ADT7420 Analog Devices, ADT7420 Datasheet - Page 12

• Manufacturer Part Number: ADT7420
• Description: 16-Bit Digital I2C Temperature Sensor
• Manufacturer: Analog Devices

ADT7420
TEMPERATURE DATA FORMAT
One LSB of the ADC corresponds to 0.0625°C in 13-bit mode
or 0.0078°C in 16-bit mode. The ADC can theoretically
measure a temperature range of 255°C, but the ADT7420 is
guaranteed to measure a low value temperature limit of −40°C
to a high value temperature limit of +150°C. The temperature
measurement result is stored in the 16-bit temperature value
register and is compared with the high temperature limits
stored in the T
register. It is also compared with the low temperature limit
stored in the T
Temperature data in the temperature value register, the T
setpoint register, the T
setpoint register are represented by a 13-bit twos complement
word. The MSB is the temperature sign bit. The three LSBs, Bit 0
to Bit 2, on power-up, are not part of the temperature conver-
sion result and are flag bits for T
shows the 13-bit temperature data format without Bit 0 to Bit 2.
The number of bits in the temperature data-word can be extended
to 16 bits, twos complement, by setting Bit 7 to 1 in the confi-
guration register (Register Address 0x03). When using a 16-bit
temperature data value, Bit 0 to Bit 2 are not used as flag bits
and are, instead, the LSB bits of the temperature value. The
power-on default setting has a 13-bit temperature data value.
Reading back the temperature from the temperature value register
requires a 2-byte read. Designers that use a 9-bit temperature
data format can still use the ADT7420 by ignoring the last four
LSBs of the 13-bit temperature value. These four LSBs are Bit 6
to Bit 3 in Table 5.
Table 5. 13-Bit Temperature Data Format
Temperature
−40°C
−25°C
−0.0625°C
0°C
+0.0625°C
+25°C
+105°C
+125°C
+150°C
CRIT
LOW
Digital Output
(Binary) Bits[15:3]
1 1101 1000 0000
1 1110 0111 0000
1 1111 1111 1111
0 0000 0000 0000
0 0000 0000 0001
0 0001 1001 0000
0 0110 1001 0000
0 0111 1101 0000
0 1001 0110 0000
setpoint register.
setpoint register and the T
HIGH
setpoint register, and the T
CRIT
, T
HIGH
, and T
Digital Output (Hex)
0x1D80
0x1E70
0x1FFF
0x000
0x001
0x190
0x690
0x7D0
0x960
HIGH
LOW
setpoint
. Table 5
LOW
CRIT
Rev. PrA | Page 12 of 2
TEMPERATURE CONVERSION FORMULAS
16-Bit Temperature Data Format
where ADC Code uses all 16 bits of the data byte, including the
sign bit.
where Bit 15 (sign bit) is removed from the ADC code.
13-Bit Temperature Data Format
where ADC Code uses the first 13 MSBs of the data byte,
including the sign bit.
where Bit 15 (sign bit) is removed from the ADC code.
10-Bit Temperature Data Format
where ADC Code uses all 10 bits of the data byte, including the
sign bit.
where Bit 9 (sign bit) is removed from the ADC code.
9-Bit Temperature Data Format
where ADC Code uses all nine bits of the data byte, including
the sign bit.
where Bit 8 (sign bit) is removed from the ADC code.
Positive Temperature = ADC Code (dec)/128
Negative Temperature = (ADC Code (dec) – 65,536)/128
Negative Temperature = (ADC Code (dec) – 32,768)/128
Positive Temperature = ADC Code (dec)/16
Negative Temperature = (ADC Code (dec) − 8192)/16
Negative Temperature = (ADC Code (dec) – 4096)/16
Positive Temperature = ADC Code (dec)/2
Negative Temperature = (ADC Code (dec) − 1024)/2
Negative Temperature = (ADC Code (dec) − 512)/2
Positive Temperature = ADC Code (dec)
Negative Temperature = ADC Code (dec) − 512
Negative Temperature = ADC Code (dec) − 256
Preliminary Technical Data
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