USB Power Budgeting White Paper
Using a tablet to host an array of USB peripherals can greatly increase the power of these amazing devices, making many applications possible: kiosks, Point of Sale (PoS) systems, manufacturing control, and so forth. That’s all well and good, but the reality is somewhat more complicated. Unlike desktop computers, and to a degree laptops, tablets are designed to run very lean, using minimal power.
When it comes time to hook USB peripherals to a tablet’s USB port operating in USB Host mode (also known as USB On-The-Go or OTG mode), problems can arise specifically related to the power that the tablet is able to supply to attached peripherals.
This white paper looks at powering peripherals on the USB bus, specifically in the context of the SimulCharge USB Host Mode and Charging adapter.
The white paper starts with a bit of electrical theory, describing the relationship between voltage, amperage, resistance, and power.
It then takes these variables to a discussion of USB power supplies, and sketches out how a system can go over budget in its use of USB power through the number of USB peripherals attached to the USB bus power. That is followed with a discussion of cables and voltage drop that they can introduce. shedding light on an often-overlooked cause of power budgeting problems.
Finally, this white paper looks at powered USB hubs as a possible means of supplying additional USB power to a system, and what technical considerations must be kept in mind for such systems to work.