LTC3727LX-1
High Efficiency, 2-Phase
Synchronous Step-Down
Switching Regulator
U
FEATURES
DESCRIPTIO
TheLTC®3727LX-1isahighperformancedualstep-down
switching regulator controller that drives all N-channel
synchronouspowerMOSFETstages.Aconstant-frequency
currentmodearchitectureallowsphase-lockablefrequency
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.
■
Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 14V
■
Out-of-Phase Controllers Reduce Required Input
Capacitance and Power Supply Induced Noise
OPTI-LOOP® Compensation Minimizes COUT
■
■
±1.5% Output Voltage Accuracy
Power Good Output Voltage Monitor
■
■
Phase-Lockable Fixed Frequency 250kHz to 550kHz
■
Dual N-Channel MOSFET Synchronous Drive
OPTI-LOOP compensation allows the transient response
tobeoptimizedoverawiderangeofoutputcapacitanceand
ESRvalues.Thereisa precision0.8Vreferenceandapower
good output indicator. A wide 4V to 28V (32V maximum)
input supply range encompasses all battery chemistries.
■
Wide VIN Range: 4V to 32V Operation
■
Very Low Dropout Operation: 99% Duty Cycle
■
Adjustable Soft-Start Current Ramping
■
Foldback Output Current Limiting
■
Output Overvoltage Protection
Table 1
■
Low Shutdown IQ: 20µA
Selectable Constant-Frequency or Burst Mode®
PART
V
IN
V
REF
ACCURACY
LATCH- MINIMUM
■
NUMBER
RANGE OVERTEMPERATURE
OFF
ON-TIME
120ns
180ns
180ns
120ns
Operation
LTC3727LX-1 4V to 32V
±1.5%
±1%
No
■
Small 28-Lead SSOP and 5mm × 5mm QFN Packages
LTC3727
4V to 36V
4V to 36V
Yes
No
U
LTC3727-1
±1%
APPLICATIO S
LTC3727A-1 4V to 36V
±1%
No
■
Telecom Systems
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst
Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6304066, 5705919.
■
Automotive Systems
■
Distributed DC Power Systems
U
TYPICAL APPLICATIO
V
IN
18V TO 28V
+
22µF
1µF
CERAMIC
50V
4.7µF
CERAMIC
V
IN
PGOOD INTV
CC
M1
M3
M4
TG1
TG2
0.1µF
BOOST1
SW1
BOOST2
SW2
0.1µF
15µH
8µH
LTC3727LX-1
M2
BG1
BG2
PLLIN
SENSE1
PGND
+
–
+
SENSE2
1000pF
1000pF
220pF
0.015Ω
0.015Ω
–
SENSE2
SENSE1
V
V
V
12V
4A
OUT1
5V
5A
OUT2
V
OSENSE1
TH1
OSENSE2
105k
1%
280k
1%
I
I
TH2
+
56µF
220pF
15k
+
20k
1%
47µF
6V
SP
RUN/SS1
RUN/SS2
SGND
15V
SP
20k
1%
15k
0.1µF
0.1µF
M1, M2, M3, M4: FDS6680A
3727LX1 F01
Figure 1. High Efficiency Dual 12V/5V Step-Down Converter
3727lx1fa
1