TIDUES0E June 2019 – April 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
Figure 3-2 shows the primary voltage sensing circuit. The maximum primary input voltage to be sensed is 800 V and is scaled down by a resistor divider network to 1.57 V, which is compatible to the 2-V input of the AMC1311. Figure 3-2 shows eight 634-kΩ resistors and one 10-kΩ resistor used to drop the primary voltage signal. The signal is then processed by one channel of the OPA2320, which converts it in the range of 0 V to 3.3 V as required by the ADC.
Figure 3-2 shows the isolated power supply circuit for powering the AMC1311. An isolated 3.3-V supply is needed to power the primary side of the AMC1311. The isolated power supply is shared with a low-side gate driver bias supply, generated by a UCC1414-Q1. The 15-V output voltage of the UCC14141-Q1 is used but a TLV760 is necessary to generate the 5 V for the AMC1311. This isolated supply is also used for the isolated current sensing on the primary side.