LTC3875_15 Datasheet, PDF (1/44 Pages) Linear Technology – Dual, 2-Phase, Synchronous Controller with Low Value DCR Sensing and Temperature Compensation

LTC3875
Features
Dual, 2-Phase, Synchronous
Controller with Low Value DCR Sensing
and Temperature Compensation
Description
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 VIN 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 Package}
Applications
n _{Servers and Instruments}
n _{Telecom Systems}
n _{DC Power Distribution Systems}
The LTC^®3875 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 QFN package.
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.
Typical Application
High Efficiency Dual Phase 1.2V/60A Step-Down Converter
(OPTIONAL)
THERMAL
SENSOR
0.3µH
(0.32mΩ DCR)
INTV_CC
4.7µF
V_OUT
+
470µF
2.5V ×2
SP
V_IN INTV_CC PHASMD
CLKOUT
RUN1,2
PGOOD
ILIM
IFAST
ENTMPB MODE/PLLIN
TG1
TG2
BOOST1
BOOST2
SW1 LTC3875 SW2
EXTV_CC
BG1
BG2
TAVG
TRSET1
SNSA1⁺
SNS1^–
SNSD1⁺
PGND
TRSET2
SNSA2⁺
SNS2^–
SNSD2⁺
TCOMP1
VV_{OOSSNNSS11+–}
I_TH1
TCOMP2
FREQ
VV_{OOSSNNSS22+–}
TK/SS1 TK/SS2 I_TH2
0.1µF
1500pF
122k 15k
V_IN
22µF ^{6V TO 14V}
16V ×4
(OPTIONAL)
THERMAL
SENSOR
0.3µH
(0.32mΩ DCR)
20k
20k
+
V_OUT
1.2V
60A
470µF
2.5V ×2
SP
3875 TA01a
For more information www.linear.com/LTC3875
Efficiency and Power Loss
vs Load Current
100
14
12V_IN
1.8V_O
95 ~400kHz
12
CCM
10
90
8
85
6
80
4
0.32mΩ
75
1.5mΩ
0.32mΩ PLOSS
2
1.5mΩ PLOSS
70
0
0 10 20 30 40 50 60
LOAD CURRENT (A)
3875 TA01b
3875fa
1