Hi i am using anolog device aduc812 microcontroller i tryed to accesses buit in adc with out giving input i am getting output 0xFFF i.e maximum value in all channel except channel 8 ie temp sensor.taht gives some value ie 423 what is the problem please help me
But you did connect the + of the battery to ground, and the - of the battery to the ADC input?
That would represent -3.3V on the input, and the absolute limit is -0.3V - i.e. you did connect a 11 times as high voltage as allowed. That is more than enough to kill the input unless you had a resistor with a very high value in series.
By the way - have you connected AVCC to a suitable voltage? If AVCC is low, all inputs will most probably also also show 0xfff.
If AVCC is low, all inputs will most probably also also show 0xfff.
But that's not what he sees. He has one channel reporting 0x4??. So he either has some AVCC connected, or his chip can work without it.