20-151-0178 Rabbit Semiconductor, 20-151-0178 Datasheet - Page 67

• Manufacturer Part Number: 20-151-0178
• Description: CABLE CONVERTER RS-232 TO USB
• Manufacturer: Rabbit Semiconductor

Specifications of 20-151-0178

• Accessory Type: USB to RS232 Adapter
• Product: Microcontroller Accessories
• For Use With/related Products: Rabbit-based Boards
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 20-151-0178; 316-1181

5.5 DACs
To produce an analog signal for the DAC channel outputs, the Rabbit generates precisely timed pulses
using PWM (pulse width modulation). The digital signal, which is either 0 V or 5 V, is a train of pulses.
This means that if the signal is taken to be usually at 0 V (or ground), there will be 5 V pulses. The voltage
will be 0 V for a given time, then jump to 5 V for a given time, then back to ground for a given time, then
back to 5 V, and so on. The digital signal is a value between 0 and 1024. This value is used to set the duty
cycle of the PWM channel by passing it to the function pwm_set().
Thus, the software only needs to vary the time the signal is at 5 V with respect to the time the signal is at 0
V to achieve any desired voltage between 0 V and 5 V.
The quality of the analog signal is determined largely by the settling time, the slew rate and the output res-
olution of the DAC channel.
RabbitFLEX User’s Manual
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the analog signal.
Settling Time – This is the time it takes for the analog signal to achieve a full-scale change in volt-
Slew Rate – This is the maximum rate at which the DAC channel can change the voltage level of
Output Resolution – This is the number of bits in the digital input that results in the analog output.
Figure 5.3 Duty Cycle Examples
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