13.20.3 External MOSFET Short-Circuit Current

Short-circuit protection monitors the voltage across the external MOSFETs during an On condition. The high-side driver voltage is measured from HVDD to PH[A:C]. The low-side driver voltage is measured from PH[A:C] to ground. If a monitored voltage rises above a user-configurable threshold after the driver HS[A:C] or LS[A:C] output voltage has been driven high, all drivers will be turned off. A driver Fault will be indicated to the host dsPIC DSC on the open-drain FAULT output pin and also via a DE2 communications Status_1 message. This is a latched Fault. Clearing the Fault requires either removal of device power or toggling the OE input pin low-to-high. This protection feature helps detect internal motor failures, such as winding to case shorts.

Note: The driver short-circuit protection is dependent on application parameters. A configuration message is provided for a set number of threshold levels. The MOSFET Gate Driver UVLO and short-circuit protection features have the option to be disabled.

The short-circuit voltage may be set via a DE2 Set_Cfg_0 message. The EXTOC[1:0] bits of the CFG0 register are used to select the voltage level for the short-circuit comparison. If a monitored voltage differential between HVDD and PH[A:C], or between PH[A:C] and PGND, exceeds the selected voltage level when the MOSFET Gate Driver is active, a Fault will be triggered. The selectable voltage levels are 250 mV, 500 mV, 750 mV and 1000 mV. The EXTSC bit of the CFG0 register is used to enable or disable the MOSFET Gate Driver short-circuit detection.