LTC3251_15 Datasheet, PDF (1/16 Pages) Linear Technology – 500mA High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converter

LTC3251/
LTC3251-1.2/LTC3251-1.5
500mA High Efficiency,
Low Noise, Inductorless
Step-Down DC/DC Converter
FEATURES
■ _{Up to 500mA Output Current}
■ _{No Inductors}
■ _{2.7V to 5.5V Input Voltage Range}
■ _{2x Efficiency Improvement Over LDOs}
■ _{2-Phase, Spread Spectrum Operation}
for Low Input and Output Noise
■ _{Shutdown Disconnects Load from VIN}
■ _{Adjustable Output Voltage Range: 0.9V to 1.6V}
Fixed Output Voltages: 1.2V, 1.5V
■ _{Super Burst, Burst and Burst Defeat Operating Modes}
■ _{Low Operating Current: IIN = 35µA (Burst Mode}^®
Operation)
■ _{Super Burst Operating Current: IIN = 10µA}
■ _{Low Shutdown Current: IIN = 0.01µA Typ}
■ _{Soft-Start Limits Inrush Current at Turn-On}
■ _{Short-Circuit and Overtemperature Protected}
■ _{Available in a Thermally Enhanced}
10-Pin MSOP Package
U
APPLICATIO S
■ _{Handheld Devices}
■ _{Cellular Phones}
■ _{Portable Electronic Equipment}
■ _{DSP Power Supplies}
DESCRIPTIO
The LTC^®3251/LTC3251-1.2/LTC3251-1.5 are 2-phase
charge pump step-down DC/DC converters that produce a
regulated output from a 2.7V to 5.5V input. The parts use
switched capacitor fractional conversion to achieve twice
the typical efficiency of a linear regulator. No inductors are
required. V_OUT is resistor programmable from 0.9V to 1.6V
or fixed at 1.2V or 1.5V, with up to 500mA of load current
available.
A unique 2-phase spread spectrum architecture provides
a very low noise regulated output as well as low noise at the
input.* The parts have four operating modes: Continuous
Spread Spectrum, Spread Spectrum with Burst Mode
operation, Super Burst^TM mode operation and shutdown.
Low operating current (35µA in Burst Mode operation,
10µA in Super Burst mode operation) and low external
parts count make the LTC3251/LTC3251-1.2/LTC3251-1.5
ideally suited for space-constrained battery-powered
applications. The parts are short-circuit and overtempera-
ture protected, and are available in a thermally enhanced
10-pin MSOP package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
Super Burst is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by US Patents including 6411531.
TYPICAL APPLICATIO
1-CELL Li-Ion
OR
3-CELL NiMH
Spread Spectrum Step-Down Converter
OFF ON
19
MD0 MD1
LTC3251-1.5
2
V_IN
V_OUT ⁷
1µF
3 _C1+
C2^{+ 8}
1µF _{4 C1–}
C2^{– 6}
1µF
5, 11
10
GND MODE
V_OUT = 1.5V
500mA
10µF
3251 TA01
1.5V Efficiency vs Input Voltage
(Burst Mode Operation)
100
I_OUT = 200mA
90
LTC3251-1.5
80
70
60
50
LDO
40
30
20
10
0
3
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
3251 TA02
32511215fb
1