Datasheet

DocID023278 Rev 4 29/75
L6480 Functional description
75
6.9 Overcurrent detection
The L6480 measures the load current of each half-bridge sensing the V
DS
voltage of all the
Power MOSFETs (Figure 12). When any of the V
DS
voltages rise over the programmed
threshold, the OCD flag in the STATUS register is forced low until the event expires and a
GetStatus command is sent to the device (Section 9.1.24 on page 59 and Section 9.2.20 on
page 71). The overcurrent event expires when all the Power MOSFET V
DS
voltages fall
below the programmed threshold.
The overcurrent threshold can be programmed by the OCD_TH register in one of 32
available values ranging from 31.25 mV to 1 V with steps of 31.25 mV (Table 18 on page 50
Section 9.1.17 on page 50).
Figure 12. Overcurrent detection-principle scheme
The overcurrent detection comparators are disabled, in order to avoid wrong voltage
measurements, in the following cases:
 The respective half-bridge is in high impedance state (both MOSFETs forced off)
 The respective half-bridge is commutating
 The respective half-bridge is commutated and the programmed blanking time has not
yet elapsed
 The respective gate is turned off.
It is possible to set if an overcurrent event causes the bridge turn-off or not through the
OC_SD bit in the CONFIG register.
When the power bridges are turned off by an overcurrent event, they cannot be turned on
until the OCD flag is released by a GetStatus command.
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