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DAC8814: Abnormal output

Part Number: DAC8814
Other Parts Discussed in Thread: THS4141

Conditions of use:

1. SPI control output of DAC8814 through SPARAN6 FPGA of XILINX;

2. DAC88144 channels are used for simultaneous output, of which one channel is converted from single-ended output to differential output.

3. The reference voltage is 10V.

4. The output waveform of the design is amplitude (+10V) and the frequency is 220 KHz square wave.

Schematic diagram:

Principle Diagram of DAC8814 Output Current-to-Voltage Conversion

Principle diagram of DAC8814 output single-ended output to differential output

Output waveform measured by oscilloscope:

Debugging problems:

1. When jumping from + 10V to - 10V, or from - 10V to + 10V (full range jump), there is a jitter within 500 ns or so, as shown in the red circle of the above-illustrated wave, and the amplitude is close to 4V.

2. In steady state, the waveform also has a burr of about 200 mV.

  • Hi Shuang,

    This looks like opamp overshoot which is clipping at the 12V supply rails. Overdrive recovery might be impacting the response as well. I think in general this circuit is not compensated correctly, which is why you are seeing such large ringing. Let me loop in some people from the high-speed amplifier team.

  • Hi Shuang,

    I am unable to replicate your scope measurements in simulation. There is a 2.65kHs low pass filter created by the 12nF capacitor and the 5k feedback resistor on the first stage of your amplifier design. If the 12nF capacitor is removed, I get a square wave without much ringing. You could add 1pF feedback capacitors on the THS4141 to compensate any parasitic capacitance if it helps.


    Best regards,