LTC3633A-2/LTC3633A-3
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-2 is a high efficiency, dual-channel mono -
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3A Output Current per Channel
lithic 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 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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Available in (4mm 5mm) QFN-28 and 28-Lead
the on-time of the internal one-shot timer to match the
TSSOP Packages
frequency of the internal clock or an applied external clock.
APPLICATIONS
The LTC3633A-2 can select between forced continuous
mode and high efficiency Burst Mode operation. The
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Distributed Power Systems
LTC3633A-2 and LTC3633A-3 differ in their output volt-
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Battery Powered Instruments
age sense range (refer to Table 1 in the Operation section
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Point of Load Power Supplies
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
Efficiency vs Load Current
V
IN
6V TO 20V
100
47F
PV PV SV
IN2 IN1 IN Burst Mode
x2
90 OPERATION
RUN1 INTV
CC
80
RUN2 ITH1
2.2F
LTC3633A-2 70
ITH2
RT
60
MODE/SYNC
50
PHMODE
40
TRACKSS2 TRACKSS1
PGOOD2 PGOOD1 30
BOOST2 BOOST1
20
1.5H 1H
0.1F 0.1F
V V
OUT2 OUT1 V = 5V
SW2 SW1 10 OUT
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
3633a23 TA01b
3633a23 TA01a
3633a23fb
For more information www.linear.com/LTC3633A-2 1
EFFICIENCY (%)LTC3633A-2/LTC3633A-3
ABSOLUTE MAXIMUM RATINGS (Note 1)
PV , PV , SV ...................................... 0.3V to 20V RUN1 ............................................. 0.3V to SV + 0.3V
IN1 IN2 IN IN
PGOOD1, PGOOD2, V , V ................. 0.3V to 18V RUN2 ......................................................... 0.3V to 20V
ON1 ON2
BOOST1, BOOST2 ...................................... 0.3V to 23V Operating Junction Temperature Range
BOOST1-SW1, BOOST2-SW2 ................... 0.3V to 3.6V (Notes 3, 4) ............................................ 40C to 125C
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
V , V , PHMODE. .................. 0.3V to INTV + 0.3V
FB1 FB2 CC
PIN CONFIGURATION
TOP VIEW TOP VIEW
1 V
ITH1 28
ON1
2 SW1
TRACKSS1 27
3 SW1
V 26
FB1
28 27 26 25 24 23
4 PV
PGOOD1 25
PGOOD1 1 22 PV IN1
IN1
5 PV
PHMODE PHMODE 24
2 21 PV IN1
IN1
6 SV
RUN1 3 20 SV RUN1 23
IN IN
MODE/SYNC 4 19 BOOST1 7 BOOST1
MODE/SYNC 22
29
29
PGND
PGND
RT 5 18 INTV
8 INTV
CC RT 21
CC
RUN2 6 17 BOOST2
9 BOOST2
RUN2 20
SGND 7 16
PV
IN2
10 PV
SGND 19
IN2
PGOOD2 8 15 PV
IN2
11 PV
PGOOD2 18
IN2
9 10 11 12 13 14
12 SW2
V 17
FB2
13 SW2
TRACKSS2 16
14 V
ITH2 15
ON2
UFD PACKAGE
FE PACKAGE
28-LEAD (4mm 5mm) PLASTIC QFN
28-LEAD PLASTIC TSSOP
T = 125C, = 43C/W
JMAX JA T = 125C, = 25C/W
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-2#PBF LTC3633AEUFD-2#TRPBF 633A2 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AIUFD-2#PBF LTC3633AIUFD-2#TRPBF 633A2 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AEFE-2#PBF LTC3633AEFE-2#TRPBF LTC3633AFE-2 28-Lead Plastic TSSOP 40C to 125C
LTC3633AIFE-2#PBF LTC3633AIFE-2#TRPBF LTC3633AFE-2 28-Lead Plastic TSSOP 40C to 125C
LTC3633AEUFD-3#PBF LTC3633AEUFD-3#TRPBF 633A3 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AIUFD-3#PBF LTC3633AIUFD-3#TRPBF 633A3 28-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3633AEFE-3#PBF LTC3633AEFE-3#TRPBF LTC3633AFE-3 28-Lead Plastic TSSOP 40C to 125C
LTC3633AIFE-3#PBF LTC3633AIFE-3#TRPBF LTC3633AFE-3 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: