ADN8834 problem

Hi minkyo,

Thanks for using the ADN8834.
Upon checking the schematic, the chopper amplifier 1 inputs are connected to ground. With this configuration, output can possibly railed to VDD which is observed on your data. Article on below link is a good read.

https://www.analog.com/en/analog-dialogue/raqs/raq-issue-46.html

"Grounding both inputs, or shorting them together at some other potential, also causes the output stage to saturate, since the offset voltage of an op-amp is never exactly zero; shorting them together and not biasing them has the same latch-up risks."

One thing I can recommend, since the chopper 1 is unused  you can configure it to voltage follower (shorting the IN1N to OUT1) then connect the IN1P to GND. This way, OUT1 will be zero and this will eliminate the risk of mistrigger other pins.

However just to confirm, is the input voltage in the table is actual "measured" voltage in the IN2P pin? or just in the program of a DAC setting voltage to IN2P pin.

In addition, the ILIM setting via resistor divider is incorrect. Upon rechecking, the  ITEC_MAX_COOLING : 0.5219A while  ITEC_MAX_HEATING : -0.4762A which should be a positive value. 

Thanks and regards,

Noel

Thank you for the answer.

Yes I measured data with scope.

I connected IN1N to OUT1 and checked OUT1 0V.

But TEC- is not bigger thank TEC +.

Also the TEC-, TEC+ is different form data sheet graph.

Thanks

You said ITEC_MAX_HEAING should be a positive value.

But in ADN8834 eval guide table, there is no positive value for ITEC_MAX_HEATING.

How could be? 

Hi @minkyo,

It is understood that heating current is negative. Setting it in negative value in the computation is redundant. See below sample computation using the first value in the table you sent. 

Regards.

Do you have a fresh unit to try the circuit implementing the corrections on your component values?