ADT7316 Datasheet, PDF (19/32 Pages) Analog Devices – SPI/I2C Compatible, 10-Bit Digital Temperature Sensor and Quad Voltage Output 12/10/8-Bit DAC

PRELIMINARY TECHNICAL DATA
(V_REF = 2.25 V) then this corresponds to 0V representing -
40°C and 1.48V representing +127°C. This of course will
give an upper deadband between 1.48V and V_REF.
The Internal and External Analog Temperature Offset
registers can be used to vary this upper deadband and con-
sequently the temperature that 0V corresponds to. Tables
4 and 5 give examples of how this is done using a DAC
output voltage span of V_REF and 2V_REF respectivily. Simply
write in the temperature value, in 2’s complement format,
that you want 0V to start at. For example, if you are using
the DAC A output and you want 0V to start at -40°C then
program D8h into the Internal Analog Temperature Off-
set register (address 21h). This is an 8-bit register and
thus only has a temperature offset resolution of 1°C for all
device models. Use the following formulas to determine
the value to program into the offset registers.
Negative temperatures : -
Offset Register Code(d)* = (0V Temp) + 128
*D7 of Offset Register Code is set to 1 for negative temperatures.
Example : -
Offset Register Code(d) = (-40) + 128
= 88d = 58h
Since a negative temperature has been inputted into the
equation, DB7 (MSB) of the Offset Register code is set to
a 1. Therefore 58h becomes D8h.
58h + DB7(1) ⇒ D8h
Positive temperatures : -
Offset Register Code(d) = 0V Temp
Example : -
Offset Register Code (d) = 10d = 0Ah
Table 4. Thermal Voltage Output (0V-V_REF)
O/P Voltage Default °C Max °C Sample °C
0V
-40
-128
0
0.5V
+17
-71
+56
1V
+73
-15
+113
1.12V
+87
-1
+127
1.47V
+127
+39
UDB*
1.5V
UDB*
+42
UDB*
2V
UDB*
+99
UDB*
2.25V
UDB*
+127
UDB*
* Upper deadband has been reached. DAC output is not capable of increasing.
Reference Figure 6.
ADT7316/7317/7318
0.75V
+3
-85
43
1V
+17
-71
+57
1.12V
+23
-65
+63
1.47V
+43
-45
+83
1.5V
+45
-43
+85
2V
+73
-15
+113
2.25V
+88
0
+127
2.5V
+102
+14
UDB*
2.75V
+116
+28
UDB*
3V
UDB*
+42
UDB*
3.25V
UDB*
+56
UDB*
3.5V
UDB*
+70
UDB*
3.75V
UDB*
+85
UDB*
4V
UDB*
+99
UDB*
4.25V
UDB*
+113
UDB*
4.5V
UDB*
+127
UDB*
* Upper deadband has been reached. DAC output is not capable of increasing.
Reference Figure 6.
The following equation is used to work out the various
temperatures for the corresponding 8-bit DAC output :-
8-Bit Temp = (DAC O/P ÷ 1 LSB) + ( 0V Temp)
For example, if the output is 1.5V, V_REF = 2.25 V, 8-bit
DAC has an LSB size = 2.25V/255 = 8.82x10^-3, and 0V
Temp is at -128°C then the resultant temperature works
out to be :-
(1.5 ÷8.82x10^-3) + (-128) = +42°C
The following equation is used to work out the various
temperatures for the corresponding 10-bit DAC output :-
10-Bit Temp = ((DAC O/P ÷ 1 LSB)x0.25) + ( 0V Temp)
For example, if the output is 0.4991V, V_REF = 2.25 V, 10-
bit DAC has an LSB size = 2.25V/1024 = 2.197x10^-3, and
0V Temp is at -40°C then the resultant temperature works
out to be :-
((0.4991 ÷2.197x10^-3)x0.25) + (-40) = +16.75°C
Figure 14 shows a graph of DAC output vs temperature
for a V_REF = 2.25 V.
Table 5.
O/P Voltage
0V
0.25V
0.5V
Thermal Voltage Output, (0V-2V_REF)
Default °C Max °C Sample °C
-40
-128
0
-26
-114
14
+12
-100
+28
REV. PrN
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