BTS54040-LBF_15 Datasheet, PDF (43/67 Pages) Infineon Technologies AG – SPI Power Controller

BTS54040-LBF
Diagnosis
CS
DCR.MUX 110
I_IS
000
t_{sIS (EN)}
001
t _sIS(MUX)
Figure 23 Current Sense Multiplexer Timings
110
t_{dIS (MUX )}
t
t
Diagnosis_MuxTiming.emf
8.2.3 Open Load at ON Diagnosis
If a channel is ON in Open Load condition, a small current can still flow, for example because of humidity. The
parameter I_L(OL) gives the threshold of recognition for such leakage current. If the voltage measured at the sense
resistor R_SENSE corresponds to a current I_IS(OL) (4 µA), then the current flowing at the output in ON state is within
the limits given by I_L(OL). Figure 24 shows the sense current behavior once a channel in Open Load at ON
condition is selected with the sense current multiplexer. The red curve show a typical product curve. The blue line
shows the ideal k_ILIS ratio.
I_IS
IIS(OL )
I_IS(en)
Figure 24 Current Sense Ratio in Open Load at ON condition
I_{L(OL )}
I_L
8.3
Switch Bypass Monitor Diagnosis
To detect short circuit to V_S, there is a switch bypass monitor implemented. In case of short circuit between the
output pin OUT and VS in ON-state, the current flows through the power transistor as well as through the short
circuit (bypass) with undefined share between the two. As a result, the current sense signal shows lower values
than expected by the load current. In OFF-state, the output voltage remains close to V_S potential which leads to a
small V_DS.
The switch bypass monitor compares the threshold V_DS(SB) with the voltage V_DS across the power transistor of that
channel which is selected by the current sense multiplexer (DCR.MUX). The result of the comparison can be read
in SPI register DCR.SBM.
Data Sheet
43
Rev. 2.1, 2014-12-05