LTC3727-1_15 Datasheet, PDF (1/32 Pages) Linear Technology – High Efficiency, 2-Phase Synchronous Step-Down Switching Regulators

LTC3727/LTC3727-1
High Efficiency, 2-Phase
Synchronous Step-Down Switching Regulators
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% Output Voltage Accuracy}
■ _{Power Good Output Voltage Monitor}
■ _{Phase-Lockable Fixed Frequency 250kHz to 550kHz}
■ _{Latched Short-Circuit Shutdown (LTC3727 Only)}
■ _{Dual N-Channel MOSFET Synchronous Drive}
■ _{Wide VIN Range: 4V to 36V 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 Package}
■ _{LTC3727-1 Also Available in the 5mm × 5mm QFN}
Package
U
APPLICATIO S
■ _{Telecom Systems}
■ _{Automotive Systems}
■ _{Battery-Operated Digital Devices}
DESCRIPTIO
The LTC^®3727/LTC3727-1 are high performance dual
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. There is a precision 0.8V reference and a power
good output indicator. A wide 4V to 30V (36V maximum)
input supply range encompasses all battery chemistries.
A RUN/SS pin for each controller provides soft-start, and
on the LTC3727GN, optional timed, short-circuit shut-
down. Current foldback limits MOSFET heat dissipation
during short-circuit conditions when overcurrent latchoff
is disabled. Output overvoltage protection circuitry latches
on the bottom MOSFET until V_OUT 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.
, 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
BOOST2
SW1
SW2
LTC3727/
BG1 _LTC3727-1 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
3727 F01
Figure 1. High Efficiency Dual 12V/5V Step-Down Converter
3727fc
1