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PDF LTC3773 Data sheet ( Hoja de datos )
| Número de pieza | LTC3773 | |
| Descripción | Triple Output Synchronous 3-Phase DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
■ Current Mode Controller with Onboard
MOSFET Drivers
■ Programmable Power Up/Down Tracking
■ Wide VIN Range: 3.3V to 36V (VCC = 5V)
■ ±1% 0.6V VFB Accuracy Over Temperature
■ Power Good Output Voltage Monitor
■ Phase-Lockable or Adjustable Frequency:
160kHz to 700kHz
■ OPTI-LOOP® Compensation Minimizes COUT
■ Current Foldback and Overvoltage Protection
■ Selectable Continuous, Discontinuous or
Burst Mode® Operation at Light Load
■ Programmable Phase Operation
■ Available in 5mm x 7mm QFN and 36-Lead
SSOP Packages
APPLICATIONS
■ Servers, Telecom, Industrial Power Supplies
■ General Purpose Multiple Rail DC/DC
■ FPGA and DSP Requirements
LTC3773
Triple Output Synchronous
3-Phase DC/DC Controller with
Up/Down Tracking
DESCRIPTION
The LTC®3773 is a high performance, 3-phase, triple output
synchronous step-down switching regulator controller
with output voltage power up/down tracking capability.
The controller allows for sequential, coincident or ratio-
metric tracking.
This 3-phase controller drives its output stages with 120°
phase separation at frequencies of up to 700kHz per phase
minimizing the RMS input current. Light load efficiency can
be maximized by using selectable Burst Mode operation.
The 0.6V precision reference supports output voltages
from 0.6V to 5V.
Fault protection features include output overvoltage, input
undervoltage lockout plus current foldback under short-
circuit or overload conditions.
, LT, LTC, LTM, Burst Mode and OPTI-LOOP are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents including 5408150, 5481178, 5705919, 5929620,
6144194, 6177787, 6304066, 6498466, 6580258, 6611131.
wwwT.DYataPShIeCetA4UL.comAPPLICATION
High Efficiency, 3-Phase, Triple Synchronous DC/DC Step-Down Controller
10k
PGOOD
0.1μF
SW1, 2, 3
PGOOD VCC
POWER UP/SHUTDOWN SDB1, 2, 3
TRACK1, 2, 3
0.01μF
VOUT1
2.5V/15A 0.003Ω
VIN
2.2μH
COUT1
TG1
SW1
BG1
BOOST1, 2, 3 VDR
TG2
SW2
BG2
LTC3773
SENSE2+
SENSE2–
VFB2
TG3
SW3
BG3
31.6k
10k
SENSE1+
SENSE1–
VFB1
ITH1, 2, 3
PLLFLTR
SGND
PGND
SENSE3+
SENSE3–
VFB3
3773 F01
VCC
4.5V TO 6V
10μF
1.5μH
VOUT2
0.003Ω 1.8V/15A
+
COUT2
VIN
4.5V TO 22V
CIN
20k
VIN
1.2μH
VOUT3
0.003Ω 1.2V/15A
10k
COUT3
20k
20k
3773fb
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC3773
Efficiency vs Load Current,
Shutdown CH2 and CH3
100
90
80
10000
1000
70
60 CONTINUOUS 100
50 MODE
40
30
20
10
0
0.001
0.01
DISCONTINUOUS
MODE
10
Burst Mode
OPERATION
1
EFFICIENCY
POWER LOSS 0.1
0.1 1 10 100
CHANNEL 1 LOAD CURRENT (A)
VIN = 12V, VCC = 5V, VOUT1 = 2.5V
fSW = 220kHz
3773 G01
Efficiency vs VIN
Shutdown CH2 and CH3
100 VCC = 5V, VOUT1 = 2.5V, IOUT1 = 5A
SHUTDOWN CH2 AND CH3
95
4.0
3.2
90 PLLFLTR = 5V
fSW = 560kHz
PLLFLTR FLOATS
85
fSW = 400kHz
PLLFLTR = 0V
fSW = 220kHz
www.DataSheet4U.com
80
75
0 5 10 15
VIN (V)
2.4
1.6
0.8
EFFICIENCY
POWER LOSS
0.0
20 25
3773 G03
Line Regulation
2.5
VCC = 5V, VOUT = 2.5V, IOUT = 5A
2.0
1.0
0.8
1.5 0.6
1.0 0.4
0.5 0.2
00
–0.5 –0.2
–1.0 –0.4
–1.5 –0.6
–2.0 –0.8
–2.5
0
–1.0
5 10 15 20 25
VIN (V)
3773 G05
Efficiency vs Load Current,
Power-Up CH2 and CH3
100
10000
90
80 1000
70
60
50
40
30
20
10
0
0.001
0.01
CONTINUOUS 100
MODE
DISCONTINUOUS
MODE
10
Burst Mode
OPERATION
1
EFFICIENCY
POWER LOSS 0.1
0.1 1 10 100
CHANNEL 1 LOAD CURRENT (A)
VIN = 12V, VCC = 5V, VOUT1 = 2.5V
VOUT2 = 1.8V (NO LOAD), VOUT3 = 1.2V (NO LOAD)
fSW = 220kHz
3773 G02
Load Regulation
5
VIN = 12V, VCC = 5V, VOUT = 2.5V
0
0.2
0.0
–5 –0.2
–10 –0.4
–15
–20
–25
0
CONTINUOUS MODE
DISCONTINUOUS MODE
Burst Mode OPERATION
5 10 15
LOAD CURRENT (A)
–0.6
–0.8
–1.0
20
3773 G04
Current Limit vs VIN
25
RSENSE = 3mΩ
20
15
RSENSE = 5mΩ
10
5
VCC = 5V, VOUT = 2.5V, fSW = 220kHz
0
0 5 10 15 20
VIN (V)
25
3773 G06
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5 Page 
LTC3773
PIN FUNCTIONS (G/UHF)
PLLIN/FC (Pin 20/Pin 17): Synchronization Input to the
Phase Detector and Forced Continuous Control Input.
