Datasheet

AD7414/AD7415
Rev. F | Page 10 of 20
In the AD7415, only three of the bits are used (D7, D6, and D2)
to set the operating modes (see Table 12). D0, D1, and D3 to D5
are used for factory settings and must have zeros written to
them during normal operation.
Table 12. AD7415 Configuration Register Settings
D7 Full power-down if = 1.
D6 Bypass SDA and SCL filtering if = 0.
D2 Initiate a one-shot temperature conversion if set to 1.
The bit status is not stored; thus this bit is 0 if read.
If the AD7414/AD7415 are in power-down mode (D7 = 1), a
temperature conversion can still be initiated by the one-shot
operation. This involves a write operation to the configuration
register and setting the one-shot bit to 1 (D2 = 1), which causes
the AD7414/AD7415 to power up, perform a single conversion,
and power down again. This is a very power efficient mode.
TEMPERATURE VALUE REGISTER (ADDRESS 0X00)
The temperature value register is a 10-bit, read-only register
that stores the temperature reading from the ADC in twos
complement format. Two reads are necessary to read data from
this register. Table 13 shows the contents of the first byte to be
read, while Table 14 and Tabl e 15 show the contents of the
second byte to be read from the AD7414 and AD7415,
respectively. In Tabl e 14, D3 to D5 of the second byte are used
as flag bits and are obtained from other internal registers. They
function as follows:
ALERT_Flag: The state of this bit is the same as that of the
ALERT pin.
T
HIGH
_Flag: This flag is set to 1 when the temperature
measured goes above the T
HIGH
limit. It is reset
when the second temperature byte (Table 14) is
read. If the temperature is still greater than the
T
HIGH
limit after the read operation, the flag is
again.
T
LOW
_Flag: This flag is set to 1 when the temperature
measured goes below the T
LOW
limit. It is reset
when the second temperature byte (Table 14) is
read. If the temperature is still less than the T
LOW
limit after the read operation, the flag is set again.
The full theoretical span of the ADC is 255°C, but in practice
the temperature measurement range is limited to the operating
range of the device, −40°C to +125°C for the A grade.
Table 13. Temperature Value Register (First Read)
D15 D14 D13 D12 D11 D10 D9 D8
MSB B8 B7 B6 B5 B4 B3 B2
Table 14. AD7414 Temperature Value Register (Second Read)
D7 D6 D5 D4 D3 D2 D1 D0
B1 LSB ALERT_Flag T
HIGH
_Flag T
LOW
_Flag 0 0 0
Table 15. AD7415 Temperature Value Register (Second Read)
D7 D6 D5 D4 D3 D2 D1 D0
B1 LSB N/A N/A N/A N/A N/A N/A
AD7414 T
HIGH
REGISTER (ADDRESS 0X02)
The T
HIGH
register (see Table 16) is an 8-bit, read/write register
that stores the upper limit that activates the ALERT output.
Therefore, if the value in the temperature value register is
greater than the value in the T
HIGH
register, the ALERT pin is
activated (that is, if ALERT is enabled in the configuration
register). Because it is an 8-bit register, the temperature
resolution is 1°C.
Table 16. T
HIGH
Register
D7 D6 D5 D4 D3 D2 D1 D0
MSB B6 B5 B4 B3 B2 B1 B0
AD7414 T
LOW
REGISTER (ADDRESS 0X03)
The T
LOW
register (see Table 17) is an 8-bit read/write register
that stores the lower limit that deactivates the ALERT output.
Therefore, if the value in the temperature value register is less
than the value in the T
LOW
register, the ALERT pin is
deactivated (that is, if ALERT is enabled in the configuration
register).
Because it is an 8-bit register, the temperature resolution is 1°C.
Table 17. T
LOW
Register
D7 D6 D5 D4 D3 D2 D1 D0
MSB B6 B5 B4 B3 B2 B1 B0