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PDF LTC3709 Data sheet ( Hoja de datos )
| Número de pieza | LTC3709 | |
| Descripción | No RSENSE Synchronous DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC3709 (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
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LTC3709
Fast 2-Phase, No RSENSETM,
Synchronous DC/DC Controller
with Tracking/Sequencing
FEATURES
DESCRIPTIO
■ PolyPhaseTM Valley Current Mode Controller
■ Synchronizable to an External Clock with PLL
■ Coincident or Ratiometric Tracking
■ Sense Resistor Optional
■ 2% to 90% Duty Cycle at 200kHz
■ tON(MIN) < 100ns
■ True Remote Sensing Differential Amplifier
■ High Efficiency at Both Light and Heavy Loads
■ Power Good Output Voltage Monitor
■ 0.6V ±1% Reference
■ Adjustable Current Limit
■ Programmable Soft-Start and Operating Frequency
■ Output Overvoltage Protection
■ Optional Short-Circuit Shutdown Timer
■ 32-Lead (5mm × 5mm) QFN Package
U
APPLICATIO S
■ Notebook Computers
■ Power Supply for DSP, ASIC, Graphic Processors
The LTC®3709 is a single output, dual phase, synchronous
step-down switching regulator. The controller uses a
constant on-time, valley current control architecture to
deliver very low duty cycles without requiring a sense
resistor. Operating frequency is selected by an external
resistor and is compensated for variations in input supply
voltage. An internal phase-locked loop allows the LTC3709
to be synchronized to an external clock.
A TRACK pin is provided for tracking or sequencing the
output voltage among several LTC3709 chips or an
LTC3709 and other DC/DC regulators. Soft-start is ac-
complished using an external timing capacitor.
Fault protection is provided by an output overvoltage com-
parator and an optional short-circuit shutdown timer. The
current limit level is user programmable. A wide supply
range allows voltages as high as 31V to step down to 0.6V.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No RSENSE and PolyPhase are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6476589, 6144194, 5847554, 6177678,
6304066, 6580258, 6674274, 6462525, 6593724.
TYPICAL APPLICATIO
High Efficiency Dual Phase 1.5V/30A Step-Down Converter
5V
4.7µF
10Ω
324k
47.5k
1µF
10k
100k
0.1µF
3.32k
100nF
680pF
20k
10k
15k
VCC DRVCC ION
TRACK
TG1
VRNG
FCB
BOOST1
PGOOD
SW1
SENSE1+
RUN/SS
BG1
EXTLPF SENSE1–
INTLPF
PGND1
ITH LTC3709
SGND
VFB
DIFFOUT
VOS–
VOS+
TG2
BOOST2
SW2
SENSE2+
BG2
SENSE2–
PGND2
1µF
1µF
PGND1
PGND2
0.22µF
HAT2168H
10µF
35V
×3
1.22µH
HAT2165H
VIN
4.5V TO 28V
0.22µF
HAT2168H
HAT2165H
VIN
1.22µH
VOUT
1.5V
30A
+ 330µF
2.5V
×4
Efficiency and Power Loss
100
VIN = 12V
95
10
9
90
EFFICIENCY
85
8
7
80 6
75 5
70 4
65 3
POWER LOSS
60 2
55 1
50
0.01
0.1 1
10
LOAD CURRENT (A)
0
100
3709 TA01b
3709 TA01a
3709f
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TYPICAL PERFOR A CE CHARACTERISTICS
LTC3709
Start-Up
VRUN/SS
5V/DIV
VOUT
1V/DIV
IL1
10A/DIV
IL2
10A/DIV
1ms/DIV
Continuous Current Mode (CCM)
Discontinuous Current Mode (DCM)
SW1
5V/DIV
SW2
5V/DIV
3709 G01
2µs/DIV
SW1
5V/DIV
SW2
1V/DIV
3709 G02
10µs/DIV
3709 G03
Transient Response (CCM)
Transient Response (DCM)
ILOAD
3A-18A
VOUT
50mV/DIV
VSW1
20V/DIV
VSW2
20V/DIV
ILOAD
3A-18A
VOUT
50mV/DIV
VSW1
20V/DIV
VSW2
20V/DIV
20µs/DIV
3709 G04
20µs/DIV
3709 G05
Power Loss vs Load Current
10
VIN = 12V
VOUT = 1.5V
f = 220kHz
1
0.1
0.01
Efficiency vs VIN
100
VOUT = 1.5V
ILOAD = 10A
f = 220kHz
95
90
85
Efficiency vs Load Current
100
VIN = 12V
95 VOUT = 1.5V
90 f = 220kHz
85
80
75
70
65
60
55
50
10
100
1000
10000 100000
LOAD (mA)
3709 G06
Quiescent Current at VCC = 5V
3.0
2.8
2.6
2.4
2.2
0.001
10
100
1000
10000
LOAD CURRENT (mA)
100000
3709 G07
80
4
8 12 16 20 24
VIN (V)
3709 G08
2.0
–40 –20 0
20 40 60
TEMPERATURE (°C)
80
3709 G09
3709f
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OPERATIO (Refer to Functional Diagram)
DRVCC
Power for the top and bottom MOSFET drivers and most
of the internal controller circuitry is derived from the
DRVCC pin. The top MOSFET driver is powered from a
floating bootstrap capacitor CB. This capacitor is normally
recharged from DRVCC through an external Schottky di-
ode DB when the top MOSFET is turned off.
Differential Amplifier
This amplifier provides true differential output voltage
sensing. Sensing both VOUT+ and VOUT– benefits regula-
tion in high current applications and/or applications hav-
ing electrical interconnection losses. This sensing also
isolates the physical power ground from the physical
signal ground, preventing the possibility of troublesome
“ground loops” on the PC layout and preventing voltage
errors caused by board-to-board interconnects.
LTC3709
Dual Phase Operation
An internal phase-lock loop (PLL1) ensures that channel
2 operates exactly at the same frequency as channel 1 and
is also phase shifted by 180°, enabling the LTC3709 to
operate optimally as a dual phase controller. The loop filter
connected to the INTLPF pin provides stability to the PLL.
For external clock synchronization, a second PLL (PLL2)
is incorporated into the LTC3709. PLL2 will adjust the on-
time of channel 1 until its frequency is the same as the
external clock. When locked, the PLL2 aligns the turn on
of the top MOSFET of channel 1 to the rising edge of the
external clock. Compensation for PLL2 is through the
EXTLPF pin.
Second Channel Shutdown During Light Loads
When FCB is tied to VCC, discontinuous mode is selected.
In this mode, no reverse current is allowed. The second
channel is off when ITH is less than 0.8V for better
efficiency. When FCB is tied to ground, forced continuous
mode is selected, both channels are on and reversed
current is allowed.
3709f
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC3709.PDF ] | |
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