LTC3787_15 Datasheet, PDF (1/36 Pages) Linear Technology – PolyPhase Synchronous Boost Controller

LTC3787
PolyPhase Synchronous
Boost Controller
FEATURES
n _{2-Phase Operation Reduces Required Input and}
Output Capacitance and Power Supply Induced Noise
n _{Synchronous Operation for Highest Efficiency and}
Reduced Heat Dissipation
n _{Wide VIN Range: 4.5V to 38V (40V Abs Max) and}
Operates Down to 2.5V After Start-Up
n _{Output Voltage Up to 60V}
n _{±1% 1.200V Reference Voltage}
n _{RSENSE or Inductor DCR Current Sensing}
n _{100% Duty Cycle Capability for Synchronous MOSFET}
n _{Low Quiescent Current: 135μA}
n _{Phase-Lockable Frequency (75kHz to 850kHz)}
n _{Programmable Fixed Frequency (50kHz to 900kHz)}
n _{Power Good Output Voltage Monitor}
n _{Low Shutdown Current, IQ < 8μA}
n _{Internal LDO Powers Gate Drive from VBIAS or EXTVCC}
n _{Thermally Enhanced Low Profile 28-Pin 4mm × 5mm}
QFN Package and Narrow SSOP Package
APPLICATIONS
n _Industrial
n _Automotive
n _Medical
n _Military
DESCRIPTION
The LTC^®3787 is a high performance PolyPhase^® single
output synchronous boost converter controller that drives
two N-channel power MOSFET stages out-of-phase.
Multiphase operation reduces input and output capacitor
requirements and allows the use of smaller inductors than
the single-phase equivalent. Synchronous rectification in-
creases efficiency, reduces power losses and eases thermal
requirements, enabling high power boost applications.
A 4.5V to 38V input supply range encompasses a wide
range of system architectures and battery chemistries.
When biased from the output of the boost converter or
another auxiliary supply, the LTC3787 can operate from
an input supply as low as 2.5V after start-up. The operat-
ing frequency can be set for a 50kHz to 900kHz range or
synchronized to an external clock using the internal PLL.
PolyPhase operation allows the LTC3787 to be configured
for 2-, 3-, 4-, 6- and 12-phase operation.
The SS pin ramps the output voltage during start-up. The
PLLIN/MODE pin selects Burst Mode^® operation, pulse-
skipping mode or forced continuous mode at light loads.
L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, OPTI-LOOP and PolyPhase
are registered trademarks and No R_SENSE and ThinSOT are trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners. Protected by
U. S. Patents, including 5408150, 5481178, 5705919, 5929620, 6144194, 6177787, 6580258.
TYPICAL APPLICATION
12V to 24V/10A 2-Phase Synchronous Boost Converter
V_IN 4.5V TO 24V START-UP VOLTAGE
OPERATES THROUGH TRANSIENTS DOWN TO 2.5V
V_IN
4mΩ
4.7μF
4.7μF
TG1 VBIAS INTV_CC TG2
3.3μH
BOOST1
0.1μF
SW1
BOOST2
0.1μF
SW2
BG1 ^LTC3787
SENSE1⁺
BG2
232k
SENSE1^–
SENSE2⁺
VFB
FREQ
SENSE2^–
PLLIN/MODE
PGND
12.1k
15nF
8.66k
ITH SS SGND
100pF
0.1μF
4mΩ
47μF
3.3μH
V_OUT
24V AT 10A
220μF
3787 TA01a
Efficiency and Power Loss
vs Output Current
100
10000
90
80
1000
70
60
100
50
40
10
30
20
10
0
0.00001 0.0001 0.001
V_IN = 12V
1
V_OUT = 24V
Burst Mode OPERATION
FIGURE 10 CIRCUIT
0.1
0.01 0.1 1 10
OUTPUT CURRENT (A)
3787 TA01b
BURST EFFICIENCY
BURST LOSS
3787fc
1