PCM1792 - I/V-Stage-OP burns my fingers.

Additional informations:

The current of the OPA4134 is 60mA on the -15V and 12mA on the +15V Rail.

Each amp of the OPA4134 drives 12mA on BPZ.

Thats IMHO all seems to be OK, i wonder about the heating of the i/v-Stage......

Best regards

Frank

Frank,

The temperature can definitely get warm on these devices, but how warm depends on the operating point of the output. For example if V+ is sourcing 12mA and and the V- is sinking 60mA, and the output is at 0V, then the total dissapation is (12mA*15V)+(60mA*15V)=1.08 Watts. Now looking at the thermal resistance of the part (on the bottom of page 2 of the datasheet) it is 110C/W from the die junction to ambient temperature.

This means that the temperature will rise from the ambient by 1.08W*110C/W=119C. Just enough to burn your fingers.

If the output is less than 0V, then less of the power is dissipated by the package and more is dissipated by the load.

Joseph Wu and Marek Lis

Frank,

Are you really trying to drive 12mA per op-amp? It's a lot to be sourcing (or sinking if it's coming from V- supply).

You really should try to reduce the current especially if the temperature is getting close to the 150C limit.

Joseph Wu

Hello Jospeh,

thank you for your reply.

The schematic is nearly in the datasheet from the pcm1792 page 35:

http://www.ti.com/lit/gpn/pcm1792a

So i wonder about the current and the temperatur.

Now i have fixed heatsinks on the op-amps (13K/W) and the tempertur is at ~50°C. Tomorrow we will install the DAC in our test car, the i will try to reduce the current.

Reguards
Frank 

Frank,

Just to make sure, I'll just contact you directly.

Joseph Wu