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Application Report
SLVA037A – March 2005
1
Designing a USB Power Distribution System Using the
TPS2014 and TPS2015 Power Distribution Switches
PMP Systems Power
ABSTRACT
The USB specification (version 1.0) defines the power distribution requirements for self-
powered hubs (including hosts) and bus-powered hubs. This application report explains
how the TPS2014 and TPS2015 power distribution switches provide the power switching
and overcurrent protection needed to meet the USB requirements and how they are
superior to other devices commonly used to accomplish the same functions.
Overcurrent protection devices such as fuses and PTC resistors (also called polyfuses or
polyswitches) have slow trip times, high on-resistance, and lack the necessary circuitry for
USB-required fault reporting. The faster trip times of the TPS2014 and TPS2015 power
distribution allow designers to design hubs that can operate through faults. The TPS2014
and TPS2015 have low on-resistance and internal fault-reporting circuitry that help the
designer to meet voltage regulation and fault notification requirements. Because the
TPS2014 and TPS2015 are also power switches, the designer of self-powered hubs has
the flexibility to turn off power to output ports. Unlike a normal MOSFET, the TPS2014
and TPS2015 have controlled rise and fall times to provide the needed inrush current
limiting required for the bus-powered hub power switch.
Contents
1
Introduction .....................................................................................................................................3
2 TPS2014 and TPS2015 Power Distribution Switches ..................................................................3
3 USB Power Distribution..................................................................................................................4
3.1 Self-Powered Hub (Including Host) ...........................................................................................4
3.1.1 Overcurrent Protection Device ......................................................................................4
3.1.2 DC Voltage Regulation ..................................................................................................5
3.1.3 Transient Regulation .....................................................................................................6
3.1.4 Self-Powered Hub Reference Designs..........................................................................7
3.2 Bus-Powered Hub .....................................................................................................................9
3.2.1 Power Switch.................................................................................................................9
3.2.2 DC Voltage Regulation ................................................................................................10
3.2.3 Transient Regulation ...................................................................................................11
3.2.4 Bus-Powered Hub Reference Designs........................................................................11
4 ESD.................................................................................................................................................11
5 Summary........................................................................................................................................11
6 References.....................................................................................................................................12
Appendix A. Fault Testing....................................................................................................................13
Appendix B. Transient Load Testing...................................................................................................16
