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PDF AP2952 Data sheet ( Hoja de datos )
| Número de pieza | AP2952 | |
| Descripción | 18V Synchronous Rectified Step-Down Converter | |
| Fabricantes | Chipown | |
| Logotipo |  |
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AP2952
Description
The AP2952 is a monolithic synchronous buck regulator. The
device integrates 130mΩ MOSFETS that provide 2A
continuous load current over a wide operating input voltage
of 4.75V to 18V. Current mode control provides fast transient
response and cycle-by-cycle current limit.
An adjustable soft-start prevents inrush current at turn-on. In
shutdown mode, the supply current drops below 1μA.
This device, available in an 8-pin SOP package, provides a
very compact system solution with minimal reliance on
external components.
Applications
Distributed Power Systems
Networking Systems
FPGA, DSP, ASIC Power Supplies
Green Electronics/ Appliances
Notebook Computers
Chipown
2A, 18V Synchronous Rectified
Step-Down Converter
Features
2A Output Current
Wide 4.75V to 18V Operating Input Range
Integrated 130mΩ Power MOSFET Switches
Output Adjustable from 0.925V to 15V
Up to 95% Efficiency
Programmable Soft-Start
Fixed 450KHz Frequency
Cycle-by-Cycle Over Current Protection
Input Under Voltage Lockout
Thermally Enhanced 8-Pin SOP Package
Package
8
27
36
45
Typical Application Circuit
Figure 1. Typical Application Circuit
100
90
80
70
60
50
40
30
20
10
0
0
Vout=5V
Vin=9V
Vin=12V
Vin=18V
400 800 1200 1600 2000
Load(mA)
Figure 2. Typical Efficiency Curve
8/F, ChuangYuan Building No.21-1 Changjiang Road, Wuxi New Destrict Tel: +86(510)8521-7718 http://www.chipown.com.cn
V2.0
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1 page  
AP2952
Chipown
Application Information
Component Selection
Setting the Output Voltage
The output voltage is set using a resistive voltage divider from
the output voltage to FB (see Typical Application circuit on page
1). The voltage divider divides the output voltage down by the
ratio:
Where VOUT is the output voltage, VIN is the input voltage,
fS is the switching frequency, and ΔIL is the peak-to-peak
inductor ripple current.
Choose an inductor that will not saturate under the maximum
inductor peak current. The peak inductor current can be
calculated by:
Where VFB is the feedback voltage and VOUT is the output
voltage.
Thus the output voltage is:
R2 can be as high as 100kΩ, but a typical value is 10kΩ.
Using the typical value for R2, R1 is determined by:
For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is
26.1kΩ. Table 1 lists recommended resistance values of R1 and
R2 for standard output voltages.
Where ILOAD is the load current.
The choice of which style inductor to use mainly depends on
the price vs. size requirements and any EMI requirements.
Optional Schottky Diode
During the transition between high-side switch and low-side
switch, the body diode of the lowside power MOSFET
conducts the inductor current. The forward voltage of this
body diode is high. An optional Schottky diode may be
paralleled between the SW pin and GND pin to improve
overall efficiency. Table 2 lists example Schottky diodes and
their Manufacturers.
Inductor
The inductor is required to supply constant current to the
output load while being driven by the switched input voltage.
A larger value inductor will result in less ripple current that
will result in lower output ripple voltage. However, the larger
value inductor will have a larger physical size, higher series
resistance, and/or lower saturation current. A good rule for
determining the inductance to use is to allow the peak-to-peak
ripple current in the inductor to be approximately 30% of the
maximum switch current limit. Also, make sure that the peak
inductor current is below the maximum switch current limit.
The inductance value can be calculated by:
Input Capacitor
The input current to the step-down converter is discontinuous,
therefore a capacitor is required to supply the AC current to the
step-down converter while maintaining the DC input voltage.
Use low ESR capacitors for the best performance. Ceramic
capacitors are preferred, but tantalum or low-ESR electrolytic
capacitors may also suffice. Choose X5R or X7R dielectrics
when using ceramic capacitors. Since the input capacitor
absorbs the input switching current it requires an adequate
ripple current rating. The RMS current in the input capacitor
can be estimated by:
8/F, ChuangYuan Building No.21-1 Changjiang Road, Wuxi New Destrict Tel: +86(510)8521-7718 http://www.chipown.com.cn V2.0
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| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet AP2952.PDF ] | |
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