L9945 datasheet(123/144 Pages) STMICROELECTRONICS

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The battery compensation feature can be activated independently on each channel by programming the

OC_Batt_comp_xx bit. Two different BCF have been implemented for Passenger Vehicle (PV) and Commercial

Vehicle (CV) applications. The BCF can be selected by programming the Batt_fact_config bit (refer to

Figure 33).

Figure 33. BCF vs.VPS

GADG2212171251PS

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.1

1.2

1.3

1.4

1.5

1.6

10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

VPS [V]

BCF (CV)

BCF (PV)

Note:

Because the algorithm is based on the assumption made for Eq. (6), the battery compensation feature is

recommended only in case of resistive load. Usage either in case of different load types or in case of small

resistive loads may lead to performances worse than the uncompensated strategy.

6.3.8

Reading the compensated OC threshold

In general, the overcurrent threshold can be evaluated as follows:

Eq. (9): Overcurrent threshold compensation formula

VOCcomp=BCF×TCF×VOC

(9)

Where VOC is the value programmed in the OC_config_xx bit, BCF is the battery compensation factor and TCF

is the temperature compensation factor. When a compensation feature is disabled, its compensation factor is set

to 1 (no effect on VOC).

Note:

It is recommended to enable battery and temperature compensation simultaneously only in case of resistive load

with DSM. Different usage may lead to performances worse than the uncompensated strategy.

When configuring the device, the OC_read_xx can be used to select whether reading the programmed threshold

VOC or the compensated one VOCcomp.

6.3.9

OC detection schematics

Figure 34 shows the OC detection implementation in case of LS configuration. It can also be applied to the HS

scenario with NFET (see description). In case DSM is selected RSH must not be mounted and the pins SNGPx

and PGNDxx must be shorted.

Figure 35 shows the OC detection implementation in case of HS configuration with PMOS. In case DSM is

selected RSH must not be mounted and the pins GNSPx and BATTxx must be shorted.

L9945

Safety & diagnostics

DS12275 - Rev 10

page 123/144

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