LTC3786_15 Datasheet, PDF (1/34 Pages) Linear Technology – Low IQ Synchronous Boost Controller

Features
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 Voltages Up to 60V}
n _{±1% 1.2V Reference Voltage}
n _{RSENSE or Inductor DCR Current Sensing}
n _{100% Duty Cycle Capability for Synchronous MOSFET}
n _{Low Quiescent Current: 55µA}
n _{Phase-Lockable Frequency (75kHz to 850kHz)}
n _{Programmable Fixed Frequency (50kHz to 900kHz)}
n _{Adjustable Output Voltage Soft-Start}
n _{Power Good Output Voltage Monitor}
n _{Low Shutdown Current IQ: <8µA}
n _{Internal 5.4V LDO for Gate Drive Supply}
n _{Thermally Enhanced 16-Pin 3mm × 3mm QFN and}
MSOP Packages
Applications
n _{Industrial and Automotive Power Supplies}
n _{Automotive Start-Stop Systems}
n _{Medical Devices}
n _{High Voltage Battery-Powered Systems}
LTC3786
Low I_Q Synchronous
Boost Controller
Description
The LTC^®3786 is a high performance synchronous boost
converter controller that drives all N-channel power
MOSFETs. Synchronous rectification increases efficiency,
reduces power losses and eases thermal requirements,
allowing the LTC3786 to be used in 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 LTC3786 can operate from
an input supply as low as 2.5V after start-up. The 55µA
no-load quiescent current extends operating run time in
battery-powered systems.
The operating frequency can be set for a 50kHz to 900kHz
range or synchronized to an external clock using the
internal PLL. The LTC3786 also features a precision 1.2V
reference and a power good output indicator. The SS pin
ramps the output voltage during start-up. The PLLIN/MODE
pin selects among Burst Mode^® operation, pulse-skipping
mode or continuous inductor current mode at light loads.
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, Linear Technology and the Linear logo are
registered trademarks and No R_SENSE is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U. S. Patents, including
5408150, 5481178, 5705919, 5929620, 6177787, 6498466, 6580258, 6611131.
Typical Application
12V to 24V/5A Synchronous Boost Converter
VBIAS
SENSE⁺
0.1µF
LTC3786
PGOOD
SENSE^–
PLLIN/MODE
RUN
FREQ
TG
SS
15nF
8.66k
ITH
220pF
SW
BOOST
BG
12.1k
VFB
INTV_CC
232k
GND
V_IN 4.5V TO 24V
0.1µF
4mΩ
220µF
3.3µH
220µF
V_OUT
24V
5A
4.7µF
3786 TA01a
Efficiency and Power Loss
vs Load Current
100
10000
90
80
BURST
EFFICIENCY
70
60
BURST
LOSS
1000
100
50
40
10
30
20
10
0
0.00001 0.0001 0.001
V_IN = 12V
V_OUT = 24V
1
Burst Mode OPERATION
FIGURE 8 CIRCUIT
0.1
0.01 0.1 1 10
OUTPUT CURRENT (A)
3786 TA01b
3786fa
1