LTC3633A-1_15 Datasheet, PDF (1/30 Pages) Linear Technology – Dual Channel 3A, 20V Monolithic Synchronous Step-Down Regulator

FEATURES
n _{3.6V to 20V Input Voltage Range}
n _{3A Output Current per Channel}
n _{Up to 95% Efficiency}
n _{Low Duty Cycle Operation: 5% at 2.25MHz}
n _{Selectable 0°/180° Phase Shift Between Channels}
n _{Adjustable Switching Frequency: 500kHz to 4MHz}
n _{External Frequency Synchronization}
n _{Current Mode Operation for Excellent Line and}
Load Transient Response
n _{0.6V Reference Allows Low Output Voltages}
n _{User Selectable Burst Mode}^® _{Operation or Forced}
Continuous Mode Operation
n _{Output Voltage Tracking and Soft-Start Capability}
n _{Short-Circuit Protected}
n _{Overvoltage Input and Overtemperature Protection}
n _{Power Good Status Outputs}
n _{LTC3633: 16V Absolute Maximum VIN}
n _{LTC3633A: 20V Absolute Maximum VIN, Pin Compatible}
with LTC3633
n _{Low Profile (4mm × 5mm) QFN-28 and 28-Lead}
TSSOP Packages
APPLICATIONS
n _{Distributed Power Systems}
n _{Battery Powered Instruments}
n _{Point of Load Power Supplies}
LTC3633A/LTC3633A-1
Dual Channel 3A, 20V
Monolithic Synchronous
Step-Down Regulator
DESCRIPTION
The LTC^®3633A is a high efficiency, dual-channel monolithic
synchronous buck regulator using a controlled on-time,
current mode architecture, with phase lockable switching
frequency. The two channels can run 180° out of phase to
relax the requirements for input and output capacitance. The
operating supply voltage range is from 3.6V to 20V, making
it suitable for lithium-ion battery stacks as well as point of
load power supply applications from a 12V or 5V supply.
The operating frequency is programmable from 500kHz to
4MHz with an external resistor and may be synchronized
to an external clock signal. The high frequency capabil-
ity allows the use of small surface mount inductors and
capacitors. The unique constant frequency/controlled on-
time architecture is ideal for high step-down ratio applica-
tions that operate at high frequency while demanding fast
transient response. An internal phase locked loop servos
the on-time of the internal one-shot timer to match the
frequency of the internal clock or an applied external clock.
The LTC3633A can select between forced continuous mode
and high efficiency Burst Mode operation. The LTC3633A
and LTC3633A-1 differ in their output voltage sense range
(refer to Table 1 in the Operation section for a description
of the entire LTC3633A product family).
L, LT, LTC, LTM, Burst Mode, 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, 5847554, 6580258, 6304066, 6476589,
6774611.
TYPICAL APPLICATION
V_OUT2
5V AT 3A
V_IN
6V TO 20V
47µF
x2
1.5µH _0.1µF
22µF ^73.2k
RUN1 ^VIN2
RUN2
V_{IN1 INTVCC}
ITH1
ITH2
LTC3633A
RT
MODE/SYNC
PHMODE
V2P5
TRACKSS2
TRACKSS1
PGOOD2
PGOOD1
BOOST2
BOOST1
SW2
V_ON2
10k ^{VFB2 SGND PGND}
SW1
V_ON1
V_FB1
2.2µF
0.1µF ^1µH
10k ^45.3k
V_OUT1
3.3V AT 3A
22µF
3633a TA01a
For more information www.linear.com/LTC3633A
Efficiency vs Load Current
100
Burst Mode
90 OPERATION
80
70
60
50
40
30
20
10
V_IN = 12V
0
0.001
0.01
0.1
V_OUT = 5V
V_OUT = 3.3V
1
10
LOAD CURRENT (A)
3633a TA01b
3633a1fb
1