mc68hc05l25 Freescale Semiconductor, Inc, mc68hc05l25 Datasheet - Page 113

• Manufacturer Part Number: mc68hc05l25
• Description: M68hc05 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 12
Analog Subsystem
12.1 Introduction
The MC68HC05L25 includes a 2-channel, multiplexed input, 8-bit, successive approximation
analog-to-digital (A/D) converter. The A/D subsystem shares its inputs with port A pins PA4 and PA5.
12.2 Analog Section
The following paragraphs describe the operation and performance of analog modules within the analog
subsystem.
12.3 Ratiometric Conversion
The A/D converter is ratiometric, with pin V
input voltage equal to V
equal to V
with no overflow indication. For ratiometric conversions, V
supply voltage being used by the analog signal being measured and should be referenced to V
12.3.1 V
The reference supply for the A/D converter is tied to V
pin internally.
12.3.2 Accuracy and Precision
The 8-bit conversion result is accurate to within ±1.5 LSB, including quantization; however, the accuracy
of conversions is tested and guaranteed only with external oscillator operation at V
12.4 Conversion Process
The A/D reference inputs are applied to a precision digital-to-analog (D/A) converter. Control logic drives
the D/A and the analog output is successively compared to the selected analog input which was sampled
at the beginning of the conversion cycle. The conversion process is monotonic and has no missing codes.
12.5 Digital Section
The following paragraphs describe the operation and performance of digital modules within the analog
subsystem.
Freescale Semiconductor
SS
REFH
produces a conversion result of $00. An input voltage greater than V
REFH
produces a conversion result of $FF (full scale). Applying an input voltage
MC68HC05L25 Data Sheet, Rev. 3.1
REFH
= V
DD
DD
supplying the high reference voltage. Applying an
internally. The low reference is tied to the V
REFH
should be at the same potential as the
REFH
DD
will convert to $FF
= 5 V.
SS
.
SS
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