TIDUCL0 January 2017
The sense amplifiers on the DRV8323S can be configured to amplify the voltage across the low-side FETs. During this mode of operation, leave the SPX pins unconnected. The positive input of the amplifier is internally connected to the SHX pin. An internal clamp prevents high voltage on the SHX pin from damaging the sense amplifier inputs.
When the CSA_FET bit is set to '1', the negative reference for the low-side VDS monitor is automatically set to SNX, regardless of the state of the LS_REF bit. This is implemented in order to prevent the low-side VDS monitor from being disabled. If the system is intended to operate in FET sensing mode, take care to route the SHX an SNX pins to kelvin connections across the drain and source of the low-side FETs.
When operating in FET sensing mode, the amplifier is enabled at the end of TDRIVE. At this time, the amplifier input is connected to SHX, and the SOX output will be valid. Whenever a low-side FET receives a signal to turn off, the amplifier inputs are shorted together. When GLX is low, SPX and SNX are internally shorted.
The current shunt amplifiers have the following features:
Figure 6 shows the current sense amplifier simplified block diagram.