When programming the HMC703 via the SPI, can I just write to the register of interest and see the effect immediately, or do I need to do some sort of reset or clear first? Example, I want to program to enter power down mode, if I just address register 01 and put in 0, that doesn't seem to put the device in power down mode. My feeling is that there are a lot of steps missing here. Thanks.
Power down the HMC703 by writing Reg 0x01=0. It's that simple.
If you are using our eval board you will see the 5.5V current drop from around 350mA to 290mA. It will not go down to the 100uA specified in the datasheet since the 5.5V also powers the VCO, reference and opamp circuits. To measure the HMC703 power down current from the 5.5V input you must:
With all these modification you will still measure about 4.5mA on the 5.5V when powered down due to the ground current through the HMC860 LDO regulator and the 2.5V bias for the loop filter (R26 and R27).