LTC3897
FEATURES
PolyPhase Synchronous
Boost Controller with Input/
Output Protection
DESCRIPTION
n Input Supply Range: 4.5V to 65V (Up to 75V Surge)
n Reverse Input Protection to –40V
n In-Rush Current Control, Overcurrent Protection
and Output Disconnect for Boost Converter
n Input Voltage Surge Protection with Adjustable
Clamp Voltage
n Onboard Ideal Diode Controller
n Low Quiescent Current: 55µA
n 2-Phase Operation Reduces Required Input and
Output Capacitance and Noise
n Output Voltage Up to 60V
n Adjustable Gate Drive Level 5V to 10V (OPTI-DRIVE)
for Logic-Level or Standard Threshold FETs
n No External Bootstrap Diodes Required
APPLICATIONS
n Industrial
n Automotive
n Military/Avionics
The LTC®3897 is a synchronous boost DC/DC controller
with surge stopper and ideal diode controller.
The boost controller drives two N-channel power MOSFET
stages out-of-phase to reduce input and output capacitor
requirements, allowing the use of smaller inductors than
the single-phase equivalent. Synchronous rectification
reduces power loss and eases thermal requirements.
The surge stopper controls the gate of an external
N-channel MOSFET to protect against high voltage input
transients and provides in-rush current control, over-
current protection and output disconnect for the boost
converter. The integrated ideal diode controller drives
another N-channel MOSFET to replace a Schottky diode
for reverse input protection and voltage holdup or peak
detection. It controls the forward voltage drop across the
MOSFET and minimizes reverse current flow.
The LTC3897 is available in thermally-enhanced 38-pin
leadless QFN or 38-lead TSSOP packages.
All registered trademarks and trademarks are the property of their respective owners.
Protected by U.S. patents, including 5408150, 5481178, 5705919, 5929620, 6144194,
6177787, 6580258.
TYPICAL APPLICATION
24V/10A 2-Phase Synchronous Boost Converter with Surge Protection and Reverse Protection
INPUT VOLTAGE SURGE PROTECTION
IN-RUSH/OVERCURRENT PROTECTION
REVERSE CURRENT PROTECTION (IDEAL DIODE)
REVERSE INPUT VOLTAGE PROTECTION
5mΩ 3.5µH
VIN
6V TO
55V
10Ω
2mΩ
33µF
549k
12.1k
VBIAS
SPFB
SENSE1+
SENSE1–
BG1
0.1µF
BOOST1
10nF
IS–
SW1
IS+
DG
TG1
5mΩ
CS
SENSE2+
SG
LTC3897 SENSE2–
VIN
0.1µF
RUN
BG2
0.1µF
SS
15nF
8.66k
1µF
ITH
BOOST2
SW2
TG2
PINS NOT SHOWN IN THIS CIRCUIT:
PLLIN/MODE, ILIM, PHASMD,
CLKOUT, EXTVCC, SGEN, DGEN
VIN OPERATES THROUGH TRANSIENTS UP TO 75V.
WHEN VIN > 24V, VOUT FOLLOWS VIN UP TO 57V.
INTVCC
VFB
4.7µF DRVCC
DRVSET
DTC
DRVUV FREQ GND TMR
1nF
3.5µH
475k
24.9k
3897 TA01a
VOUT
24V
10A
220µF
Efficiency and Power Loss
vs Output Current
100
100k
BURST EFFICIENCY
90
80
10k
70
60
1k
BURST LOSS
50
40
100
30
20
10
0
0.001
VIN = 12V
VOUT = 24V
10
Burst Mode OPERATION
FIGURE 17 CIRCUIT
1
0.01
0.1
1
10
OUTPUT CURRENT (A)
3897 TA01b
Rev. A
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