JAJU858 December 2022
The pilot signal is required to travel down several meters of cable and through a load resistance. The pilot signal is also a bipolar ±12-V signal, which requires special consideration. To accommodate these parameters, an amplifier with a wide input range and reasonable power output is selected. The TLV1805 device has a voltage rating of ±18 V and a current rating of 475 mA, making the device a good match for the application. In addition, while most EVSEs do not require an automotive qualification, a Q1-rated variant of the TLV1805-Q1 device exists, if this feature is desired.
The amplification circuit is a simple rail-to-rail output configuration of the TLV1805 device, with the MCU I/O driving the positive input. The output of the pilot amplifier is also fed into a simple voltage divider so that the MCU can measure the voltage during operation and detect the load resistance of the vehicle. Figure 2-3 shows the full schematic of this subsystem.
To validate the architecture, the design was tested in the TINA-TI™ software from TI, which is a spice-based simulation tool.