Design Insight Between Voltage Levels 1.5, 1.8, 2.775, 3.0, 3.15, 3.3 and 5 VDC

[tarun172]

Hi Everyone,

Recently, while working on a design consisting of an FPGA and an ARM A8-based processor, I came across non-standard voltage levels such as 1.5, 1.8, 2.775, 3.0, and 3.15. After reading through the datasheets and reference manual, I understood that these nominal voltage levels are part of chip design, meaning I will need to design an interface circuit using voltage level shifters. I wondered why chip designers came up with non-standard voltage values like 1.5, 2.775, or 3.15 VDC. I understand that the purpose of the 1.8 V and 3.3 V logic levels was to reduce over-chip power consumption. Does anyone know anything about this specification for chip design?

Example: The image processing unit pins on the i.Mx. processor from NXP specify 2.775V as nominal voltage rating.

Spartan-6 Vccaux pin provides the option to use 2.5V or 3.3V DC.

Thanks,
tarun172

[ataradov]

2.775 V happens a lot. It is not as standard as 3.3V, but it is a very common voltage in high-level system. No idea why this specific value is used. It is 11% over 2.5 V. This is the only rationale I can come up with. Something like 10%+a bit.

But the overall range of values has the same goal - reduce power consumption. But it is much less coarse than simple 1.8 V or 3.3 V. There are lots of things that can't work at 1.8 V and don't need 3.3 V. And on a PC motherboard consuming 100s of Watts, every bit you can save matters, and given the complexity of the system, one more voltage regulator is not a huge deal.


In case of the image processing unit, I think MIPI uses that as a standard voltage too.

[coromonadalix]

3.3v 1.8v 1.275v 1.1v an 1.0v   even an 0.8v     in my company fpga circuits, Zynq based with ultra high speed adc's

i have about 10 different voltages on this pcb