Cell
n
5V at 800mA in SEPIC Mode from Four NiCd Cells
n
Fixed Frequency Operation: 600kHz
n
Boost Converter Outputs up to 34V
n
Starts into Heavy Loads
n
Automatic Burst Mode™ Operation at
Light Load (LT1308A)
n
Continuous Switching at Light Loads (LT1308B)
n
Low V
CESAT
Switch: 300mV at 2A
n
Pin-for-Pin Upgrade Compatible with LT1308
n
Lower Quiescent Current in Shutdown: 1µA (Max)
n
Improved Accuracy Low-Battery Detector
Reference: 200mV ±2%
n
Available in 8-Lead SO and 14-Lead TSSOP Packages
n
GSM/CDMA Phones
n
Digital Cameras
n
LCD Bias Supplies
n
Answer-Back Pagers
n
GPS Receivers
n
Battery Backup Supplies
n
Handheld Computers
Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
V
IN
SW
FB
LT1308B
L1
4.7µH
D1
LBO
LBI
47k
R2
100k
R1*
309k
5V
1A
100pF
1308A/B F01a
C1
47µF
C2
220µF
Li-Ion
CELL
V
C
GND
SHDNSHUTDOWN
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
+
+
L1: MURATA LQH6C4R7
*R1: 887k FOR V
OUT
= 12V
LOAD CURRENT (mA)
1
EFFICIENCY (%)
95
90
85
80
75
70
65
60
55
50
10 100 1000
1308A/B F01b
V
IN
= 4.2V
V
IN
= 1.5V
V
IN
= 2.5V
V
IN
= 3.6V
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.