U1AFS250-2FG256YI
| Model | U1AFS250-2FG256YI |
| Description | Field Programmable Gate Array, |
| PDF file | Total 334 pages (File size: 18M) |
| Chip Manufacturer | MICROSEMI |
Fusion Family of Mixed Signal FPGAs
The diode’s voltage is measured at each current level and the temperature is calculated based on
kT I
TMSLO
-
V
TMSLO
–
V
TMSHI
=
n
------
⎛
ln
-----------------
⎞
q
⎝
I
TMSHI
⎠
EQ 7
where
I
TMSLO
is the current when the Temperature Strobe is Low, typically 100 µA
I
TMSHI
is the current when the Temperature Strobe is High, typically 10 µA
V
TMSLO
is diode voltage while Temperature Strobe is Low
V
TMSHI
is diode voltage while Temperature Strobe is High
n
is the non-ideality factor of the diode-connected transistor. It is typically 1.004 for the Microsemi-
recommended transistor type 2N3904.
K
= 1.3806 x 10
-23
J/K is the Boltzman constant
Q
= 1.602 x 10
-19
C is the charge of a proton
When
I
TMSLO
/
I
TMSHI
= 10, the equation can be simplified as shown in
ΔV
=
V
TMSLO
–
V
TMSHI
=
1.986
×
10
nT
EQ 8
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
V
ADC
=
ΔV ×
12.5
=
2.5 mV
⁄ (
K
×
T
)
EQ 9
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
That is, e. 25°C is equal to 293°K and is
represented by decimal 293 counts from the ADC.
2
-
1K
=
2.5 mV
×
---------------- =
1 LSB
2.56 V
EQ 10
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
Temperature
–40°C
–20°C
0°C
1°C
10 °C
25°C
50 °C
85 °C
Temperature (K)
233
253
273
274
283
298
323
358
Digital Output
(ADC 10-bit mode)
00 1110 1001
00 1111 1101
01 0001 0001
01 0001 0010
01 0001 1011
01 0010 1010
01 0100 0011
01 0110 0110
10
–
4
Revision 3
2- 97
