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T1042 Analog Domain Filtering

Question asked by Layne Berge on Jan 28, 2015
Latest reply on Jan 28, 2015 by LPP



I am currently working with a design which uses a T1042 processor.  In designing the analog domains, I have run across an oddity in the analog domain filtering.  The datasheet for the T1042 processor requires the AVDD_PLAT, AVDD_CGA1, AVDD_CGA2 and the AVDD_D1 analog domains to use an RC filter with a 5 ohm series resistor and two caps in parallel: a 10 uF and a 1.0 uF.  Each domain pulls around 20 - 40 mW from a 1.8 V domain.  With the required amount of power for each domain, this either comes near or exceeds the maximum tolerated DC droop of the domain in the filtering resistor alone.  This leaves me without any IR loss budget for each domain.  Is there a different recommended design which does not use such a large series resistor?  Perhaps there is a method to design the filter using a much lower DC loss component, such as a ferrite bead?