LTC3861-1 Datasheet, PDF (1/36 Pages) Linear Technology – Dual, Multiphase Step-Down Voltage Mode DC/DC Controller with Accurate Current Sharing

LTC3861-1
Features
Dual, Multiphase Step-Down
Voltage Mode DC/DC Controller
with Accurate Current Sharing
Description
n _{Operates with Power Blocks, DrMOS or External}
Gate Drivers and MOSFETs
n _{Constant-Frequency Voltage Mode Control with}
Accurate Current Sharing
n _{±0.75% 0.6V Voltage Reference}
n _{Differential Remote Output Voltage Sense Amplifier}
n _{Multiphase Capability—Up to 12-Phase Operation}
n _{Programmable Current Limit}
n _{Safely Powers a Prebiased Load}
n _{Programmable or PLL-Synchronizable Switching}
Frequency Up to 2.25MHz
n _{Lossless Current Sensing Using Inductor DCR or}
Precision Current Sensing with Sense Resistor
n _{VCC Range: 3V to 5.5V}
n _{VIN Range: 3V to 24V}
n _{Power Good Output Voltage Monitor}
n _{Output Voltage Tracking Capability}
n _{Programmable Soft-Start}
n _{Available in a 32-Pin 5mm × 5mm QFN Package}
Applications
n _{High Current Distributed Power Systems}
n _{DSP, FPGA and ASIC Supplies}
n _{Datacom and Telecom Systems}
n _{Industrial Power Supplies}
The LTC^®3861-1 is a dual PolyPhase^® synchronous step-
down switching regulator controller for high current
distributed power systems, digital signal processors, and
other telecom and industrial DC/DC power supplies. It uses
a constant-frequency voltage mode architecture combined
with very low offset, high bandwidth error amplifiers and
a remote output sense differential amplifier for excellent
transient response and output regulation.
The controller incorporates lossless inductor DCR current
sensing to maintain current balance between phases and to
provide overcurrent protection. The chip operates from a
V_CC supply between 3V and 5.5V and is designed for step-
down conversion from V_IN between 3V and 24V to output
voltages between 0.6V and V_CC – 0.5V.
Inductor current reversal is disabled during soft-start to
safely power prebiased loads. The constant operating
frequency can be synchronized to an external clock or
linearly programmed from 250kHz to 2.25MHz. Up to six
LTC3861-1 controllers can operate in parallel for 1-, 2-, 3-,
4-, 6- or 12-phase operation.
The LTC3861-1 is pin-to-pin compatible with the LTC3860.
It is available in a 32-pin 5mm × 5mm QFN package. The
LTC3861is a 36-pin QFN version of the LTC3861-1, which
has dual differential output voltage sense amplifiers.
L, LT, LTC, LTM, PolyPhase, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 6144194, 5055767
Typical Application
V_CC
1µF
28.7k
V_OUT
1nF
20k 221Ω
20k
1nF
13k 220pF
V_IN, 7V TO 14V
V_CC
FREQ
VINSNS PWM1
FB2
I_LIM2
LTC3861-1
VSNSOUT
RUN1,2
I_LIM1
ISNS1P
VSNSP
ISNS1N
VSNSN
ISNS2N
CONFIG
ISNS2P
PWM2
FB1
I_AVG
COMP1,2 SS1,2 SGND CLKIN
0.1µF
V_CC
59k
LTC4449
IN
GND
V_LOGIC TG
V_CC
TS
BOOST BG
0.22µF
0.22µF
0.22µF
V_CC
100pF
LTC4449
IN
GND
V_LOGIC TG
V_CC
TS
BOOST BG
0.22µF
V_IN, 7V TO 14V
180µF
0.47µH
2.87k
V_IN
2.87k
330µF
×6
100µF
×4
V_OUT
1.2V
60A
0.47µH
38611 TA01
38611f
1