101-1272 Rabbit Semiconductor, 101-1272 Datasheet - Page 46

• Manufacturer Part Number: 101-1272
• Description: KIT MESH NETWORK ADD-ON RCM4510W
• Manufacturer: Rabbit Semiconductor
• Type: Microprocessorr

Specifications of 101-1272

• Product: Modules
• Data Bus Width: 12 bit
• Processor Type: Rabbit 4000
• Sram: 512 KB
• Number Of I/os: 20
• Description/function: Computer Module
• Interface Type: Ethernet
• For Use With/related Products: RCM4510W
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Other names: 316-1158

4.4.2 A/D Converter
The RCM4510W modules’ XBee RF module has four inputs on header J4 that may be set
up in software as analog inputs.
The four analog input pins, ADC0–ADC3, each have an input impedance of 6–7 MΩ,
depending on whether they are used as single-ended or differential inputs. The input signal
can range from -1.2 V to +1.2 V (differential mode) or from 0 V to +1.2 V (single-ended
mode).
Use a resistor divider such as the one shown in Figure 10 to measure voltages above 1.2 V
on the analog inputs.
Figure 10. Resistor Divider Network for Analog Inputs
The R1 resistors are typically 20 kΩ to 100 kΩ, with a lower resistance leading to more
accuracy, but at the expense of a higher current draw. The R0 resistors would then be
180 kΩ to 900 kΩ for a 10:1 attenuator. The capacitor filters noise pulses on the A/D
converter input.
The A/D converter can only accept positive voltages. With the R1 resistors connected to
ground, your analog circuit is well-suited to perform positive A/D conversions. When the
R1 resistors are tied to ground for differential measurements, both differential inputs must be
referenced to analog ground, and both inputs must be positive with respect to analog
ground.
40
RabbitCore RCM4500W