ADT7408CCPZ-R2 AD [Analog Devices], ADT7408CCPZ-R2 Datasheet - Page 15

• Manufacturer Part Number: ADT7408CCPZ-R2
• Description: +-2 C Accurate, 12-Bit Digital Temperature Sensor
• Manufacturer: AD [Analog Devices]

TEMPERATURE DATA FORMAT
The values used in the temperature register and three
temperature trip point registers are in twos complement format.
The temperature register has a 12-bit resolution with 256°C
range with 1 LSB = 0.0625°C (256°C/2
temperature data in the three temperature trip point registers
(alarm upper, alarm lower, and critical) is a 10-bit format with
256°C range with 1 LSB = 0.25°C (see the bit maps in the Alarm
Temperature Lower Boundary Trip Register (Read/Write)
section, the Critical Temperature Trip Register (Read/Write)
section, and the Temperature Value Register (Read Only) section.)
Bit D12 in all these registers represents the sign bit such that
0 = positive temperature and 1 = negative temperature. In twos
complement format, the data bits are inverted and add 1 if
Bit D12 (the sign bit) is negative.
Temperature Conversion Formulas
12-Bit Temperature Data Format
where d is the 12-bit digital output in decimal.
Note that Bit D12 (the sign bit) is not included in the ADC
code, but the sign is inserted in the final result.
Table 10 tabulates some temperature results vs. digital outputs.
10-Bit Temperature Data Format
Positive Temperature = ADC Code(d)/16
Negative Temperature = (ADC Code(d) − 4096)/16 (2)
Positive Temperature = ADC Code(d)/4
Negative Temperature = (ADC Code(d) − 1024)/4
12
); see Table 10. The
(1)
(3)
(4)
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Similarly, Bit D12 (the sign bit) is not included in the ADC
code, but the sign is inserted in the final result. This ADC code
contains DB2 to DB11. DB0 to DB1 are not in this calculation.
Although one LSB of the ADC corresponds to 0.0625°C, the
ADC can theoretically measure a temperature range of 255°C
(−128°C to +127°C ). The ADT7408 is guaranteed to measure
a low value temperature limit of −55°C to a high value temperature
limit of +125°C.
Reading back the temperature from the temperature value
register requires a 2-byte read.
Designers accustomed to using a 9-bit temperature data format
can still use the ADT7408 by ignoring the last three LSBs of the
12-bit temperature value.
Table 10. 12-Bit Temperature Data Format
Digital Output (Binary)
D12 to D0
1 1100 1001 0000
1 1100 1110 0000
1 1110 0110 1111
1 1111 1111 1111
0 0000 0000 0000
0 0000 0000 0001
0 0000 1010 0000
0 0001 1001 0000
0 0011 0010 0000
0 0100 1011 0000
0 0110 0100 0000
0 0111 1101 0000
Digital Output
(Hex)
C90
CE0
E6F
FFF
000
0x001
0x0A0
0x190
0x320
0x4B0
0x640
0x7D0
Temperature
−55°C
−50°C
−25°C
−0.0625°C
0°C
+0.0625°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
ADT7408