LTC3875
Dual, 2-Phase, Synchronous
Controller with Low Value DCR Sensing
and Temperature Compensation
FEATURES
DESCRIPTION
The LTC®3875 is a dual output current mode synchronous
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Low Value DCR Current Sensing
Programmable DCR Temperature Compensation
0.ꢀ5 0.6V Output Voltage Accuracy
Dual True Remote Sensing Differential Amplifiers
Optional Fast Transient Operation
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step-down DC/DC controller that drives all N-channel
synchronous power MOSFET stages. It employs a unique
architecture which enhances the signal-to-noise ratio of
the current sense signal, allowing the use of very low DC
resistance power inductors to maximize the efficiency in
high current applications. This feature also reduces the
switching jitter commonly found in low DCR applications.
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Phase-Lockable Fixed Frequency 2ꢀ0kHz to 720kHz
Dual, 180° Phased Controllers Reduce Required
Input Capacitance and Power Supply Induced Noise
Dual N-Channel MOSFET Synchronous Drive
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TheLTC3875featurestwohighspeedremotesensediffer-
ential amplifiers, programmable current sense limits from
10mVto30mVandDCRtemperaturecompensationtolimit
the maximum output current precisely over temperature.
Wide V Range: 4.5V to 38V Operation
IN
Output Voltage Range with Low DCR: 0.6V to 3.5V,
without Low DCR: 0.6V to 5V
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Adjustable Soft-Start Current Ramping or Tracking
Foldback Output Current Limiting
Clock Input and Output for Up to 12-Phase Operation
Short-Circuit Soft Recovery
Output Overvoltage Protection
Power Good Output Voltage Monitor
40-Lead QFN Packages
Auniquethermalbalancingfunctionadjustsperphasecur-
rent in order to minimize the thermal stress for multichip
single output applications. The LTC3875 also features a
precise0.6Vreferencewithguaranteedaccuracyof 0.5ꢀ
thatprovidesanaccurateoutputvoltagefrom0.6Vto3.5V.
A 4.5V to 38V input voltage range allows it to support a
wide variety of bus voltages. The LTC3875 is available
in a low profile 40-lead 6mm × 6mm (0.5mm pitch) and
40-lead 5mm × 5mm (0.4mm pitch) QFN packages.
L, LT, LTC, LTM, Linear Technology, the Linear logo OPTI-LOOP, Burst Mode and PolyPhase
APPLICATIONS
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Servers and Instruments
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are registered trademarks and No R
is a trademark of Linear Technology Corporation.
Telecom Systems
SENSE
All other trademarks are the property of their respective owners. Protected by U.S. Patents
including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.
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DC Power Distribution Systems
TYPICAL APPLICATION
High Efficiency Dual Phase 1.2V/60A Step-Down Converter
V
IN
6V TO 14V
22µF
Efficiency and Power Loss
vs Load Current
INTV
CC
16V ×4
4.7µF
V
INTV
CC
PHASMD
CLKOUT
PGOOD
IFAST
IN
(OPTIONAL)
(OPTIONAL)
RUN1,2
ILIM
ENTMPB
TG1
100
95
90
85
80
75
70
14
12
10
8
12V
IN
1.8V
O
~400kHz
CCM
THERMAL
SENSOR
THERMAL
SENSOR
MODE/PLLIN
TG2
0.3µH
0.3µH
(0.32mΩ DCR)
BOOST1
BOOST2
SW2
(0.32mΩ DCR)
LTC3875
CC
SW1
EXTV
BG1
BG2
TAVG
PGND
6
TRSET1
TRSET2
+
SNSA1
SNS1
SNSD1
+
SNSA2
–
4
–
SNS2
0.32mΩ
1.5mΩ
0.32mΩ PLOSS
1.5mΩ PLOSS
+
+
SNSD2
2
TCOMP1
TCOMP2
+
–
V
V
OUT
OSNS1
OSNS1
TH1
V
1.2V
60A
FREQ
20k
OUT
+
V
0
V
V
OSNS2
OSNS2
I
0
20
30
40
50
60
10
–
I
+
470µF
2.5V ×2
SP
LOAD CURRENT (A)
1500pF
122k 15k
TK/SS1 TK/SS2
TH2
+
470µF
2.5V ×2
20k
3875 TA01b
0.1µF
SP
3875 TA01a
3875fb
1
For more information www.linear.com/LTC3875