The TPS2140/41/50/51 is a USB 1.0 and 2.0 Specification-compatible IC containing a dual-current-limiting power switch and an adjustable low dropout regulator (LDO). Both the switch and LDO limit inrush current by controlling the turnon slew rate. The unique dual-current-limiting feature of the switch allows USB peripherals to utilize high-value capacitance at the output of the switch, while keeping the inrush current low. During turn on, the switch limits the current delivered to the capacitive load to less than 100 mA. When the output voltage from the switch reaches about 93% of the input voltage, the switch power good output goes high, and the switch current limit increases to 800mA (minimum), at which point higher current loads can be turned on. The higher current limit provides short circuit protection while allowing the peripheral to draw maximum current from the USB bus.
The switch and LDO function independently, providing flexibility in DSP applications requiring separate core and I/O voltages. For example, in a DSP application operating from a 3.3-V rail, the LDO can supply the DSP core voltage down to 0.9 V, while the switch powers the 3.3-V (typical) DSP I/O supply. If supply sequencing is required, the LDO power good output can be used to enable the switch.
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