LTC1649 Datasheet, PDF (1/16 Pages) Linear Technology – 3.3V Input High Power Step-Down Switching Regulator Controller

LTC1649
3.3V Input High Power
Step-Down Switching
Regulator Controller
FEATURES
s _{High Power 3.3V to 1.xV-2.xV Switching Regulator}
Controller: Up to 20A Output
s _{All N-Channel External MOSFETs}
s _{Provides 5V MOSFET Gate Drive with 3.3V Input}
s _{Excellent Output Regulation: ±1% Over Line, Load}
and Temperature Variations
s _{Constant Frequency Operation Minimizes}
Inductor Size
s _{High Efficiency: Over 90% Possible}
s _{No Low-Value Sense Resistor Needed}
s _{Available in 16-Lead SO Package}
U
APPLICATIO S
s _{3.3V Input Power Supply for Low Voltage}
Microprocessors and Logic
s _{Low Input Voltage Power Supplies}
s _{High Power, Low Voltage Regulators}
s _{Local Regulation for Multiple Voltage Distributed}
Power Systems
DESCRIPTIO
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.
TYPICAL APPLICATIO
V_IN
3.3V
SHDN
+
10µF
MBR0530
22Ω
C1
220pF
R_C
7.5k
C_C
0.01µF
3.3V to 2.5V, 15A Converter
R_IMAX
50k
P_VCC1
G1
P_VCC2
I_FB
V_CC
G2
LTC1649
I_MAX
FB
SHDN V_IN
C⁺
COMP
SS
C^–
GND CP_OUT
1µF
1k
1µF
Q1, Q2 ⁺
IRF7801
TWO IN
PARALLEL
C_IN
3300µF
L_EXT*
1.2µH
Q3
IRF7801
R1
12.4k
V_OUT
2.5V
@15A
+ _COUT
4400µF
R2
12.7k
0.1µF
+
MBR0530
10µF
0.33µF
IRF7801 = INTERNATIONAL RECTIFIER
MBR0530 = MOTOROLA
*12TS-1R2HL = PANASONIC
1649 TA01
100
90
80
70
60
50
40
0.1
LTC1649 Efficiency
1
LOAD CURRENT (A)
10
1649 TA02
1