rt8297a Richtek Technology Corporation, rt8297a Datasheet - Page 13

• Manufacturer Part Number: rt8297a
• Description: 1.5a, 17v, 340/800khz Synchronous Step-down Converter
• Manufacturer: Richtek Technology Corporation

WDFN-8L 2x2 packages, the thermal resistance,
120°C/W on a standard JEDEC 51-7 four-layer thermal
test board. The maximum power dissipation at
can be calculated by the following formula :
P
WDFN-8L 2x2 package
The maximum power dissipation depends on the operating
ambient temperature for fixed
resistance,
curve in
rising ambient temperature on the maximum power
dissipation.
DS8297A/B-00 March 2011
D(MAX)
Figure 3. Derating Curve for the RT8297A/B Package
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
= (125°C − 25°C) / (120°C/W) = 0.833W for
Figure 3 allows
θ
JA
. For the RT8297A/B package, the derating
25
Ambient Temperature (°C)
the designer to see the effect of
50
75
T
J(MAX)
Four-Layer PCB
100
and thermal
T
A
= 25°C
θ
JA
125
, is
Input capacitor must
be placed as close
to the IC as possible.
Layout Consideration
Follow the PCB layout guidelines for optimal performance
of the RT8297A/B
Keep the traces of the main current paths as short and
wide as possible.
Put the input capacitor as close as possible to the device
pins (VIN and GND).
LX node is with high frequency voltage swing and should
be kept at small area. Keep sensitive components away
from the LX node to prevent stray capacitive noise pickup.
Place the feedback components to the FB pin as close
as possible.
The GND and Exposed Pad should be connected to a
strong ground plane for heat sinking and noise protection.
C
C
BOOT
Figure 4. PCB Layout Guide
OUT
C
IN
SW
BOOT
L
VIN
V
SW
EN
OUT
1
2
3
4
SW should be connected to
inductor by wide and short trace.
Keep sensitive components
away from this trace.
RT8297A/B
The resistor divider must be
connected as close to the
device as possible.
9
8
7
6
5
GND
GND
PGOOD
FB
www.richtek.com
R2
R1
V
GND
OUT
13