Datasheet

Functional description L7986TA
14/43 Doc ID 022098 Rev 3
If, with V
IN
=38 V, the switching frequency is set higher than 706 kHz, during short-circuit
condition the system finds a different equilibrium with higher current. For example, with
F
SW
=800 kHz and the output shorted to ground, the output current is limited around:
Equation 5
where F
SW
* is 800 kHz divided by eight.
Figure 7. Overcurrent protection
5.5 Enable function
The enable feature allows to put the device into standby mode. With the EN pin lower than
0.3 V the device is disabled and the power consumption is reduced to less than 30 μA. With
the EN pin lower than 1.2 V, the device is enabled. If the EN pin is left floating, an internal
pull-down ensures that the voltage at the pin reaches the inhibit threshold and the device is
disabled. The pin is also V
CC
compatible.
5.6 Hysteretic thermal shutdown
The thermal shutdown block generates a signal that turns off the power stage if the junction
temperature goes above 150 °C. Once the junction temperature returns to about 120 °C, the
device restarts in normal operation. The sensing element is very close to the PDMOS area,
so ensuring an accurate and fast temperature detection.
I
OUT
V
IN
F
SW
*
⋅ V
F
T
ON_MIN
⁄–
DRC T
ON_MIN
⁄()R
DSON
DCR+()F
SW
*
⋅+
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