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AD9530 unused channels

Category: Hardware
Product Number: ad9530

I'll be using the AD9530 OUT0 to generate clock signals to drive a CML load.  I do not intend to use the remaining output ports.  I see in the datasheet the outputs should be terminated even if unused.  I intend to tie each unused output to VDD through a 50Ohm resistor .  Is this sufficient for termination requirements?  Since I will only be using OUT0 can I leave VDD at pins 35, 41, and 45 unconnected, or is power still required to be connected and then those ports can be disabled via register command?

  • Hi,

    I suppose the OUT0 output you refer in your enquiry is in reality OUT1. 

    The data sheet says that only OUT1 has to be terminated with 50 ohm to VDD even if unused. For the others, it does not say anything. 

    The chip must always be supplied at all pins, even the pins labelled as "Power supply for output" X. The reason is the chip is specified with the VDD supply being provided at all VDD pins. We do not know how the chip behaves if certain VDD pins are not supplied. 

    Then, you can leave the OUT2, 3, 4 unterminated and power these outputs down by clearing bits OUTx_LDO_EN and OUTx_EN to 0 , x=2,3,4 in various output control registers. 

    Petre

  • Apologies, yes I was referring to OUT1.  OK, thanks for clarifying all power pins are required even when not all output stages are used.  Interesting regarding termination required only on Out1 where the remaining can be left floating.