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ADT7311WTRZ-RL7

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P25
ADT7311 Data Sheet
Rev. 0 | Page 12 of 24
TEMPERATURE DATA FORMAT
One LSB of the ADC corresponds to 0.0625°C in 13-bit mode.
The ADC can theoretically measure a temperature range of
255°C, but the ADT7311 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
CRIT
setpoint register and
the T
HIGH
setpoint register. It is also compared with the low
temperature limit stored in the T
LOW
setpoint register.
Temperature data in the temperature value register, the T
CRIT
setpoint register, the T
HIGH
setpoint register, and the T
LOW
setpoint register is 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
conversion result and are flag bits for T
CRIT
, T
HIGH
, and T
LOW
.
Tabl e 5 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 configuration register (Register Address 0x01). 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 ADT7311 by ignoring the last four
LSBs of the 13-bit temperature value. These four LSBs are Bit 3
to Bit 6 in Tabl e 5.
Table 5. 13-Bit Temperature Data Format
Temperature
Digital Output
(Binary) Bits[15:3]
Digital
Output (Hex)
−40°C 1 1100 1110 0000 0x1CE0
−25°C 1 1110 0111 0000 0x1E70
−0.0625°C 1 1111 1111 1111 0x1FFF
0°C 0 0000 0000 0000 0x000
+0.0625°C 0 0000 0000 0001 0x001
+25°C 0 0001 1001 0000 0x190
+50°C 0 0011 0010 0000 0x320
+125°C 0 0111 1101 0000 0x7D0
+150°C 0 1001 0110 0000 0x960
TEMPERATURE CONVERSION FORMULAS
16-Bit Temperature Data Format
Positive Temperature = ADC Code(dec)/128
Negative Temperature = (ADC Code(dec) – 65,536)/128
where ADC Code uses all 16 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code(dec) – 32,768)/128
where the MSB is removed from the ADC code.
13-Bit Temperature Data Format
Positive Temperature = ADC Code(dec)/16
Negative Temperature = (ADC Code(dec) − 8192)/16
where ADC Code uses all 13 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code(dec) – 4096)/16
where the MSB is removed from the ADC code.
10-Bit Temperature Data Format
Positive Temperature = ADC Code(dec)/2
Negative Temperature = (ADC Code(dec) – 1024)/2
where ADC Code uses all 10 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code(dec) – 512)/2
where the MSB is removed from the ADC code.
9-Bit Temperature Data Format
Positive Temperature = ADC Code(dec)
Negative Temperature = ADC Code(dec) – 512
where ADC Code uses all nine bits of the data byte, including
the sign bit.
Negative Temperature = ADC Code(dec) – 256
where the MSB is removed from the ADC code.
Data Sheet ADT7311
Rev. 0 | Page 13 of 24
REGISTERS
The ADT7311 contains eight registers:
• A status register
• A configuration register
• Five temperature registers
• An ID register
The status register, temperature value register, and the ID
register are read-only.
Table 6. ADT7311 Registers
Register
Address
Description
Power-On
Default
0x00 Status 0x80
0x01 Configuration 0x00
0x02 Temperature value 0x0000
0x03 ID 0xC3
0x04 T
CRIT
setpoint 0x4980 (147°C)
0x05 T
HYST
setpoint 0x05 (5°C)
0x06 T
HIGH
setpoint 0x2000 (64°C)
0x07 T
LOW
setpoint 0x0500 (10°C)
STATUS REGISTER
This 8-bit read-only register (Register Address 0x00) reflects the
status of the overtemperature and undertemperature interrupts
that can cause the CT and INT pins to go active. It also reflects the
status of a temperature conversion operation. The interrupt flags
in this register are reset by a read operation to the status register
and/or when the temperature value returns within the tempera-
ture limits including hysteresis. The
RDY
bit is reset after a read
from the temperature value register. In one-shot and 1 SPS modes,
the
RDY
bit is reset after a write to the operation mode bits.
Table 7. Status Register (Register Address 0x00)
Bit
Default
Value Type Name Description
[3:0] 0000 R Unused Reads back 0.
4 0 R T
LOW
This bit is set to 1 when the temperature goes below the T
LOW
temperature limit. The bit clears to 0
when the status register is read and/or when the temperature measured goes back above the limit
set in the T
LOW
+ T
HYST
setpoint registers.
5 0 R T
HIGH
This bit is set to 1 when the temperature rises above the T
HIGH
temperature limit. The bit clears to 0
when the status register is read and/or when the temperature measured drops below the limit set
in the T
HIGH
− T
HYST
setpoint registers.
6 0 R T
CRIT
This bit is set to 1 when the temperature rises above the T
CRIT
temperature limit. This bit clears to 0
when the status register is read and/or when the temperature measured drops below the limit set
in the T
CRIT
− T
HYST
setpoint registers.
7 1 R
RDY
This bit goes low when the temperature conversion result is written into the temperature value
register. It is reset to 1 when the temperature value register is read. In one-shot and 1 SPS modes,
this bit is reset after a write to the operation mode bits.
ADT7311 Data Sheet
Rev. 0 | Page 14 of 24
CONFIGURATION REGISTER
This 8-bit read/write register (Register Address 0x01) stores various
configuration modes for the ADT7311, including shutdown,
overtemperature and undertemperature interrupts, one-shot,
continuous conversion, interrupt pins polarity, and
overtemperature fault queues.
Table 8. Configuration Register (Register Address 0x01)
Bit
Default
Value Type Name Description
[1:0] 00
R/W
Fault queue
These two bits set the number of undertemperature/overtemperature faults that can
occur before setting the INT and CT pins. This helps to avoid false triggering due to
temperature noise.
00 = 1 fault (default).
01 = 2 faults.
10 = 3 faults.
11 = 4 faults.
2 0
R/W
CT pin polarity This bit selects the output polarity of the CT pin.
0 = active low.
1 = active high.
3 0
R/W
INT pin polarity This bit selects the output polarity of the INT pin.
0 = active low.
1 = active high.
4 0
R/W
INT/CT mode This bit selects between comparator mode and interrupt mode.
0 = interrupt mode.
1 = comparator mode.
[6:5] 00
R/W
Operation mode These two bits set the operational mode for the ADT7311.
00 = continuous conversion (default). When one conversion is finished, the ADT7311
starts another.
01 = one shot. Conversion time is typically 240 ms.
10 = 1 SPS mode. Conversion time is typically 60 ms. This operational mode reduces the
average current consumption.
11 = shutdown. All circuitry except interface circuitry is powered down.
7 0
R/W
Resolution This bit sets up the resolution of the ADC when converting.
0 = 13-bit resolution. Sign bit + 12 bits gives a temperature resolution of 0.0625°C.
1 = 16-bit resolution. Sign bit + 15 bits gives a temperature resolution of 0.0078°C.
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ADT7311WTRZ-RL7

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Analog Devices Inc.
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SENSOR DIGITAL -40C-150C 8SOIC
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