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PDF LTC3637 Data sheet ( Hoja de datos )
| Número de pieza | LTC3637 | |
| Descripción | 1A Step-Down Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC3637 (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
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FEATURES
n Wide Operating Input Voltage Range: 4V to 76V
n Internal 350mΩ Power MOSFET
n No Compensation Required
n Adjustable 100mA to 1A Maximum Output Current
n Low Dropout Operation: 100% Duty Cycle
n Low Quiescent Current: 12µA
n Wide Output Range: 0.8V to VIN
n 0.8V ±1% Feedback Voltage Reference
n Precise RUN Pin Threshold
n Internal and External Soft-Start
n Programmable 1.8V, 3.3V, 5V or Adjustable Output
n Few External Components Required
n Programmable Input Overvoltage Lockout
n Low Profile (0.75mm) 3mm × 5mm DFN and
Thermally-Enhanced MSE16 Packages
APPLICATIONS
n Industrial Control Supplies
n Medical Devices
n Distributed Power Systems
n Portable Instruments
n Battery-Operated Devices
n Automotive
n Avionics
LTC3637
76V, 1A Step-Down
Regulator
DESCRIPTION
The LTC®3637 is a high efficiency step-down DC/DC
regulator with an internal high side power switch that
draws only 12μA DC supply current while maintaining a
regulated output voltage at no load.
The LTC3637 cansupply up to1A load current andfeatures
a programmable peak current limit that provides a simple
method for optimizing efficiency and for reducing output
ripple and component size. The L TC3637’s combination
of Burst Mode® operation, integrated power switch, low
quiescent current, and programmable peak current limit
provides high efficiency over a broad range of load currents.
With its wide input range of 4V to 76,Vand programmable
overvoltage lockout, the L TC3637 is a robust regulator
suited for regulating from a widevariety ofpower sources.
Additionally, the LTC3637 includesa precise run threshold
and soft-start feature to guarantee that the power system
start-up is well-controlled in any environment.
The LTC3637 is available in the thermally-enhanced
3mm × 5mm DFN and the MSE16 packages.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
12.5V to 76V Input to 12V Output, 1A Regulator
VIN
12.5V TO 76V
2.2µF
VIN SW
LTC3637
RUN VFB
SS
FBO VPRG1
VPRG2
OVLO ISET
GND
10µH
200k
VOUT
12V
47µF 1A
35.7k
3637 TA01a
Efficiency and Power Loss vs Load Current
100
90
VOUT = 12V
EFFICIENCY
80
70
60 1000
50
40 POWER LOSS
100
30
20
10
0
0.1
VIN = 24V 10
VIN = 48V
VIN = 76V 0
1.0 10 100 1000
LOAD CURRENT (mA)
3637 TA01b
For more information www.linear.com/LTC3637
3637f
1
http://www.Datasheet4U.com
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC3637
Feedback Comparator Trip
Voltage vs Temperature
0.804 VIN = 12V
0.802
0.800
0.798
0.796
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
3637 G07
Peak Current Trip Threshold
vs RISET
2800 VIN = 12V
2400
2000
1600
1200
800
400
0
0 50 100 150 200 250
RISET (kΩ)
3637 G10
vQsuiIenspcuetnVtoVltIaNgSeupply Current
20
16 SLEEP
12
8
SHUTDOWN
4
0
5 15 25 35 45 55 65 75
INPUT VOLTAGE (V)
3637 G13
Feedback Comparator Hysteresis
vs Temperature
5.5
5.4
VIN = 12V
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
3637 G08
Peak Current Trip Threshold
vs Temperature
2800
VIN = 12V
2400
ISET OPEN
2000
1600
1200
RISET = 100k
800
400 ISET = GND
0
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
3637 G11
QvsuiTeesmcepnetraVtIuNreSupply Current
30
VIN = 12V
25
20
15 SLEEP
10
5 SHUTDOWN
0
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
3637 G14
For more information www.linear.com/LTC3637
RUN and OVLO Comparator
Threshold Voltages vs Temperature
1.24
1.22 RISING
1.20
1.18
1.16
1.14
1.12 FALLING
1.10
1.08
1.06
–55 –25
5 35 65 95 125 155
TEMPERATURE (°C)
3637 G09
Peak Current Trip Threshold
vs Input Voltage
2800
2400
ISET OPEN
2000
1600
1200
RISET = 100k
800
400 ISET = 0V
0
0 10 20 30 40 50 60 70
INPUT VOLTAGE (V)
3637 G12
UVLO Threshold Voltages
