资料介绍
Many embedded applications require the generation of
analog signals. Although separate D/A converter IC’s
exist on the market today, their extra price makes them
prohibitive in cost sensitive embedded control designs.
The following application note describes two DAC
designs for generation of complex analog waveforms.:
(PWM and R-2R Ladder). Both the Pulse Width Modu-
lation (PWM) and resistor ladders require only a few
external components to create a D/A converter with the
PICmicro? microcontroller series.
These techniques can be used to generate dual-tone
multiplexed frequencies (DTMF) for telephone dialing,
controlling the speed of a motor, generating sound and
complex waveforms, and generating variable voltages
in a power supply. AN655
D/A Conversion Using PWM and R-2R Ladders to Generate Sine and DTMF Waveforms
one application to another. The designer should
Authors: Rob Stein and John Day experiment with this value to nd the most optimal num-
Microchip Technology Inc. ber for the application. These two criteria (sine fre-
quency and # of steps) lead to the required PWM
frequency:
INTRODUCTION PWM_Freq = (Sine_freq) (# of steps) 10
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