Inverse Operation Behavior
of the BTS6143 and its family members
Inverse operation behavior
Figure 4
shows a typical scope screen shot of this situation.
forward mode ON
inverse mode ON
inverse mode OFF
forward mode OFF
Switch ON
voltage across
sense resistor
Current through
DMOS stage
Voltage across
power stage
Varying output
voltage
Varying battery
voltage
V
IS
I
L
(5A/div)
V
DS
V
OUT
V
BB
InverseLong.emf
Figure 4
transient inverse current condition
Observation: It can be seen, that due to a variation in the supply voltage, an inverse current condition occurred for
a certain duration (see CH3, 2nd and 3rd division). Although the inverse load current reduces, it can be observed,
that the negative drain source voltage increases its amplitude (see M1, in 2nd division) indicating the internal
switch OFF. Once the power stage is internally switched OFF, a voltage drop across the power stage of about
600..700mV can be observed (see M1, in 2nd and 3rd division). As soon as the voltage conditions change from
inverse to forward mode, the power stage remains OFF (see M1, in 3rd division). At a certain stage the status pin
starts to report a fault condition (see CH4, 5th division). This fault conditions remains set until the “virtual” over-
temperature signal is internally cleared (see CH4, 6th division). The clearance of the “virtual” over-temperature
signal allows the automatic switch ON of the power stage again (see CH3 and M1, 7th division). As soon as the
power stage is sufficiently switched ON and the drain source voltage drops below approximately 1V the sense
starts to report the ratio of the load current again.
3.2.2
Permanent inverse currents
Any permanent inverse current condition will trigger the “Output voltage drop limitation” functionality. Therefore the
power stage will remain internally switched OFF. The inverse current will flow from the pin OUT to the pin VBB
through the body diode of the DMOS power stage. The inverse current flow -I
L
will cause a voltage drop -V
DS
(also
named -V
ON
,
V
inv
, -V
ON(inv)
) which depends on the inverse current
I
L(inv)
and the junction temperature
T
j
. The
respective values are outlined in the data sheet (see data sheet parameter -V
ON(inv)
).
The diagnosis is disabled. During inverse operation condition no current except a small leakage current will be
provided at the diagnosis pin IS.
Application Note
6
V1.1, 2008-03-31
Home Index Pages Text
Previous Next
Pages: Home Index