AN1058 Freescale Semiconductor / Motorola, AN1058 Datasheet - Page 2

• Manufacturer Part Number: AN1058
• Description: Reducing A/D Errors in Microcontroller Applications
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
ADC Types
2
popular than the multichip solution. Consequently, it is reasonable to
expect that the practicing design engineer will eventually work with an
MCU-based system. Yet despite the advantages of the MCU system,
some integrated peripherals such as the ADC offer new challenges to
the designer. By incorporating a wide bandwidth linear system, such as
an ADC, on the same die with a high-speed digital central processor unit
(CPU), ADC performance can be adversely affected. Noisy ADC
readings functionally manifest themselves in a range from merely
annoying and relatively benign glitches to more catastrophic hard
failures.
In any case, an MCU-based system does not have to be at the mercy of
poor MCU/ADC performance. Fortunately, by following some fairly
rudimentary systems-level guidelines in the design phase of the MCU-
based product, potential ADC performance problems can be avoided.
To resolve ADC performance issues, it is necessary to understand a little
about the nature of the MCU and the various areas of susceptibility of
several ADC types. Although much information presented in this
application note assumes that the ADC is resident on-chip with the CPU,
other converter types not typically found on-chip with MCUs are
discussed for those instances in which a multichip combination is
encountered. The following paragraphs also apply to these less frequent
hardware combinations.
Even when the ADC is available on-chip with an MCU where the
unpleasant task of interfacing and debugging the ADC-to-CPU interface
is done, obtaining maximum performance from the ADC requires
attention to application details of the given MCU/ADC combination. The
type of design precautions and applications details needed to avoid
problems varies as a function of the type of ADC used. Understanding
the mechanics of the given ADC is crucial to improving performance.
Freescale Semiconductor, Inc.
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MOTOROLA
AN1058