LTC3736-2
TM
Dual 2-Phase, No R
,
SENSE
Synchronous Controller
with Output Tracking
DESCRIPTION
FEATURES
TheLTC®3736-2 isa2-phasedualsynchronousstep-down
switching regulator controller with tracking that drives
external complementary power MOSFETs using few ex-
ternalcomponents.Theconstant-frequencycurrentmode
n
No Current Sense Resistors Required
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Out-of-Phase Controllers Reduce Required
Input Capacitance
Tracking Function
n
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Wide V Range: 2.75V to 9.8V
architecturewithMOSFETV sensingeliminatestheneed
IN
DS
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0.6V ±±1 Voltage Reference
forsenseresistorsandimprovesefficiency.Powerlossand
noiseduetotheESRoftheinputcapacitanceareminimized
by operating the two controllers out-of-phase.
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High Current Limit
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Constant-Frequency Current Mode Operation
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Low Dropout Operation: 100% Duty Cycle
Pulse-skipping operation provides high efficiency at light
loads. 100% duty cycle capability provides low dropout
operation, extending operating time in battery-powered
systems.
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True PLL for Frequency Locking or Adjustment
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Selectable Pulse-Skipping/Forced Continuous
Operation
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Auxiliary Winding Regulation
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Theswitchingfrequencycanbeprogrammedupto750kHz,
allowing the use of small surface mount inductors and
capacitors.Fornoisesensitiveapplications,theLTC3736-2
switching frequency can be externally synchronized from
250kHz to 850kHz. An internal soft-start, which can be
lengthened externally, smoothly ramps the output voltage
during start-up.
Internal Soft-Start Circuitry
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Power Good Output Voltage Monitor
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Output Overvoltage Protection
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Micropower Shutdown: I = 9μA
Q
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Tiny Low Profile (4mm × 4mm) QFN and Narrow
SSOP Packages
APPLICATIONS
The LTC3736-2 is available in the tiny thermally enhanced
(4mm × 4mm) QFN and 24-lead narrow SSOP packages.
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One or Two Lithium-Ion Powered Devices
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Notebook and Palmtop Computers, PDAs
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
n
No R
is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 5481178,
5929620, 6144194, 6580258, 6304066, 6611131, 6498466.
SENSE
Portable Instruments
Distributed DC Power Systems
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TYPICAL APPLICATION
High Efficiency, 2-Phase, Dual Synchronous DC/DC Step-Down Converter
Efficiency and Power Loss
vs Load Current (Figure ±5 Circuit)
V
IN
2.75V TO 9.8V
100
95
90
85
80
75
70
65
60
55
50
10
V
OUT
= 2.5V
10μF
s2
V
+
IN
+
SENSE1 SENSE2
EFFICIENCY
1
TG1
TG2
2.2μH
2.2μH
SW1
SW2
LTC3736-2
0.1
0.01
0.001
POWER LOSS
BG1
BG2
PGND
PGND
118k
187k
V
V
OUT1
2.5V
OUT2
1.8V
V
FB1
V
FB2
I
I
TH1
TH2
220pF
15k
220pF
59k
SGND
47μF
47μF
15k
59k
1
10
100
1000
10000
LOAD CURRENT (mA)
37362 TA01b
37362 TA01a
37362fb
1