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USB and the Myth of 500 Milliamps
If you’re designing a universal port, you will be expected to provide power. This was a lesson learned in the times of LPT and COM ports, where factory-made peripherals and DIY boards alike h…
This was a lesson learned in the times of LPT and COM ports, where factory-made peripherals and DIY boards alike had to pull peculiar tricks to get a few milliamps, often tapping data lines. When you’re making a device with a LiIon that aims to consume over an amp and be produced in quantity of hundreds of thousands, safety and charger compatibility is pretty crucial. By playing with analog levels on D+ and D- pins in a certain way, the Quick Charge (QC) standard lets you get 9 V, 12 V, 15 V or even 20 V out of a port; sadly, without an ability to signal the current limit.
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