Virtex-6 FPGA System Monitor
13
UG370 (v1.1) June 14, 2010
Analog-to-Digital Converter
Equation 1
Where:
k = Boltzman’s constant = 1.38 x 10
-23
T = Temperature K (Kelvin) = °C + 273.1
q = Charge on an electron = 1.6 x 10
-19
C
The output voltage of this sensor is digitized by the ADC to produce a 10-bit digital output
code (ADC code).
illustrates the digital output transfer function for this
temperature sensor.
For simplification, the temperature sensor plus the ADC transfer function is rewritten in
.
Equation 2
System Monitor also provides a digital averaging function that allows a user to average up
to 256 individual temperature-sensor measurements to produce a reading (see
). Averaging the sensor measurements helps
generate a noise-free and repeatable measurement. The result of a temperature reading is
placed in the output data registers at address
00h
on the DRP (see
). The full ADC transfer function describes temperatures outside the FPGA
operating temperature range. This does not mean that the FPGA is operational at these
temperatures (refer to
Virtex-6 FPGA Data Sheet
for temperature specifications). System
Monitor is operational over a temperature range of –40°C to +125°C on all parts
irrespective of grade.
The on-chip temperature sensor has a maximum-measurement error of ±4°C over a range
of –40°C to +125°C. Monitoring FPGA on-chip temperature avoids functional and
irreversible failures by ensuring critical operating temperatures are not exceeded.
X-Ref Target - Figure 5
Figure 5:
Ideal Temperature Sensor Transfer Function
Voltage
10
kT
(
)
q
-----------
10
( )
ln
×
×
=
Temperatur
e
°
C
(
)
ADCcode
503.975
×
1024
---------------------------------------------------
273.15
–
=
000h
001h
003h
004h
3FFh
10-bit Output Code
Full Scale
Transition
3FEh
3FDh
002h
1
0
2
3
605
1023
1022
Temperature (°C)
+230.5°C
+24.76°C
-273°C
-272.5°C
-272°C
-271.5°C
1LSB
≅
0.49°C
UG370_05_
060709
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