AN1058 Freescale Semiconductor / Motorola, AN1058 Datasheet - Page 3

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

AN1058
MOTOROLA
ADCs may be categorized into five main categories. Although each type
has unique capabilities and traits, each has surprisingly similar points of
vulnerability.
The categories are:
The integrating converter has appeal for applications requiring high
resolution (16-bit or higher) and low cost. Because the basic converter is
simply implemented (see
resolution is obtained. In addition, the integrating ADC may provide
some noise immunity that is not feasible with higher speed designs.
Although it is possible to build the integrating converter onto MCU chips
(there is nothing technologically impeding such a construct), its lower
speed has apparently been discouraged by MCU designers since it is
currently not offered on an MCU by a major manufacturer.
Whereas the integrating converter tends to be the slowest of ADC types,
the servo converter tends to have the highest resolution and fastest
conversion times in its most recent advancement — the sigma-delta
converter. The more traditional servo converter tries to balance the
charge or voltage on an input comparator by using a feedback
configuration (see
or voltage to the current input signal level applied to the other input of the
same comparator. This process is followed by appropriately changing a
digital counter up or down (in this form, the converter is often called a
tracking converter). Before the sigma-delta variation, the servo converter
was less popular than other converter types primarily due to its slew rate
limitation. Nothing about the servo converter would prevent its inclusion
onto an MCU die; once BiCMOS processes improve, this converter type
will probably become a popular feature of future MCUs (particularly the
sigma-delta variation, most of which is linear circuitry).
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Freescale Semiconductor, Inc.
For More Information On This Product,
Integrating
Servo
FLASH
Successive-approximation converter (SAC)
Hybrid
Go to: www.freescale.com
Figure
Figure
1(b)) to force slewing from a previous charge
1(a)), hardware is minimized while high
Application Note
ADC Types
3