ADT7421ARMZ-2RL ON Semiconductor, ADT7421ARMZ-2RL Datasheet - Page 9

• Manufacturer Part Number: ADT7421ARMZ-2RL
• Description: IC TEMP MONITOR 8-MSOP
• Manufacturer: ON Semiconductor
• Type: Temperature Sensorr

Specifications of ADT7421ARMZ-2RL

• Input Type: Logic
• Output Type: Logic
• Interface: 2-Wire SMBus
• Current - Supply: 4mA
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Full Temp Accuracy: +/- 2.75 C, +/- 3.25 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 4. Conversion Rate Register Codes
Limit Registers
THERM temperature limits for both local and remote
temperature measurements. The remote temperature high
and low limits span two registers each, to contain an upper
and lower byte for each limit. There is also a THERM
hysteresis register. All limit registers can be written to, and
read back over, the SMBus. See Table 8 for details of the
limit register addresses and their power−on default values.
limit registers perform a > comparison, while the low limit
registers perform a ≤ comparison. For example, if the high
limit register is programmed with 80°C, then measuring 81°C
results in an out−of−limit condition, setting a flag in the status
register. If the low limit register is programmed with 0°C,
measuring 0°C or lower results in an out−of−limit condition.
THERM low. When Pin 6 is configured as THERM2,
exceeding either the local or remote high limit asserts
THERM2 low. A default hysteresis value of 10°C is provided
that applies to both THERM channels. This hysteresis value
can be reprogrammed to any value after powerup (Register
Address 0x21).
format is the same as the temperature measurement data
format. Therefore, if the temperature measurement uses
default binary, then the temperature limits also use the binary
scale. If the temperature measurement scale is switched,
however, the temperature limits do not automatically switch.
The user must reprogram the limit registers to the desired
value in the correct data format. For example, if the remote
low limit is set at 10°C with the default binary scale, the limit
register value is 0000 1010b. If the scale is switched to offset
binary, the value in the low temperature limit register needs
to be reprogrammed to 0100 1010b.
Status Register
It contains status information for the ADT7421.
The ADT7421 has eight limit registers: high, low, and
When Pin 6 is configured as an ALERT output, the high
Exceeding either the local or remote THERM limit asserts
It is important to remember that the temperature limits data
The status register is a read−only register at Address 0x02.
0x0B to 0xFF
Code
0x0A
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
Conversion/Second
4 (Default)
Reserved
0.0625
0.125
0.25
0.5
10
20
36
1
2
5
Time (Secs)
500 m
250 m
200 m
100 m
50 m
27 m
16
8
4
2
1
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9
ADC is busy converting. The other bits in this register flag the
out−of−limit temperature measurements (Bit 6 to Bit 3, and
Bit 1 to Bit 0) and the remote sensor open circuit (Bit 2).
applies: If the local temperature measurement exceeds its
limits, Bit 6 (high limit) or Bit 5 (low limit) of the status
register asserts to flag this condition. If the remote
temperature measurement exceeds its limits, then Bit 4 (high
limit) or Bit 3 (low limit) asserts. Bit 2 asserts to flag an open
circuit condition on the remote sensor. These five flags are
NOR’ed together, so if any of them is high, the ALERT
interrupt latch is set and the ALERT output goes low.
Bit 2, provided the error conditions causing the flags to be
set have gone away. A flag bit can be reset only if the
corresponding value register contains an in−limit
measurement or if the sensor is good.
status register. It resets when the ALERT output has been
serviced by the master reading the device address, provided
the error condition has gone away and the status register flag
bits are reset.
goes low to indicate that the temperature measurements are
outside the programmed limits. The THERM output does
not need to be reset, unlike the ALERT output. Once the
measurements are within the limits, the corresponding status
register bits are automatically reset and the THERM output
goes high. The user may add hysteresis by programming
Register 0x21. The THERM output is reset only when the
temperature falls to limit value minus the hysteresis value.
temperature limits are relevant. If Flag 6 and/or Flag 4 are
set, the THERM2 output goes low to indicate that the
temperature measurements are outside the programmed
limits. Flag 5 and Flag 3 have no effect on THERM2. The
behavior of THERM2 is otherwise the same as THERM.
Table 5. Status Register Bit Assignments
Bit
*These flags stay high until the status register is read or they are
When Bit 7 of the status register is high, it indicates that the
If Pin 6 is configured as an ALERT output, the following
Reading the status register clears the five flags, Bit 6 to
The ALERT interrupt latch is not reset by reading the
When Flag 1 and/or Flag 0 are set, the THERM output
When Pin 6 is configured as THERM2, only the high
7
6
5
4
3
2
1
0
reset by POR unless Pin 6 is configured as THERM2. Then,
only Bit 2 remains high until the status register is read or is reset
by POR.
BUSY
LHIGH*
LLOW*
RHIGH*
RLOW*
OPEN*
RTHRM
LTHRM
Name
1 when ADC Converting
1 when Local High Temperature Limit Tripped
1 when Local Low Temperature Limit Tripped
1 when Remote High Temperature Limit
Tripped
1 when Remote Low Temperature Limit
Tripped
1 when Remote Sensor Open Circuit
1 when Remote THERM Limit Tripped
1 when Local THERM Limit Tripped
Function