rt8065 Richtek Technology Corporation, rt8065 Datasheet - Page 11

• Manufacturer Part Number: rt8065
• Description: 3a, 2mhz, Synchronous Step-down Converter
• Manufacturer: Richtek Technology Corporation

dissipation at T
formulas :
P
SOP-8 (Exposed Pad) package
P
WDFN-8L 3x3 package
The maximum power dissipation depends on the operating
ambient temperature for fixed T
resistance, θ
curves in Figure 3 allow the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
DS8065-03 March 2011
D(MAX)
D(MAX)
Figure 3. Derating Curve for the RT8065 Package
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
= (125°C − 25°C) / (75°C/W) = 1.333W for
= (125°C − 25°C) / (70°C/W) = 1.429W for
0
JA
A
. For the RT8065 package, the derating
=25°C can be calculated by the following
SOP-8 (Exposed Pad)
25
Ambient Temperature (°C)
50
WDFN-8L 3x3
75
J(MAX)
Four-Layer PCB
and thermal
100
125
C
C
COMP
COMP
C
C
SS
Layout Considerations
Follow the PCB layout guidelines for optimal performance
of the IC.
SS
GND
GND
Place the compensation
components as close to
the IC as possible
Place the compensation
components as close to
the IC as possible
LX node experiences high frequency voltage swings so
Keep all sensitive small signal nodes away from the LX
Connect the terminal of the input capacitor(s), C
Connect the FB pin directly to the feedback resistors.
close to the VIN pin as possible. This capacitor provides
the AC current into the internal power MOSFETs.
should be kept within a small area.
node to prevent stray capacitive noise pick up.
The resistive voltage-divider must be connected between
V
R
OUT
R
COMP
COMP
V
V
IN
Place the input and output capacitors
as close to the IC as possible
Place the input and output capacitors
as close to the IC as possible
IN
and GND.
COMP
C
C
IN
IN
VIN
EN
COMP
SS
GND
GND
VIN
Figure 4. PCB Layout Guide
EN
SS
1
2
3
4
2
3
4
GND
9
9
8
7
6
5
C
C
6
8
7
5
OUT
OUT
PGOOD
FB
RT
LX
PGOOD
FB
RT
LX
V
V
OUT
OUT
Place the feedback
resistors as close to
the IC as possible
Place the feedback
resistors as close to
the IC as possible
L1
L1
R2
R2
R
R
R1
R1
LX should be connected
to inductor by wide and
short trace, and keep
sensitive components
away from this trace
OSC
LX should be connected
to inductor by wide and
short trace, and keep
sensitive components
away from this trace
OSC
RT8065
www.richtek.com
V
V
GND
GND
OUT
OUT
IN
, as
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