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LTC6090: TFLAG and OD problem

Question asked by htf on Mar 20, 2018
Latest reply on Jun 27, 2018 by dbur



I'm using the circuit shown on page 18 "Gain of 20 Amplifier with a 40 mA Protected Output Drive" in the datasheet of the LTC6090. The only thing that I have changed, is that I've replaced the 2k resistors with 4k02 to get an amplification of 10.


The power supply I use is stablilized (7805 and 7905 + some Z-diodes at the ground pins) and delivers +/- 71 V. I tried my very best to solder the exposed pad to the PCB and ran a test with 3 x 562R in series as load with +/- 65 V output swing (at 1 kHz), but after 10 to 15 minutes there was a loud bang and the LTC 6090 was gone.


As recommended, I connected the /TFLAG and /OD pins to protect the OPA from thermal overload, but this seemed to fail.


Any ideas what killed the LTC6090?


And how can I use the /TFLAG signal to drive a relay in order to disconnect the output and load?



Best regards