Datasheet

TPS71025
LOW-DROPOUT VOLTAGE REGULATOR
SLVS162A – MAY 1997 – REVISED MAY 1998
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
THERMAL INFORMATION
Figure 17
110
90
70
50
0 50 100 150 200 250
130
150
THERMAL RESISTANCE, JUNCTION-TO-AMBIENT
vs
AIR FLOW
170
300
190
C/W
°
JAθ
R – Thermal Resistance, Junction-to-Ambient –
0 cm
2
8 cm
2
2 cm
2
4 cm
2
1 cm
2
Component/Board System
20-Lead TSSOP
Air Flow – ft/min
Figure 18
110
90
70
50
0 50 100 150 200 250
130
150
170
300
190
THERMAL RESISTANCE, JUNCTION-TO-AMBIENT
vs
AIR FLOW
0 cm
2
4 cm
2
2 cm
2
8 cm
2
1 cm
2
C/W
°
JAθ
R – Thermal Resistance, Junction-to-Ambient –
Component/Board System
20-Lead TSSOP
Includes Thermally Conductive
Compound Between Body and Board
Air Flow – ft/min
Using these figures to determine the system R
θJA
allows the maximum power-dissipation P
D(max)
limit to be
calculated with the equation:
P
D(max)
T
J(max)
T
A
R
JA(system)
Where
T
J(max)
is the maximum allowable junction temperature (i.e., 150°C absolute maximum or
125°C maximum recommended operating temperature for specified operation).
This limit should then be applied to the internal power dissipated by the TPS71025 regulator. The equation for
calculating total internal power dissipation of the device is:
P
D(total)
V
I
V
O
I
O
V
I
I
Q
Because the quiescent current is very low, the second term is negligible, further simplifying the equation to:
P
D(total)
V
I
V
O
I
O