AOZ1031AI Alpha & Omega Semiconductor Inc, AOZ1031AI Datasheet - Page 11

• Manufacturer Part Number: AOZ1031AI
• Description: IC BUCK SYNC ADJ 3A SO8
• Manufacturer: Alpha & Omega Semiconductor Inc
• Series: EZBuck™r
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of AOZ1031AI

• Featured Product: The AOZ103x Family Synchronous Buck Regulator
• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.8 V ~ 18 V
• Current - Output: 3A
• Frequency - Switching: 600kHz
• Voltage - Input: 4.5 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 785-1253-2

Equation above 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.
Thermal Management and Layout
Consideration
In the AOZ1031A buck regulator circuit, high pulsing cur-
rent 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 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 capaci-
tor, output capacitor, and PGND pin of the AOZ1031A.
In the AOZ1031A buck regulator circuit, the major power
dissipating components are the AOZ1031A and the out-
put inductor. The total power dissipation of converter cir-
cuit 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 AOZ1031A and thermal imped-
ance from junction to ambient.
The maximum junction temperature of AOZ1031A is
150
P
T
P
C
junction
Rev. 1.6 March 2010
inductor_loss
total_loss
C
°
C, which limits the maximum load current capability.
=
C
---------------------
O
R
=
×
C
=
(
R
P
V
L
=
total_loss
IN
I
O
×
2
I
×
IN
R
–
–
inductor
P
V
inductor_loss
O
×
I
O
×
1.1
) Θ
×
JA
www.aosmd.com
Please see the thermal de-rating curves for maximum
load current of the AOZ1031A under different ambient
temperature.
The thermal performance of the AOZ1031A 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 condi-
tions.
out tips are listed below for the best electric and thermal
performance. Figure 3 on the next page illustrates a PCB
layout example of AOZ1031A.
1. The LX pins are connected to internal PFET and
2. Do not use thermal relief connection to the VIN and
3. Input capacitor should be connected to the VIN pin
4. A ground plane is preferred. If a ground plane is not
5. Make the current trace from LX pins to L to Co to the
6. Pour copper plane on all unused board area and
7. Keep sensitive signal trace far away form the LX
The AOZ1031A is standard SO-8 package. Several lay-
NFET drains. They are low resistance thermal con-
duction path and most noisy switching node. Con-
nected a large copper plane to LX pin to help thermal
dissipation.
the PGND pin. Pour a maximized copper area to the
PGND pin and the VIN pin to help thermal dissipa-
tion.
and the PGND pin as close as possible.
used, separate PGND from AGND and connect them
only at one point to avoid the PGND pin noise cou-
pling to the AGND pin.
PGND as short as possible.
connect it to stable DC nodes, like VIN, GND or
VOUT.
pins.
AOZ1031AI
Page 11 of 15