Ti DAC53401 Output gets somehow pulled low by I2C?

[Gulftown]

Hello everyone,

i have a project with a DAC53401. if i write the registers after startup, the dac accepts the commands starts up and enables the output normally.
But after writing the output voltage to register 0x21 the dac does not accept any more traffic ever again.
And somehow the output voltage drops, as soon as there is data written on the bus to any device.
After the stop condtion, the output rises again.

There is no connection between the output and the i2c, the Vcc is stable at 3.3V and GND is also stable.
I can see a little bit of influence on the "CAP" pin of the dac, so the internal LDO is also experiencing a litte drop.

Does anyone of you ever had a similar problem, or is the DAC just toast?

The blue channel 4 is the dac output.

[Gulftown]

Okay, i figured it out.
I used a 10k resistor on pin A0. This is  the Address Pin and it gets sampled every i2c frame.
I gess it 10k is just to high, so the address is changing as soon as the output is enabled.

Code: [Select]

"The A0 pin input can be connected to VDD, AGND, SCL, or SDA. The A0 pin is
sampled during the first byte of each data frame to determine the address."
I still have a little bit of noise when transfering data over the i2c bus, but its a lot better now.