LTC3874-1
PolyPhase Step-Down
Synchronous Slave Controller with
Sub-Milliohm DCR Sensing
FeaTures
DescripTion
The LTC®3874-1 is a dual PolyPhase® current mode syn-
chronous step-down slave controller. It enables high cur-
rent,multiphaseapplicationswhenpairedwithacompanion
master controller by extending the phase count. Compat-
ible master controllers include the LTC3884-1, LTC3774,
LTC3875,LTC3877andLTC3866.TheLTC3874-1employs
a unique architecture that enhances the signal-to-noise
ratio of the current sense signal, allowing the use of sub-
milliohm DC resistance power inductors to maximize
efficiency while reducing switching jitter. Its peak current
mode architecture allows for accurate phase-to-phase
current sharing even for dynamic loads.
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Phase Extender for High Phase Count Voltage Rails
Operates with Power Blocks, DrMOS or External
Gate Drivers and MOSFETs
Accurate Phase-to-Phase Current Sharing
Sub-Milliohm DCR Current Sensing
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Phase-Lockable Fixed Frequency 250kHz to 1MHz
Immediate Response to Master IC's Fault
Up to 12-Phase Operation
Wide V Range: 4.5 to 38V
IN
V
Range : Up to 3.5V (LOWDCR Pin High)
OUT
Up to 5.5V (LOWDCR Pin Low)
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Proprietary Current Mode Control Loop
Programmable CCM/DCM Operation
Programmable Phase Shift Control
24-Lead (4mm × 4mm) QFN Package
Effectivelyworkingwithamastercontroller,theLTC3874-1
supports all the programmable features as well as fault
protection.
L, LT, LTC, LTM, Linear Technology, the Linear logo, PolyPhase and µModule are registered
trademarks of Analog Devices, Inc. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620, 6144194, 6177787,
6580258, 5408150.
applicaTions
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High Current Distributed Power Systems
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Telecom, Datacom and Storage Systems
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Intelligent Energy Efficient Power Regulation
Typical applicaTion
High Efficiency, 4-Phase 1.8V/120A Step-Down Supply
V
IN
7V TO 14V
4-Phase Efficiency and Power
V
IN
LTC3874-1
PWM0
PWM1
Loss vs Output Current, Sub-
(0.29mΩ DCR)
0.215µH
(0.29mΩ DCR)
0.215µH
V
OUT
Milliohm DCR vs Traditional
DCR
1.8V
DrMOS
DrMOS
120A
649Ω
649Ω
100µF
×3
100µF
×3
470µF
×2
470µF
×2
100
95
90
85
80
75
70
20
17
14
11
8
0.22µF
0.22µF
V
V
f
= 12V
+
IN
OUT
= 425kHz
+
= 1.8V
+
–
+
–
SW
I
I
I
I
SENSE0
SENSE0
SENSE1
SENSE1
CCM
EFFICIENCY
LTC3884-1
RUN0
RUN1
RUN0
INTV
CC
RUN1
V
CC0
4.7µF
FAULT0
FAULT1
PGOOD0
FAULT0
FAULT1
V
CC1
PHASMD
POWER LOSS
1.8V
MODE0 LDWDCR
+
+
V
V
SENSE0
SENSE1
PGOOD1
MODE1
TH0
ILIM
0.29mΩ
1.5mΩ
0.29mΩ
1.5mΩ
I
I
TH0
100k
5
I
I
FREQ
GND
TH1
SYNC
TH1
SYNC
2
0
10 20 30 40 50 60 70 80 90 100 110 120
LOAD CURRENT (A)
38741 TA01a
38741 TA01b
REFER TO LTC3884-1 DATA SHEET
FOR MASTER SETUP
PIN NOT USED IN THIS CIRCUIT: EXTV
CC
38741f
1
For more information www.linear/LTC3874-1