LTC3727LX-1_15 Datasheet, PDF (1/28 Pages) Linear Technology – High Efficiency, 2-Phase Synchronous Step-Down Switching Regulator

FEATURES
■ _{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}
■ _{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}
■ _{Low Shutdown IQ: 20µA}
■ _{Selectable Constant-Frequency or Burst Mode}^®
Operation
■ _{Small 28-Lead SSOP and 5mm × 5mm QFN Packages}
U
APPLICATIO S
■ _{Telecom Systems}
■ _{Automotive Systems}
■ _{Distributed DC Power Systems}
LTC3727LX-1
High Efficiency, 2-Phase
Synchronous Step-Down
Switching Regulator
DESCRIPTIO
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
NUMBER
V_IN
V_REF ACCURACY LATCH-
RANGE OVERTEMPERATURE OFF
LTC3727LX-1 4V to 32V
±1.5%
No
LTC3727 4V to 36V
±1%
Yes
LTC3727-1 4V to 36V
±1%
No
LTC3727A-1 4V to 36V
±1%
No
MINIMUM
ON-TIME
120ns
180ns
180ns
120ns
, 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.
TYPICAL APPLICATIO
8µH
0.015Ω
V_OUT1
5V
5A
+
47µF
6V
SP
105k
1%
+
4.7µF
M1
0.1µF
M2
1000pF
220pF
20k
1%
15k
V_IN PGOOD INTV_CC
TG1
TG2
BOOST1
SW1
BOOST2
SW2
LTC3727LX-1
BG1
BG2
PLLIN
SENSE1⁺
PGND
SENSE2⁺
SENSE1^–
SENSE2^–
V_OSENSE1
V_OSENSE2
I_TH1
I_TH2
RUN/SS1 SGND RUN/SS2
0.1µF
0.1µF
1µF
CERAMIC
M3
0.1µF
M4
V_IN
22µF ^{18V TO 28V}
50V
CERAMIC
15µH
1000pF
220pF
15k
280k
1%
20k
1%
0.015Ω
V_OUT2
12V
4A
56µF
15V
SP
M1, M2, M3, M4: FDS6680A
Figure 1. High Efficiency Dual 12V/5V Step-Down Converter
3727LX1 F01
3727lx1fa
1