Datasheet
SLVS354A − FEBRUARY 2001 − REVISED SEPTEMBER 2001
15
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
power dissipation
The power dissipated in the TPS6020x devices depends mainly on input voltage and output current and is
approximated by:
P
(DISS)
+ I
O
x
ǒ
2xV
I
* V
O
Ǔ
for I
(Q)
t I
O
(5)
By observing equation 5, it can be seen that the power dissipation is worst for highest input voltage V
I
and
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 390 mW. This is also the point where the charge pump operates with its lowest efficiency.
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.
R
QJA(max)
+
T
J(MAX)
* T
A
P
DISS(max)
+
125°C * 85°C
390 mW
+ 102°CńW
(6)
P
DISS
must be less than that allowed by the package rating. The thermal resistance junction to ambient of the
used 10-pin MSOP is 294°C/W for an unsoldered package. The thermal resistance junction to ambient with
the IC soldered to a printed circuit using a board layout as described in the application information section, the
R
ΘJA
is typically 200°C/W, which is higher than the maximum value calculated above. However, in a battery
powered application, both V
I
and T
A
will typically be lower than the worst case ratings used in equation 6 , and
power dissipation should not be a problem in most applications.
layout and board space
Careful board layout is necessary due to the high transient currents and switching frequency of the converter.
All capacitors should be placed in close proximity to the device. A PCB layout proposal for a one-layer board
is given in Figure 17. There is no specific EVM available for the TPS60204. However, the TPS60200EVM−145
can be used to evaluate the device.
The evaluation module for the TPS60200 can be ordered under product code TPS60200EVM−145. The EVM
uses the layout shown in Figure 17. All components including the pins are shown. The EVM is built so that it
can be connected to a 14-pin dual inline socket, therefore, the space needed for the IC, the external parts, and
eight pins is 17,9 mm x 10,2 mm = 182,6 mm
2
.