LTC1649
3.3V Input High Power
Step-Down Switching
Regulator Controller
FEATURES
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DESCRIPTION
The LTC
®
1649 is a high power, high efficiency switching
regulator controller optimized for use with very low supply
voltages. It operates from 2.7V to 5V input, and provides
a regulated output voltage from 1.26V to 2.5V at up to 20A
load current. A typical 3.3V to 2.5V application features
efficiency above 90% from 1A to 10A load. The LTC1649
uses a pair of standard 5V logic-level N-channel external
MOSFETs, eliminating the need for expensive P-channel
or super-low-threshold devices.
The LTC1649 shares its internal switching architecture
with the LTC1430, and features the same
±1%
line, load
and temperature regulation characteristics. Current limit
is user-adjustable without requiring an external low-value
sense resistor. The LTC1649 uses a 200kHz switching
frequency and voltage mode control, minimizing external
component count and size. Shutdown mode drops the
quiescent current to below 10µA.
The LTC1649 is available in the 16-pin narrow SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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High Power 3.3V to 1.xV-2.xV Switching Regulator
Controller: Up to 20A Output
All N-Channel External MOSFETs
Provides 5V MOSFET Gate Drive with 3.3V Input
Constant Frequency Operation Minimizes
Inductor Size
Excellent Output Regulation:
±
1% Over Line, Load
and Temperature Variations
High Efficiency: Over 90% Possible
No Low-Value Sense Resistor Needed
Available in 16-Lead SO Package
APPLICATIONS
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3.3V Input Power Supply for Low Voltage
Microprocessors and Logic
Low Input Voltage Power Supplies
High Power, Low Voltage Regulators
Local Regulation for Multiple Voltage Distributed
Power Systems
TYPICAL APPLICATION
3.3V to 2.5V, 15A Converter
V
IN
3.3V
MBR0530
R
IMAX
50k
1µF
Q1, Q2
IRF7801
TWO IN
PARALLEL
+
C
IN
3300µF
L
EXT
*
1.2µH
V
OUT
2.5V
@15A
P
VCC1
22Ω
P
VCC2
G1
1k
I
FB
Q3
IRF7801
R1
12.4k
EFFICIENCY (%)
G2
V
CC
LTC1649
FB
I
MAX
SHDN
10µF
R
C
7.5k
C
C
0.01µF
C1
220pF
0.1µF
+
SHDN
COMP
SS
GND
V
IN
C
+
1µF
C
–
CP
OUT
R2
12.7k
+
C
OUT
4400µF
+
MBR0530
10µF
0.33µF
IRF7801 = INTERNATIONAL RECTIFIER
MBR0530 = MOTOROLA
*12TS-1R2HL = PANASONIC
1649 TA01
U
U
U
LTC1649 Efficiency
100
90
80
70
60
50
40
0.1
1
LOAD CURRENT (A)
10
1649 TA02
1
LINER [ LINEAR TECHNOLOGY ]
