LT1308A_1 Datasheet, PDF (1/20 Pages) Linear Technology – High Current, Micropower Single Cell, 600kHz DC/DC Converters

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