Datasheet

TPS2010, TPS2011, TPS2012, TPS2013
POWER-DISTRIBUTION
SLVS097A – DECEMBER 1994 – REVISED AUGUST 1995
16
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
power dissipation and junction temperature
The low on resistance of the N-channel MOSFET allows small surface-mount packages, such as SOIC or
TSSOP to pass large currents. The thermal resistances of these packages are high compared to that of power
packages; it is good design practice to check power dissipation and junction temperature. The first step is to
find r
on
at the input voltage and operating temperature. As an initial estimate, use the highest operating ambient
temperature of interest and read r
on
from Figure 23. Next calculate the power dissipation using:
P
D
r
on
I
2
Finally, calculate the junction temperature:
T
J
P
D
R
JA
T
A
Where:
T
A
= Ambient temperature
R
θJA
= Thermal resistance SOIC = 172°C/W, TSSOP = 179°C/W
Compare the calculated junction temperature with the initial estimate. If they do not agree within a few degrees,
repeat the calculation using the calculated value as the new estimate. Two or three iterations are generally
sufficient to get a reasonable answer.
thermal protection
Thermal protection is provided to prevent damage to the IC when heavy-overload or short-circuit faults are
present for extended periods of time. The faults force the TPS201x into its constant current mode, which causes
the voltage across the high-side switch to increase; under short-circuit conditions, the voltage across the switch
is equal to the input voltage. The increased dissipation causes the junction temperature to rise to dangerously
high levels. The protection circuit senses the junction temperature of the switch and shuts it off. The switch
remains off until the junction has dropped approximately 20°C. The switch continues to cycle in this manner until
the load fault or input power is removed.
ESD protection
All TPS201x terminals incorporate ESD-protection circuitry designed to withstand a 6-kV human-body-model
discharge as defined in MIL-STD-883C. Additionally, the output is protected from discharges up to 12 kV.