Datasheet
SLVS324A − JULY 2001 REVISED NOVEMBER 2004
20
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APPLICATION INFORMATION
OUT
IN
C1−
TPS60400
C1+
GND
5
4
1
2
3
C
(fly)
1 µF
5V6
C
O
1 µF
C
I
1 µF
V
I
GND
V
O
(V
I
/2)
GND
Figure 36.
power dissipation
As given in the data sheet, the thermal resistance of the unsoldered package is R
θJA
= 347°C/W. Soldered on
the EVM, a typical thermal resistance of R
θJA(EVM)
= 180°C/W was measured.
The terminal resistance can be calculated using the following equation:
R
qJA
+
T
J
* T
A
P
D
Where:
T
J
is the junction temperature.
T
A
is the ambient temperature.
P
D
is the power that needs to be dissipated by the device.
R
qJA
+
T
J
* T
A
P
D
The maximum power dissipation can be calculated using the following equation:
P
D
= V
I
× I
I
− V
O
× I
O
= V
I(max)
× (I
O
+ I
(SUPPLY)
) − V
O
× I
O
The maximum power dissipation happens with maximum input voltage and maximum output current.
At maximum load the supply current is 0.7 mA maximum.
P
D
= 5 V × (60 mA + 0.7 mA) − 4.4 V × 60 mA = 40 mW
With this maximum rating and the thermal resistance of the device on the EVM, the maximum temperature rise
above ambient temperature can be calculated using the following equation:
∆T
J
= R
θJA
× P
D
= 180°C/W × 40 mW = 7.2°C
This means that the internal dissipation increases T
J
by <10°C.
The junction temperature of the device shall not exceed 125°C.
This means the IC can easily be used at ambient temperatures up to:
T
A
= T
J(max)
− ∆T
J
= 125°C/W − 10°C = 115°C