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PDF AIC2573 Data sheet ( Hoja de datos )
| Número de pieza | AIC2573 | |
| Descripción | DC/DC Controller | |
| Fabricantes | Analog Intergrations Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AIC2573 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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AIC2573
Synchronous Buck DC/DC Controller
FEATURES
High Efficiency: Up to 93%
Single-Powered N-channel MOSFETs Synchro-
nous Driver
Wide Input Voltage Operation Range 4.5V to 25V
Accurate Internal temperature compensated 0.8V
Bandgap Reference Voltage with ±1% precision.
Fast Transient Response
- Duty cycle 0% to 95 %
PWM Operation at 300KHz
Built-in Soft-Start function.
Over Voltage Protection with Latch Up.
Under Voltage Protection at Vout with Latch Up.
Over Current Protection.
Package: MSOP10
APPLICATIONS
Information Appliances
LCD TV
Graphic Card
Telecomm Equipments
GENERAL DESCRIPTION
The AIC2573 is a voltage mode synchronous buck
PWM controller that drives external N-channel
power MOSFET using a 300kHz fixed frequency
architecure. This device is capable of producing
an output voltage as low as 0.8V. It uses external
divider to adjust output voltage with the exact right
line and load regulation.
The AIC2573 provides adjustable overcurrent pro-
tection threshold from external component, fixed
threshold both undervoltage and overvoltage pro-
tection. LDO is built in to provide AIC2573 logic
power source, and application circuit just uses one
single power supply.
A multifunction pin (COMP) allows external com-
pensation for optimum load step response and
shutdown. Soft start can also be implemented with
this pin to properly sequence supplies.
The AIC2573 is available in space-saving 10 pins
MSOP package.
Analog Integrations Corporation
Si-Soft Research Center
3A1, No.1, Li-Hsin Rd. I , Science Park , Hsinchu 300, Taiwan , R.O.C.
TEL: 886-3-5772500
FAX: 886-3-5772510 www.analog.com.tw
DS-2573G-01 061008
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
Vin=12v
Vout=5v
Vin=12v
Vout=2.5v
Vin=12v
Vout=3.3v
Vin=12v
Vout=1.8v
Vin=12v
Vout=5v
AIC2573
Fig.2 Efficiency vs. Output Current
Rising Threshold
Fig.3 Frequency vs. Temperature
Vin=12v
Vout=5v
Falling Threshold
Vin=12v
Vout=5v
Fig.4 Power On Reset vs. Temperature
Fig.5 Reference Voltage vs. Temperature
Vin 10V/Div
UGATE 10V/Div
COMP 2V/Div
Vout 2V/Div
Time 10mS/Div
Fig.6 Power On
Vin 10V/Div
COMP 2V/Div
UGATE 10V/Div
Vout 2V/Div
Time 10mS/Div
Fig.7 Power Off
5
5 Page 
AIC2573
Component Selection Guidelines
Output Inductor Selection
The inductor value determines the ripple current. The
approximate ripple current and inductance value are
measured by the following equations:
∆IL
=
VOUT (1− D)
LfSW
Where ∆IL = inductor ripple current
fSW = free running frequency
D = duty cycle, Vout/Vin
Increasing the value of inductance will reduce the out-
put ripple current and ripple voltage. However, in-
creasing the inductance value will slow the converter
response time to a load transient.
pation and heat sink are the dominant design factor.
The power dissipation includes two losses section:
conduction loss and switching loss.
Upper MOSFET conduction loss
≅
I2
OUT
× RDS_ON
×
D
Lower MOSFET conduction loss
≅
I2
OUT
×
R DS_ON
×
(1−
D)
Switching loss
≅
1
2
×
IOUT
× VIN
× t ON,OFF
× fSW
Where tON,OFF = switching interval
Large gate-charge (Ciss, MOSFET input capacitance)
will increase the switching interval, tON,OFF, which in-
crease the MOSFET switching loss. Selects low
RDS_ON and low Ciss can reduce the MOSFET power
dissipation.
Input Capacitor Selection
Select input capacitors with voltage and current ratings
above the maximum input voltage and the circuit re-
quires the largest RMS current. The capacitor voltage
rating should be at least 1.25 times greater then maxi-
mum input voltage. The RMS current rating require-
ment is approximately 1/2 of the DC load current.
Output Capacitor Selection
The buck filter capacitor selection depends on series
resistance (ESR), output ripple voltage and ripple cur-
rent. These factors can be calculated as follows:
∆VOUT
=
∆IL
8CfSW
,
ESR
=
∆VOUT
∆IL
,
IC(RMS)
=
∆IL
23
Where IC(RMS) = capacitor ripple current
PCB Layout Considerations
The voltage spikes is the thought-provoking problem in
switching converter design. It can affect the applica-
tion-circuit’s stability and performance. Careful com-
ponent layout and printed circuit board design mini-
mizes the voltage spikes in the converter.
The voltage spikes comes from MOSFET switching,
therefore; placeing the input capacitors and high-
frequency ceramic decoupling capacitors are helpful to
reduce voltage spike at input power supply. Laying the
output inductor and output capacitors between the
MOSFET and the load are effective to reduce voltage
spike at output load. These components must be
closed jointly to minimize the voltage spikes.
It is necessary to use a shorter and wider power plane
that provides lower impedance to reduce the voltage
drop. For this reason, a multi-layer printed circuit
board is recommended. It is shown the connections of
the critical components in the converter in Fig 17:
Switch MOSFET Selection
In high current applications, the MOSFET power dissi-
The capacitors, Cin and Cout representing nu-
merous physical capacitors.
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet AIC2573.PDF ] | |
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