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Número de pieza | FAC2576 | |
Descripción | 3A 52Khz PWM Buck DC/DC Converter | |
Fabricantes | First Silicon | |
Logotipo | ||
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TECHNICAL DATA
FAC2576www.DataSheet4U.com
General Description
Features
The FAC2576 is a series of easy to use fixed and
adjustable step-down (buck) switch-mode voltage
regulators. These devices are available in fixed
output voltage of 3.3V, 5V, and an adjustable
output version. Both versions are capable of
driving a 3A load with excellent line and load
regulation.
Requiring a minimum number of external
components, these regulators are simple to use
and include internal frequency compensation, and
a fixed-frequency oscillator.
The output voltage is guaranteed to ±3%
tolerance under specified input voltage and
output load conditions. The oscillator frequency is
guaranteed to ±15%. External shutdown is
included, featuring typically 80 µA standby current.
Self protection features include a two stage
frequency reducing current limit for the output
switch and an over temperature shutdown for
complete protection under fault conditions.
The FAC2576 is available in TO-220B-5L
TO220-5L and TO-263-5L packages.
• 3,3V,5V and adjustable output versions
• Output adjustable from 1.23v to 43V
• Fixed 52KHz frequency internal oscillator
• Guaranteed 3A output load current
• Input voltage range up to 45V
• Low power standby mode, IQ typically 80 µA
• TTL shutdown capability
• Excellent line and load regulation
• Requires only 4 external components
• High efficiency
• Thermal shutdown and current limit protection
• Available in TO-220B/TO220 and TO-263
packages
Applications
• Simple High-efficiency step-down regulator
• On-card switching regulators
• Positive to negative converter
• LCD monitor and LCD TV
• DVD recorder and PDP TV
• Battery charger
• Step-down to 3.3V for microprocessors
Package Types
TO220B-5L
TO220-5L
TO263-5L
Figure 1. Package Types of FAC2576
2008. 02. 18
Revision No : 1
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1 page FAC2576
www.DataSheet4U.com
3A 52KHZ PWM Buck DC/DC Converter
VIH Threshold voltage
IH
IL
ON/OFF pin input current
θJC
Thermal Resistance
Junction to Case
Thermal Resistance
θJA Junction to Ambient
(Note1)
FAC2576 Vout: Output Voltage
ADJ η: Efficiency
FAC2576 Vout: Output Voltage
3.3V
η: Efficiency
FAC2576 Vout: Output Voltage
5V η: Efficiency
High (Regulator OFF)
2.0 1.3
VLOGIC=2.5V(Regulator OFF)
5
VLOGIC=0.5V(Regulator ON)
TO220B-5L/TO220-5L
TO263-5L
TO220B-5L/TO220-5L
TO263-5L
11V ≤ VIN ≤ 45V, 0.2A ≤
ILOAD≤3A, VOUT for 9V
VIN=12V,VOUT=9V,ILOAD=3A
4.75V ≤ VIN ≤ 45V, 0.2A ≤
ILOAD≤3A
VIN=12V, ILOAD=3A
7V≤VIN≤45V, 0.2A≤ILOAD
≤3A
1.193/
1.180
3.168/
3.135
4.800/
4.750
VIN=12V, ILOAD=3A
0.02
2.5
3.5
28
23
1.23
88
3.3
76
5.0
83
15
5
1.267/
1.280
3.432/
3.465
5.200/
5.250
V
uA
uA
OC/W
OC/W
V
%
V
%
V
%
Specifications with boldface type are for full operationg temperature range, the other type are for
TJ=25OC.
Note1: Thermal resistance with copper area of approximately 3 in2.
2008. 02. 18
Revision No : 1
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5 Page FAC2576
www.DataSheet4U.com
3A 52KHZ PWM Buck DC/DC Converter
Function Description
Pin Functions
+VIN
This is the positive input supply for the IC
switching regulator. A suitable input bypass
capacitor must be present at this pin to minimize
voltage transients and to supply the switching
currents needed by the regulator
Ground
Circuit ground.
Output
Internal switch. The voltage at this pin switches
between (+VIN – VSAT) and approximately – 0.5V,
with a duty cycle of approximately VOUT / VIN. To
minimize coupling to sensitive circuitry, the PC
board copper area connected to this pin should
be kept a minimum.
Feedback
Senses the regulated output voltage to complete
the feedback loop.
ON/OFF
Allows the switching regulator circuit to be
shutdown using logic level signals thus dropping
the total input supply current to approximately
80uA. Pulling this pin below a threshold voltage of
approximately 1.3V turns the regulator on, and
pulling this pin above 1.3V (up to a maximum of
25V) shuts the regulator down. If this shutdown
feature is not needed, the ON /OFF pin can be
wired to the ground pin or it can be left open, in
either case the regulator will be in the ON
condition.
Thermal Considerations
The FAC2576 is available in two packages, a 5-pin
TO-220B/TO-220 and a 5-pin surface mount
TO-263.
The TO-220B/TO-220 package needs a heat sink
under most conditions. The size of the heatsink
depends on the input voltage, the output voltage,
the load current and the ambient temperature.
The FAC2576 junction temperature rises above
ambient temperature for a 3A load and different
input and output voltages. The data for these
curves was taken with the FAC2576
(TO-220B/TO-220 package) operating as a buck
switching regulator in an ambient temperature of
25oC (still air). These temperature rise numbers
are all approximate and there are many factors
that can affect these temperatures. Higher
ambient temperatures require more heat sinking.
The TO-263 surface mount package tab is
designed to be soldered to the copper on a
printed circuit board. The copper and the board
are the heat sink for this package and the other
heat producing components, such as the catch
diode and inductor. The PC board copper area
that the package is soldered to should be at least
0.4 in2, and ideally should have 2 or more square
inches of 2 oz. Additional copper area improves
the thermal characteristics, but with copper areas
greater than approximately 6 in2, only small
improvements in heat dissipation are realized. If
further thermal improvements are needed, double
sided, multilayer PC board with large copper
areas and/or airflow are recommended.
The FAC2576 (TO-263 package) junction
temperature rise above ambient temperature with
a 3A load for various input and output voltages.
This data was taken with the circuit operating as a
buck switching regulator with all components
mounted on a PC board to simulate the junction
temperature under actual operating conditions.
This curve can be used for a quick check for the
approximate junction temperature for various
conditions, but be aware that there are many
factors that can affect the junction temperature.
When load currents higher than 3A are used,
double sided or multilayer PC boards with large
copper areas and/or airflow might be needed,
especially for high ambient temperatures and
high output voltages.
For the best thermal performance, wide copper
traces and generous amounts of printed circuit
board copper should be used in the board layout.
(Once exception to this is the output (switch) pin,
which should not have large areas of copper.)
Large areas of copper provide the best transfer of
heat (lower thermal resistance) to the surrounding
air, and moving air lowers the thermal resistance
even further.
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output voltage to FB The
voltage divider divides the
2008. 02. 18
Revision No : 1
11/16
11 Page |
Páginas | Total 16 Páginas | |
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Número de pieza | Descripción | Fabricantes |
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