BTS54040-LBF_15 Datasheet, PDF (42/67 Pages) Infineon Technologies AG – SPI Power Controller

BTS54040-LBF
Diagnosis
8.2
Load Current Sense Diagnosis
There is a current sense signal available at pin IS which provides a current proportional to the load current of one
selected channel. The selection is done by a multiplexer which is configured via SPI.
8.2.1 Current Sense Signal
The current sense signal (ratio k_ILIS = I_L / I_S) is provided during ON-state as long as no failure mode occurs. For
dedicated channels the ratio k_ILIS can be adjusted to the load type (LED or bulb) via SPI register LGCR. The
accuracy of the ratio k_ILIS depends on the load current and temperature. Usually a resistor R_IS is connected to the
current sense pin. It is recommended to use resistors 1.5 kΩ < R_IS < 5 kΩ. A typical value is 2.7 kΩ.
The current sense signal of a channel is not active when the channel is OFF or when the protection functions
(current limitation, over temperature or dynamic temperature sensors) are active. If the maximum number of
automatic reactivations n_retry is reached (n = n_retry), the current sense signal of the affected channel is deactivated
until the reset of the counters by setting HWCR.CTC bit to 1.
Details about timings between the current sense signal I_IS and the output voltage V_OUT and the load current I_L can
be found in Figure 22.
IN /
OUT.OUTn
VOUT
OFF
ON
tON
I_L
OFF
tOFF
t
t
t_{sIS (ON)}
t_{sIS (LC)}
t_{dIS (OFF)}
t
I_IS
Figure 22 Current Sense Signal Timings
t
Diagnosis _SenseTiming.emf
8.2.2 Current Sense Multiplexer
There is a current sense multiplexer implemented in the BTS54040-LBF that routes the sense current of the
selected channel to the diagnosis pin IS. The channel is selected via SPI register DCR.MUX. The sense current
can also be disabled by SPI register DCR.MUX. For details on timing of the current sense multiplexer, please refer
to Figure 23.
Data Sheet
42
Rev. 2.1, 2014-12-05