Inverse Operation Behavior
of the BTS6143 and its family members
Countermeasures and Hints
4
Countermeasures and Hints
In case inverse operation conditions can occur in the targeted application and have to be “covered” a wide range
of measures are available. The following chapter outlines an excerpt of possible examples.
4.1
Measures supporting the use of the BTS6143D
Among the measures that support the use of the BTS6143D and its family members covering “inverse operation”
are software measures as well as hardware measures.
The BTS6143D and its family members will automatically switch ON again while encountering a transitions from
inverse mode back to forward mode and while being commanded ON. Therefore the processing readout logic
should “blank” the signalling during inverse operation and during the delayed switch ON. Since the reporting of the
“virtual” over-temperature signal after the transition from inverse to forward mode provides the same signal level
as any over-current-during-ON, over-temperature-switch-OFF and over-current-switch-OFF condition, special
attention has to be paid to this signal readout and handling. One example is to introduce a certain filter time until
such a fault condition is validated. Another example beside “blanking” is the “verification” and “differentiation”
between the transition event from inverse to forward mode and an occurred over-temperature-switch-OFF and
over-current-switch-OFF condition by utilizing the potential of the OUT pin.
Beside the software measures it is also possible, to introduce measures on hardware level that suppress or limit
the current flow through the power stage body diode. One example is the usage of an additional series diode in
the output path. This series diode can possibly be required anyhow to protect a secondary connected electrolytic
capacitors against reverse battery condition. The second example is the usage of an anti-parallel diode to the
output stage. Such an anti-parallel diode would have to be dimensioned in such a manner, that any inverse current
will flow across this diode only and not across the power stage body diode. A third example is the usage of “pull
down” resistor parallel to the generating or energy storing load. Using this approach offers two benefits. First of all
the susceptibility against very fast inverse transients reduces since the additional current for the paralleled resistor
reduces the likeliness of forward voltage drop activation during forward mode. Secondly any induced or stored
voltage at the OUT will be additionally sink by such resistor.
Figure 5
shows these hardware counter measure example.
+V
S
measure 2
R
IN
IN
IS
+V
IN
+V
IS
R
Sense
measure3
VBB
OUT
measure1
M
InverseCounterMeasure
.emf
GND
Figure 5
BTS6143D inverse counter measure examples
4.2
Measures supporting the use of the BTS6143D alternatives
In case the above countermeasures can not be introduced for whatever reason, the designer can profit in most
cases from the pin compatibility of this high side switch family. Infineon offers several products that do not include
the “forward voltage drop limitation” feature and that can therefore better cope with transient inverse current
conditions. In case of the example of the BTS6143D alternatively the BTS6133 can be used as direct replacement.
All key parameters (such as resistance, voltage class, kilis ratio) are equal to the BTS6143D. This alternative
device differs only in the “forward voltage drop limitation” feature offering less current sense accuracy at low load
currents but offering better inverse robustness.
Application Note
7
V1.1, 2008-03-31
Home Index Pages Text
Previous Next
Pages: Home Index