ZHCSIS2B september 2018 – december 2020 TPS7A11
PRODUCTION DATA
The internal foldback current limit circuit is used to protect the LDO against high-load current faults or shorting events. The foldback mechanism lowers the current limit as the output voltage decreases and limits power dissipation during short-circuit events, while still allowing for the device to operate at the rated output current; see Figure 6-12.
For example, when VOUT is 90% of VOUT(nom), the current limit is ICL (typical); however, if VOUT is forced to 0 V, the current limit is ISC (typical). In many LDOs, the foldback current limit can prevent start up into a constant-current load or a negatively-biased output. A brick-wall current limit is when there is an abrupt current stop after the current limit is reached. The foldback mechanism for this device goes into a brick-wall current limit when VOUT is 90% of VOUT(nom), thus limiting current to ICL (typical). When VOUT is approximately 0 V, current is limited to ISC (typical) in order to provide normal start up into a variety of loads. Thermal shutdown can be activated during a current-limit event because of the high power dissipation typically found in these conditions. To provide proper operation of the current limit, minimize the inductances to the input and load. Continuous operation in current limit is not recommended.