ADM1021ARQZ ON Semiconductor, ADM1021ARQZ Datasheet - Page 12

• Manufacturer Part Number: ADM1021ARQZ
• Description: IC SENSOR TEMP DUAL3/5.5V 16QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1021ARQZ

• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 100°C, External Sensor
• Output Type: SMBus™
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

possibilities:
NOTES:
When reading data from a register there are two
1. If the ADM1021A’s address pointer register value
2. If the address pointer register is known to be
1. Although it is possible to read a data byte from a
2. Remember that the ADM1021A registers have
is unknown or not the desired value, it is first
necessary to set it to the correct value before data
can be read from the desired data register. This is
done by performing a write to the ADM1021A as
before, but only the data byte containing the
register read address is sent, because data is not to
be written to the register. This is shown in
Figure 15.
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 16.
already at the desired address, data can be read
from the corresponding data register without first
writing to the address pointer register, so Figure 15
can be omitted.
data 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; this is because the first
data byte of a write is always written to the
address pointer register.
different addresses for read 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 is not 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.
SDATA
SDATA
SCLK
SCLK
START BY
START BY
MASTER
MASTER
A6
A6
1
1
A5
A5
Figure 16. Reading Data from a Previously Selected Register
SERIAL BUS ADDRESS BYTE
SERIAL BUS ADDRESS BYTE
Figure 15. Writing to the Address Pointer Register Only
A4
A4
A3
A3
FRAME 1
FRAME 1
A2
A2
A1
A1
http://onsemi.com
A0
A0
ADM1021A
R/W
R/W
12
ADM1021A
ADM1021A
ACK. BY
ACK. BY
9
9
ALERT Output
measurement is detected, or if the remote temperature sensor
is open−circuit. It is an open drain and requires a 10 kW
pullup to V
together so the common line goes low if one or more of the
ALERT outputs goes low.
processor, or it can be used as an SMBALERT. Slave devices
on the SMBus cannot normally signal to the master that they
want to talk, but the SMBALERT function allows them to do
so.
SMBALERT line connected to the master. When the
SMBALERT line is pulled low by one of the devices, the
following procedure occurs, as shown in Figure 17.
The ALERT output goes low whenever an out−of−limit
The ALERT output can be used as an interrupt signal to a
One or more ALERT outputs are connected to a common
MASTER
RECEIVES
SMBALERT
D7
D7
1
1
START ALERT RESPONSE ADDRESS RD ACK
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 more than one device’s ALERT output is low,
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. The address of the device is
now known and it can be interrogated in the usual
way.
the one with the lowest device address has priority,
in accordance with normal SMBus arbitration.
D6
D6
DD
FRAME 2 DATA BYTE FROM ADM1021A
ADDRESS POINTER REGISTER BYTE
Figure 17. Use of SMBALERT
. Several ALERT outputs can be wire−ANDed
D5
D5
MASTER SENDS
ARA AND READ
COMMAND
D4
D4
FRAME 2
D3
D3
D2
D2
D1
D1
DEVICE SENDS
ITS ADDRESS
ADDRESS
D0
D0
DEVICE
BY MASTER
ADM1021A
NO ACK.
ACK. BY
9
9
ACK
NO
STOP BY
STOP BY
STOP
MASTER
MASTER