LTC3875
1
3875fb
For more information
www.linear.com/LTC3875
TYPICAL APPLICATION
FEATURES
DESCRIPTION
Dual, 2-Phase, Synchronous
Controller with Low Value DCR Sensing
and Temperature Compensation
is a dual output current mode synchronous
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.
The LTC3875 features two high speed remote sense differ-
ential amplifiers, programmable current sense limits from
10mV to 30mV and DCR temperature compensation to limit
the maximum output current precisely over temperature.
A unique thermal balancing function adjusts per phase cur-
rent in order to minimize the thermal stress for multichip
single output applications. The LTC3875 also features a
precise 0.6V reference with guaranteed accuracy of ±0.5%
that provides an accurate output voltage from 0.6V to 3.5V.
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.
High Efficiency Dual Phase 1.2V/60A Step-Down Converter
APPLICATIONS
n
Low Value DCR Current Sensing
n
Programmable DCR Temperature Compensation
n
±0.5% 0.6V Output Voltage Accuracy
n
Dual
True Remote Sensing Differential Amplifiers
n
Optional Fast Transient Operation
n
Phase-Lockable Fixed Frequency 250kHz to 720kHz
n
Dual, 180° Phased Controllers Reduce Required
Input Capacitance and Power Supply Induced Noise
n
Dual N-Channel MOSFET Synchronous Drive
n
Wide V
IN
Range: 4.5V to 38V Operation
n
Output Voltage Range with Low DCR: 0.6V to 3.5V,
without Low DCR: 0.6V to 5V
n
Adjustable Soft-Start Current Ramping or Tracking
n
Foldback Output Current Limiting
n
Clock Input and Output for Up to 12-Phase Operation
n
Short-Circuit Soft Recovery
n
Output Overvoltage Protection
n
Power Good Output Voltage Monitor
n
40-Lead QFN Packages
n
Servers and Instruments
n
Telecom Systems
n
DC Power Distribution Systems
L
, LT, LTC, LTM, Linear Technology, the Linear logo OPTI-LOOP, Burst Mode and PolyPhase
are registered trademarks and No R
SENSE
is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents
including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.
+
INTV
CC
INTV
CC
4.7µF
LTC3875
BOOST1
BOOST2
SW2
0.3µH
(0.32mΩ DCR)
BG2
PGND
TRSET2
SNSA2
+
SNS2
–
SNSD2
+
TCOMP2
FREQ
V
OSNS2
+
V
OSNS2
–
I
TH2
SW1
EXTV
CC
BG1
TAVG
TRSET1
SNSA1
+
SNS1
–
SNSD1
+
TCOMP1
V
OSNS1
+
V
OSNS1
–
I
TH1
PHASMD
CLKOUT
PGOOD
IFAST
MODE/PLLIN
TG2
RUN1,2
ILIM
ENTMPB
TG1
V
IN
TK/SS2
TK/SS1
THERMAL
SENSOR
22µF
16V
×
4
V
IN
6V TO 14V
0.3µH
(0.32mΩ DCR)
THERMAL
SENSOR
(OPTIONAL)
(OPTIONAL)
122k
0.1µF
470µF
2.5V
×
2
SP
+
470µF
2.5V
×
2
SP
V
OUT
15k
20k
3875 TA01a
20k
V
OUT
1.2V
60A
1500pF
LOAD CURRENT (A)
0
70
EFFICIENCY (%)
POWER LOSS (W)
75
80
85
90
100
10
20
30
40
3875 TA01b
50
60
95
0
4
2
6
8
10
14
12
0.32mΩ
1.5mΩ
0.32mΩ PLOSS
1.5mΩ PLOSS
12V
IN
1.8V
O
~400kHz
CCM
Efficiency and Power Loss
vs Load Current
