Analog to digital in EVB9S12NE64

[ibrahim2110]

hi i've a problem with atd in EVB9S12NE64 i want to make the V refernce high to be 5volt (extrnaly)  instead of the 3.3 v supplied internaly by the kit

idon't know if the atd channels can withstand that 5volt

please if any one know how to do that reply me.

thanks for ur help

[EMontanez]

For the NE64:

ATD references -

VRL: min = VSSA, max = VDDA/2
VRH: min = VDDA/2, max = VDDA

Where, VDDA: min = 3.135, max = 3.465. Therefore, a 5V ATD reference is not allowed. This kind of reference will cause internal diodes on these ATD pins to clamp.

[peg]

Hi,

The supply to the analogue section is generally the same voltage level as the main chips supply. (just cleaner hopefully)

If you want to measure voltages greater than this generally you use a resistive voltage divider into a rail-to-rail non-inverting op-amp connected to the ATD input.

The divider changes the 5V to 3 or so volts, then the buffer which is fed from the same analogue supply as the micros ADC section buffers it and provides a low source impedance to the ADC.

Hope that helps

Peg