RT8075 Datasheet, PDF (9/11 Pages) Richtek Technology Corporation – Dual 1A, 1.25MHz Synchronous Step-Down Converter

RT8075
The maximum power dissipation depends on operating
ambient temperature for fixed T_J(MAX) and thermal
resistance θ_JA. For RT8075 package, the Figure 2 of
derating curve allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation allowed.
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
Four Layers PCB
25
50
75
100
125
Ambient Temperature (°C)
Figure 2. Derating Curves for RT8075 Package
Layout Considerations
Follow the PCB layout guidelines for optimal performance
of RT8075.
` Keep the trace of the main current paths as short and
wide as possible.
` Put the input capacitor as close as possible to the device
pins (VIN1 / VIN2 and GND).
` LX 1 / LX 2 node is with high frequency voltage swing
and should be kept at small area. Keep analog
components away from the LX 1 / LX 2 node to prevent
stray capacitive noise pick-up.
` Place the feedback components as close as possible to
the FB1 / FB2 pins.
` The GND and Exposed Pad must be connected to a
strong ground plane for heat sinking and noise protection.
V_OUT1
C_IN2
C_OUT2
V_OUT2
C_FF1
R2
EN1 1
FB1 2
R1
VIN2 3
GND 4
L2 _LX2 5
L1
10 LX1
V_OUT1
C_OUT1
9 _GND
8 _VIN1
7 FB2
11
EN2
C_IN1
R3
V_OUT2
R4
C_FF2
GND
Figure 3. PCB Layout Guide
DS8075-04 April 2011
www.richtek.com
9