Datasheet
SLVS273− FEBRUARY 2000
14
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
power dissipation
The power dissipated in the TPS6014x depends mainly on input voltage and output current and is described
by the following:
P
(DISS)
+ I
O
ǒ
3xV
I
–V
O
Ǔ
By observation of the above equation, it can be seen that the power dissipation is worse for the highest input
voltage V
I
and the highest output current I
O
. For an input voltage of 3.6 V and an output current of 100 mA, the
calculated power dissipation P
(DISS)
is 580 mW. This is also the point where the charge pump operates with its
lowest efficiency, which is only 45%, and hence with the highest power losses.
P
(DISS)
must be less than that allowed by the package rating. The thermal resistance junction to ambient of the
thermally enhanced TSSOP is 178°C/W for an unsoldered package. The thermal resistance junction to case,
with the exposed thermal pad soldered to an infinitive heat sink, is 3.5°C/W.
With the recommended maximum junction temperature of 125°C and an assumed maximum ambient operating
temperature of 85°C, the maximum allowed thermal resistance junction to ambient of the system can be
calculated as follows:
R
ΘJA
max +
T
J
max – T
A
P
(DISS)
max
+
125°C–85°C
580 mW
+ 69°CńW
Using a board layout as described in the application information section, R
ΘJA
is typically 56°C/W for an
unsoldered PowerPad and 41°C/W for a soldered PowerPad.
For more information, refer to the PowerPad application report (Literature Number: SLMA002).
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