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Stability in Viso ADUM5000

Question asked by Cris on Apr 4, 2011
Latest reply on Apr 5, 2011 by Cris

Hello,

 

I have a 2ch A/D Converter with A freescale MCU. It communicates with the PC through FT232R. All of this is isolated with ADUM5000 and ADUM4160. (It´s a USB bus-powered A/D converter)

All works fine, but I´m afraid of the Viso in the ADUM5000...

 

The signal for measure is 0-5V. With a Rail to Rail Operational Amplifier I can manage the buffer for the Analog Signals, so I can put after de buffer a resistive voltage divider, in the way that the MCU sees [0-4]V in each channel.

 

My fear is the Vcc provide to the buffer (Gain=1), so if I receive a signal of 5V my buffer must follow it with 5V.

 

I have 3 prototypes running OK. Just because the ADUM5000 provides [5.03 - 5.11] and never goes down 5V.

In one board I have a LED connected to the MCU, it seems the ADUM5000 reduce the Viso a little (5.03V)

In the other two boards Viso=5.11V (without LED)

 

Question is:

 

Should I expect that Viso will be always the same? If Viso goes down from 4.95 there will be a little problem

 

In the datasheet says that Viso can vary from (4,7V - 5,3V) But I cannot find any more information about how and when this voltage could change.

 

If once running the ADUM5000 shows Viso=5,03V will this value change through the time or temperature??

Or simply will I receive some chips with differents Viso from the market? <-- that would be neat!

 

Information about this will be much appreciated.

 

Regards.

 

Cris.

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