101-1272 Rabbit Semiconductor, 101-1272 Datasheet - Page 47

• 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

If a device such as a battery is
connected across two channels
for a differential measurement,
and it is not referenced to
analog ground, then the current
from the device will flow
through both sets of attenuator
resistors without flowing back
to analog ground as shown in
Figure 11. This will generate a
negative voltage at one of the
inputs, ADC1, which will almost
certainly lead to inaccurate A/D
conversions. To make such differential measurements, connect the R1 resistors to the A/D
converter’s internal reference voltage, which is 1.2 V. This internal reference voltage can
be configured in software to be available on pin 6 of header J4 as VREF, and allows you to
convert analog input voltages that are negative with respect to analog ground.
4.4.3 Other Pin Features
There are two other features brought out on the auxiliary I/O header J4.
• There is a +3.3 V power supply point on pin 8, which can deliver up to 25 mA at 3.3 V
• The SYS_PWR_ON signal on pin 9 is used by the XBee RF module to place the
User’s Manual
DC. This power supply point is essentially a filtered and isolated version of the regu-
lated +3.3 V DC power that is supplied to the RCM4510W RabbitCore module through
pin 1 of header J1 from the motherboard.
remaining circuitry on the RCM4510W RabbitCore module into a powered-down
“sleep” mode or to bring it back up to normal operation.
NOTE: This software configuration option for VREF and differential measurements are
NOTE: The amplifier inside the A/D converter’s internal voltage reference circuit has a
not supported at this time.
very limited output-current capability. The internal buffer can source up to 20 mA and
sink only up to 20 µA. Use a separate buffer amplifier if you need to supply any load
current.
Figure 11. Current Flow from Ungrounded
I
or Floating Source
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