LTC1147-5_15 Datasheet, PDF (1/16 Pages) Linear Technology – High Efficiency Step-Down Switching Regulator Controllers

LTC1147-3.3
LTC1147-5/LTC1147L
High Efficiency Step-Down
Switching Regulator Controllers
FEATURES
s _{Very High Efficiency: Over 95% Possible}
s _{Wide VIN Range: 3.5V* to 16V}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{High Efficiency Maintained Over Three Decades of}
Output Current
s _{Low 160µA Standby Current at Light Loads}
s _{Logic Controlled Micropower Shutdown: IQ < 20µA}
s _{Short-Circuit Protection}
s _{Very Low Dropout Operation: 100% Duty Cycle}
s _{High Efficiency in a Small Amount of Board Space}
s _{Output Can Be Externally Held High in Shutdown}
s _{Available in 8-Pin SO Package}
U
APPLICATIO S
s _{Notebook and Palmtop Computers}
s _{Portable Instruments}
s _{Battery-Operated Digital Devices}
s _{Cellular Telephones}
s _{DC Power Distribution Systems}
s _{GPS Systems}
DESCRIPTIO
The LTC^®1147 series are step-down switching regulator
controllers featuring automatic Burst Mode^TM operation to
maintain high efficiencies at low output currents. These
devices drive an external P-channel power MOSFET at
switching frequencies exceeding 400kHz using a constant
off-time current mode architecture providing constant
ripple current in the inductor.
The operating current level is user-programmable via an
external current sense resistor. Wide input supply range
allows operation from 3.5V* to 14V (16V maximum).
Constant off-time architecture provides low dropout regu-
lation limited by only the R_DS(ON) of the external MOSFET
and resistance of the inductor and current sense resistor.
The LTC1147 series incorporates automatic power saving
Burst Mode operation to reduce switching losses when
load currents drop below the level required for continuous
operation. Standby power is reduced to only 2mW at
V_IN = 10V (at I_OUT = 0). Load currents in Burst Mode
operation are typically 0mA to 300mA.
For applications where even higher efficiency is required,
refer to the LTC1148 data sheet and Application Note 54.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
*LTC1147L and LTC1147L-3.3 only.
TYPICAL APPLICATI
+
1µF
0V = NORMAL
>1.5V = SHUTDOWN
R_C
1k
C_C
3300pF
C_T
470pF
V_IN (5.2V TO 14V)
V_IN
PDRIVE
LTC1147-5
SHDN
SENSE ⁺
I_TH
C_T
SENSE ^–
GND
+ _CIN
100µF
P-CHANNEL
Si4431DY ^L*
50µH
R_SENSE**
0.05Ω
V_OUT
5V/2A
1000pF
D1
MBRD330
+ _COUT
390µF
LT1147 • F01
*COILTRONICS CTX50-2-MP
**KRL SL-1-C1-0R050J
Figure 1. High Efficiency Step-Down Converter
LTC1147-5 Efficiency
100
95
V_IN = 6V
90
V_IN = 10V
85
80
75
70
0.001
0.01
0.1
LOAD CURRENT (A)
1
LT1147 • TA01
sn1147 1147fds
1