SLVSFE3B November 2020 – May 2021 TPS2661
The TPS2661x devices feature a fixed IOL: 32-mA typical, bidirectional current limit. For use in unipolar systems like 4-20-mA current loops where negative current is not desired, connect -Vs to GND pin to cutoff when there is a flow of reverse current (OUT to IN). If the current tries to exceed the IOL limit, the device regulates the current and eventually reducing the output voltage. Overload current threshold and time for overload protection can be selected by MODE pin. See Device Functional Modes for details. The power dissipation across the device during current regulation will be (VIN - VOUT) x IOUT and this could heat up the device and lead to thermal shutdown. After thermal shutdown device goes into auto retry. The mode pin selects the auto retry period. See Table 8-2 and Figure 8-21 for selection of auto retry period.
The TPS2661x devices also feature a fast trip comparator. During fast transient events like output short circuit, miswiring, hotplug, etc the current through the device increases rapidly. Due to limited bandwidth, the current limit amplifier cannot respond quickly to these events . Hence the fast-trip comparator architecture is included for fast turn OFF of the internal FET during these events. The device turns off the internal FETs within a time of t(FASTTRIP). See Timing Requirements in Specifications for t(FASTTRIP). The fast-trip circuit holds the internal FET off for a short duration (50μs), after which the device turns back on slowly, allowing the current-limit loop to regulate the output current to current limit as per MODE pin configuration. Figure 8-3 and Figure 8-5 illustrate the current limit behavior of TPS2661x devices. Figure 8-6 illustrates the fast-trip protection of TPS2661x devices and Figure 8-7 illustrates the auto-retry behavior in overload fault.