LTC3859AL_15 Datasheet, PDF (1/44 Pages) Linear Technology – Triple Output, Buck/Buck/Boost Synchronous Controller with 28A Burst Mode IQ

LTC3859AL
Triple Output,
Buck/Buck/Boost Synchronous
Features
Controller with 28µA Burst Mode I_Q
Description
n _{Low Operating IQ: 28μA (One Channel On)}
n _{Dual Buck Plus Single Boost Synchronous Controllers}
n _{Outputs Remain in Regulation Through Cold Crank}
Down to 2.5V
n _{Wide Bias Input Voltage Range: 4.5V to 38V}
n _{Buck Output Voltage Range: 0.8V ≤ VOUT ≤ 24V}
n _{Boost Output Voltage Up to 60V}
n _{RSENSE or DCR Current Sensing}
n _{100% Duty Cycle for Boost Synchronous MOSFET}
Even in Burst Mode^® Operation
n _{Phase-Lockable Frequency (75kHz to 850kHz)}
n _{Programmable Fixed Frequency (50kHz to 900kHz)}
n _{Selectable Continuous, Pulse-Skipping or Low Ripple}
Burst Mode Operation at Light Loads
n _{Very Low Buck Dropout Operation: 99% Duty Cycle}
n _{Adjustable Output Voltage Soft-Start or Tracking}
n _{Low Shutdown IQ: 10μA}
n _{Small 38-Lead 5mm × 7mm QFN and TSSOP Packages}
Applications
n _{Automotive Always-On and Start-Stop Systems}
n _{Battery Operated Digital Devices}
n _{Distributed DC Power Systems}
n _{Multioutput Buck-Boost Applications}
The LTC^®3859AL is a high performance triple output (buck/
buck/boost) synchronous DC/DC switching regulator
controller that drives all N-channel power MOSFET stages.
Constant frequency current mode architecture allows
a phase-lockable switching frequency of up to 850kHz.
The LTC3859AL operates from a wide 4.5V to 38V input
supply range. When biased from the output of the boost
converter or another auxiliary supply, the LTC3859AL can
operate from an input supply as low as 2.5V after start-up.
The 28μA no-load quiescent current extends operating
runtime in battery powered systems. OPTI-LOOP com-
pensation allows the transient response to be optimized
over a wide range of output capacitance and ESR values.
The LTC3859AL features a precision 0.8V reference for
the bucks, 1.2V reference for the boost and a power good
output indicator. The PLLIN/MODE pin selects among
Burst Mode operation, pulse-skipping mode, or continu-
ous inductor current mode at light loads.
Compared to the LTC3859 and the LTC3859A, the
LTC3859AL is fully pin-compatible, but with lower Burst
Mode operation I_Q (28µA with one channel on).
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP and µModule 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 5481178, 5705919,
5929620, 6144194, 6177787, 6580258.
Typical Application
V_OUT3
REGULATED AT 10V WHEN V_IN < 10V
FOLLOWS V_IN WHEN V_IN > 10V
220µF
1µF
499k
V_FB3
V_BIAS
68.1k
TG1
V_IN
2.5V TO 38V
(START-UP ABOVE 5V)
2mΩ 1.2µH
220µF
4.7µF
SW1, 2, 3
TG3
SW1
SW3 _LTC3859AL BG1
BG3
SENSE3^–
SENSE3⁺
INTV_CC
BOOST1, 2, 3
0.1µF
I_{TH1, 2, 3}
SENSE1⁺
SENSE1^–
V_FB1
RUN1, 2, 3
EXTV_CC
TG2
SW2
BG2
V_OUT1
4.9µH _6mΩ
68.1k ^357k
6.5µH _8mΩ
0.1µF
SENSE2+
TRACK/SS1, 2
SENSE2–
SS3
V_FB2
PGND SGND
3859al TA01a
68.1k ^649k
V_OUT1
5V
5A
220µF
V_OUT2
8.5V
3A
68µF
For more information www.linear.com/3859AL
Efficiency and Power Loss vs
Output Current
100
V_IN = 12V
90
80
70
V_OUT1 = BURST
EFFICIENCY
10000
1000
60
100
50
40
10
30
V_OUT1 = BURST LOSS
20
1
10
0
0.0001
0.001 0.01 0.1
OUTPUT CURRENT (A)
0.1
1
10
3859al TA01b
3859alf
1