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As a curious ignorant - what's used now instead of 5V? Why was there a transition away from 5V? I'm assuming this means 5 volts and not something more arcane.

by tgb 6y ago

mumblemumble 6y ago
3.3V seems to be where everything is going in the hobbyist space. If your device is powered by batteries, 3.3V will let you get longer battery life than 5V. I think I recall hearing that 3.3V can reduce power consumption by as much as 50% relative to 5V. If your device is powered by USB, which is nominally 5V, 3.3V can still be nice because USB power supplies don't always supply the cleanest power, so regulating it down to 3.3V can result in a more reliable power supply.
wongarsu 6y ago
Most microcontrollers moved to 3.3V, or even 1.8V. Some of them have some 5V tolerant ports to communicate with 5V devices, but for the most part embedded now runs on and communicates over 3.3V. The reason is mostly power efficiency and the option for higher frequencies as far as I'm aware
tssva 6y ago
3.3v and 1.2v are probably the most common these days but there are other voltages in use. Lower power usage, less heat and smaller packaging are the main drivers for lower voltages.
Someone 6y ago
Power usage is proportional to the square of the voltage. So, you want to keep the voltage low for battery life or to prevent your CPU from overheating. Lower voltages also make transistors slower, though. That can be offset by making them smaller, but we couldn’t do that decades ago (https://electronics.stackexchange.com/questions/109533/why-a-lower-voltage-is-better-for-modern-fast-cpu-and-other-similar-chips https://electronics.stackexchange.com/questions/109533/why-a..., https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_and_clock_speed https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_...) I guess there also is some effect along the lines “higher voltages decrease sensitivity to noise” that prevented early designs from using lower voltages and lower currents. As to what’s used now: 3.3V was the new 5V, but state of the art CPUs are even lower at ≈1.2V
phire 6y ago
Modern stuff used as little voltage as possible. We are taking under 1v at times for silicon core voltage. They also use VRMs to dynamically adjust voltage depending on load. These days, IO voltage is usually detached from core voltage, and there may actually be multiple IO voltages. Memory and PCIe often get their own carefully turned IO voltages. For lower speed, low cost devices, 3.3v is basically standardized, though on battery powered devices you will commonly see 1.8v. Anything hobbyist is being dragged to 3.3v. 5v devices keep getting harder and harder to find.
pantalaimon 6y ago
3.3V

As a curious ignorant - what's used now instead of 5V? Why was there a transition away from 5V? I'm assuming this means 5 volts and not something more arcane.

by tgb 6y ago

As a curious ignorant - what's used now instead of 5V? Why was there a transition away from 5V? I'm assuming this means 5 volts and not something more arcane.

mumblemumble 6y ago

3.3V seems to be where everything is going in the hobbyist space. If your device is powered by batteries, 3.3V will let you get longer battery life than 5V. I think I recall hearing that 3.3V can reduce power consumption by as much as 50% relative to 5V. If your device is powered by USB, which is nominally 5V, 3.3V can still be nice because USB power supplies don't always supply the cleanest power, so regulating it down to 3.3V can result in a more reliable power supply.

wongarsu 6y ago

Most microcontrollers moved to 3.3V, or even 1.8V. Some of them have some 5V tolerant ports to communicate with 5V devices, but for the most part embedded now runs on and communicates over 3.3V. The reason is mostly power efficiency and the option for higher frequencies as far as I'm aware

tssva 6y ago

3.3v and 1.2v are probably the most common these days but there are other voltages in use. Lower power usage, less heat and smaller packaging are the main drivers for lower voltages.

Someone 6y ago

Power usage is proportional to the square of the voltage. So, you want to keep the voltage low for battery life or to prevent your CPU from overheating. Lower voltages also make transistors slower, though. That can be offset by making them smaller, but we couldn’t do that decades ago (https://electronics.stackexchange.com/questions/109533/why-a-lower-voltage-is-better-for-modern-fast-cpu-and-other-similar-chips https://electronics.stackexchange.com/questions/109533/why-a..., https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_and_clock_speed https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_...) I guess there also is some effect along the lines “higher voltages decrease sensitivity to noise” that prevented early designs from using lower voltages and lower currents. As to what’s used now: 3.3V was the new 5V, but state of the art CPUs are even lower at ≈1.2V

phire 6y ago

Modern stuff used as little voltage as possible. We are taking under 1v at times for silicon core voltage. They also use VRMs to dynamically adjust voltage depending on load. These days, IO voltage is usually detached from core voltage, and there may actually be multiple IO voltages. Memory and PCIe often get their own carefully turned IO voltages. For lower speed, low cost devices, 3.3v is basically standardized, though on battery powered devices you will commonly see 1.8v. Anything hobbyist is being dragged to 3.3v. 5v devices keep getting harder and harder to find.

pantalaimon 6y ago

3.3V