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AD7745 (CDC) problem with inverse EXCA, EXCB

Question asked by Taras on Nov 23, 2011
Latest reply on Nov 23, 2011 by Taras

Good day.

 

I make device based on the CN0129.

 

Outs EXCA and EXCB  AD7745 make in inverse mode signal with not full amplitude.

 

in the oscillogram i show 2 outs in direct and inverse mode,

in direct mode EXCA and EXCb working right wih amplitude of supply voltage.

when switch one of outs in the inverse mode reg_EXC_setup = 0x3B or 0x2F

i see full amplitude 4,5 V in the direct outputs, and signal with amplitude 260 mV

on inverse EXCA or 100 mV in inverse EXCB.

 

What that can be?

 

Resistor 100 kOm not should be load outs.

I am solded 3 different ICs, bying from 2 seller, and see the same effect.

 

Thanks fo help.

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