Datasheet

Ballout and Package Information
Intel
®
Quark™ microcontroller D2000
January 2016 Datasheet
Document Number: 333577-002EN 39
3.5.4 ADC
A simple filter is recommended to be put on board on Analog Inputs [19:0] connected
to ADC, to reduce external noise. It should be understood that any additional
frequency signals within the band of interest will be present in the output spectrum
contributing for a performance impact. Additionally the input signal is disturbed by the
fast transients due to the fast charging of the ADC input capacitor during the start of
the sampling period. These transients should vanish quite rapidly and the voltage
across the ADC input capacitance should reach a steady state very fast. Nevertheless
in case the ADC input network is not correctly terminated these transients can travel
back and forth through the input line between the ADC driver and ADC input
generating a ringing. This will lead to an incorrect sampling of input signal.
A recommended input scheme to prevent this possible consequence can be
• 50 ohm resistor (in ADC side). The resistor level should match the characteristic
impedance of PCB trace;
• 470pF capacitor to ground (in ADC driver side);
In order that they are effective, resistor and capacitor must be connected very close to
each other and placed towards the ADC Analog input (SoC side), as follows:
Power supply decoupling on AVDD rail input shall be done with 1uF || 10 nF
decoupling capacitors. The 10 nF capacitor shall be ceramic (good quality) and must
be placed as close as possible to the SoC.