LTC1148_15 Datasheet, PDF (1/20 Pages) Linear Technology – High Efficiency Synchronous Step-Down Switching Regulators

LTC1148
LTC1148-3.3/LTC1148-5
High Efficiency Synchronous
Step-Down Switching Regulators
FEATURES
■ _{Ultrahigh Efficiency: Over 95% Possible}
■ _{Current-Mode Operation for Excellent Line and Load}
Transient Response
■ _{High Efficiency Maintained Over Three Decades of}
Output Current
■ _{Low 160µA Standby Current at Light Loads}
■ _{Logic Controlled Micropower Shutdown: IQ < 20µA}
■ _{Wide VIN Range: 3.5V* to 20V}
■ _{Short-Circuit Protection}
■ _{Very Low Dropout Operation: 100% Duty Cycle}
■ _{Synchronous FET Switching for High Efficiency}
■ _{Adaptive Nonoverlap Gate Drives}
■ _{Output Can Be Externally Held High in Shutdown}
■ _{Available in 14-Pin Narrow SO Package}
U
APPLICATIO S
■ _{Notebook and Palmtop Computers}
■ _{Portable Instruments}
■ _{Battery-Operated Digital Devices}
■ _{Cellular Telephones}
■ _{DC Power Distribution Systems}
■ _{GPS Systems}
DESCRIPTIO
The LTC^®1148 series is a family of synchronous step-
down switching regulator controllers featuring automatic
Burst Mode^TM operation to maintain high efficiencies at
low output currents. These devices drive external comple-
mentary power MOSFETs at switching frequencies up to
250kHz using a constant off-time current-mode architec-
ture 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 18V (20V 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 LTC1148 series combines synchronous switching for
maximum efficiency at high currents with an automatic low
current operating mode, called Burst Modeoperation, which
reduces switching losses. 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 operation up to 48V input, see the LTC1149 and
LTC1159 data sheets and Application Note 54.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
* LTC1148L and LTC1148L-3.3 only.
Protected by U.S. Patents, including 6580258, 5481178.
TYPICAL APPLICATIO
+
1µF
0V = NORMAL
>1.5V = SHUTDOWN
R_C
1k
C_C
3300pF
C_T
470pF
V_IN (5.2V TO 18V)
V_IN
P-DRIVE
LTC1148HV-5
SHUTDOWN
SENSE ⁺
I_TH
C_T
SENSE ^–
N-DRIVE
SGND PGND
1000pF
P-CHANNEL
Si4431DY
N-CHANNEL
Si4412DY
+ _CIN
100µF
L*
62µH
R_SENSE**
0.05Ω
V_OUT
5V/2A
D1
MBRS140T3
+ _COUT
390µF
LT1148 • TA01
*COILTRONICS CTX62-2-MP
**KRL SL-1-C1-0R050J
Figure 1. High Efficiency Step-Down Converter
LTC1148-5 Efficiency
100
V_IN = 6V
95
V_IN = 10V
90
85
80
0.02
0.2
LOAD CURRENT (A)
2
LTC1148 • TA01
114835fd
1