vs Temperature
3.70
RISING
3.65
3.60
3.55
FALLING
3.50
3.45
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
3637 G15
3637f
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5 Page 
LTC3637
APPLICATIONS INFORMATION
The basic LTC3637 application circuit is shown on the front mode to maximize efficiency and to facilitate a trade-off
page of the data sheet. External component selection is between efficiency and light load output voltage ripple, as
determined by the maximum load current requirement and described in the Optimizing Output Voltage Ripple section
begins with the selection of the peak current programming of the Applications Information. For maximum efficiency,
resistor, RISET. The inductor value L can then be determined,
followed by capacitors CIN and COUT.
minimize the capacitance on the I SET pin and place the
RISET resistor as close to the pin as possible.
Peak Current Resistor Selection
The peak current comparator has a guaranteed peak current
limit of 2A (2.4A typical), which guarantees a maximum
average load current of 1A. For applications that demand
less current, the peak current threshold can be reduced to
as little as 200mA (240mA typical). This lower peak current
allows the use of lower value, smaller components (input
capacitor, output capacitor, and inductor), resulting in
lower supply ripple and a smaller overall DC/DC regulator.
The threshold can be easily programmed using a resis-
tor (RISET) between the ISET pin and ground. The voltage
generated on the ISET pin by RISET and the internal 5µA
current source sets the peak current. The voltage on the
ISET pin is internally limited within the range of 0.1V to
1.0V. The value of resistor for a particular peak current can
be selected by using Figure 2 or the following equation:
RISET = 140k • IPEAK – 24k
where 200mA < IPEAK < 2A.
The internal 5μA current soucr e is reduced to 1μA in sleep
The typical peak current is internally limited to be within the
range of 240mA to 2.4A. Shorting the ISET pin to ground
programs the current limit to 240mA, and leaving it float
sets the current limit to the maximum value of 2.4A. When
selecting this resistor value, be aware that the maximum
average output current for this architecture is limited to
half of the peak current. Therefore, be sure to select a value
that sets the peak current with enough margin to provide
adequate load current under all conditions. Selecting the
peak current to be 2.2 times greater than the maximum
load current is a good starting point for mostapplications.
Inductor Selection
The inductor, input voltage, output voltage, and peak cur-
rent determine the switching frequency during a burst
cycle of the LTC3637. For a given input voltage, output
voltage, and peak current, the inductor value sets the
switching frequency during a burst cycle when the output
is in regulation. Generally, switching between 50kHz and
250kHz yields high efficiency, and 200kHz is a good first
choice for many applications. The inductor value can be
determined by the following equation:
260
240
220
200
180
160
140
120
100
80
60
40
20
0
0
200 400 600 800 1000
MAXIMUM LOAD CURRENT (mA)
3637 F02
Figure 2. RISET Selection
L
=
f
VOUT
• IPEAK
•
1–
VOUT
VIN
The variation in switching frequency during a burst cycle
with input voltage and inductance is shown in Figure 3. For
lower values of IPEAK, multiply the frequency in Figure 3
by 2.4A/IPEAK.
An additional constraint on the inductor value is the
LTC3637’s 150ns minimum on-time of the high side switch.
Therefore, in order to keep the current in the inductor
well-controlled, the inductor value must be chosen so that
it is larger than a minimum value which can be computed
For more information www.linear.com/LTC3637
3637f
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11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC3637.PDF ] | |
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