aoz1010 Alpha & Omega Semiconductor, aoz1010 Datasheet - Page 10

• Manufacturer Part Number: aoz1010
• Description: Ezbuck 2a Simple Regulator
• Manufacturer: Alpha & Omega Semiconductor

The zero given by the external compensation network,
capacitor C
Figure 1), is located at:
f
To design the compensation circuit, a target crossover
frequency f
crossover frequency is where control loop has unity gain.
The crossover frequency is also called the converter
bandwidth. Generally a higher bandwidth means faster
response to load transient. However, the bandwidth
should not be too high because of system stability
concerns. 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 switching frequency. The AOZ1010
operates at a fixed switching frequency range from
350kHz to 600kHz. The recommended crossover
frequency is less than 30kHz.
The strategy for choosing R
over frequency with R
with C
calculate R
where;
f
V
G
A/V, and
G
5.64 A/V.
The compensation capacitor C
make a zero. This zero is put somewhere close to the
dominate pole, f
crossover frequency. C
C
f
R
C
Z 2
C
FB
EA
CS
Rev. 1.0 November 2006
C
C
is the desired crossover frequency,
is 0.8V,
=
is the error amplifier transconductance, which is 200 x 10
is the current sense circuit transconductance, which is
=
=
=
C
30kHz
. Using selected crossover frequency, f
------------------------------------ -
2π
f
------------------------------------ -
2π C
C
C
C
×
×
C
×
:
for close loop must be selected. The system
-----------
V
R
(C
V
1.5
1
FB
C
C
5
O
P1
in Figure 1), and resistor R
×
×
, but lower than 1/5 of the selected
×
f
R
P 1
----------------------------- -
G
C
C
2π C
EA
C
and set the compensator zero
can is selected by:
×
×
C
G
and C
O
CS
C
and resistor R
C
is to set the cross
C
(R
C
C
, to
together
1
in
www.aosmd.com
-6
The previous equation can also be simplified to:
An easy-to-use application software which helps to
design and simulate the compensation loop can be found
at www.aosmd.com.
Table 3 lists the values for a typical output voltage design
when output is 44µF ceramics capacitor.
Table 3.
Thermal Management and Layout
Consideration
In the AOZ1010 buck regulator circuit, high pulsing cur-
rent flows through two circuit loops. The first loop starts
from the input capacitors, to the V
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 PGND pin of the
AOZ1010, and to the LX pins of the AZO1010. Current
flows in the second loop when the low side diode is on.
In 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 AOZ1010.
In the AOZ1010 buck regulator circuit, the two major
power dissipating components are the AOZ1010 and
output inductor. The total power dissipation of converter
circuit can be measured by input power minus output
power.
The power dissipation of inductor can be approximately
calculated by output current and DCR of inductor.
C
P
P
C
total _loss
inductor _loss
V
1.8V
3.3V
=
OUT
5V
8V
C
----------------------
O
R
×
C
=
R
V
L
=
IN
2.2µH
3.3µH
4.7µH
10µH
I
L1
O
×
2
I
×
IN
R
–
inductor
V
O
31.6kΩ
49.9kΩ
80.6kΩ
20kΩ
×
R
IN
C
I
O
pin, to the LX pins, to
×
1.1
AOZ1010
Page 10 of 14
0.82nF
1.5nF
1.0nF
1.0nF
C
C