ADT7420

Preliminary Technical Data

Rev. PrA | Page 14 of 4

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

CONFIGURATION REGISTER

RDY bit is reset after a write to the operation mode bits.

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

[0:3]

0000

R

Unused

Reads back 0.

4

0

R

T

LOW

This bit is set to 1 when the temperature goes below the T

when the status register is read and/or when the temperature measured goes back above the limit

set in the setpoint T

5

0

R

T

HIGH

This bit is set to 1 when the temperature goes above the T

when the status register is read and/or when the temperature measured goes back below the limit

set in the setpoint T

6

0

R

T

CRIT

This bit is set to 1 when the temperature goes above the T

when the status register is read and/or when the temperature measured goes back below the limit

set in the setpoint T

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 one-shot bits.

Table 11. Configuration Register (Register Address 0x03)

Bit

Default

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.

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

[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.

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.