LT1308A/LT1308B
High Current, Micropower
Single Cell, 600kHz
DC/DC Converters
FEATURES
■
■
■
■
■
■
■
■
■
■
■
■
DESCRIPTIO
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
TM
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
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 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.
, 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.
APPLICATIO S
■
■
■
■
■
■
■
GSM/CDMA Phones
Digital Cameras
LCD Bias Supplies
Answer-Back Pagers
GPS Receivers
Battery Backup Supplies
Handheld Computers
TYPICAL APPLICATIO
L1
4.7μH
Converter Efficiency
D1
5V
1A
95
90
85
V
IN
= 3.6V
V
IN
= 4.2V
+
Li-Ion
CELL
V
IN
C1
47μF
SHUTDOWN
LBI
LT1308B
SHDN
V
C
47k
100pF
SW
LBO
FB
GND
R2
100k
EFFICIENCY (%)
R1*
309k
+
80
75
70
65
60
55
V
IN
= 1.5V
C2
220μF
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
L1: MURATA LQH6C4R7
*R1: 887k FOR V
OUT
= 12V
1308A/B F01a
50
1
10
100
LOAD CURRENT (mA)
1000
1308A/B F01b
Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
U
V
IN
= 2.5V
1308abfa
U
U
1
LINER [ LINEAR TECHNOLOGY ]
