Datasheet

ADT7420 Data Sheet
Rev. 0 | Page 14 of 24
STATUS REGISTER
This 8-bit read-only register reflects the status of the overtempera-
ture 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 temperature 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.
CONFIGURATION REGISTER
This 8-bit read/write register stores various configuration modes
for the ADT7420, including shutdown, overtemperature and
undertemperature interrupts, one-shot, continuous conversion,
interrupt pins polarity, and overtemperature fault queues.
Table 10. Status Register (Register Address 0x02)
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 setpoint T
LOW
+ T
HYST
registers.
5 0 R T
HIGH
This bit is set to 1 when the temperature goes above the T
HIGH
temperature limit. The bit clears to 0
when the status register is read and/or when the temperature measured goes back below the limit
set in the setpoint T
HIGH
− T
HYST
registers.
6 0 R T
CRIT
This bit is set to 1 when the temperature goes above the T
CRIT
temperature limit. This bit clears to 0
when the status register is read and/or when the temperature measured goes back below the limit
set in the setpoint T
CRIT
− T
HYST
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.
Table 11. Configuration Register (Register Address 0x03)
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 ADT7420.
00 = continuous conversion (default). When one conversion is finished, the ADT7420 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.