SLVSFE3B November 2020 – May 2021 TPS2661
TPS26610 allows bipolar current limited conduction through the device even when the external +Vs/-Vs supplies are not there. When the external supply is not there, the device switches to loop power mode and derives its operating power from the 4 - 20-mA or ±20-mA current loop. This feature of TPS26610 enables the field installation engineer to check the wiring of the whole current loop system by passing a test current through the current loop without actually powering on the system. This feature also helps in design of safety critical redundant systems with two redundant measurements for the same current loop. In case power is not available in one system, a second system connected in the loop will still be able to read the current information since the loop is not broken. During loop testing without ±Vs supply, the device has a voltage drop of V(IN-OUT)no_Vs, the current through device is is limited to IOL_noVs. During loop testing, device draws a current of IOL_noVs from IN pin. See Electrical Characteristics in Specifications for V(IN-OUT)no_Vs, Iqno_Vs and IOL_noVs.The device provide thermal protection during loop testing, if the power dissiption in device increases above 500 mW (typ), the devices turns-off internal FET for short durations to limit the power dissipation. Figure 8-13 and Figure 8-14 illustrate the thermal protection during loop testing.
+Vs = 15 V, –Vs = –15 V, ROUT = 250 Ω, VIN = 21 V
|+Vs = 15 V, –Vs = –15 V, ROUT = 250 Ω, VIN = –21 V|