The TMP390 requires two resistors to set the high and low trip points and hysteresis, and two pullup resistors for the open-drain device. TI also highly recommends to place a 0.1-µF, power-supply bypassing capacitor close to the VDD supply pin. To minimize the internal power dissipation, use two pullup resistors greater than 1 kΩ from the OUTA and OUTB pins to the VDD pin. A separate supply, VDDIO, may be used for the pullup voltage to set the output voltage level to the level required by the MCU, as shown in Figure 8-1. The open-drain output gives flexibility of pulling up to any voltage independent of VDD (VDDIO must be less than or equal to VDD + 0.3 V). This allows for use of longer cables or different power supply options. If a separate voltage level is not required, TI recommends to tie the pullup to the TMP390 VDD.

If the SETA or SETB connected resistor value is outside the legal range, the associated output goes to permanent output zero stage and the channel cannot be used. The other channel still will be in operating condition, and device can be used in one channel mode. If the SETB input is grounded or left floating, the Channel B cannot be used and the hysteresis for Channel A will be 20°C. The SETA and SETB connected resistors are measured during POR. If two consecutive measurements are not matching each other, then the device sets the associated channel output to zero and repeats the resistor measurements until the measurements match. When the measurements match, the channel output is released. Note that it is possible to connect some device outputs together by shorting the OUTA or OUTB line.