LTC3250 Datasheet, PDF (1/12 Pages) Linear Technology – High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converter

LTC3250-1.5/LTC3250-1.2
High Efficiency, Low Noise,
Inductorless Step-Down
DC/DC Converter
FEATURES
s _{2.7V to 5.5V Input Voltage Range}
s _{No Inductors}
s _{Li-Ion (3.6V) to 1.5V with 81% Efficiency}
s _{Low Noise Constant Frequency Operation}
s _{Output Voltages: 1.5V ±4%, 1.2V ±4%}
s _{Output Current: 250mA}
s _{Shutdown Disconnects Load from VIN}
s _{Low Operating Current: IQ = 35µA}
s _{Low Shutdown Current: ISD < 1µA}
s _{Oscillator Frequency = 1.5MHz}
s _{Soft-Start Limits Inrush Current at Turn-On}
s _{Short-Circuit and Overtemperature Protected}
s _{Low Profile (1mm) SOT-23 Package}
U
APPLICATIO S
s _{Handheld Computers}
s _{Cellular Phones}
s _{Digital Cameras}
s _{Handheld Medical Instruments}
s _{Low Power DSP Supplies}
DESCRIPTIO
The LTC^®3250-1.5/LTC3250-1.2 are charge pump step-
down DC/DC converters that produce a 1.5V or 1.2V
regulated output from a 2.7V to 5.5V input. The parts use
switched capacitor fractional conversion to achieve typi-
cal efficiency two times higher than that of a linear regu-
lator. No inductors are required.
A unique constant frequency architecture provides a low
noise regulated output as well as lower input noise
than conventional charge pump regulators.* High
frequency operation (f_OSC = 1.5MHz) simplifies filtering
to further reduce conducted noise. The part also uses
Burst Mode^® operation to improve efficiency at light loads.
Low operating current (35µA with no load, <1µA in
shutdown) and low external parts count (three small
ceramic capacitors) make the LTC3250-1.5/LTC3250-1.2
ideally suited for space constrained battery powered appli-
cations. The parts are short-circuit and overtemperature
protected, and are available in a low profile (1mm) 6-pin
ThinSOT^TM package.
, LTC and LT are registered trademarks of Linear Technology Corporation
Burst Mode is a registered trademark of Linear Technology Corporation
ThinSOT is a trademark of Linear Technology Corporation.
*U.S. Patent #6, 411, 531
TYPICAL APPLICATIO
Li-Ion to 1.5V Output with Shutdown
1µF
V_IN
3.2V TO 4.2V
Li-Ion 1µF
OFF ON
C^–
C⁺
V_IN
V_OUT
LTC3250-1.5 4.7µF
SHDN GND
V_OUT = 1.5V ± 4%
100mA
3250 TA1a
Efficiency vs Input Voltage
(I_OUT = 100mA)
100
90
80
LTC3250-1.5
70
60
50
40
LDO
30
20
10
0
3.0
3.5
4.0 4.5
5.0
5.5
V_IN (V)
3250 TA01b
3250fa
1