LTC6090: TFLAG and OD problem

Hello,

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

Helmut

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