Data Sheet

Arty FPGA Board Reference Manual
Copyright Digilent, Inc. All rights reserved.
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wish to monitor the voltage of an external supply may configure Channel 2 of the XADC as a unipolar input and
perform a conversion to receive a digital value corresponding to the input voltage. The figure below provides an
overview that allows an external supply voltage to be monitored.
Figure 3.1.1. Monitoring external voltage supply.
3.2 FPGA Core Supply Current Monitoring
The Arty board includes circuitry for monitoring the current consumed by the FPGA core. The current is monitored
by measuring the voltage across a 10 milliohm sense resistor that’s placed between the output of the 0.95V
switching regulator (IC11, Channel 2) and the VCC0V95 network. A current sense amplifier (IC15, Texas
Instrument’s INA199A1) connected across the sense resistor provides a gain of 50 and produces an output voltage
of 500 millivolts per amp of current. The output of the current sense amplifier is fed into Auxiliary Channel 10 on
the XADC of the Artix 35T. Applications that wish to monitor the current consumption of the FPGA Core and Block
RAM may configure Channel 10 of the XADC as a unipolar input and perform a conversion to receive a digital value
that corresponds to the amplified sense resistor voltage. The figure below provides an overview of the circuitry
that allows the FPGA Core Supply current to be monitored.
Figure 3.2.1. FPGA core supply current monitoring.
3.3 5V Supply Power Monitoring
The Arty board includes circuitry for monitoring the voltage of the 5 Volt supply as well as the current consumed
from this supply. A voltage divider is used to scale the 5V input voltage to be within the range (0-1V) that the on-
chip 12-bit ADC is capable of measuring. The 5V supply voltage is divided by 5.99 and then fed into auxiliary
Channel 1 on the XADC of the Artix 35T. A combination of a 5 milliohm current sense resistor and a current sense
amplifier (IC14, Texas Instruments INA199A1) are used to produce an output voltage of 250 millivolts per amp of
current. The output of the current sense amplifier is fed into Auxiliary channel 9 on the XADC of the Artix 35T.
Applications that wish to monitor the instantaneous power consumption of the Arty board may configure Channels
1 and 9 of the XADC as unipolar inputs and then perform a simultaneous conversion of the two channels to receive
digital values that can be used to compute the instantaneous power consumption. The figure below provides an
overview of the circuitry that allows the 5V Supply power consumption to be monitored.