When floating, it sits around 1.6V, and the controller enters
discontinuous mode operation at light load. Shorting this
pin low or high for more than 20μs enables Burst Mode
operation or forced continuous current mode operation,
respectively. During frequency synchronization, the phase
locked loop will force the controller to operate in continu-
ous mode and the rising top gate signal of controller 1 to
be synchronized with the rising edge of the PLLIN signal.
When synchronization is not required, it is advisable to
bypass the PLLIN/FC pin with a 1000pF capacitor to avoid
noise coupling.
CLKOUT (Pin 18 UHF Only): CLK Output. Output clock
signal available to synchronize other controller ICs for
additional MOSFET controller stages/phases.
BG3 (Pin 21/Pin 19): Channel 3 Bottom Gate Drive. See
BG1.
PGND (Pin 22/Pin 39): Driver’s Power Ground. This pin
connects directly to the sources of the bottom N-channel
external MOSFETs and the (–) terminals of CIN. The backside
exposed pad (QFN) must be soldered to PCB ground.
VDR (Pin 23/Pin 20): Driver Supply. Provides supply to the
drivers for the bottom gates. Also used for charging the
bootstrap capacitors. This pin needs to be very carefully
and closely decoupled to the IC’s PGND pin. If the VDR
wwwp.DoatteanShtieaelt4isU.cloomwer than VCC potential by 1V, the drivers
will be disabled.
BG2 (Pin 24/Pin 21): Channel 2 Bottom Gate Drive. See
BG1.
BG1 (Pin 25/Pin 22): Channel 1 Bottom Gate Drive. Drives
the gate of the bottom N-channel MOSFET between ground
and VDR.
SW3 (Pin 26/Pin 23): Channel 3 Switching Node. See
SW1.
TG3 (Pin 27/Pin 24): Channel 3 Top Gate Drive. See
TG1.
BOOST3 (Pin 28/Pin 25): Channel 3 Top Gate Driver Sup-
ply. See BOOST1.
BOOST2 (Pin 29/Pin 26): Channel 2 Top Gate Driver Sup-
ply. See BOOST1.
TG2 (Pin 30/Pin 27): Channel 2 Top Gate Drive. See TG1.
SW2 (Pin 31/Pin 28): Channel 2 Switching Node.
See SW1.
SW1 (Pin 32/Pin 29): Channel 1 Switching Node. The (–)
terminal of the bootstrap capacitor connects here. This
pin swings from a Schottky diode (external) voltage drop
below ground to VIN (where VIN is the external MOSFET
supply rail).
TG1 (Pin 33/Pin 30): Channel 1 Top Gate Drive. The TG1
pin drives the top N-channel MOSFET with a voltage
swing equal to VDR superimposed on the switch node
voltage SW.
BOOST1 (Pin 34/Pin 31): Channel 1 Top Gate Driver Supply.
The (+) terminal of the bootstrap capacitor connects here.
This pin swings from approximately VDR up to VIN + VDR
(where VIN is the external MOSFET supply rail).
PGOOD (Pin 35/Pin 32): Open Drain Power Good Output.
This open-drain output is pulled low during shutdown or
when any of the three output voltages has been outside
the PGOOD tolerance window for more than 100μs.
PHASEMD (Pin 36/Pin 33): Phase Select Input. This pin
controls the phase relationship between controller 1,
controller 2, controller 3 and CLKOUT. When PHASEMD
is floating, its value is around 1.6V, the three channels
switch 120° out of phase, and CLKOUT synchronizes to
the rising edge of TG1. When PHASEMD is grounded,
TG1 leads CLKOUT by 60°. When PHASEMD is shorted
to VCC, TG1 leads TG2, TG3, and CLKOUT by 90°, 270°
and 180°, respectively.
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11 Page | ||
| Páginas | Total 32 Páginas | |
| PDF Descargar | [ Datasheet LTC3773.PDF ] | |
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