aoz1605 Alpha & Omega Semiconductor, aoz1605 Datasheet - Page 11

• Manufacturer Part Number: aoz1605
• Description: 500 Ma / 3 Mhz Ezbuck Regulator
• Manufacturer: Alpha & Omega Semiconductor

Enable
The EN pin of the AOZ1605 is active high. Connect the
EN pin to VIN if enable function is not used. Pull it to
ground will disable the AOZ1605. Do not leave it open.
The voltage on EN pin must be above 2 V to enable
the AOZ1605. When voltage on EN pin falls below 0.6 V,
the AOZ1605 is disabled. If an application circuit requires
the AOZ1605 to be disabled, an open drain or open
collector circuit should be used to interface to EN pin.
Low Drop Out Operation
The AOZ1605 can operate at 100% duty cycle. In this
state, the high side p-channel MOSFET is always on.
This will allow the output to follow the input voltage as it
drops below the regulation voltage.
Rev. 1.0 March 2011
www.aosmd.com
Thermal Management and Layout
Considerations
In the AOZ1605 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 low side NMOSFET.
Current flows in the second loop when the low side
NMOSFET 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 input
capacitor, output capacitor, and PGND pin of the
AOZ1605.
In the AOZ1605 buck regulator circuit, the major power
dissipating components are the AOZ1605 and the 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.
The actual junction temperature can be calculated with
power dissipation in the AOZ1605 and thermal
impedance from junction to ambient.
The maximum junction temperature of AOZ1605 is
140 ºC, which limits the maximum load current capability.
Please see the thermal de-rating curves for maximum
load current of the AOZ1605 under different ambient
temperature.
The thermal performance of the AOZ1605 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.
T
P
P
junction
total_loss
inductor_loss
=
=
(
P
V
=
total_loss
IN
I
O
×
2
I
×
IN
R
–
inductor
–
V
P
O
inductor_loss
×
I
O
×
1.1
) Θ
AOZ1605
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