ADT7461AR-REEL7 ON Semiconductor, ADT7461AR-REEL7 Datasheet - Page 12

• Manufacturer Part Number: ADT7461AR-REEL7
• Description: IC SENSOR TEMP 2-CH 8SOIC
• Manufacturer: ON Semiconductor

Specifications of ADT7461AR-REEL7

• Rohs Status: RoHS non-compliant
• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 127°C, External Sensor
• Output Type: SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 120°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)

ADT7461
Table 8. Conversion Rate Register Codes
Code
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B to 0xFF
Limit Registers
The ADT7461 has eight limit registers: high, low, and 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 12 for address details of the limit registers and their
power-on default values.
When Pin 6 is configured as an ALERT output, the high 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.
Exceeding either the local or remote THERM limit asserts
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 may be reprogrammed
to any value after power-up (Register Address 0x21).
It is important to remember that the temperature limits data
format is the same as the temperature measurement data
format. So, if the temperature measurement uses default binary,
the temperature limits also use the binary scale. If the
temperature measurement scale is switched, however, the
temperature limits do not switch automatically. 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
and the default binary scale is being used, the limit register
value should be 0000 1010b. If the scale is switched to offset
binary, the value in the low temperature limit register should be
reprogrammed to be 0100 1010b.
Status Register
The status register is a read-only register at Address 0x02. It
Conversion/Second
0.0625
0.125
0.25
0.5
1
2
4
8
16
32
64
Reserved
Average Supply Current
μA Typ at V
121.33
128.54
131.59
146.15
169.14
233.12
347.42
638.07
252.44
417.58
816.87
DD
Rev. 3 | Page 12 of 23 | www.onsemi.com
= 5.5 V
contains status information for the ADT7461.
Bit 7 of the status register indicates the ADC is busy converting
when it is high. The other bits in this register flag the out-of-
limit temperature measurements (Bits 6 to 3 and Bits 1 to 0) and
the remote sensor open circuit (Bit 2).
If Pin 6 is configured as an ALERT output, the following 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’ d together so if any of them is high, the
ALERT interrupt latch is set and the ALERT output goes low.
Reading the status register clears the five flags, Bits 6 to 2, pro-
vided 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.
The ALERT interrupt latch is not reset by reading the 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.
When Flag 1 and/or Flag 0 are set, the THERM output goes low
to indicate 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 reset
automatically 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 hysteresis value.
When Pin 6 is configured as THERM2, only the high tempera-
ture limits are relevant. If Flag 6 and/or Flag 4 are set, the
THERM2 output goes low to indicate 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 9. Status Register Bit Assignments
Bit
7
6
5
4
3
2
1
0
1
These flags stay high until the status register is read or they are reset by POR.
Name
BUSY
LHIGH
LLOW
RHIGH
RLOW
OPEN
RTHRM
LTHRM
1
1
1
1
1
Function
1 when ADC is converting
1 when local high temperature limit is tripped
1 when local low temperature limit is tripped
1 when remote high temperature limit is tripped
1 when remote low temperature limit is tripped
1 when remote sensor is an open circuit
1 when remote THERM limit is tripped
1 when local THERM limit is tripped