RT8482
13
DS8482-02 May 2012 www.richtek.com
©
Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
Figure 5. Derating Curve of Maximum Power Dissipation
Layout Consideration
PCB layout is very important when designing power
switching converter circuits. Some recommended layout
guidelines are suggested as follows :
` The power components L1, D1, C
IN
, M1 and C
OUT
must
be placed as close to each other as possible to reduce
the ac current loop area. The PCB trace between power
components must be as short and wide as possible
due to large current flow through these traces during
operation.
` The input capacitor C
VCC
must be placed as close to
VCC
pin as possible.
` Place the compensation components as close to VC
pin as possible to avoid noise pick up.
` Connect GND pin and Exposed Pad to a large ground
plane for maximum power dissipation and noise
reduction.
Figure 6. PCB Layout Guide
P
D(MAX)
= (125°C − 25°C) / (68°C/W) = 1.471W for
WQFN-16L 3x3 packages
P
D(MAX)
= (125°C − 25°C) / (85°C/W) = 1.176W for
SOP-16 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T
J(MAX)
and thermal
resistance θ
JA
. The Figure 5 of derating curves allows the
designer to see the effect of rising ambient temperature
on the maximum power allowed.
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
0 25 50 75 100 125
Ambient Temperature (°C)
Maximum Power Dissipation (W) 1
SOP-16
WQFN-16L 3x3
Four Layers PCB
Place these components as close to each other as possible
Locate input
capacitor as
close to VCC
as possible
GBIAS
GATE
NC
ISW
NC
ISP
ISN
VC ACTL
DCTL
SS
NC
EN
OVP
VCC
GND
2
98
7
6
5
4
3
10
16
15
14
13
12
11
C
VCC
C
IN
R
SW
M1
C
OUT
D1
L1
GND
R
VC
C
VC
C
SS
GND
V
IN
R
SENS
Locate the compensation components as
close to VC pin as possible
