Datasheet

TPS71025
LOW-DROPOUT VOLTAGE REGULATOR
SLVS162A – MAY 1997 – REVISED MAY 1998
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
THERMAL INFORMATION
For a 20-lead TSSOP/FR4 board system with thermally conductive compound between the board and the
device body, where T
A
= 55°C, airflow = 100 ft/min, and copper heat sink area = 1 cm
2
, the maximum
power-dissipation limit can be calculated. As indicated in Figure 18, the system R
θJA
is 94°C/W; therefore, the
maximum power-dissipation limit is:
P
D(max)
T
J(max)
T
A
R
JA(system)
125 C 55 C
94 C W
745 mW
°
°°
If the system implements a TPS71025 regulator where V
I
= 3.3 V and I
O
= 385 mA, the internal power dissipation
is:
P
D(total)
V
I
V
O
I
O
(3.3 2.5) 0.385 308 mW
Comparing P
D(total)
with P
D(max)
reveals that the power dissipation in this example does not exceed the
maximum limit. When it does, one of two corrective actions can be taken. The power-dissipation limit can be
raised by increasing the airflow or the heat-sink area. Alternatively, the internal power dissipation of the regulator
can be lowered by reducing the input voltage or the load current. In either case, the above calculations should
be repeated with the new system parameters.