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PDF AOZ1094 Data sheet ( Hoja de datos )
| Número de pieza | AOZ1094 | |
| Descripción | 5A Simple Buck Regulator | |
| Fabricantes | Alpha & Omega Semiconductors | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AOZ1094 (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
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AOZ1094
EZBuck™ 5A Simple Buck Regulator
General Description
The AOZ1094 is a high efficiency, simple to use, 5A buck
regulator. The AOZ1094 works from a 4.5V to 16V input
voltage range, and provides up to 5A of continuous
output current with an output voltage adjustable down
to 0.8V.
The AOZ1094 comes in SO-8 and DFN-8 packages
and is rated over a -40°C to +85°C ambient temperature
range.
Features
● 4.5V to 16V operating input voltage range
● 28mΩ internal PFET switch for high efficiency:
up to 95%
● Internal soft start
● Output voltage adjustable to 0.8V
● Built-in Overvoltage Protection (OVP)
– 18% OVP threshold
● 5A continuous output current
● Fixed 500kHz PWM operation
● Cycle-by-cycle current limit
● Short-circuit protection
● Thermal shutdown
● Small size SO-8 and DFN-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
VIN
Enable
RC
CC
EN U1
AOZ1094
COMP
C5
1000pF
AGND GND
LX
FB
L1 3.3μH
Rs
20Ω
D1
Cs
1nF
VOUT
3.3V
R1
C2
22μF
C3
22μF
R2
Rev. 1.3 October 2010
Figure 1. 3.3V/5A Buck Down Regulator
www.aosmd.com
Page 1 of 19
1 page  
AOZ1094
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
2s/div
Full Load to Startup
Vin
ripple
100mV/div
Vout
ripple
20mV/div
IL
2A/div
VLX
10V/div
2s/div
Light Load to Startup
Vin
ripple
200mV/div
Vout
ripple
20mV/div
IL
2A/div
VLX
10V/div
2ms/div
Vin
5V/div
Vout
2V/div
lin
2A/div
50% to 100% Load Transient
2ms/div
Vin
5V/div
Vout
2V/div
lin
200mA/div
200s/div
Vout ripple
200mV/div
lout
2A/div
Rev. 1.3 October 2010
www.aosmd.com
Page 5 of 19
5 Page 
AOZ1094
Output ripple voltage specification is another important
factor for selecting the output capacitor. In a buck con-
verter circuit, output ripple voltage is determined by
inductor value, switching frequency, output capacitor
value and ESR. It can be calculated by the equation
below:
ΔVO
=
ΔIL
×
⎛
⎝
ES
RCO
+
-8----×-----f--1-×-----C-----O--⎠⎞
where,
CO is output capacitor value, and
ESRCO is the equivalent series resistance of the output
capacitor.
When low ESR ceramic capacitor is used as output
capacitor, the impedance of the capacitor at the
switching frequency dominates. Output ripple is mainly
caused by capacitor value and inductor ripple current.
The output ripple voltage calculation can be simplified to:
ΔVO
=
ΔIL
×
------------1-------------
8 × f × CO
If the impedance of ESR at switching frequency
dominates, the output ripple voltage is mainly decided by
capacitor ESR and inductor ripple current. The output
ripple voltage calculation can be further simplified to:
ΔVO = ΔIL × ESRCO
For lower output ripple voltage across the entire
operating temperature range, X5R or X7R dielectric type
of ceramic, or other low ESR tantalum or aluminum
electrolytic capacitors are recommended to be used as
output capacitors.
In a buck converter, output capacitor current is contin-
uous. The RMS current of output capacitor is decided
by the peak to peak inductor ripple current. It can be
calculated by:
ICO_RMS
=
--Δ----I--L--
12
Usually, the ripple current rating of the output capacitor is
a smaller issue because of the low current stress. When
the buck inductor is selected to be very small and
inductor ripple current is high, output capacitor could be
overstressed.
Schottky Diode Selection
The external freewheeling diode supplies the current to
the inductor when the high side PMOS switch is off. To
reduce the losses due to the forward voltage drop and
recovery of diode, Schottky diode is recommended to
use. The maximum reverse voltage rating of the chosen
Schottky diode should be greater than the maximum
input voltage, and the current rating should be greater
than the maximum load current.
Loop Compensation
The AOZ1094 employs peak current mode control for
easy use and fast transient response. Peak current mode
control eliminates the double pole effect of the output
L&C filter. It greatly simplifies the compensation loop
design.
With peak current mode control, the buck power stage
can be simplified to be a one-pole and one-zero system
in frequency domain. The pole is dominant pole and can
be calculated by:
fP1
=
-----------------1-----------------
2π × CO × RL
The zero is a ESR zero due to output capacitor and its
ESR. It is can be calculated by:
fZ1
=
-----------------------1-------------------------
2π × CO × ESRCO
where;
CO is the output filter capacitor,
RL is load resistor value, and
ESRCO is the equivalent series resistance of output capacitor.
The compensation design is actually to shape the
converter close loop transfer function to get desired gain
and phase. Several different types of compensation
network can be used for the AOZ1094. For most cases, a
series capacitor and resistor network connected to the
COMP pin sets the pole-zero and is adequate for a stable
high-bandwidth control loop.
In the AOZ1094, FB pin and COMP pin are the inverting
input and the output of internal transconductance error
amplifier. A series R and C compensation network
connected to COMP provides one pole and one zero.
The pole is:
fP2
=
----------------G-----E----A-----------------
2π × CC × GVEA
where;
GEA is the error amplifier transconductance, which is 200 x 10-6
A/V,
GVEA is the error amplifier voltage gain, which is 500 V/V, and
CC is compensation capacitor.
Rev. 1.3 October 2010
www.aosmd.com
Page 11 of 19
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet AOZ1094.PDF ] | |
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