The VREFIO of AD9106 is higher than normal numerical value, and it is higher than 2 volts. What causes this? Thanks.
What else is connected to the REFIO (pin18) besides the recommended 0.1uF capacitor to ground? The REFIO pin is a high impedance pin. Essentially a 100uA current source driving an on board nominal10 K resistor, thus 1.0 V. The on board 10 K resistor is adjustable through the SPI register over a nominal range as shown in figure 37 of the datasheet. As you can see the REFIO should never be higher than around 1.25 V (or lower than 0.85) if you only have an external filter capacitor connected to the pin. In other words there is no way the chip itself can generate a higher voltage.