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ADUM4135 operation when over temperature protection activates

Question asked by bob1960 on Sep 26, 2017
Latest reply on Sep 27, 2017 by bob1960

An issue with the ADUM4135 operation. Application is a mosfet H-bridge driver. Secondary power is via a low power (250mW) isolated source. Desaturation feature not used and connected to ground. No negative bias, only VDD2 set at 14.5V nominal. VSS2 grounded.


IC works correctly including all status signals until its internal over temperature protection activates. Once temperature protection is activated only removing power will restore normal operation.


The READY signal is low once the over temperature protection is activated as expected. However, even after allowing the IC to cool >5 minutes, the READY signal does not return to "ok" status. External pull-up are used.


Part of the issue is the isolated source is loaded significantly when the over temperature protection activates reducing its output voltage (2.6V) below that required by the IC UV protection. Hence causing the READY signal to remain low. This voltage never returns to nominal level (14.5V) after the IC cools. Adding a secondary power source capable of >50mA of power to VDD2 and the voltage still does not return to expected level.


Cycling power is the only method found to restore normal operation. 


Any insight into the cause of this issue would be appreciated.