RT9183 RICHTEK [Richtek Technology Corporation], RT9183 Datasheet - Page 11

• Manufacturer Part Number: RT9183
• Description: Ultra Low Dropout 1.5A Linear Regulator
• Manufacturer: RICHTEK [Richtek Technology Corporation]

The maximum power dissipation depends on the thermal
resistance of IC package, PCB layout, the rate of
surroundings airflow and temperature difference between
junction to ambient. The maximum power dissipation can
be calculated by following formula:
P
Where T
temperature 125°C, T
the θ
For recommended operating conditions specification of
RT9183, where T
temperature of the die (125°C) and T
ambient temperature. The junction to ambient thermal
resistance (θ
is 115°C/W, SOT-223 package (F-Type) is 135°C/W,
SOP-8 package is 125°C/W, TO-252 package is 68°C/
W, TO-252 package (F-Type) is 75°C/W and TO-263
package is 45°C/W on standard JEDEC 51-3 thermal test
board.
The maximum power dissipation depends on operating
ambient temperature for fixed T
θ
allows the designer to see the effect of rising ambient
temperature on the maximum power allowed.
DS9183-14 April 2008
JA
D(MAX)
. For RT9183 packages, the Figure 4 of derating curves
2400
2000
1600
1200
JA
800
400
is the junction to ambient thermal resistance.
= ( T
0
0
J(MAX)
TO-263
TO-252
SOT-223
SOT-223
(F-Type)
J(MAX)
JA
is layout dependent) for SOT-223 package
is the maximum operation junction
- T
25
J(MAX)
Ambient temperature ( ℃ )
A
SOP-8
) /θ
A
Figure 4
is the ambient temperature and
JA
50
is the maximum junction
J(MAX)
TO-252
(F-Type)
and thermal resistance
75
A
is the maximum
(°C)
100
125
PCB Layout
Good board layout practices must be used or instability
can be induced because of ground loops and voltage drops.
The input and output capacitors MUST be directly
connected to the input, output, and ground pins of the
device using traces which have no other currents flowing
through them.
The best way to do this is to layout C
device with short traces to the V
The regulator ground pin should be connected to the
external circuit ground so that the regulator and its
capacitors have a“single point ground” .
It should be noted that stability problems have been seen
in applications where “vias” to an internal ground plane
were used at the ground points of the device and the input
and output capacitors. This was caused by varying ground
potentials at these nodes resulting from current flowing
through the ground plane. Using a single point ground
technique for the regulator and it's capacitors fixed the
problem. Since high current flows through the traces going
into V
leads to these pins so there is no voltage drop in series
with the input and output capacitors.
Optimum performance can only be achieved when the
device is mounted on a PC board according to the diagram
below :
EN
IN
and coming from V
GND
+
SOP-8 Board Layout
+
V
IN
GND
OUT
, Kelvin connect the capacitor
GND
IN
, V
OUT
IN
and C
, and ground pins.
RT9183
www.richtek.com
OUT
ADJ
V
OUT
near the
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