ADT7420
Preliminary Technical Data
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 hysterisis. 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)
Default
Bit
Value Type Name Description
[0:3] 0000
R
Unused Reads back 0.
4
0
5
0
6
0
7
1
R
TLOW
This bit is set to 1 when the temperature goes below the TLOW 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 TLOW + THYST registers.
R
THIGH
This bit is set to 1 when the temperature goes above the THIGH 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 THIGH − THYST registers.
R
TCRIT
This bit is set to 1 when the temperature goes above the TCRIT 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 TCRIT − THYST registers.
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 one-shot bits.
Table 11. Configuration Register (Register Address 0x03)
Default
Bit Value Type Name
Description
[0:1] 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.
20
R/W CT pin polarity This bit selects the output polarity of the CT pin.
0 = active low.
1 = active high.
30
R/W INT pin polarity This bit selects the output polarity of the INT pin.
0 = active low.
1 = active high.
40
R/W INT/CT mode This bit selects between comparator mode and interrupt mode.
0 = interrupt mode
1 = comparator mode
[5:6] 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.
70
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.
Rev. PrA | Page 14 of 4