We are using AD9081 for baseband signal converting. Thus we hope to use the DC-coupled method. Here are the questions after studying the doc UG-1578:
I. ADC direction:
1. It is said in Section "Calibration and Specifying Nyquist Zone" that timing and gain calibration should be disabled. In Table 28, the bits for backgroud gain calibration is Bit 7-4 in Register 0x2117. But on page 312, the control bits is Bit 3-0. Which is correct?
2. In function adi_ad9081_adc_analog_input_buffer_set, the update for register 0x2112, the third parameter should be 0x100, right? There are two place, search the word CAL_FREEZE_GLOBAL.
II. DAC direction:
1. The Figure 84 and Figure 89 show internal resistor of 50ohm and 25ohm separately. Which one is correct? Or is there any way to change the internal resistor?
2. The Figure 89 shows the common mode voltage is 0.3V with IoutFS set to 20mA. My understand is that the common mode voltage should be 10mA*25ohm/2= 125mV, as the internal and external resistors are both 25ohm. So how to calculate the 0.3V common mode voltage.
3. We had some test on AD9081, and found the performance is acceptable for our application when the common mode voltage is 430mV. Can we use it? Or it could damage the device in a long run?