BTS54040-LBF_15 Datasheet, PDF (44/67 Pages) Infineon Technologies AG – SPI Power Controller

BTS54040-LBF
Diagnosis
8.4
Gate Back Regulation
To increase the current sense accuracy, the Gate Back Regulation (GBR) function is implemented. This function
monitors the V_DS voltage at the output and if the value is equal to or lower than V_DS(NL) the output DMOS gate is
partially discharged. This increases output DMOS resistance so that V_DS = V_DS(NL) even for very small output
currents. The V_DS increase allows the current sensing circuitry to work with better accuracy, providing tighter k_ILIS
values for output currents in the low range.
This function is active by default (LGCR.GBRn bits set to “1” after a reset). According to output current, GBR
function can be left active or disabled. Even if left active, Gate Back Regulation circuitry may not be working
because the measured V_DS is bigger than V_DS(NL) (depending on output current, junction temperature, output
DMOS resistance).
Due to production and temperature variations, GBR circuitry can affect kILIS performance in negative way for
some output current values. For this reason, Table 10 indicates for which output currents it is necessary to
deactivate GBR (setting the corresponding LGCR.GBRn bit to “0”) to reach the desired current accuracy. If no
indication is given, then the GBR function is assumed to be enabled (LGCR.GBRn bit set to “1”). It is recommended
to keep GBR circuitry enabled for Open Load at ON diagnosis.
The circuitry that controls GBR function can be deactivated with the following SPI command sequence:
• SWCR.SWR = 1 (SPI command: 11001100_B)
• LGCR.GBRn = 0 (SPI command: 1101aaaa_B where “aaaa”_B is the new value for LGCR.GBRn bits)
• (optional but recommended: SWCR.SWR = 0 (SPI command: 11000100_B)
Refer to Chapter 9.7 for more details.
Data Sheet
44
Rev. 2.1, 2014-12-05