Chapter 18 Gate Drive Unit (GDU2PHV2)MC9S12ZVMB Family Reference Manual Rev. 1.3NXP Semiconductors 60518.4.8 Current Sense Amplifier and Overcurrent ComparatorThe current sense amplifier is usually connected as a differential amplifier ( see Figure 18-23). It sensesthe current flowing through the external power FET as a voltage across the current sense resistor R sense.In order to measure both positive and negative currents, an external reference has to be used. The outputof the current sense amplifier can be connected to an ADC channel. For more details on ADC channelassignment, refer to Device Overview Internal Signal Mapping Section. The input offset voltage of thecurrent sense amplifier can be adjusted with the GCSO[2:0] bits in the GDUCSO register. (see Figure 18-11) The output of the current sense amplifier is connected to the plus input of the overcurrent comparator.The minus input is driven by the output voltage of a 6 Bit DA converter. The digital input of the DAconverter is {1,GOCT0[4:0]}. In order to use the overcurrent comparator GOCE0 and GCSE0 have to beset.Figure 18-23. Current Sense Amplifier Connected as Differential Amplifier18.4.9 GDU DC Link Voltage MonitorIn addition to the feature described in Section 18.3.2.8, “GDU Phase Mux Register (GDUPHMUX) thevoltage on pin GHD divide by 5 is routed to an ADC channel. See device specific information for ADCchannel number. This feature is only available if GFDE is set.+-AMPP0R senseVoffsetGCSO0[2:0]=AMPM0AMP0R n / aR nVref =R p / aR pVsenseOutput Voltage to ADCVAMP = a Vsense + VrefGCSE0I-+GOCE0VoctGOCT0[4:0]Overcurrent Conditiona Vsense + Vref > Voct 6 bitDAC
