AD9957 is a bad boy!

It looks like the AD9957 needs four power supplies. So the digital and analog rails are split and there is a pair for 3.3V and pair for 1.8V.

tfilt

Usual solution is to use single dual regulator with bunch of T filters. Like this guy who made a DAB radio transmitter using this same chip. But it would seem the current requirement is bit weird so this power scheme is not very good option

power

So after spending some time i think i will start with 150 mA dual regulator (tested in old design) with only one T filter, and use extra 700 mA regulator for the demanding 1.8V DVDD.

ddsAnyway, both could be switched off via Inhibit pin, so the quadrature upconveter could be off if not needed in RX mode and save more than 800 mA. There is also a need to complete the signal part of the module, to follow…

2 thoughts on “AD9957 is a bad boy!

    1. m0nka Post author

      Hello,

      Very good point! But… this is still preliminary schematics, even if it goes to the Alpha board will be just for testing/building firmware, etc. Too many things are unknown – first the consumption figure i got from the pdf, but is based on clocking scheme. Those chips are design for Ghz frequencies, not 3-30 Mhz. No one in the industry uses our HF band, well they do for the switching regulator ICs. So until i have better idea on overall view on everything – any component selection is experimental.

      73, Chris

      Reply

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