1
LTC3727LX-1
3727lx1fa
High Efficiency, 2-Phase
Synchronous Step-Down
Switching Regulator
Figure 1. High Efficiency Dual 12V/5V Step-Down Converter
■
Wide Output Voltage Range: 0.8V ≤ V
OUT
≤ 14V
■
Out-of-Phase Controllers Reduce Required Input
Capacitance and Power Supply Induced Noise
■
OPTI-LOOP
®
Compensation Minimizes C
OUT
■
±1.5% Output Voltage Accuracy
■
Power Good Output Voltage Monitor
■
Phase-Lockable Fixed Frequency 250kHz to 550kHz
■
Dual N-Channel MOSFET Synchronous Drive
■
Wide V
IN
Range: 4V to 32V Operation
■
Very Low Dropout Operation: 99% Duty Cycle
■
Adjustable Soft-Start Current Ramping
■
Foldback Output Current Limiting
■
Output Overvoltage Protection
■
Low Shutdown I
Q
: 20µA
■
Selectable Constant-Frequency or Burst Mode
®
Operation
■
Small 28-Lead SSOP and 5mm × 5mm QFN Packages
The LTC
®
3727LX-1 is a high performance dual step-down
switching regulator controller that drives all N-channel
synchronous power MOSFET stages. A constant-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. There is a precision 0.8V reference and a power
good output indicator. A wide 4V to 28V (32V maximum)
input supply range encompasses all battery chemistries.
Table 1
PART V
IN
V
REF
ACCURACY LATCH- MINIMUM
NUMBER RANGE OVERTEMPERATURE OFF ON-TIME
LTC3727LX-1 4V to 32V ±1.5% No 120ns
LTC3727 4V to 36V ±1% Yes 180ns
LTC3727-1 4V to 36V ±1% No 180ns
LTC3727A-1 4V to 36V ±1% No 120ns
■
Telecom Systems
■
Automotive Systems
■
Distributed DC Power Systems
+
4.7µF
M2
M1
0.1µF
105k
1%
1000pF
8µH
220pF
1µF
CERAMIC
22µF
50V
CERAMIC
+
47µF
6V
SP
0.015Ω
20k
1%
15k
V
OUT1
5V
5A
M4
M3
0.1µF
280k
1%
15µH
220pF
1000pF
+
56µF
15V
SP
0.015Ω
20k
1%
15k
V
OUT2
12V
4A
TG1 TG2
BOOST1 BOOST2
SW1 SW2
BG1 BG2
SGND
PGND
SENSE1
+
SENSE2
+
SENSE1
–
SENSE2
–
V
OSENSE1
V
OSENSE2
I
TH1
I
TH2
V
IN
PGOOD INTV
CC
RUN/SS1 RUN/SS2
V
IN
18V TO 28V
M1, M2, M3, M4: FDS6680A
3727LX1 F01
0.1µF
0.1µF
LTC3727LX-1
PLLIN
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
, 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.