LTC1626_15 Datasheet, PDF (1/12 Pages) Linear Technology – Low Voltage, High Efficiency Step-Down DC/DC Converter

LTC1626
OBSOLETE:
FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
Low Voltage, High Efficiency
Step-Down DC/DC Converter
FEATURES
I _{Wide Input Supply Voltage Range: 2.5V to 6V}
I _{High Efficiency: Up to 95%}
I _{Low RDS(ON) Internal Switch: 0.32Ω (VIN = 4.5V)}
I _{Current Mode Operation for Excellent Line and Load}
Transient Response
I _{Short-Circuit Protected}
I _{Low Dropout Operation: 100% Duty Cycle}
I _{Built-In Low-Battery Detector}
I _{Low Quiescent Current at Light Loads: IQ = 165µA}
I _{Ultralow Shutdown Current: IQ = 0.5µA}
I _{Peak Inductor Current Independent of Inductor Value}
I _{Available in 14-Pin SO Package}
U
APPLICATIONS
I _{Single Cell Li-Ion Step-Down Converters}
I _{3- or 4-Cell NiMH Step-Down Converters}
I _{Cellular Telephones}
I _{5V to 3.3V Conversion}
I _{3.3V to 2.5V Conversion}
I _{Inverting Converters}
I _{Portable Instruments}
DESCRIPTION
The LTC^®1626 is a monolithic, low voltage, step-down
current mode DC/DC converter featuring Burst Mode^TM
operation at low output current.
The input supply voltage range of 2.5V to 6V makes the
LTC1626 ideal for single cell Li-Ion and 3- or 4-cell NiCd/
NiMH applications. A built-in 0.32Ω switch (V_IN = 4.5V)
allows up to 0.6A of output current.
The LTC1626 incorporates automatic power saving Burst
Mode operation to reduce gate charge losses when the
load current drops below the level required for continuous
operation. With no load, the converter draws only 165µA.
In shutdown, it draws a mere 0.5µA—making it ideal for
current sensitive applications.
The inductor current is user-programmable via an external
current sense resistor. In dropout, the internal P-channel
MOSFET switch is turned on continuously, maximizing
battery life.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
V_IN
2.7V TO 6V
C_IN†
47µF
16V
0.1µF
PWR V_IN
SHDN
V_IN
SW
LTC1626
3900pF _470Ω
I_TH
PGND
SENSE⁺
C_T
SENSE^–
C_T
270pF
SGND ^VFB
* COILTRONICS CTX33-4
** IRC 1206-R100F
† _{AVX TPSD476KO16}
†† _{AVX TPSC107M006R0150}
L*
33µH
R_SENSE**
0.1Ω
D1
MBRS130LT
+
1000pF
10k
V_OUT
2.5V
0.25A
C_{OUT†â€} 
100µF
6.3V
100pF
10k
1626 F01
Figure 1. High Efficiency 2.5V Step-Down Converter
100
95
90
85
80
75
70
0.01
Efficiency
V_IN = 3.5V
L1 = 33µH
V_OUT = 2.5V
R_SENSE = 0.1Ω
C_T = 270pF
0.1
OUTPUT CURRENT (A)
1
1626 F01a
1