Datasheet

STLQ50xx Application information
Doc ID 13205 Rev 5 11/18
T
A
is the ambient temperature;
R
thJA
is the junction-to-ambient thermal resistance of the package (see Tab le 4 thermal
data).
The power dissipation can be calculated simply as:
Equation 4
P
D
= (V
I
- V
O
) x I
O
In every application condition, P
D
must be lower than P
DMAX
.
7.3 Protection
The PMOS pass element has an internal diode with anode connected to V
O
and cathode to
V
I
. In case V
O
> V
I
, the current will flow from output to input without limitation. In this case, a
proper limiting network is recommended.
The current limitation is automatically provided by the characteristics of the PMOS pass
element (see typical characteristics), so the short-circuit current is dependent on the input
voltage. When considering short-circuit current, take care in any case not to exceed the
maximum sustainable power dissipation of the device.
The STLQ50 features an internal thermal protection that linearly reduces the output current
when the internal temperature increases. Consequently, at a given load, the output voltage
decreases also. The action of the thermal protection starts at 125 °C when the output
voltage slightly decreases, while close to 163 °C the output voltage drops to 0 V. Since this
is a linear control, sudden overcurrent conditions can quickly raise the chip temperature
without giving time for the thermal protection to act, so it cannot be used as a limitation for
the output current.