LTC3633A/LTC3633A-1
Dual Channel 3A, 20V
Monolithic Synchronous
Step-Down Regulator
FEATURES DESCRIPTION
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3.6V to 20V Input Voltage Range
The LTC 3633A is a high efficiency, dual-channel monolithic
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3A Output Current per Channel
synchronous buck regulator using a controlled on-time,
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Up to 95% Efficiency
current mode architecture, with phase lockable switching
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Low Duty Cycle Operation: 5% at 2.25MHz
frequency. The two channels can run 180 out of phase to
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Selectable 0/180 Phase Shift Between Channels
relax the requirements for input and output capacitance. The
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Adjustable Switching Frequency: 500kHz to 4MHz
operating supply voltage range is from 3.6V to 20V, making
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External Frequency Synchronization
it suitable for lithium-ion battery stacks as well as point of
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Current Mode Operation for Excellent Line and
load power supply applications from a 12V or 5V supply.
Load Transient Response
The operating frequency is programmable from 500kHz to
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0.6V Reference Allows Low Output Voltages
4MHz with an external resistor and may be synchronized
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User Selectable Burst Mode Operation or Forced
to an external clock signal. The high frequency capabil-
Continuous Mode Operation
ity allows the use of small surface mount inductors and
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Output Voltage Tracking and Soft-Start Capability
capacitors. The unique constant frequency/controlled on-
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Short-Circuit Protected
time architecture is ideal for high step-down ratio applica-
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Overvoltage Input and Overtemperature Protection
tions that operate at high frequency while demanding fast
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Power Good Status Outputs
transient response. An internal phase locked loop servos
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LTC3633: 16V Absolute Maximum V
IN
the on-time of the internal one-shot timer to match the
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LTC3633A: 20V Absolute Maximum V , Pin Compatible
IN
frequency of the internal clock or an applied external clock.
with LTC3633
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The LTC3633A can select between forced continuous mode
Low Profile (4mm 5mm) QFN-28 and 28-Lead
and high efficiency Burst Mode operation. The LTC3633A
TSSOP Packages
and LTC3633A-1 differ in their output voltage sense range
APPLICATIONS
(refer to Table 1 in the Operation section for a description
of the entire LTC3633A product family).
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Distributed Power Systems
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
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Battery Powered Instruments
of Linear Technology Corporation. All other trademarks are the property of their respective
n owners. Protected by U.S. Patents including 5481178, 5847554, 6580258, 6304066, 6476589,
Point of Load Power Supplies
6774611.
TYPICAL APPLICATION
Efficiency vs Load Current
V
IN
6V TO 20V
100
47F Burst Mode
V V
IN2 IN1
RUN1 INTV
CC
x2 90 OPERATION
RUN2 ITH1
2.2F
80
ITH2
LTC3633A 70
RT
MODE/SYNC 60
PHMODE
50
V2P5
40
TRACKSS2 TRACKSS1
30
PGOOD2 PGOOD1
BOOST2 BOOST1 20
1.5H 1H
0.1F 0.1F
V V
V = 5V
OUT2 OUT1 OUT
10
SW2 SW1
5V AT 3A 3.3V AT 3A V = 12V V = 3.3V
IN OUT
V V
ON2 ON1 0
0.001 0.01 0.1 1 10
V V
FB2 FB1
SGND PGND LOAD CURRENT (A)
73.2k 45.3k
22F 10k 10k 22F
3633a TA01b
3633a TA01a
3633a1fb
For more information www.linear.com/LTC3633A 1
EFFICIENCY (%)LTC3633A/LTC3633A-1
ABSOLUTE MAXIMUM RATINGS (Note 1)
V , V ................................................... 0.3V to 20V V , V , PHMODE. .................. 0.3V to INTV + 0.3V
IN1 IN2 FB1 FB2 CC
PGOOD1, PGOOD2, V , V ................. 0.3V to 18V RUN1, RUN2 .................................... 0.3V to V + 0.3V
ON1 ON2 IN
BOOST1, BOOST2 ...................................... 0.3V to 23V Operating Junction Temperature Range
BOOST1-SW1, BOOST2-SW2 ................... 0.3V to 3.6V (Notes 2, 3) ............................................ 40C to 125C
V2P5, INTV , TRACKSS1, TRACKSS2 ...... 0.3V to 3.6V Storage Temperature Range ................... 65C to 150C
CC
ITH1, ITH2, RT, MODE/SYNC ........ 0.3V to INTV + 0.3V
CC
PIN CONFIGURATION
TOP VIEW TOP VIEW
ITH1 1 28 V
ON1
TRACKSS1 2 27 SW1
V 3 26 SW1
FB1
28 27 26 25 24 23
PGOOD1 4 25 V
PGOOD1 1 22 IN1
V
IN1
PHMODE 5 24 V
PHMODE 2 21 V IN1
IN1
RUN1 3 20 BOOST1 RUN1 6 23 BOOST1
MODE/SYNC 4 19 INTV
MODE/SYNC 7 22 INTV
CC 29 CC
29
PGND
PGND
RT 5 18 V2P5
RT 8 21 V2P5
RUN2 6 17
BOOST2
RUN2 9 20 BOOST2
7 16
SGND V
IN2
SGND 10 19 V
IN2
PGOOD2 8 15 V
IN2
PGOOD2 11 18 V
IN2
9 10 11 12 13 14
V 12 17 SW2
FB2
TRACKSS2 13 16 SW2
ITH2 14 15 V
ON2
UFD PACKAGE
FE PACKAGE
28-LEAD (4mm 5mm) PLASTIC QFN
28-LEAD PLASTIC TSSOP
T = 125C, = 43C/W
T = 125C, = 30C/W
JMAX JA
JMAX JA
EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3633AEUFD#PBF LTC3633AEUFD#TRPBF 3633A 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AIUFD#PBF LTC3633AIUFD#TRPBF 3633A 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AEFE#PBF LTC3633AEFE#TRPBF LTC3633AFE 28-Lead Plastic TSSOP 40C to 125C
LTC3633AIFE#PBF LTC3633AIFE#TRPBF LTC3633AFE 28-Lead Plastic TSSOP 40C to 125C
LTC3633AEUFD-1#PBF LTC3633AEUFD-1#TRPBF 633A1 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AIUFD-1#PBF LTC3633AIUFD-1#TRPBF 633A1 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AEFE-1#PBF LTC3633AEFE-1#TRPBF LTC3633AFE-1 28-Lead Plastic TSSOP 40C to 125C
LTC3633AIFE-1#PBF LTC3633AIFE-1#TRPBF LTC3633AFE-1 28-Lead Plastic TSSOP 40C to 125C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: