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PDF LTC3639 Data sheet ( Hoja de datos )
| Número de pieza | LTC3639 | |
| Descripción | 150V 100mA Synchronous Step-Down Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3639
High Efficiency, 150V
100mA Synchronous
Step-Down Regulator
Features
n Wide Operating Input Voltage Range: 4V to 150V
n Synchronous Operation for Highest Efficiency
n Internal High Side and Low Side Power MOSFETs
n No Compensation Required
n Adjustable 10mA to 100mA 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 or External Soft-Start
n Programmable 1.8V, 3.3V, 5V or Adjustable Output
n Few External Components Required
n Programmable Input Overvoltage Lockout
n Thermally Enhanced High Voltage MSOP Package
Applications
n Industrial Control Supplies
n Medical Devices
n Distributed Power Systems
n Portable Instruments
n Battery-Operated Devices
n Automotive
n Avionics
Description
The LTC®3639 is a high efficiency step-down DC/DC
regulator with internal high side and synchronous power
switches that draws only 12μA typical DC supply current
while maintaining a regulated output voltage at no load.
The LTC3639 can supply up to 100mA load current and
features a programmable peak current limit that provides
a simple method for optimizing efficiency and for reduc-
ing output ripple and component size. The LTC3639’s
combination of Burst Mode® operation, integrated power
switches, 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 150V and programmable
overvoltage lockout, the LTC3639 is a robust regulator
suited for regulating from a wide variety of power sources.
Additionally, the LTC3639 includes a precise run threshold
andhttp://www.DataSheet4U.net/ soft-start feature to guarantee that the power system
start-up is well-controlled in any environment. A feedback
comparator output enables multiple LTC3639s to be con-
nected in parallel for higher current applications.
The LTC3639 is available in a thermally enhanced high
voltage-capable 16-lead MSE package with four missing pins.
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
5V to 150V Input to 5V Output, 100mA Step-Down Regulator
VIN
5V TO 150V
1µF
200V
VIN SW
LTC3639
RUN VFB
OVLO
SS
VPRG2 VPRG1
GND
470µH
3639 TA01a
VOUT
5V
10µF 100mA
Efficiency and Power Loss vs Load Current
100
90
VOUT = 5V
EFFICIENCY
80
70 1000
60
VIN = 12V
VIN = 36V
50
40
VIN = 72V
VIN = 150V
100
30
POWER LOSS
10
20
10 1
0
0.1 1 10 100
LOAD CURRENT (mA)
3639 TA01b
For more information www.linear.com/LTC3639
3639f
1
datasheet pdf - http://www.DataSheet4U.net/
1 page  
Typical Performance Characteristics
LTC3639
Quiescent Supply Current
vs Input Voltage
15
SLEEP
10
5
SHUTDOWN
0
0 30 60 90 120 150
VIN VOLTAGE (V)
3639 G10
Switch On-Resistance
vs Input Voltage
7
6
5
TOP
4
3
BOTTOM
2
1
0 30 60 90 120 150
VIN VOLTAGE (V)
3639 G13
Quiescent Supply Current
vs Temperature
30
VIN = 150V
25
20
15 SLEEP
10
5
0
–55 –25
SHUTDOWN
5 35 65 95
TEMPERATURE (°C)
125 155
3639 G11
Switch Leakage Current
vs Temperature
8
7
VIN = 150V
6
5
4
3
2 SW = 150V
1
0
–1 SW = 0V
–2
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
3639 G12
Switch On-Resistance
vs Temperature
8
7
6
5
TOP
http://www.DataSheet4U.net/
4
BOTTOM
3
2
Load Step Transient Response
OUTPUT
VOLTAGE
50mV/DIV
LOAD
CURRENT
50mA/DIV
VIN = 48V
200µs/DIV
VOUT = 3.3V
1mA TO 100mA LOAD STEP
FIGURE 15 CIRCUIT
3639 G15
1
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
3639 G14
Operating Waveforms, VIN = 48V
Operating Waveforms, VIN = 150V
OUTPUT
VOLTAGE
50mV/DIV
OUTPUT
VOLTAGE
50mV/DIV
SWITCH
VOLTAGE
20V/DIV
SWITCH
VOLTAGE
50V/DIV
INDUCTOR
CURRENT
200mA/DIV
INDUCTOR
CURRENT
200mA/DIV
VIN = 48V
10µs/DIV
VOUT = 3.3V
IOUT = 100mA
FIGURE 15 CIRCUIT
3639 G16
VIN = 150V
10µs/DIV
VOUT = 3.3V
IOUT = 50mA
FIGURE 15 CIRCUIT
3639 G17
Short-Circuit and Recovery
OUTPUT
VOLTAGE
1V/DIV
INDUCTOR
CURRENT
100mA/DIV
500µs/DIV
FIGURE 15 CIRCUIT
3639 G18
For more information www.linear.com/LTC3639
3639f
5
datasheet pdf - http://www.DataSheet4U.net/
5 Page 
LTC3639
Applications Information
140 ISET OPEN
120
100 L = 100µH
10000
80 L = 220µH
60
1000
40 L = 330µH
20
0
0 30 60 90 120 150
VIN INPUT VOLTAGE (V)
3639 F03
Figure 3. Switching Frequency for VOUT = 3.3V
100
10
100 300
PEAK INDUCTOR CURRENT (mA)
3639 F04
Figure 4. Recommended Inductor Values for Maximum Efficiency
the inductor value must be chosen so that it is larger than a Inductor Core Selection
minimum value which can be computed as follows:
Once the value for L is known, the type of inductor must
L
>
VIN(MAX) • tON(MIN)
IPEAK
• 1.2
be selected. High efficiency regulators generally cannot
afford the core loss found in low cost powdered iron cores,
forcing the use of the more expensive ferrite cores. Actual
where VIN(MAX) is the maximum input supply voltage when
switching is enabled, tON(MIN) is 150ns, IPEAK is the peak
current, and the factor of 1.2 accounts for typical inductor
tolerance and variation over temperature.
For applications that have large input supply transients,
the OVLO pin can be used to disable switching above the
maximum operating voltage VIN(MAX) so that the minimum
inductor value is not artificially limited by a transient
core loss is independent of core size for a fixed inductor
value but is very dependent of the inductance selected.
As the inductance increases, core losses decrease. Un-http://www.DataSheet4U.net/
fortunately, increased inductance requires more turns of
wire and therefore copper losses will increase.
Ferrite designs have very low core losses and are pre-
ferred at high switching frequencies, so design goals
can concentrate on copper loss and preventing satura-
condition. Inductor values that violate the above equation tion. Ferrite core material saturates “hard,” which means
will cause the peak current to overshoot and permanent that inductance collapses abruptly when the peak design
damage to the part may occur.
current is exceeded. This results in an abrupt increase in
Although the previous equation provides the minimum
inductor value, higher efficiency is generally achieved with
inductor ripple current and consequently output voltage
ripple. Do not allow the core to saturate!
a larger inductor value, which produces a lower switching Different core materials and shapes will change the size/
frequency. For a given inductor type, however, as induc- current and price/current relationship of an inductor. Toroid
tance is increased DC resistance (DCR) also increases. or shielded pot cores in ferrite or permalloy materials are
Higher DCR translates into higher copper losses and lower small and do not radiate energy but generally cost more
current rating, both of which place an upper limit on the than powdered iron core inductors with similar charac-
inductance. The recommended range of inductor values teristics. The choice of which style inductor to use mainly
for small surface mount inductors as a function of peak depends on the price versus size requirements and any
current is shown in Figure 4. The values in this range are a radiated field/EMI requirements. New designs for surface
good compromise between the trade-offs discussed above.
For applications where board area is not a limiting factor,
inductors with larger cores can be used, which extends
mount inductors are available from Coiltronics, Coilcraft,
TDK, Toko, and Sumida.
the recommended range of Figure 4 to larger values.
3639f
For more information www.linear.com/LTC3639
11
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11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC3639.PDF ] | |
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