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PDF AOZ1017A Data sheet ( Hoja de datos )
| Número de pieza | AOZ1017A | |
| Descripción | 3A Simple Regulator | |
| Fabricantes | Alpha & Omega Semiconductors | |
| Logotipo |  |
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AOZ1017A
EZBuck™ 3A Simple Regulator
General Description
The AOZ1017A is a high efficiency, simple to use, 3A
buck regulator. The AOZ1017A works from a 4.5V to 16V
input voltage range, and provides up to 3A of continuous
output current with an output voltage adjustable down to
0.8V.
The AOZ1017A comes in an SO-8 package and is rated
over a -40°C to +85°C ambient temperature range.
Features
● 4.5V to 16V operating input voltage range
● 50mΩ internal PFET switch for high efficiency:
up to 95%
● Internal soft start
● Output voltage adjustable to 0.8V
● 3A continuous output current
● Fixed 500kHz PWM operation
● Cycle-by-cycle current limit
● Short-circuit protection
● Output over voltage protection
● Thermal shutdown
● Small size SO-8 packages
Applications
● Point of load DC/DC conversion
● PCIe graphics cards
● Set top boxes
● DVD drives and HDD
● LCD panels
● Cable modems
● Telecom/Networking/Datacom equipment
Typical Application
VIN
C1
22µF Ceramic
VIN
From µPC
RC
CC
EN U1
AOZ1017A LX
COMP
FB
C5
AGND GND
L1
4.7µH
D1
VOUT
3.3V
R1
C2, C3
22µF Ceramic
R2
Figure 1. 3.3V/3A Buck Regulator
Rev. 1.2 April 2009
www.aosmd.com
Page 1 of 15
Free Datasheet http://www.datasheet4u.com/
1 page  
AOZ1017A
Typical Performance Characteristics
Circuit of Figure 1. TA = 25°C, VIN = VEN = 12V, VOUT = 3.3V unless otherwise specified.
Light Load (DCM) Operation
Full Load (CCM) Operation
Vin ripple
50mV/div
Vo ripple
50mV/div
IL
2A/div
IL
10V/div
1μs/div
1μs/div
Startup to Full Load
Full Load to Turnoff
Vin ripple
0.1V/div
Vo ripple
50mV/div
IL
2A/div
IL
10V/div
Vin
5V/div
Vin
5V/div
400μs/div
Vo
2V/div
lin
1A/div
50% to 100% Load Transient
1ms/div
No Load to Turnoff
Vo
1V/div
lin
1A/div
100μs/div
Vo Ripple
0.1V/div
lo
2A/div
1s/div
Vin
5V/div
Vo
1V/div
lin
1A/div
Rev. 1.2 April 2009
www.aosmd.com
Page 5 of 15
Free Datasheet http://www.datasheet4u.com/
5 Page 
AOZ1017A
concern. When designing the compensation loop,
converter stability under all line and load condition must
be considered.
Usually, it is recommended to set the bandwidth to be
less than 1/10 of the switching frequency. The
AOZ1017A operates at a fixed switching frequency range
from 400kHz to 600kHz. It is recommended to choose a
crossover frequency less than 50kHz.
fC = 50kHz
The strategy for choosing RC and CC is to set the cross
over frequency with RC and set the compensator zero
with CC. Using selected crossover frequency, fC, to
calculate RC:
RC
=
fC
×
--V----O----
VFB
×
-----2---π-----×-----C-----O------
GEA × GCS
where;
fC is desired crossover frequency,
VFB is 0.8V,
GEA is the error amplifier transconductance, which is 200x10-6
A/V, and
GCS is the current sense circuit transconductance, which is
6.68 A/V.
The compensation capacitor CC and resistor RC together
make a zero. This zero is put somewhere close to the
dominate pole fp1 but lower than 1/5 of selected cross-
over frequency. CC can is selected by:
CC
=
--------------1---.--5---------------
2π × RC × fp1
The equation above can also be simplified to:
CC
=
C-----O-----×-----R-----L-
RC
An easy-to-use application software which helps to
design and simulate the compensation loop can be found
at www.aosmd.com.
Thermal Management and Layout
Consideration
In the AOZ1017A buck regulator circuit, high pulsing
current flows through two circuit loops. The first loop
starts from the input capacitors, to the VIN pin, to the LX
pins, to the filter inductor, to the output capacitor and
load, and then returns to the input capacitor through
ground. Current flows in the first loop when the high side
switch is on. The second loop starts from inductor, to the
output capacitors and load, to the anode of Schottky
diode, to the cathode of Schottky diode. Current flows in
the second loop when the low side diode is on.
In the PCB layout, minimizing the two loops area reduces
the noise of this circuit and improves efficiency. A ground
plane is strongly recommended to connect the input
capacitor, output capacitor, and PGND pin of the
AOZ1017A.
In the AOZ1017A buck regulator circuit, the major power
dissipating components are the AOZ1017A, the Schottky
diode and output inductor. The total power dissipation of
converter circuit can be measured by input power minus
output power.
Ptotal_loss = VIN × IIN – VO × IO
The power dissipation in Schottky can be approximated
as:
Pdiode_loss = IO × (1 – D) × VFW_Schottky
where;
VFW_Schottky is the Schottky diode forward voltage drop.
The power dissipation of inductor can be approximately
calculated by output current and DCR of inductor.
Pinductor_loss = IO2 × Rinductor × 1.1
The actual junction temperature can be calculated
with power dissipation in the AOZ1017A and thermal
impedance from junction to ambient.
Tjunction =
(Ptotal_loss – Pdiode_loss – Pinductor_loss) × ΘJA + Tamb
Rev. 1.2 April 2009
www.aosmd.com
Page 11 of 15
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet AOZ1017A.PDF ] | |
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