PCM1796 with passive termination?

Tibor Racz101989

Other Parts Discussed in Thread: PCM1796, PCM1794

Hi,

Can somebody help me? I would like to use the PCM1796 with passive termination. I need 0,4Vpp differential output voltage. I looked for but I didn't find any details about the current segment DAC of PCM1796.

The output of the DAC between is between -1,5m..-5,5mA I thought it is a current sink DAC. But in the recommended Application Circuit (datasheet page34) U1 output voltage is -1,23V...-4,51V to the ground that means for me the converter is an current source DAC. What is the "truth" or what did I missed?

Is the passive termination possible like on the picture or connect to VCC?

over 13 years ago

0 Don Dapkus over 13 years ago

TI__Guru**** 189401 points

Hi, Tibor,

Check out page 55 of the d/s. It discusses output current.

Unfortunately, we don't have any experience doing what you're trying. You are going to low-pass filter the signal somewhere in your design. And, I'm a little worried the output current source is not going to be as linear as you'd like driving such a low resistance.

-d2

0 Tibor Racz101989 over 13 years ago in reply to Don Dapkus

Prodigy 20 points

Thanks for the quick answer.

Tibor

0 Gaston Picard over 13 years ago in reply to Don Dapkus

Prodigy 40 points

Hi Don!

pp 55 of the datasheet points to the schematic of figure 36. That one shows a couple I/V converters with the 5534. Those I/V converters are meant to present a virtual ground node to the PCM1794 / PCM1796, and as such, 0 volts and (theoretical) zero ohms.

May be that you meant that the existence of voltage other than zero would make the current source less linear ?

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PCM1796 with passive termination?