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PDF LTC3861 Data sheet ( Hoja de datos )
| Número de pieza | LTC3861 | |
| Descripción | Multiphase Step-Down Voltage Mode DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3861
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 Dual Differential Output Voltage Sense Amplifiers
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 36-Pin 5mm × 6mm QFN Package
Applications
n High Current Distributed Power Systems
n DSP, FPGA and ASIC Supplies
n Datacom and Telecom Systems
n Industrial Power Supplies
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
The LTC®3861 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 per channel 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
VCC supply between 3V and 5.5V and is designed for step-
down conversion from VIN between 3V and 24V to output
voltages between 0.6V and VCC – 0.5V.
The TRACK/SS pins provide programmable soft-start or
tracking functions. 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 controllers can operate in
parallel for 1-, 2-, 3-, 4-, 6- or 12-phase operation.
The LTC3861isavailableina36-pin 5mm × 6mmQFNpack-
age. LTC3861-1 is a 32-pin QFN version of the LTC3861,
which has a single differential remote output voltage sense
amplifier.
Typical Application
VIN
VCC
1µF
28k
VOUT
10k
3.3nF 10k
10k 280Ω
4.7nF 5.9k 100pF
VCC
FREQ
VINSNS PWM1
FB2
ILIM2
LTC3861
VSNSOUT1
VSNSP1
VSNSN1
VSNSOUT2
VSNSP2
RUN1,2
ILIM1
ISNS1P
ISNS1N
ISNS2N
ISNS2P
VSNSN2
CONFIG
PWM2
FB1 IAVG
COMP1,2 SS1,2 SGND CLKIN
0.1µF
VCC
59k
LTC4449
IN GND
VLOGIC
VCC
BOOST
TG
TS
BG
0.22µF
0.22µF
0.22µF
VCC
100pF
LTC4449
IN GND
VLOGIC
VCC
BOOST
TG
TS
BG
0.22µF
VIN, 7V TO 14V
TG1
SW1
BG1
180µF
0.47µH
2.87k
VIN 2.87k
330µF
×6
TG2
SW2
0.47µH
3861 TA01
BG2
For more information www.linear.com/LTC3861
100µF
×4
VOUT
1.2V
60A
3861fb
1
1 page  
LTC3861
Typical Performance Characteristics
Load Step Transient Response
(Single Phase Using LTC4449)
Load Step Transient Response
(2-Phase Using D12S1R845A
Power Block)
Load Step Transient Response
(3-Phase Using FDMF6707B
DrMOS)
ILOAD
20A/DIV
IL
10A/DIV
VOUT
50mV/DIV
AC-COUPLED
VIN = 12V
VOUT = 1.2V
ILOAD
20A/DIV
IL1
20A/DIV
IL2
20A/DIV
VOUT
50mV/DIV
AC-COUPLED
50µs/DIV
3861 G01
ILOAD STEP = 0A TO 18A
fSW = 300kHz
VIN = 12V
VOUT = 1.2V
IL1
10A/DIV
IL2
10A/DIV
IL3
10A/DIV
100µs/DIV
VOUT
100mV/DIV
AC-COUPLED
3861 G02
ILOAD STEP = 0A TO 20A
fSW = 400kHz
VIN = 12V
VOUT = 1V
50µs/DIV
3861 G03
ILOAD STEP = 0A TO 30A
fSW = 500kHz EXTERNAL CLOCK
Load Step Transient Response
(4-Phase Using TDA21220
DrMOS)
Line Step Transient Response
(2-Phase Using LTC4449)
ILOAD
40A/DIV
VOUT
100mV/DIV
AC-COUPLED
VIN = 12V
VOUT = 1V
VIN
10V/DIV
IL1
10A/DIV
IL2
10A/DIV
VOUT
50mV/DIV
AC-COUPLED
50µs/DIV
3861 G04
ILOAD STEP = 40A TO 80A
fSW = 500kHz EXTERNAL CLOCK
20µs/DIV
3861 G05
VIN = 7V TO 14V IN 20µs ILOAD = 20A
VOUT = 1.2V
fSW = 300kHz
Efficiency vs Load Current
96
94
92
90
88
86
84
82
80
78
76
74
72
70
VIN = 12V, VOUT = 1V
4-PHASE TDA21220 DrMOS
fSW = 500kHz EXTERNAL CLOCK
0 10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (A)
3861 G07
Feedback Voltage
vs Temperature
VFB
601.00
600.75
600.50
600.25
600.00
599.75
599.50
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3861 G08
For more information www.linear.com/LTC3861
Efficiency vs Load Current
100
95
90
85
80
75
70
65
60
VIN = 12V
VOUT = 1.2V
55
50
2-PHASE, LTC4449
fSW = 300kHz
0 10 20 30 40 50 60 70
LOAD CURRENT (A)
3861 G06
Regulated VFB vs Supply Voltage
604
602
600
598
596
3
45
SUPPLY VOLTAGE (V)
6
3861 G09
3861fb
5
5 Page 
Functional Diagram
LTC3861
5 VSNSOUT1
3 VSNSP1
4 VSNSN1
DA
6 VSNSOUT2
8 VSNSP2
7 VSNSN2
2 COMP1 BG/BIAS
REF
TRACK/SS1
35
1 FB1
+
+ EA1
–
REF
TRACK/SS2
11
FB2
10
9 COMP2
+
+ EA2
–
25 ISNS1P
24 ISNS1N
+
x18.5
–
ISNS2P
22
ISNS2N
23
+
x18.5
–
36 21
26 33
28
VCC SGND SGND CONFIG
RUN1
VCC 100k
VCC
100k
1.5µA
1.5µA
VCC
19 31
16
RUN2
PGOOD1 PGOOD2
PGOOD
VFB1
VFB2
DA
SD/UVLO
+
VFB1
ILIM1
VFB2
ILIM2
S
+
MASTER/SLAVE/
INDEPENDENT
VCC
20µA
OC1 OC2
OV1 OV2
NOC1
NOC2
LOGIC
PWM1 29
PWMEN1 30
PWM2 18
PWMEN2 17
RAMP/SLOPE/
FEEDFORWARD
VINSNS 34
S
IAVG
32
VCC
20µA
ILIM2
20
ILIM1
27
OC1
NOC1
VCC
OC2
NOC2
20µA
PLL/VCO
FREQ PHSMD CLKOUT CLKIN
12 15
14
13
3861 BD
For more information www.linear.com/LTC3861
3861fb
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3861.PDF ] | |
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