RT8113 RICHTEK [Richtek Technology Corporation], RT8113 Datasheet - Page 19

• Manufacturer Part Number: RT8113
• Description: Single Phase VR11.1 PWM Controller with 7-bit VID
• Manufacturer: RICHTEK [Richtek Technology Corporation]

f
cancel the ESR zero. And f
frequency to cancel high frequency noise.
For given bandwith, R2, f
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of IC
package, PCB layout, rate of surrounding airflow and
temperature difference between junction to ambient. The
maximum power dissipation can be calculated by following
the formula :
P
where T
the ambient temperature and θ
thermal resistance.
For recommended operating conditions specification of
the RT8113, the maximum junction temperature is 125°C
and T
thermal resistance θ
WQFN-24L 4x4 packages, the thermal resistance θ
52°C/W on the standard JEDEC 51-7 four-layer thermal
test board. The maximum power dissipation at T
can be calculated by the following formula :
P
WQFN-24L 4x4 package
The maximum power dissipation depends on operating
ambient temperature for fixed T
resistance θ
in Figure 11 allows the designer to see the effect of rising
ambient temperature on the maximum power dissipation.
DS8113-02 April 2011
R1 =
R3 =
C1 =
C3 =
C2 =
LC
D(MAX)
D(MAX)
, and place f
A
2
2
2 x f
2 x f
2
is the ambient temperature. The junction to ambient
G
π
π
= (T
π
π
π
J(MAX)
= (125°C − 25°C) / (52°C/W) = 1.923W for
MOD@BW
x f
x f x R2
x f
J(MAX)
JA
Z2
P2
P3
Z1
C
1
1
1
is the maximum junction temperature, T
. For RT8113 package, the derating curve
x R2
Z2
x C3
x C3
x C1 x R2 -1
C1
− T
at f
A
LC
) / θ
. f
JA
Z1
JA
P2
, f
is layout dependent. For
P3
is usually placed at f
Z2
JA
is placed below switching
, f
is the junction to ambient
P2
, f
J (MAX)
P3
, then
and thermal
A
= 25°C
ESR
JA
A
to
is
is
Layout Considerations
For best performance of the RT8113, the following
guidelines must be strictly followed :
The power components should be placed first. Keep
the connection between power components as short as
possible.
The shape of the phase plane (the connection plane
between high side MOSFETs, low-side MOSFETs and
output inductors) has to be as square as possible. Long
traces, thin bars or separated islands must be avoided
in the phase plane.
Keep snubber circuits or damping elements near its
objects. Phase RC snubbers have to be close to low-
side MOSFETs, UGATE damping resistor has to be
close to high-side MOSFETs, and boot to phase damping
resistor has to be close to high-side MOSFETs and
phase plane. Also, keep the traces of these snubber
circuits as short as possible.
The area of V
plane (output bulk capacitors and inductor connection
plane) has to be as wide as possible. Long traces or
thin bars must be avoided in these planes. The plane
trace width must be wide enough to carry large input/
output current (40mm/A).
The following traces have to be wide and short : UGATE,
LGATE, BOOT, PHASE, and VCC12. Make sure the
widths of these traces are wide enough to carry large
driving current (at least 40mm).
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
Figure 11. Derating Curves for RT8113 Package
0
IN
25
plane (power stage 12V V
Ambient Temperature (°C)
50
75
RT8113
Four-Layer PCB
www.richtek.com
100
IN
) and V
125
OUT
19