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PDF AOZ1268QI-01 Data sheet ( Hoja de datos )
| Número de pieza | AOZ1268QI-01 | |
| Descripción | 28V/10A Synchronous EZBuck Regulator | |
| Fabricantes | Alpha & Omega Semiconductors | |
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AOZ1268QI-01
28V/10A Synchronous EZBuckTM Regulator
General Description
The AOZ1268-01 is a high-efficiency, easy-to-use DC/DC
synchronous buck regulator that operates up to 28V.
The device is capable of supplying 10A of continuous
output current with an output voltage adjustable down to
0.8V (±1.0%).
The AOZ1268-01 integrates an internal linear regulator
to generate 5.3V VCC from input. If input voltage is lower
than 5.3V, the linear regulator operates at low drop-
output mode, which allows the VCC voltage is equal to
input voltage minus the drop-output voltage of the
internal linear regulator.
A proprietary constant on-time PWM control with input
feed-forward results in ultra-fast transient response while
maintaining relatively constant switching frequency over
the entire input voltage range. The switching frequency
can be externally programmed up to 1MHz.
The device features multiple protection functions such as
VCC under-voltage lockout, cycle-by-cycle current limit,
output over-voltage protection, short-circuit protection, as
well as thermal shutdown.
The AOZ1268-01 is available in a 4mm x 4mm QFN-23L
package and is rated over a -40°C to +85°C ambient
temperature range.
Features
Wide input voltage range
– 6.5V to 28V
10A continuous output current
Output voltage adjustable down to 0.8V (±1.0%)
Low RDS(ON) internal NFETs
– 28m high-side
– 8m low-side
Constant On-Time with input feed-forward
Programmable frequency up to 1MHz
Selectable PFM light load operation
Ceramic capacitor stable
Adjustable soft start
Power Good output
Integrated bootstrap diode
Cycle-by-cycle current limit
Short-circuit protection
Thermal shutdown
Thermally enhanced 4mm x 4mm QFN-23L package
Applications
Portable computers
Compact desktop PCs
Servers
Graphics cards
Set-top boxes
LCD TVs
Cable modems
Point-of-load DC/DC converters
Telecom/Networking/Datacom equipment
Rev. 2.0 July 2014
www.aosmd.com
Page 1 of 15
1 page  
AOZ1268QI-01
Electrical Characteristics (Continued)
TA = 25°C, VIN = 12V, VCC = 5V, EN = 5V, unless otherwise specified. Specifications in BOLD indicate a temperature range of
-40°C to +85°C.
Symbol
Parameter
Soft-Start
ISS_OUT SS Source Current
Power Good Signal
VPG_LOW PGOOD Low Voltage
PGOOD Leakage Current
VPGH
PGOOD Threshold
(Low Level to High Level)
VPGL
PGOOD Threshold
(High Level to Low Level)
PGOOD Threshold Hysteresis
TPG_L PGOOD Fault Delay Time (FB falling)
Under Voltage and Over Voltage Protection
VPL
TPL
VPH
TUV_LX
Under Voltage Threshold
Under Voltage Delay Time
Over Voltage Threshold
Under Voltage Shutdown Blanking Time
Power Stage Output
RDS(ON)
High-Side NFET On-Resistance
High-Side NFET Leakage
RDS(ON)
Low-Side NFET On-Resistance
Low-Side NFET Leakage
Over-current and Thermal Protection
ILIM Valley Current Limit
Thermal Shutdown Threshold
Conditions
VSS = 0
CSS = 0.001F to 0.1F
IOL = 1mA
FB rising
FB falling
FB rising
FB falling
Min.
7
87
107
112
82
FB falling
82
FB rising
VIN = 12V, VEN = 0V, VCC = 5V
112
VIN = 12V, VCC = 5V
VEN = 0V, VLX = 0V
VLX = 12V, VCC = 5V
VEN = 0V
VCC = 5V
TJ rising
TJ falling
12
Typ.
11
90
110
115
85
3
50
85
128
115
20
28
8
145
100
Max Units
15 A
0.5 V
±1 A
93
113
%
118
88
%
%
s
88 %
s
118 %
ms
35 m
10 A
10 m
10 A
A
°C
Rev. 2.0 July 2014
www.aosmd.com
Page 5 of 15
5 Page 
AOZ1268QI-01
Output Capacitor
The output capacitor is selected based on the DC output
voltage rating, output ripple voltage specification and
ripple current rating.
The selected output capacitor must have a higher rated
voltage specification than the maximum desired output
voltage including ripple. De-rating needs to be
considered for long term reliability.
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:
VO
=
IL
ES
RCO
+
-8---------f--1------C-----O--
where,
CO is output capacitor value and
ESRCO is the Equivalent Series Resistor of output capacitor.
When a 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:
VO = IL -8---------f--1------C-----O--
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:
VO = IL ESRCO
For lower output ripple voltage across the entire
operating temperature range, X5R or X7R dielectric type
of ceramic, or other low ESR tantalum are recommended
to be used as output capacitors.
In a buck converter, output capacitor current is
continuous. The RMS current of output capacitor is
decided by the peak to peak inductor ripple current.
It can be calculated by:
ICO_RMS
=
------I--L--
12
Thermal Management and Layout
Consideration
In the AOZ1268-01 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 the inductor, to
the output capacitors and load, to the low side switch.
Current flows in the second loop when the low side
switch is on.
In 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
AOZ1268-01.
In the AOZ1268-01 buck regulator circuit, the major
power dissipating components are the AOZ1268-01 and
output inductor. The total power dissipation of the con-
verter circuit can be measured by input power minus out-
put power.
Ptotal_loss = VIN IIN – VO IO
The power dissipation of inductor can be approximately
calculated by output current and DCR of inductor and
output current.
Pinductor_loss = IO2 Rinductor 1.1
The actual junction temperature can be calculated with
power dissipation in the AOZ1268-01 and thermal
impedance from junction to ambient.
Tjunction = Ptotal_loss–Pinductor_loss JA
The maximum junction temperature of AOZ1268-01 is
150ºC, which limits the maximum load current capability.
The thermal performance of the AOZ1268-01 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.
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, the output capacitor could
be overstressed.
Rev. 2.0 July 2014
www.aosmd.com
Page 11 of 15
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet AOZ1268QI-01.PDF ] | |
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