LM324QT - Is it OK to connect GND to the exposed pad with a dual-polarity supply?

[onlya-inx]

LM324QT (QFN16 package) was used in my design as an amplifier. The design has a dual-polarity power supply with +12V, GND and -12V.

I connected its exposed centre pad to GND, while connecting the VCC+ to +12V and VCC- to -12V. However, the datasheet states that "The exposed pads of the QFN16 3x3 can be connected to VCC- or left floating".

I have already got my board made and tested. What I have noticed is that the GND is not pulled to VCC- and VCC- is not pushed to GND, which seems right. However, I can feel the chips are quite hot.

Does this design need to be totally abandoned or is this not the root case of the heat? Is the "exposed pad" internally connected to the VCC- via some low-resistance substrate or totally floating?

[Peter BENSCH]

Welcome, @onlya-inx​, to the community!

I recommend that the design be abandoned. The cause of the heat development may well be to be found elsewhere, however, without a relevant part of the schematics, one cannot make a statement about this.

The "exposed pad" is not connected to VCC-, but it is internally connected and not potential-free, which is why the data sheet advises to either connect it to VCC- or let it float.

Does it answer your question?

Regards

/Peter