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PDF AOZ1056 Data sheet ( Hoja de datos )
| Número de pieza | AOZ1056 | |
| Descripción | 2A Simple Buck Regulator | |
| Fabricantes | Alpha & Omega Semiconductors | |
| Logotipo |  |
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AOZ1056
EZBuck™ 2A Simple Buck Regulator
General Description
The AOZ1056 is a high efficiency, simple to use, 2A buck
regulator. The AOZ1056 works from a 4.5V to 16V input
voltage range, and provides up to 2A of continuous
output current with an output voltage adjustable down
to 0.8V.
The AOZ1056 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
● 100mΩ internal PFET switch for high efficiency:
up to 95%
● Internal Schottky Diode
● Externally soft start
● Output voltage adjustable to 0.8V
● 2A continuous output current
● Fixed 340kHz PWM operation
● Cycle-by-cycle current limit
● Short-circuit protection
● Under voltage lockout
● Output over voltage protection
● Thermal shutdown
● Small size SO-8 package
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
Css
82nF SS VIN
EN U1
L1
6.8µH
VOUT
3.3V
AOZ1056 LX
COMP
R1
RC C5
FB C2, C3
22µF Ceramic
CC
AGND
PGND
R2
Rev. 1.2 September 2008
Figure 1. 3.3V/2A Buck Regulator
www.aosmd.com
Page 1 of 15
Free Datasheet http://www.datasheet4u.com/
1 page  
AOZ1056
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
0.1V/div
Vo ripple
20mV/div
2s/div
Startup to Full Load
VLX
5V/div
2s/div
Short Circuit Protection
Vo
2V/div
Vin ripple
0.1V/div
Vo ripple
20mV/div
VLX
5V/div
Vo
2V/div
lin
1A/div
4ms/div
50% to 100% Load Transient
Vo Ripple
50mV/div
lL
1A/div
10ms/div
Short Circuit Recovery
Vo
2V/div
400s/div
lo
1A/div
1ms/div
IL
1A/div
Rev. 1.2 September 2008
www.aosmd.com
Page 5 of 15
Free Datasheet http://www.datasheet4u.com/
5 Page 
AOZ1056
Usually, it is recommended to set the bandwidth to be
less than 1/10 of switching frequency. It is recommended
to choose a crossover frequency less than 34kHz.
fC = 34kHz
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--V---F-O--B-- × -G----2E---π-A----×-×----C-G----OC----S--
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
5.64 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
crossover frequency. CC can is selected by:
CC = 2----π-----×-----R1---.-C-5----×-----f--p---1-
The previous equation above can also be simplified to:
CC = C-----O--R---×--C---R-----L-
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 AOZ1056 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
pin, to the filter inductor, to the output capacitor and load,
and then return 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 PGND pin of the AOZ1056, to
the LX pin of the AZO1056. 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 recommended to connect input capacitor, output
capacitor, and PGND pin of the AOZ1056.
In the AOZ1056 buck regulator circuit, the two major
power dissipating components are the AOZ1056 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 of inductor can be approximately
calculated by output current and DCR of inductor.
Pinductor_loss = IO × (1 – D) × VFW_Schottky
The actual AOZ1056 junction temperature can be
calculated with power dissipation in the AOZ1056 and
thermal impedance from junction to ambient.
Tjunction =
(Ptotal_loss – Pdiode_loss – Pinductor_loss) × ΘJA + Tamb
The maximum junction temperature of AOZ1056 is
150°C, which limits the maximum load current capability.
The thermal performance of the AOZ1056 is strongly
affected by the PCB layout. Extra care should be taken
by users during design process to ensure that the IC
will operate under the recommended environmental
conditions.
Several layout tips are listed below for the best electric
and thermal performance. Figure 3 below illustrates a
single layer PCB layout example as reference.
1. Do not use thermal relief connection to the VIN and
the PGND pin. Pour a maximized copper area to
the PGND pin and the VIN pin to help thermal
dissipation.
2. Input capacitor should be connected to the VIN pin
and the PGND pin as close as possible.
3. A ground plane is preferred. If a ground plane is
not used, separate PGND from AGND and connect
them only at one point to avoid the PGND pin noise
coupling to the AGND pin. In this case, a decoupling
capacitor should be connected between VIN pin and
AGND pin.
4. Make the current trace from LX pin to L to Co to the
PGND as short as possible.
Rev. 1.2 September 2008
www.aosmd.com
Page 11 of 15
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet AOZ1056.PDF ] | |
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