LTC7851/LTC7851-1
Quad Output, Multiphase Step-Down Voltage Mode
DC/DC Controller with Accurate Current Sharing
FEATURES DESCRIPTION
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Operates with Power Blocks, DrMOS or External The LTC 7851/LTC7851-1 are quad output multiphase syn-
Gate Drivers and MOSFETs chronous step-down switching regulator controllers that
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Voltage Mode Control with Accurate Current Sharing employ a constant frequency voltage mode architecture.
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0.75% 0.6V Voltage Reference They maintain excellent current balance between channels
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Quad Differential Output Voltage Sense Amplifiers when paralleled with their internal current sharing loop.
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Multiphase Capability Lossless DCR or a low value R is used for output
SENSE
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Phase-Lockable Fixed Frequency 250kHz to 2.25MHz current sensing. Multiple LTC7851/LTC7851-1 devices can
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Lossless Current Sensing Using Inductor DCR or be used for high phase count operation.
Precision Current Sensing with Sense Resistor or
A very low offset, high bandwidth error amplifier, combined
DrMOS with Integrated Current Sensing
with remote output voltage sensing, provides excellent
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V Range: 3V to 5.5V
CC
transient response and output regulation. The LTC7851/
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V Range: 0.6V to V 0.5V
OUT CC
LTC7851-1 operates with a V supply voltage from 3V to
CC
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Power Good Output Voltage Monitor
5.5V and is designed for step-down conversion with V
IN
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Output Voltage Tracking Capability with Soft-Start
from 3V to 27V* and produces an output voltage from
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Available in 58-Lead 5mm 9mm QFN Package
0.6V to V 0.5V.
CC
APPLICATIONS The LTC7851-1 is identical to the LTC7851 except it has
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High Current Distributed Power Systems a lower current sense amplifier gain, making it ideal for
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DSP, FPGA and ASIC Supplies DrMOS devices with internal current sense.
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Datacom, Telecom and Computing Systems All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. Patents, including 6144194, 5055767.
*See Note 5.
TYPICAL APPLICATION
Dual-Output Converter: 1V/90A and 1.5V/30A with DrMOS
V
IN
7V TO 14V
VINSNS
0.25H 0.25H
DrMOSDrMOS PWM3 PWM2 DrMOSDrMOS
3.57k 3.57k
LTC7851
0.22F 0.22F
ISNS3P ISNS2P
ISNS3N ISNS2N
V
CC
V FB2,3 V
CC CC
5V
1F
100k 100k
0.25H 0.25H
PGOOD4 PGOOD1
V V
OUT2 OUT1
DrMOS PWM4 PWM1 DrMOS
1.5V/30A 1.0V/90A
+ +
100F RUN1 TRACK/SS1 100F
330F 330F
3.57k 3.57k
x 2 x 6
RUN2 TRACK/SS2
0.22F 0.22F
x 3 x 9
RUN3 TRACK/SS3
PINS NOT USED
ISNS4P ISNS1P
15k 10k
IN THIS CIRCUIT:
ISNS4N ISNS1N
CLKIN
VSNSP4 VSNSP1
CLKOUT
VSNSN4 VSNSN1
VSNSP2
VSNSOUT4 VSNSOUT1,2,3
VSNSP3 6.04k 4.02k
3.3nF 3.3nF
10k 15k
COMP4 COMP1,2,3
VSNSN2
10k 10k
FB4 FB1
VSNSN3
332 2.2nF 100pF 100pF 2.2nF 332
FREQ I
PGOOD2 AVG1,2,3
I I
PGOOD3 LIM4 LIM1,2,3
SGND
RUN4 30.9k 42.2k 42.2k
100pF
I
AVG4
7851 TA01
TRACK/SS4
Rev A
1
Document Feedback For more information www.analog.comLTC7851/LTC7851-1
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Note 1)
TOP VIEW
V Voltage .............................................. 0.3V to 6.5V
CC
VINSNS Voltage ........................................ 0.3V to 30V
RUN1, RUN2, RUN3,
58 57 56 55 54 53 52 51 50 49
RUN4 Voltage ............................0.3V to (V +0.3V)
CC
COMP1 1 48 I
LIM1
ISNS1P, ISNS1N,
VSNSP1 2 47 I
AVG1
ISNS2P, ISNS2N ....................... 0.3V to (V + 0.1V)
CC
VSNSN1 46 ISNS1P
3
ISNS3P, ISNS3N,
VSNSOUT1 4 45 ISNS1N
ISNS4P, ISNS4N ....................... 0.3V to (V + 0.1V)
SGND 5 44 ISNS2N
CC
VSNSOUT2 6 43 ISNS2P
All Other Pin Voltages ...................0.3V to (V + 0.3V)
CC
VSNSN2 7 42 I
AVG2
Operating Junction Temperature Range ... 40 to 125C
VSNSP2 8 I
41
LIM2
Storage Temperature Range .................. 65C to 150C
COMP2 9 40 TRACK/SS2
59
FB2 10 39 VINSNS
SGND
V 11 38 PGOOD2
CC
FB3 12 37 TRACK/SS3
COMP3 13 36 I
LIM3
VSNSP3 14 35 I
AVG3
VSNSN3 15 34 ISNS3P
VSNSOUT3 16 33 ISNS3N
VSNSOUT4 17 32 ISNS4N
VSNSN4 18 31 ISNS4P
VSNSP4 19 30 I
AVG4
20 21 22 23 24 25 26 27 28 29
UHH PACKAGE
58-LEAD (5mm 9mm) PLASTIC QFN
LEAD PITCH 0.4mm
= 49C/W, = 15.5C/W
JA JC
EXPOSED PAD (PIN 59) IS SGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC7851EUHH#PBF LTC7851EUHH#TRPBF 7851 58-LEAD (5mm 9mm) Plastic QFN 40C to 125C
LTC7851IUHH#PBF LTC7851IUHH#TRPBF 7851 58-LEAD (5mm 9mm) Plastic QFN 40C to 125C
LTC7851EUHH-1#PBF LTC7851EUHH-1#TRPBF 78511 58-LEAD (5mm 9mm) Plastic QFN 40C to 125C
LTC7851IUHH-1#PBF LTC7851IUHH-1#TRPBF 78511 58-LEAD (5mm 9mm) Plastic QFN 40C to 125C
Consult ADI Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
Rev A
2
For more information www.analog.com
COMP4 FB1
FB4 TRACK/SS1
TRACK/SS4 FREQ
CLKIN
RUN4
PWM4 CLKOUT
PGOOD4 RUN1
PWM3 PWM1
RUN3 RUN2
PWM2
PGOOD3
I PGOOD1
LIM4