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PDF LTC3769MPUF Data sheet ( Hoja de datos )
| Número de pieza | LTC3769MPUF | |
| Descripción | 60V Low IQ Synchronous Boost Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FeaTures
n Synchronous Operation for Highest Efficiency and
Reduced Heat Dissipation
n Wide VIN Range: 4.5V to 60V (65V Abs Max);
Operates Down to 2.3V After Start-Up
n Output Voltage Up to 60V
n ±1% 1.200V Reference Voltage
n RSENSE or Inductor DCR Current Sensing
n 100% Duty Cycle Capability for Synchronous MOSFET
n Low Quiescent Current: 28μA
n Phase-Lockable Frequency (75kHz to 850kHz)
n Programmable Fixed Frequency (50kHz to 900kHz)
n Power Good Output Voltage Monitor
n Low Shutdown Current: 4µA
n Internal LDO Powers Gate Drive from VBIAS or EXTVCC
n Thermally Enhanced Low Profile 24-Pin 4mm × 4mm
QFN Package and 20-Lead TSSOP Package
applicaTions
n Industrial
n Automotive
n Medical
n Military
LTC3769
60V Low IQ Synchronous
Boost Controller
DescripTion
The LTC3769 样片 is a high performance single output
syn- chronous boost converter controller that drives
an all N-channel power MOSFET stage. Synchronous
rectifica- tion increases efficiency, reduces power losses
and eases thermal requirements, simplifying high power
boost ap- plications. The 28µA no-load quiescent
current extends operating run time in battery-powered
systems.
A 4.5V to 60V input supply range encompasses a wide
range of system architectures and battery chemistries.
When biased from the output of the boost converter or
another auxiliary supply, the LTC3769 can operate from an
input supply as low as 2.3V after start-up. The operating
frequency can be set within a 50kHz to 900kHz range or
synchronized to an external clock using the internal PLL.
The SS pin ramps the output voltage during start-up. The
PLLIN/MODE pin selects Burst Mode® operation, pulse-
skipping mode or forced continuous mode at light loads.
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, 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 5408150, 5481178, 5705919,
5929620, 6177787, 6498466, 6580258, 6611131.
Typical applicaTion
120W, 12V to 24V/5A Synchronous Boost Converter
VIN
4.5V TO 60V
DOWN TO 2.3V
AFTER START-UP IF
VBIAS IS POWERED
FROM VOUT
22µF
10nF
15nF 8.66K
100pF
4mfi
3.3µH
RUN
SS
ITH
VBIAS
SENSE+
SENSE–
LTC3769 BG
PLLIN/MODE
FREQ
OVMODE
TG
SW
BOOST
ILIM
INTVCC
PGOOD
GND
VFB
EXTVCC
3769 TA01a
0.1µF
4.7µF
220µF
VOUT
24V/5A
VOUT FOLLOWS VIN FOR VIN > 24V
232k
Efficiency and Power Loss
vs Output Current
100 10
90
EFFICIENCY
80
1
70
POWER
0.1
LOSS
60
0.01
50
40
0.0001
0.001
0.001 0.01 0.1 1 10
OUTPUT CURRENT (A)
3769 TA01b
12.1k
For more 设计资料、应用案例、样片申请请见 ictry 样片申请网
3769f
1
1 page  
LTC3769
Typical perForMance characTerisTics TA = 25°C unless otherwise noted.
Efficiency and Power Loss
vs Output Current
100
10
90
80 1
70
60 0.1
50
40
30
20
10
0
0.01
VIN = 12V
VOUT = 24V
0.01
FIGURE 8 CIRCUIT
FCM EFFICIENCY
FCM LOSS
0.001
PULSE-SKIPPING EFFICIENCY
PULSE-SKIPPING LOSS
0.0001
0.1 1 10
OUTPUT CURRENT (A)
3769 G01
Efficiency and Power Loss
vs Output Current
100
10
90
EFFICIENCY
80
1
70
POWER
0.1
LOSS
60
50
40
0.0001 0.001 0.01
0.01
VIN = 12V
VOUT = 24V
FIGURE 8 CIRCUIT
0.001
0.1 1 10
OUTPUT CURRENT (A)
3769 G02
Efficiency vs Input Voltage
100
ILOAD = 2A
99 FIGURE 8 CIRCUIT
98
VOUT = 12V
97
VOUT = 24V
96
Load Step
Forced Continuous Mode
LOAD STEP
2A/DIV
INDUCTOR
CURRENT
5A/DIV
VOUT
500mV/DIV
95
94
93
0
5 10 15 20
INPUT VOLTAGE (V)
25
3769 G03
VIN = 12V
200µs/DIV
VOUT = 24V
LOAD STEP FROM 200mA TO 2.5A
FIGURE 8 CIRCUIT
3769 G04
Load Step
Burst Mode Operation
LOAD STEP
2A/DIV
INDUCTOR
CURRENT
5A/DIV
VOUT
500mV/DIV
VIN = 12V
200µs/DIV
VOUT = 24V
LOAD STEP FROM 200mA TO 2.5A
FIGURE 8 CIRCUIT
3769 G05
Load Step
Pulse-Skipping Mode
LOAD STEP
2A/DIV
INDUCTOR
CURRENT
5A/DIV
VOUT
500mV/DIV
VIN = 12V
200µs/DIV
VOUT = 24V
LOAD STEP FROM 200mA TO 2.5A
FIGURE 8 CIRCUIT
Inductor Currents at Light Load
Soft Start-Up
FORCED
CONTINUOUS
MODE
Burst Mode
OPERATION
5A/DIV
PULSE-
SKIPPING MODE
3769 G06
VIN = 12V
5µs/DIV
VOUT = 24V
ILOAD = 200µA
FIGURE 8 CIRCUIT
VOUT
5V/DIV
3769 G07
VRUN
5V/DIV
0V
VIN = 12V
20ms/DIV
VOUT = 24V
FIGURE 8 CIRCUIT
3769 G08
For more 设计资料、应用案例、样片申请请见 ictry 样片申请网
3769f
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5 Page 
LTC3769
operaTion
Main Control Loop
The LTC3769 uses a constant-frequency, current mode
