2.5 Open-Drain Output

Pullup resistors are located at the open-drain OUTA and OUTB outputs. TI recommends to tie the pullup voltage to the VDD of the TMP390. If this is not possible, however, an external voltage may be used for VDDIO that must be less than or equal to VDD of the TMP390. To connect an external VDDIO, the 0-Ω resistor at R7 may be desoldered to remove connection to VDD, then resoldered at R9 to connect an external supply at TP5 as shown in Figure 6.