Datasheet

SLVA037A
12 Designing a USB Power Distribution System Using the TPS2014 and TPS2015 Power Distribution Switches
A PTC resistor (also known as polyfuse and polyswitch) provides maintenance-free overcurrent
protection but tends to have a high resistance. To meet the USB voltage regulation
requirements, a device in the 2.5 A or higher range must be chosen. Unfortunately, a device in
this current range may not meet the 5-A current limit required by UL. A PTC resistor also tends
to have long trip times and may not provide adequate protection to the hub or host. As with
fuses, PTC resistors do not provide fault indication and thus require additional circuitry.
The TPS2014 and TPS2015 power distribution switches are designed to integrate all of the
functions required for USB power distribution into a single, cost-effective package. The fast fault-
clearing time provides robust and maintenance-free overcurrent protection. The overcurrent
logic output provides the hub or host with the required fault notification.
Unlike fuses or polyfuses, the TPS2014 and TPS2015 switches offer controlled rise and fall
times. They provide the self-powered hub or host with the option of turning off a port in the event
of a fault or low-power modes. The TPS2014 and TPS2015 switches also provide a bus-
powered hub with the inrush current limiting needed to meet the USB maximum hot-insertion
load requirement.
6 References
1. Universal Serial Bus Specification, Version 1.0, Universal Serial Bus-Implementers Forum
(USB-IF), January 19, 1996.
2. USB Voltage Drop and Droop Measurement, Intel Corporation, November 29, 1996.