LTC3727A-1 Datasheet, PDF (1/32 Pages) Linear Technology – 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}
■ _{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}
U
APPLICATIO S
■ _{Telecom Systems}
■ _{Automotive Systems}
■ _{Battery-Operated Digital Devices}
LTC3727A-1
High Efficiency, 2-Phase
Synchronous Step-Down
Switching Regulators
DESCRIPTIO
The LTC^®3727A-1 is a high performance dual step-down
switching regulator controller that drives all N-channel
synchronous power MOSFET stages. A constant fre-
quency 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.
The LTC3727A-1 is an improved version of the LTC3727
family of parts. It has smaller output ripple while in the
drop-out condition and shorter minimum on-time.
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.
Current foldback limits MOSFET heat dissipation during
short-circuit conditions. Output overvoltage protection
circuitry protects the controller until V_OUT returns to
normal.
, LTC and LT 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
LTC3727A-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
3727 F01
Figure 1. High Efficiency Dual 12V/5V Step-Down Converter
3727a1f
1