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L9945 Datasheet(PDF) 122 Page - STMicroelectronics

Part # L9945
Description  Automotive fully configurable 8-channel High/Low side MOSFET pre-driver suitable for 12 V and 24 V systems
PDF  144 Pages
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Manufacturer  STMICROELECTRONICS [STMicroelectronics]
Direct Link  http://www.st.com
Logo STMICROELECTRONICS - STMicroelectronics

L9945 Datasheet(HTML) 122 Page - STMicroelectronics

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Figure 32. TCF vs. Tj
GADG2212171232PS
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
Tj [°C]
TCF (Δ = 25°C)
TCF (Δ = 40°C)
TCF (Δ = 60°C)
Note:
This feature is recommended only in case of DSM, because the compensation algorithm is based on RDSon
variations. The external FET must have a characteristic RDSon vs. TjFET that matches the 0.38 %/°C slope. In
case of shunt measurement, the algorithm may show performances worse than the uncompensated strategy.
6.3.7
Battery compensation for OC threshold
The device offers the possibility to compensate the OC threshold against battery variations. This feature can be
enabled when driving a resistive output load RL, and helps preventing the load resistance from dropping below a
minimum threshold RLmin. Given Eq. (3), the IOC can be evaluated as the current flowing when the battery is at its
maximum operating value (18 V for passenger vehicles or 36 V for commercial vehicles) and the load resistance
assumes its minimum allowed value RLmin:
Eq. (6): Overcurrent detection in case of resistive load
IOC≅VBATTmax
RLmin VOC=ROC×VBATTmax
RLmin
(6)
Eq. (6) assumes that RL >> ROC. The sensing resistance ROC can be either the shunt resistor or the RDSon.
Referring to Figure 34 and Figure 35, the device measures:
Eq. (7): Overcurrent sensing in case of resistive load
VSENSE=ROC×ILOAD=ROC×VBATTRL
(7)
The device is able to monitor the battery voltage on the VPS pin through the on board VPS ADC. This information
can be used to compensate the VOC with respect to VBATT variations. Therefore, the OC detection occurs only
when VSENSE = VOC due to a RL variation.
The internal algorithm compensates the OC threshold based on a multiplicative factor:
Eq. (8): Battery Compensation Factor (BCF)
VOCcomp=BCF×VOC
(8)
L9945
Safety & diagnostics
DS12275 - Rev 10
page 122/144



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