aoz1950 Alpha & Omega Semiconductor, aoz1950 Datasheet - Page 11

• Manufacturer Part Number: aoz1950
• Description: Boost Regulator White Led Driver
• Manufacturer: Alpha & Omega Semiconductor

Based on the duty cycle arrangement, the controller will
signal the internal driver to turn-off the NMOS to initiate
the fixed off time. After the NMOS is fully off, the
continuous inductor current continues to freewheel
through the output boost diode. The key parasitics in this
Below are some key tips in minimize the two main
switching loops and improving noise immunity
1. Maximized the copper area to the GND pin and the
2. Incorporate a ground plane on both top and bottom
3. To minimize trace inductance connects the device to
4. Add thermal vias for the GND pad for improved
5. To maximize thermal dissipation pour incorporate
6. Route sensitive signals such as FB and COMP
Rev. 1.0 January 2010
VIN pin for improved thermal dissipation.
layers if possible.
the LX pin with a short wire and adoption of this
technique for connections to the output capacitor and
ground.
thermal dissipation between top and bottom layers.
copper planes in unused areas.
pins a far distance away from the LX switching node
and pin.
R
SET
V
IN
DIM
C
COMP
C
R
C
COMP
GND
C1
Figure 14. Example of AOZ1950 PCB Layout and DFN-10 Pin-out
EN
LX
L1
C
STRING
OUT
v
LED
OUT
AOZ1950
LED Boost Driver
www.aosmd.com
D1
Alpha and Omega
LED Boost Driver
loop consist of PBC trace inductance from the anode to
the LX connection and lastly the connection from cathode
to power ground return. Both input and output capacitors
should be ceramic in type to achieve low ESR and ESL
specifications.
In the AOZ1950 boost regulator circuit, the three major
power dissipating components are the AOZ1950 and
output inductor. The total power dissipation of converter
circuit can be measured by difference between the input
and output power.
The power dissipation of inductor can be approximately
calculated by input current and DCR of inductor.
The actual AOZ1950 junction temperature can be
calculated with power dissipation and the thermal
impedance from junction to ambient.
The maximum junction temperature of AOZ1950 is rated
at 145ºC The thermal performance of the AOZ1950 is
strongly affected by the PCB layout and proper care
should be taken to ensure that the device will operate
under the recommended environmental conditions.
T
P
P
junction
inductor_loss
total_loss
=
PGND
VOUT
(
=
IND
VIN
P
FB
total_loss
(
=
V
IN
1
2
3
4
5
I
IN
×
2
I
×
IN
3x3 DFN-10
AOZ1950DI
R
–
(Top View)
)
(AGND)
inductor
P
PAD1
PAD2
–
(LX)
inductor_loss
(
V
O
×
×
I
O
1.1
)
10
9
8
7
6
(Eq. 14)
(Eq. 15)
)
AOZ1950
LX
EN
AGND
DIM
COMP
Page 11 of 14
×
Θ
+
(Eq. 15)
T
amb