AN2475 Freescale Semiconductor / Motorola, AN2475 Datasheet - Page 2

• Manufacturer Part Number: AN2475
• Description: Generating a PWM Signal Modulated by an Analog Input Using the MC68HC908QY4 Microcontroller
• Manufacturer: Freescale Semiconductor / Motorola

AN2475/D
Analog-to-Digital Converter (ADC)
Voltage Conversion
Conversion Time
Continuous
Conversion versus
Single Conversion
2
The 8-bit, 4-channel ADC module is only available on the MC68HC908QY2,
MC68HC908QT2, MC68HC908QY4, and MC68HC908QT4. Features include:
When the input voltage to the ADC equals V
$FF (full scale). If the input voltage equals V
Input voltages between V
All other input voltages will result in $FF if greater than V
than V
Sixteen internal clock cycles are required to perform one conversion. The ADC
starts a conversion on the first rising edge of the ADC internal clock
immediately following a write to the ADC status and control register (ADSCR).
If the internal clock is selected to run at 1 MHz, then one conversion will take
16 µs to complete. The highest sample rate at this frequency is 62.5 kHz.
In the continuous conversion mode, the ADC continuously converts the
selected channel filling the ADC data register (ADR) with new data after each
conversion. Data from the previous conversion will be overwritten whether that
Generating a PWM Signal Modulated by an Analog Input
Freescale Semiconductor, Inc.
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For More Information On This Product,
Using the MC68HC908QY4 Microcontroller
SS
Selectable trip point low-voltage inhibit (LVI)
Computer operating properly (COP) timer
Flexible high-current input/output (I/O) and keyboard interrupts
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MC68HC908QY4, MC68HC908QY2, and MC68HC908QY1 are
available in these packages:
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MC68HC908QT4, MC68HC908QT2, and MC68HC908QT1 are
available in these packages:
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4 channels with multiplexed input
Linear successive approximation with monotonicity
8-bit resolution
Single or continuous conversion
Conversion complete flag or conversion complete interrupt
Selectable ADC clock
.
13 bidirectional
1 input only
16-pin plastic dual in-line package (PDIP)
16-pin small outline integrated circuit (SOIC) package
16-pin thin shrink small outline package (TSSOP)
8-pin PDIP
8-pin SOIC
8-pin dual flat no lead (DFN) package
Go to: www.freescale.com
DD
and V
SS
are a straight-line linear conversion.
DD
SS ,
, the ADC converts the signal to
the ADC converts it to $00.
DD
and $00 if less
MOTOROLA