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
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.