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PDF LTC3861-1 Data sheet ( Hoja de datos )
| Número de pieza | LTC3861-1 | |
| Descripción | Multiphase Step-Down Voltage Mode DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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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
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.
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
VCC
1µF
28.7k
VOUT
1nF
20k 221Ω
20k 1nF 13k 220pF
VIN, 7V TO 14V
VCC
FREQ
VINSNS PWM1
FB2
ILIM2
LTC3861-1
VSNSOUT
RUN1,2
ILIM1
ISNS1P
VSNSP
ISNS1N
VSNSN
ISNS2N
CONFIG
ISNS2P
PWM2
FB1 IAVG
COMP1,2 SS1,2 SGND CLKIN
0.1µF
VCC
59k
LTC4449
IN
VLOGIC
VCC
BOOST
GND
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
180µF
0.47µH
2.87k
VIN 2.87k
330µF
×6
100µF
×4
VOUT
1.2V
60A
0.47µH
38611 TA01
For more information www.linear.com/LTC3861-1
38611fb
1
1 page  
LTC3861-1
Typical Performance Characteristics
Load Step Transient Response
(Single Phase Using LTC4449)
Load Step Transient Response
(2-Phase Using LTC4449)
Load Step Transient Response
(2-Phase Using D12S1R845A
Power Block)
IL
10A/DIV
ILOAD
20A/DIV
IL1
10A/DIV
ILOAD
20A/DIV
VOUT
50mV/DIV
AC-COUPLED
VIN = 12V
VOUT = 1.2V
IL2
10A/DIV
VOUT
50mV/DIV
AC-COUPLED
20µs/DIV
38611 G01
ILOAD STEP = 3A TO 18A TO 3A
fSW = 300kHz
VIN = 12V
VOUT = 1.2V
VOUT
50mV/DIV
AC-COUPLED
40µs/DIV
38611 G02
ILOAD STEP = 0A TO 20A TO 0A
fSW = 300kHz
VIN = 12V
VOUT = 1.2V
50µs/DIV
38611 G03
ILOAD STEP = 4A TO 20A TO 4A
fSW = 400kHz
Load Step Transient Response
(3-Phase Using FDMF6707B
DrMOS)
Load Step Transient Response
(4-Phase Using TDA21220
DrMOS)
Line Step Transient Response
(2-Phase Using LTC4449)
IL1
10A/DIV
IL2
10A/DIV
IL3
10A/DIV
VOUT
100mV/DIV
AC-COUPLED
VIN = 12V
VOUT = 1.2V
ILOAD
40A/DIV
VOUT
50mV/DIV
AC-COUPLED
50µs/DIV
38611 G04
ILOAD STEP = 0A TO 30A TO 0A
fSW = 500kHz EXTERNAL CLOCK
VIN = 12V
VOUT = 1V
VIN
10V/DIV
IL1
10A/DIV
IL2
10A/DIV
VOUT
50mV/DIV
AC-COUPLED
40µs/DIV
38611 G05
ILOAD STEP = 40A TO 80A TO 40A
fSW = 500kHz EXTERNAL CLOCK
20µs/DIV
38611 G06
VIN = 7V TO 14V IN 20µs ILOAD = 20A
VOUT = 1.2V
fSW = 300kHz
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)
38611 G07
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)
38611 G08
For more information www.linear.com/LTC3861-1
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)
38611 G09
38611fb
5
5 Page 
Functional Diagram
LTC3861-1
4 VSNSOUT
6 VSNSP
5 VSNSN
BG/BIAS
DA
3 COMP1
REF
TRACK/SS1
32
FB1
2
+
+ EA1
–
REF
9 TRACK/SS2
FB2
8
7 COMP2
+
+ EA2
–
22 ISNS1P
21 ISNS1N
+
x18.5
–
ISNS2P
19
20 ISNS2N
+
x18.5
–
1 29 30
VCC SGND CONFIG
VCC 100k
24
RUN1
VCC
100k
1.5µA
1.5µA
VCC
17 27
14
RUN2
PGOOD1 PGOOD2
PGOOD
VFB1
VFB2
SD/UVLO
+
OC1 OC2
OV1 OV2
VFB1
ILIM1
VFB2
ILIM2
S
+
MASTER/SLAVE/
INDEPENDENT
VCC
20µA
NOC1
NOC2
LOGIC
RAMP/SLOPE/
FEEDFORWARD
VCC OC1
NOC1
S 20µA
VCC
OC2
NOC2
20µA
PLL/VCO
PWM1 25
PWMEN1
26
PWM2 16
PWMEN2 15
VINSNS 31
IAVG
28
ILIM2
18
ILIM1
23
FREQ PHSMD CLKOUT CLKIN
10 13
12
11
38611 BD
For more information www.linear.com/LTC3861-1
38611fb
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3861-1.PDF ] | |
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