CS5460A cicuit configuration

[navisiv]

Hi
I'm korean and sorry for poor at english
but i can read english well:smile: so please help me

I am making an Energy meter Using CS5460A interfaced to
microcontroller ATMEGA128

in korea using 220V one phase 2 wire power line

so i make the circuit refer to the following diagram on datasheet

i found all the value of resistor on datasheet
but i can't find the value of R1/R2/Rshunt
can anyone guide me how to caclulate the value of R1/R2/Rshunt?

**broken link removed**

 

[keith1200rs]

I don't know the chip, but looking at the data sheet the maximum differential input voltage is 500mV so I guess you would scale R1/R2 to suit that. With 220VAC you have 311V peak plus any mains tolerance (at least 10%, I would say). A safe starting point would be to select R1 and R2 to divide by 1000 giving 311mV peak nominally. So, R1=1k and R2=1M for example.

Rshunt depends on the current you want to monitor. Depending on the gain setting you have the same 500mV maximum limit. You can have higher gain and then the maximum input is 100mV (presumably to minimise the power dissipation in the resistor Rshunt). So, if you want to handle say 13A, which could mean peak currents of 18A I would suggest maybe 20m ohms with gain=50 or 5m ohms for gain=10. With those values you will keep below the maximum 500mV or 100mV. If you maximum current will always be lower then a larger resistor could be used.

In general, pick safe values first to get it working without blowing anything up. You can then change the components later when you have something that works.

Keith.