afs600 Actel Corporation, afs600 Datasheet - Page 102

• Manufacturer Part Number: afs600
• Description: Actel Fusion Programmable System Chips Mixed-signal Family With Optional Arm Support
• Manufacturer: Actel Corporation

The diode’s voltage is measured at each current level and
the temperature is calculated based on
where
When I
as shown in
In the Fusion TMB, the ideality factor n for 2N3904 is
1.004 and ΔV is amplified 12.5 times by an internal
amplifier; hence the voltage before entering the ADC is
as given in
This means the temperature to voltage relationship is
2.5 mV per degree Kelvin. The unique design of Fusion
has made the Temperature Monitor System simple for
the user. When the 10-bit mode ADC is used, each LSB
represents 1 degree Kelvin, as shown in
25°C is equal to 293°K and is represented by decimal 293
counts from the ADC.
2 -8 8
Actel Fusion Programmable System Chips
I
is Low, typically 100 µA
I
is High, typically 10 µA
V
is Low
V
is High
n is the non-ideality factor of the diode-connected
transistor. It is typically 1.004 for the Actel-
recommended transistor type 2N3904.
K = 1.3806 x 10
Q = 1.602 x 10
TMSLO
TMSHI
TMSLO
TMSLO
TMSHI
ΔV
EQ
V
EQ
is the current when the Temperature Strobe
ADC
is the current when the Temperature Strobe
/ I
V
is diode voltage while Temperature Strobe
=
is diode voltage while Temperature Strobe
1K
2-8.
TMSLO
TMSHI
2-7.
V
TMSLO
=
=
ΔV 12.5
2.5 mV
–
-19
= 10, the equation can be simplified
-23
V
–
×
TMSHI
C is the charge of a proton
V
J/K is the Boltzman constant
TMSHI
×
=
---------------- -
2.56 V
=
2
n
=
10
2.5 mV
kT
----- - ln
q
1.986
⎛
⎝
=
I
---------------
I
TMSLO
TMSHI
1 LSB
⁄
×
(
EQ
K T
EQ
10
×
⎞
⎠
–
2-6.
4
2-9. That is, e.
nT
)
EQ 2-6
EQ 2-7
EQ 2-8
EQ 2-9
A d v a n c e d v 1 . 4
If 8-bit mode is used for the ADC resolution, each LSB
represents 4 degrees Kelvin; however, the resolution
remains as 1 degree Kelvin per LSB, even for 12-bit
mode, due to the Temperature Monitor design. An
example of the temperature data format for 10-bit mode
is shown in
Table 2-38 • Temperature Data Format
Terminology
Resolution
Resolution defines the smallest temperature change
Fusion Temperature Monitor can resolve. For ADC
configured as 8-bit mode, each LSB represents 4°C, and
1°C per LSB for 10-bit mode. With 12-bit mode, the
Temperature Monitor can still only resolve 1°C due to
Temperature Monitor design.
Offset
The Fusion Temperature Monitor has a systematic offset
of +5°C, excluding error due board resistance and
ideality factor of the external diode, between the
operation range of –40°C to +85°C. For instance, 25°C
will be read by the Temperature Monitor as 30°C plus
error. The user can remove any offset error through
hardware or software during the calibration routine.
Temperature
–40°C
–20°C
0°C
1°C
10 °C
25°C
50 °C
85 °C
Table
2-38.
Temperature
233
213
273
274
284
298
323
358
(K)
(ADC 10-bit mode)
Digital Output
00 1110 1001
00 1101 0101
01 0001 0001
01 0001 0010
01 0001 1100
01 0010 1010
01 0100 0011
10 0001 1010