Data Sheet 17 Rev. 1.0, 2008-03-18
BTS4300SGA
Diagnostic Mechanism
7 Diagnostic Mechanism
For diagnosis purpose, the BTS4300SGA provides a status pin.
7.1 ST Pin
BTS4300SGA status pin is an open drain, active low circuit. Figure 11 shows the equivalent circuitry. As long as
no “hard” failure mode occurs (Short circuit to GND / Over temperature or open load in OFF), the signal is
permanently high, and due to a required external pull-up to the logic voltage will exhibit a logic high in the
application. A suggested value for the R
PU ST
is 15kΩ.
.
Figure 11 Status output circuitry
7.2 ST Signal in Case of Failures
Table 3 gives a quick reference for the logical state of the ST pin during device operation.
7.2.1 Diagnostic in Open Load, Channel OFF
For open load diagnosis in OFF-state, an external output pull-up resistor (R
OL
) is recommended. For calculation
of the pull-up resistor value, the leakage currents and the open load threshold voltage
V
OL(OFF)
has to be taken into
account. Figure 12 gives a sketch of the situation and Figure 13 shows the typical timing diagram.
I
leakage
defines the leakage current in the complete system, including I
L(OFF)
(see Chapter 5.4) and external
leakages e.g due to humidity, corrosion, etc... in the application.
Table 3 ST pin truth table
Device operation IN OUT ST
Normal operation L L H
HHH
Open Load channel L H L
HHH
Over temp channel L L H
HLL
Short circuit to GND L L H
H
L
1)
1) V
ouT
< 2V typ.
L
ST pin full diag.vsd
GND
ST
R
ST
ZD
ESD
R
PU ST
V
ccµC
Channel 0
Diagnostic
Logic
