RT8279 RICHTEK [Richtek Technology Corporation], RT8279 Datasheet - Page 12

• Manufacturer Part Number: RT8279
• Description: 5A, 36V, 500kHz Step-Down Converter
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT8279
The maximum power dissipation depends on operating
ambient temperature for fixed T
resistance θ
curves allows the designer to see the effect of rising
ambient temperature on the maximum power dissipation
allowed.
www.richtek.com
12
(a) Copper Area = (2.3 x 2.3) mm
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Figure 5. Derating Curves for RT8279 Package
(c) Copper Area = 30mm
(b) Copper Area = 10mm
0
JA
. For the RT8279, the Figure 5 of
25
Ambient Temperature (°C)
50
2
2
, θ
, θ
75
J (MAX)
JA
JA
2
, θ
= 64°C/W
= 54°C/W
Four Layer PCB
JA
Copper Area
70mm
50mm
30mm
10mm
Min.Layout
= 75°C/W
and thermal
100
2
2
2
2
derating
125
Layout Consideration
Follow the PCB layout guidelines for optimal performance
of the RT8279.
wide as possible.
Put the input capacitor as close as possible to the device
pins (VIN and GND).
SW node is with high frequency voltage swing and should
be kept at small area. Keep analog components away
from the SW node to prevent stray capacitive noise pick-
up.
Connect feedback network behind the output capacitors.
Keep the loop area small. Place the feedback
components near the RT8279.
Connect all analog grounds to a common node and then
connect the common node to the power ground behind
the output capacitors.
An example of PCB layout guide is shown in Figure 6 for
reference.
Figure 4. Thermal Resistance vs. Copper Area Layout
Keep the traces of the main current paths as short and
(e) Copper Area = 70mm
(d) Copper Area = 50mm
Design
DS8279-01
2
2
, θ
, θ
JA
JA
= 49°C/W
= 51°C/W
December 2011