LTC3728LCGN(RevA) Просмотр технического описания (PDF) - Linear Technology
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LTC3728LCGN Datasheet PDF : 32 Pages
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FEATURES
s Dual, 180° Phased Controllers Reduce Required
Input Capacitance and Power Supply Induced Noise
s OPTI-LOOP® Compensation Minimizes COUT
s ±1% Output Voltage Accuracy (LTC3728LC)
s Power Good Output Voltage Indicator
s Phase-Lockable Fixed Frequency 250kHz to 550kHz
s Dual N-Channel MOSFET Synchronous Drive
s Wide VIN Range: 4.5V to 28V Operation
s Very Low Dropout Operation: 99% Duty Cycle
s Adjustable Soft-Start Current Ramping
s Foldback Output Current Limiting
s Latched Short-Circuit Shutdown with Defeat Option
s Output Overvoltage Protection
s Low Shutdown IQ: 20µA
s 5V and 3.3V Standby Regulators
s 3 Selectable Operating Modes: Constant Frequency,
Burst Mode® Operation and PWM
s 5mm × 5mm QFN and 28-Lead Narrow SSOP
Packages
U
APPLICATIO S
s Notebook and Palmtop Computers
s Telecom Systems
s Portable Instruments
s Battery-Operated Digital Devices
s DC Power Distribution Systems
LTC3728L/LTC3728LX
Dual, 550kHz, 2-Phase
Synchronous Regulators
DESCRIPTIO
The LTC®3728L/LTC3728LX are dual high performance
step-down switching regulator controllers that drive all
N-channel synchronous power MOSFET stages. A con-
stant frequency current mode architecture allows phase-
lockable frequency of up to 550kHz. Power loss and noise
due to the ESR of the input capacitors are minimized by
operating the two controller output stages out of phase.
OPTI-LOOP compensation allows the transient response
to be optimized over a wide range of output capacitance and
ESR values. The precision 0.8V reference and power good
output indicator are compatible with future microproces-
sor generations, and a wide 4.5V to 28V (30V maximum)
input supply range encompasses all battery chemistries.
A RUN/SS pin for each controller provides both soft-start
and optional timed, short-circuit shutdown. Current
foldback limits MOSFET dissipation during short-circuit
conditions when overcurrent latchoff is disabled. Output
overvoltage protection circuitry latches on the bottom
MOSFET until VOUT returns to normal. The FCB mode pin
can select among Burst Mode, constant frequency mode
and continuous inductor current mode or regulate a
secondary winding. The LTC3728L/LTC3728LX include a
power good output pin that indicates when both outputs
are within 7.5% of their designed set point.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
M1
L1
3.2µH
+
4.7µF
D3
VIN PGOOD INTVCC
D4
TG1
TG2
CB1, 0.1µF
fIN
500kHz
BOOST1
BOOST2
SW1
SW2
LTC3728L/
BG1 LTC3728LX BG2
PLLIN
PGND
CB2, 0.1µF
1µF
CERAMIC
VIN
CIN 5.2V TO 28V
22µF
50V
M2
CERAMIC
L2
3.2µH
RSENSE1
0.01Ω
VOUT1
5V
R2
5A
+
105k
COUT1 1%
47µF
6V
SP
R1
20k
1%
1000pF
CC1
220pF
RC1
15k
SENSE1+
SENSE2+
SENSE1–
SENSE2–
VOSENSE1
ITH1
VOSENSE2
ITH2
RUN/SS1 SGND RUN/SS2
CSS1
0.1µF
CSS2
0.1µF
1000pF
CC2
220pF
RC2
15k
RSENSE2
0.01Ω
R4
63.4k
R3
20k
1%
1% COUT
56µF
6V
SP
M1, M2: FDS6982S
Figure 1. High Efficiency Dual 5V/3.3V Step-Down Converter
VOUT2
3.3V
5A
3728 F01
3728lxfa
1
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