step-up architecture. During normal operation, each
external bottom MOSFET is turned on when the clock for
that channel sets the RS latch, and is turned off when the
main current comparator, ICMP, resets the RS latch. The
peak inductor current at which ICMP trips and resets the
latch is controlled by the voltage on the ITH pin, which is
the output of the error amplifier EA. The error amplifier
compares the output voltage feedback signal at the VFB
pin (which is generated with an external resistor divider
connected across the output voltage, VOUT, to ground), to
the internal 1.200V reference voltage. In a boost converter,
the required inductor current is determined by the load
current, VIN and VOUT . When the load current increases,
it causes a slight decrease in VFB relative to the reference,
which causes the EA to increase the ITH voltage until the
average inductor current in each channel matches the new
requirement based on the new load current.
After the bottom MOSFET is turned off each cycle, the
top MOSFET is turned on until either the inductor current
starts to reverse, as indicated by the current comparator,
IREV, or the beginning of the next clock cycle.
INTVCC/EXTVCC Power
Power for the top and bottom MOSFET drivers and most
other internal circuitry is derived from the INTVCC pin.
When the EXTVCC pin is tied to a voltage less than 4.8V,
the VBIAS LDO (low dropout linear regulator) supplies
5.4V from VBIAS to INTVCC. If EXTVCC is taken above
4.8V, the VBIAS LDO is turned off and an EXTVCC LDO is
turned on. Once enabled, the EXTVCC LDO supplies 5.4V
from EXTVCC to INTVCC. Using the EXTVCC pin allows the
INTVCC power to be derived from an external source, thus
removing the power dissipation of the VBIAS LDO.
Shutdown and Start-Up (RUN and SS Pins)
The LTC3769 can be shut down using the RUN pin. Pulling
this pin below 1.28V shuts down the main control loops.
Pulling this pin below 0.7V disables the controller and
most internal circuits, including the INTVCC LDOs. In this
state, the LTC3769 draws only 4μA of quiescent current.
NOTE: Do not apply a heavy load to the boost converter for
an extended time while the LTC3769 is in shutdown. The
top MOSFET is turned off during shutdown and the output
load may cause excessive dissipation in the body diode.
The RUN pin may be externally pulled up or driven directly
by logic. When driving the RUN pin with a low impedance
source, do not exceed the absolute maximum rating of
8V. The RUN pin has an internal 11V voltage clamp that
allows the RUN pin to be connected through a resistor to
a higher voltage (for example, VIN), as long as the maxi-
mum current into the RUN pin does not exceed 100μA.
An external resistor divider connected to VIN can set the
threshold for converter operation. Once running, a 4.5μA
current is sourced from the RUN pin allowing the user to
program hysteresis using the resistor values.
The start-up of the controller’s output voltage VOUT is
controlled by the voltage on the SS pin. When the voltage
on the SS pin is less than the 1.2V internal reference, the
LTC3769 regulates the VFB voltage to the SS pin voltage
instead of the 1.2V reference. This allows the SS pin to
be used to program a soft-start by connecting an external
capacitor from the SS pin to SGND. An internal 10μA
pull-up current charges this capacitor creating a voltage
ramp on the SS pin. As the SS voltage rises linearly from
0V to 1.2V (and beyond up to INTVCC), the output voltage
rises smoothly to its final value.
Light Load Current Operation—Burst Mode Operation,
Pulse-Skipping or Continuous Conduction
(PLLIN/MODE Pin)
The LTC3769 can be enabled to enter high efficiency Burst
Mode operation, constant-frequency, pulse-skipping
mode or forced continuous conduction mode at low
load currents. To select Burst Mode operation, tie the
PLLIN/MODE pin to ground (e.g., SGND). To select
forced continuous operation, tie the PLLIN/MODE pin to
INTVCC. To select pulse-skipping mode, tie the PLLIN/
MODE pin to a DC voltage greater than 1.2V and less
than INTVCC – 1.3V.
When the controller is enabled for Burst Mode opera-
tion, the minimum peak current in the inductor is set to
For more 设计资料、应用案例、样片申请请见 ictry 样片申请网
3769f
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| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3769MPUF.PDF ] | |
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