Pin 1 is the RXD output of the TPIC1021. It is an open drain output and requires an external pull-up resistor in the range of 1 to 10 kΩ to function properly. If the micro-processor paired with the transceiver does not have an integrated pullup and external resistor should be placed between RXD and the regulated voltage supply for the micro-processor.
Pin 2 is the EN input pin for the device that is used to place the device in low power sleep mode. If this feature is not used on the device, the pin should be pulled high to the regulated voltage supply of the micro-processor through a series 1-kΩ to 10-kΩ series resistor. Additionally, a series resistor may be placed on the pin to limit the current on the digital lines in the case of an overvoltage fault.
Pin 3 is a high-voltage local wake up input pin. The device is typically externally controlled by a normally open switch tied between NWAKE and ground. When the momentary switch is pressed the NWAKE pin is pulled to ground signaling a local wake-up event. A series resistor between VBATT and the switch, and NWAKE and the switch should be placed to limit current. If the NWAKE local wake-up feature is not used, the pin can be tied to VSUP through a 1-kΩ to 10-kΩ pullup resistor.
Pin 4 is the transmit input signal to the device. A series resistor can be placed to limit the input current to the device in the case of an overvoltage on this pin. Also a capacitor to ground can be placed close to the input pin of the device to filter noise.
Pin 5 is the ground connection of the device. This pin should be tied to a ground plane through a short trace with the use of two vias to limit total return inductance.
Pin 6 is the LIN bus connection of the device. For responder applications a 220pF bus capacitor is implemented. For commander applications an additional series resistor and blocking diode should be placed between the LIN pin and the VSUP pin.
Pin 7 is the supply pin for the device. A 100-nF decoupling capacitor should be placed as close to the device as possible.
Pin 8 is a high-voltage output pin that may be used to control the local power supplies. If this feature is not used the pin may be left floating.
Note:
All ground and power connections should be made as short as possible and use at least two vias to minimize the total loop inductance.