LTC3252_15 Datasheet, PDF (1/12 Pages) Linear Technology – Dual, Low Noise, Inductorless Step-Down DC/DC Converter

FEATURES
s _{2.7V to 5.5V Input Voltage Range}
s _{No Inductors}
s _{Typical Efficiency 50% Higher than LDOs}
s _{Spread Spectrum Operation}
s _{Low Input and Output Noise}
s _{Shutdown Disconnects Load from VIN}
s _{Dual Adjustable Independent Outputs}
(Range: 0.9V to 1.6V)
s _{Output Current: 250mA Each Output}
s _{Low Operating Current: IIN = 60µA Typ}
(35µA with One Output Enabled)
s _{Low Shutdown Current: IIN = 0.01µA Typ}
s _{Soft-Start Limits Inrush Current at Turn On}
s _{Short Circuit and Over Temperature Protected}
s _{Available in 4mm × 3mm 12-Pin DFN Package}
U
APPLICATIO S
s _{Handheld Electronic Devices}
s _{Cellular Phones}
s _{Low Voltage Logic Supplies}
s _{DSP Power Supplies}
s _{3.3V to 1.5V Conversion}
LTC3252
Dual, Low Noise,
Inductorless Step-Down
DC/DC Converter
DESCRIPTIO
The LTC^®3252 is a switched capacitor step-down DC/DC
converter that produces two adjustable regulated outputs
from a single 2.7V to 5.5V input. The part uses switched
capacitor fractional conversion to achieve a typical effi-
ciency increase of 50% over that of a linear regulator. No
inductors are required.
A unique constant frequency, spread spectrum architec-
ture provides a very low noise regulated output as well as
low noise at the input. The part also has Burst Mode^®
operation to provide high efficiency at low output currents,
as well as ultralow current shutdown.
Low operating currents (60µA with both outputs enabled,
35µA with one output enabled) and low external parts
count make the LTC3252 ideally suited for space-con-
strained battery-powered applications. The part is short-
circuit and overtemperature protected and is available in a
tiny 4mm × 3mm 12-pin DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
1.5V and 1.2V Output Voltages with Shutdown
1-CELL
Li-ION
OR 3-CELL
NiMH
OFF ON
OFF ON
4.7µF
2
11
3
4
1µF ₆
10
1µF ₈
7
5
EN1
OUT1
EN2
1
V_IN
FB1
C1 ⁺ _LTC3252
C1^–
C2⁺
9
OUT2
C2^–
12
GND
FB2
470k
510k
261k
510k
V_OUT = 1.5V
I_OUT ≤ 250mA
4.7µF
V_OUT = 1.2V
I_OUT ≤ 250mA
4.7µF
3252 TA01
1.5V/1.2V Efficiency vs Input Voltage
100
90
I_OUT (1.5V) = 100mA
I_OUT (1.2V) = 100mA
80
LTC3252-1.5V
70
60 LTC3252-1.2V
50
40
LDO-1.5V
30
20
LDO-1.2V
10
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
V_IN (V)
3252 TA01a
3252f
1