Question asked by NidhiSingh on Mar 21, 2016
Latest reply on Mar 29, 2016 by NidhiSingh

Hi,

I have set the ADN8831 EVM with the following specifications

1) Tset = 25degCelcius, Tlow = 20degCelcius, Thigh = 30degCelcius

Vtempset = 1.25V

2) Single set point configuration with

R1=Rth=10Kohm

R2=0

R3=60Kohm

3) The limiting cooling/heating current calculated as per the equation in datasheet

Limiting current cooling = 500mA (Vlimc = 1.5V)

Limiting current heating = -300mA (Vlimh = 1.1V)

4) When I connected the TEC and Thermistor and measured the current through TEC I got the following values

Cooling current = 442mA (max)

Heating current = -53mA (max)

The heating current is not going beyond the above value although it is set to -300mA. So I reduced the voltage at limiting current heating pin to Vlimh = 0.9V and got the following current values through the TEC.

Cooling current = 443mA (max)

Heating current = -235mA (max)

As per the equation given in the datasheet, for Vlimh = 0.9V, maximum heating current would be around -700mA. This is a huge discrepancy.

Please let me know what could be the reason of such a behaviour.

Regards,

Nidhi Singh