Freescale Semiconductor, Inc.
GENERAL RELEASE SPECIFICATION
8
2
SECTION 9
ANALOG-TO-DIGITAL CONVERTER
3
4
9.1 Introduction
5
The MC68HC805P18 includes a 4-channel, multiplexed input, 8-bit successive
approximation analog-to-digital (A/D) converter. The A/D subsystem shares its
inputs with port C pins PC3 through PC7.
6
7
9.2 Analog Section
The following paragraphs describe the operation and performance of analog
modules within the analog subsystem.
8
9
9.2.1 Ratiometric Conversion
10
11
12
13
14
A
The A/D converter is ratiometric, with pin V
voltage. Applying an input voltage equal to V
$FF (full scale). Applying an input voltage equal to V produces a conversion
result of $00. An input voltage greater than V
supplying the high reference
REFH
produces a conversion result of
REFH
SS
will convert to $FF with no
REFH
overflow indication. For ratiometric conversions, V
should be at the same
REFH
potential as the supply voltage being used by the analog signal being measured
and referenced to V .
SS
9.2.2 V
REFH
The reference supply for the A/D converter shares pin PC7 with port C. The low
reference is tied to the V pin internally. V
can be any voltage between V
SS
REFH
SS
and V ; however, the accuracy of conversions is tested and guaranteed only for
DD
V
= V .
REFH
DD
16
17
18
19
20
ANALOG-TO-DIGITAL CONVERTER
Rev. 1.0
For More Information On This Product,
Go to: www.freescale.com
FREESCALE [ Freescale ]
