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PDF AS5422A Data sheet ( Hoja de datos )
| Número de pieza | AS5422A | |
| Descripción | 18V High Efficiency Synchronous Step-Down Converter | |
| Fabricantes | A1semi | |
| Logotipo |  |
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A1
A1semi
2A, 18V High Efficiency
Electronics Ltd Synchronous Step-Down Converter
AS5422A
General Description
The AS5422A is a wide input range, high-efficiency,
DC- DC step-down switching regulator, capable
of delivering up to 2A of output current. Current
mode PWM control allows the use of small external
components, such as ceramic input and output
caps, as well as small inductors, while still providing
low output ripples. On top of the integrated internal
synchronous rectifier that eliminates external
Schottky diode, AS5422A also employs a proprietary
control scheme that switches the device into a
power save mode during light load, thereby
extending the range of high efficiency operation.
Therefore, AS5422A is a much superior solution in
comparison to other competitions in terms of
efficiency and cost. Cycle-by-cycle current limit
provides output short-circuit protection and an input
OVP function guards AS5422A against possible input
voltage surge. Overall, AS5422A is a highly efficient
and robust solution for DC-DC step-down
applications that requires wide input ranges.
AS5422A is housed in a SOP8 Package.
Features
Wide Input Operating Range from 4.5V to 18V
High Efficiency:
Up to 90%at Light Load
Up to 95% at Heavy Load
Capable of Delivering 2A
Input OVP at 20V
No External Schottky Diode Needed
Current Mode control
0.923V Reference for Low Output voltages
Logic Control Shutdown
Thermal shutdown and UVLO
Applications
LCD TVs
Notebook computer
Constant Current Source
LED drivers
FPGA power supplies
Typical Application
AS5422AVer1.0
Figure1. Typical Application Circuit
1
http://www.a1semi.com
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A1
A1semi
2A, 18V High Efficiency
Electronics Ltd Synchronous Step-Down Converter
AS5422A
Functional Decriptions
Loop Operation
The AS5422A is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable of
delivering up to 2A of output current, integrated with a 110mΩ synchronous MOSFET, eliminating the need for
external diode. It uses a PWM current-mode control scheme. An error amplifier integrates error between the FB
signal and the internal reference voltage. The output of the integrator is then compared to the sum of a current-
sense signal and the slope compensation ramp. This operation generates a PWM signal that modulates the duty
cycle of the power MOSFETs to achieve regulation for output voltage.
Current Limit
There is a cycle-by-cycle current limit on the high-side MOSFET of 3A(typ). When the current flowing out of SW
exceeds this limit, the high-side MOSFET turns off and the synchronous rectifier turns on. Unlike the traditional
method of current limiting by limiting the voltage at the compensation pin, which usually has large variation due
to duty cycle variance, this type of peak current limiting scheme provides a relatively more accurate limit for
output current, thereby lowering the requirements for system design.
Light Load Operation
Traditionally, a fixed constant frequency PWM DC-DC regulator always switches even when the output load is
small. When energy is shuffling back and forth through the power MOSFETs, power is lost due to the finite RDSONs
of the MOSFETs and parasitic capacitances. At light load, this loss is prominent and efficiency is therefore very low.
AS5422A employs a proprietary control scheme that improves efficiency in this situation by enabling the device
into a power save mode during light load, thereby extending the range of high efficiency operation.
Application Infornation
Components Selection
VOUT (V)
8
5
3.3
2.5
1.8
1.2
COUT (μF)
22x2
22x2
22x2
22x2
22x2
22x2
L（ μ H)
22
15
10
6.8
4.7
3.3
AS5422AVer1.0
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5 Page | ||
| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet AS5422A.PDF ] | |
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