ADT7461ARMZ-2 ON Semiconductor, ADT7461ARMZ-2 Datasheet - Page 14

• Manufacturer Part Number: ADT7461ARMZ-2
• Description: IC SENSOR TEMP DGTL 2CH 8MSOP
• Manufacturer: ON Semiconductor

Specifications of ADT7461ARMZ-2

• 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-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

possibilities.
register without first writing to the address pointer register,
if the address pointer register is already at the correct value,
it is not possible to write data to a register without writing to
the address pointer register because the first data byte of a
write is always written to the address pointer register.
and write operations. The write address of a register must be
written to the address pointer if data is to be written to that
register, but it may not be possible to read data from that
address. The read address of a register must be written to the
address pointer before data can be read from that register.
ALERT Output
output. The ALERT output goes low whenever an
out-of-limit measurement is detected, or if the remote
temperature sensor is open circuit. It is an open-drain output
and requires a pullup to V
be wire-ORed together, so the common line goes low if one
or more of the ALERT outputs goes low.
processor, or it may be used as an SMBALERT. Slave
devices on the SMBus cannot normally signal to the bus
master that they want to talk, but the SMBALERT function
allows them to do so.
common SMBALERT line that is connected to the master.
When the SMBALERT line is pulled low by one of the
devices, the procedure shown in Figure 19 occurs.
When reading data from a register there are two
Although it is possible to read a data byte from a data
Also, some of the registers have different addresses for read
This is applicable when Pin 6 is configured as an ALERT
The ALERT output can be used as an interrupt signal to a
One or more ALERT outputs can be connected to a
1. If the ADT7461’s address pointer register value is
2. If the address pointer register is known to be at the
unknown or not the desired value, it is necessary
to set it to the correct value before data can be read
from the desired data register. This is done by
writing to the ADT7461 as before, but only the
data byte containing the register read address is
sent, since data is not to be written to the register.
This is shown in Figure 17.
A read operation is then performed consisting of
the serial bus address, R/W bit set to 1, followed
by the data byte read from the data register. This is
shown in Figure 18.
desired address, data can be read from the
corresponding data register without first writing to
the address pointer register and the bus transaction
shown in Figure 17 can be omitted.
DD
. Several ALERT outputs can
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14
Low Power Standby Mode
by set-ting Bit 6 of the configuration register. When Bit 6 is
low, the ADT7461 operates normally. When Bit 6 is high,
the ADC is inhibited, and any conversion in progress is
terminated without writing the result to the corresponding
value register.
standby mode is reduced to less than 10 mA if there is no
SMBus activity or 100 mA if there are clock and data signals
on the bus.
initiate a one-shot conversion of both channels by writing to
the one-shot register (Address 0x0F), after which the device
returns to standby. It does not matter what is written to the
one-shot register, as all data written to it is ignored. It is also
possible to write new values to the limit register while in
standby mode. If the values stored in the temperature value
registers are now outside the new limits, an ALERT is
generated even though the ADT7461 is still in standby.
The ADT7461 can be put into low power standby mode
The SMBus is still enabled. Power consumption in the
When the device is in standby mode, it is still possible to
START
MASTER
RECEIVES
SMBALERT
1. SMBALERT is pulled low.
2. Master initiates a read operation and sends the
3. The device whose ALERT output is low responds
4. If the ALERT output is low on more than one
5. Once the ADT7461 has responded to the alert
alert response address (ARA = 0001 100). This is
a general call address that must not be used as a
specific device address.
to the alert response address and the master reads
its device address. As the device address is seven
bits, an LSB of 1 is added. The address of the
device is now known and can be interrogated in
the usual way.
device, the one with the lowest device address has
priority, in accordance with normal SMBus
arbitration.
response address, it resets its ALERT output,
provided the error condition that caused the
ALERT no longer exists. If the SMBALERT line
remains low, the master sends the ARA again; this
sequence continues until all devices whose
ALERT out-puts were low have responded.
ALERT RESPONSE
MASTER SENDS
ARA AND READ
Figure 19. Use of SMBALERT
ADDRESS
COMMAND
RD
ACK
DEVICE SENDS
ITS ADDRESS
ADDRESS
DEVICE
ACK
NO
STOP