Datasheet

Data Sheet 19 Rev. 1.0, 2008-03-18
BTS4130QGA
Diagnostic Mechanism
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 13 gives a sketch of the situation and Figure 14 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.
To reduce the stand-by current of the system, an open load resistor switch S
OL
is recommended.
If the channel is OFF, the output is no longer pulled down by the load and V
OUT
voltage rises to nearly V
S
. This is
recognized by the device as open load. The voltage threshold is given by
V
OL(OFF)
. In that case, the ST 0/1 signal
is switched to a logical low
V
ST01(L)
.
Figure 13 Open load detection in OFF electrical equivalent circuit
Figure 14 ST 0/1 in open load condition
OUT
V
S
R
leakage
R
OL
S
OL
V
bat
V
OL(OFF)
I
leak age
I
LOFF
OL
comp.
Open Load in OFF.vsd
GND
R
GND
IN
V
OUT
ST 0/1 or ST 2/3
I
L
Diagnostic In Open load quad shared diag.vs
d
t
t
t
t
V
ST(HIGH)
V
(OL)
V
ST(LOW)