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.

There is really only an external filter capacitor connected to the pin，and the VREFIO is normal before，but it changed higher suddenly at some time，I don’t know what causes this.

Assumed answered offline.