Hello,

I am new to ADE7880. We plan to use this metering IC on a new project.

On the data sheet, Rev. A, page 61, register VTHD, ITHD, harmonic distortion registers, it says "... VTHD, ITHD 24-bit registers in 3.21 signed format. This means the rations are limited to +3.9999 an all greater results are clamped to it...". I don't know what 3.21 signed format is, and how to convert the hex code to the real value (floating point value).

Also are there some application notes of ADE7880 I could download?

Thank you in advance for the help

Karen Shi

Hi Karen Shi

The 3.21 signed format is a representation by which the 24 bit register is viewed as : 3 bits for the integral value of the decimal number and remaining 21 bits after the decimal point. However, the first of the 3 bits represents the sign of the number and the other two represent the value as such. So, the maximum value that is possible to represent using this format( for a 24 bit register) would be +3.9999 and that happens when the sign bit is 0 and all other bits are 1.

On a simpler note, you can get the actual value of the register if you divide the register value by 2^21.

And for the application note, you can click on the 'Technical documentation' link on the corresponding product's page on Analog Devices website.

This is the link for ADE7880's Application Note(s):

http://www.analog.com/en/analog-to-digital-converters/energy-measurement/ade7880/products/technical-documentation/index.html

Regards

hmani