LTC3899_15 Datasheet, PDF (1/38 Pages) Linear Technology – 60V Low IQ, Triple Output, Buck/Buck/Boost Synchronous Controller

LTC3899
Features
60V Low I_Q, Triple
Output, Buck/Buck/Boost
Synchronous Controller
Description
n _{Dual Buck Plus Single Boost Synchronous Controllers}
n _{Wide Bias Input Voltage Range: 4.5V to 60V}
n _{Outputs Remain in Regulation Through Cold Crank}
Down to a 2.2V Input Supply Voltage
n _{Buck and Boost Output Voltages Up to 60V}
n _{Adjustable Gate Drive Level 5V to 10V (OPTI-DRIVE)}
n _{No External Bootstrap Diodes Required}
n _{Low Operating IQ: 29μA (One Channel On)}
n _{100% Duty Cycle for Boost Synchronous MOSFET}
n _{Phase-Lockable Frequency (75kHz to 850kHz)}
n _{Programmable Fixed Frequency (50kHz to 900kHz)}
n _{Very Low Dropout Operation: 99% Duty Cycle (Bucks)}
n _{Low Shutdown IQ: 3.6μA}
n _{Fixed or Adjustable Boost Output Voltage Saves IQ}
n _{Small 38-Lead 5mm × 7mm QFN and TSSOP Packages}
Applications
n _{Automotive Always-On and Start-Stop Systems}
n _{Distributed DC Power Systems}
n _{Multioutput Buck-Boost Applications}
The LTC^®3899 is a high performance triple output (buck/
buck/boost) DC/DC switching regulator controller that
drives all N-channel synchronous power MOSFET stages.
The constant frequency current mode architecture allows
a phase-lockable frequency of up to 850kHz. The LTC3899
operates from a wide 4.5V to 60V input supply range.
When biased from the output of the boost converter or
another auxiliary supply, the LTC3899 can operate from
an input supply as low as 2.2V after start-up.
The gate drive for the LTC3899 can be programmed from
5V to 10V to allow the use of logic-level or standard-level
FETs and to maximize efficiency. Internal switches in the
top gate drivers eliminate the need for external bootstrap
diodes. The 29μA no-load quiescent current extends op-
erating run time in battery-powered systems. OPTI-LOOP^®
compensation allows the transient response to be optimized
over a wide range of output capacitance and ESR values.
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, Linear Technology and the Linear logo are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents including 5481178, 5705919, 5929620,
6144194, 6177787, 6580258.
Typical Application
High Efficiency Wide Input Range Dual 5V/8.5V Converter
V_OUT3
REGULATED AT 10V
WHEN V_IN < 10V
FOLLOWS V_IN WHEN
V_IN > 10V
33µF
V_IN
2.2V TO 60V
(START-UP
ABOVE 5V)
3mΩ ^1.2µH
33µF
4.7µF
RUN1, 2, 3 V_BIAS
V_FB3
TG1
0.1µF
0.1µF
TG3
BOOST1
SW1
BOOST3
SW3
BG1
LTC3899
BG3
SENSE1⁺
SENSE1^–
SENSE3^–
SENSE3⁺
V_FB1
DRV_CC
INTV_CC
0.1µF
TG2
0.1µF
ITH1,2,3 BOOST2
SW2
BG2
DRVSET
SENSE2⁺
SENSE2^–
VPRG3
V_FB2
GND
4.9µH 9mΩ
V_OUT1
5V
5A
357k
68.1k
220µF
6.5µH 15mΩ
V_OUT2
8.5V
3A
649k
68.1k
68µF
3899 TA01a
For more information www.linear.com/LTC3899
Efficiency vs Output Current
95
V_IN = 12V
94
V_OUT = 5V
Burst Mode OPERATION
93
92
91
90
89
88
0.01
GATE DRIVE (DRV_CC)
5V
6V
8V
10V
0.1
1
OUTPUT CURRENT(A)
10
3899 TA01b
3899f
1