I am experimenting with the AD9910 evaluation board and specifically have queries with the power down option.
I program the device using the supplied GUI software and select Full Power Down from External PD Mode. But rather than use the software to apply the External power down, I am interested to do it by hardware via the EXT_PWR_DWN pin. So I drive this pin by toggling between logic high (3.3V) and logic lo (0V).
What is the recommended way to drive the EXT_PWR_DWN pin this way? Driving it directly with the above logic voltage levels, I find that during logic hi, a current is drawn by the EXT_PWR_DWN pin and it is ~130mA. Further, this current decreases as VCC_USB is reduced?! Looking at the schematics given on the ADI webpage for the AD9910 eval board, it does not appear to indicate that these supplies are linked? Or have I missed something
Many thanks in advance for any tips