l6928 STMicroelectronics, l6928 Datasheet - Page 9

• Manufacturer Part Number: l6928
• Description: High Efficiency Monolithic Synchronous Step Down Regulator
• Manufacturer: STMicroelectronics

L6928
4.2
Short circuit protection
During the device operation, the inductor current increases during the high side turn ON
phase and decrease during the high side turn off phase based on the following equations:
Equation 1
Equation 2
In strong overcurrent or shortcircuit conditions the V
case ∆I
current limit, the high side mosfet turns off and so the T
value (250ns typ.) in order to reduce as much as possible ∆I
Anyway, if V
because during the T
Due to this reason a second protection that fixes the maximum inductor valley current has
been introduced. This protection doesn't allow the high side MOSFET to turn on if the
current flowing through the inductor is higher that a specified threshold (valley current limit).
Basically the T
this threshold.
So, the maximum peak current in worst case conditions will be:
Equation 3
Where IPEAK is the valley current limit (1.4A typ.) and T
high side MOSFET.
ON
increases and ∆I
OUT
OFF
is low enough it can be that the inductor peak current further increases
is increased as much as required to bring the inductor current down to
OFF
the current decays very slowly.
OFF
I
PEAK
decreases. When the inductor peak current reaches the
∆I
∆I
ON
=
OFF
=
I
VALLEY
(
---------------------------------- T
=
V
IN
(
------------------ - T
V
–
OUT
L
L
+
V
OUT
V
-------- - T
L
)
IN
⋅
OUT
)
⋅
OFF
⋅
ON_MIN
ON
ON
can be very close to zero. In this
ON_MIN
is reduced down to the minimum
ON
.
is the minimum T
Operation description
ON
of the
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