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Doubt regarding 1) -ve voltage input to AD7864 2) 12-bit Word generated by the AD7864

Question asked by Janz on Jan 19, 2013
Latest reply on Jan 26, 2013 by Janz

Hi,

I would be very grateful, if someone could answer my questions.

 

1) I am using the AD7864 adc(schematics have been attached). Though i am not giving any -ve voltage as Vcc (My Vcc is +5V only) i am able to get even -ve cycles of sinewaves or whatever -ve voltage i give as input to pins VINAx at my output( my Output is the output of DAC AD5447).

How is this possible??

According to my understanding, for Bi-polar operation of any device both +Vcc and -Vcc must be present. If possible please clear my doubt.

 

2) The datasheet says that For the ±5 V range, 1 LSB = 10 V/4096 = 2.44 mV.

What word does this (2.44mV) correspond to??

What word will be generated if +5V is given as input to the ADC??

 

Any help or any link to a document will be greatly appreciated ;-)

 

Thanks in advance.

 

best wishes

janmay

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