ADT7421ARMZ-2RL7 ON Semiconductor, ADT7421ARMZ-2RL7 Datasheet - Page 16

• Manufacturer Part Number: ADT7421ARMZ-2RL7
• Description: IC TEMP MONITOR 8-MSOP
• Manufacturer: ON Semiconductor
• Type: Temperature Sensorr

Specifications of ADT7421ARMZ-2RL7

• 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

•
•
ADT7421 Register Details
Table 10. Status/Configuration Registers
GND
GND
Not Applicable
02
03
04
Not Applicable
22
3D
FE
FF
Read Address
inductance and reduce noise pickup, a 5−mil track
width and spacing is recommended. Provide a ground
plane under the tracks, if possible.
Try to minimize the number of copper/solder joints that
can cause thermocouple effects. Where copper/solder
joints are used, make sure that they are in both the D+
and D− path and at the same temperature.
Thermocouple effects should not be a major problem as
1°C corresponds to about 200 mV, and thermocouple
voltages are about 3 mV/°C of temperature difference.
Unless there are two thermocouples with a big
temperature differential between them, thermocouple
voltages should be much less than 200 mV.
D+
D–
Figure 16. Typical Arrangement of Signal Tracks
(Hex)
CPU THERMAL
Not Applicable
Not Applicable
09
0A
0F
22
Not Applicable
Not Applicable
Not Applicable
Write Address
2N3906
CPU
DIODE
or
(Hex)
SHIELD
Address Pointer
Status
Configuration
Conversion Rate
One−Shot
Consecutive ALERT
Device ID
Manufacturer ID
Die Revision Code
Figure 17. Typical Application Circuit
D+
D–
ADT7421
GND
THERM2
ALERT/
THERM
SDATA
SCLK
V
http://onsemi.com
DD
5MIL
5MIL
5MIL
5MIL
5MIL
5MIL
5MIL
Name
0.1mF
FAN ENABLE
16
V
DD
•
•
current sources, excessive cable or filter capacitance can
affect the measurement. When using long cables, the filter
capacitance can be reduced or removed.
Application Circuit
ADT7421, using a discrete sensor transistor connected via
a shielded, twisted pair cable. The pull−ups on SCLK,
SDATA, and ALERT are required only if they are not
provided elsewhere in the system.
TYP 10k
Because the measurement technique uses switched
Figure 17 shows a typical application circuit for the
For really long distances (up to 100 feet), use a shielded
twisted pair, such as the Belden No. 8451 microphone
cable. Connect the twisted pair to D+ and D− and the
shield to GND close to the ADT7421. Leave the remote
end of the shield unconnected to avoid ground loops.
Place a 0.1 mF bypass capacitor close to the V
extremely noisy environments, place an input filter
capacitor across D+ and D− close to the ADT7421.
This capacitance can effect the temperature
measurement, so ensure that any capacitance seen at D+
and D− is, at maximum, 2200 pF. This maximum value
includes the filter capacitance, plus any cable or stray
capacitance between the pins and the sensor transistor.
If the distance to the remote sensor is more than
8 inches, the use of twisted pair cable is recommended.
A total of 6 feet to 12 feet is needed.
W
TYP 10k
FAN CONTROL
3V TO 3.6V
CONTROLLER
CIRCUIT
W
SMBUS
0000 1000
0000 0110
0000 0001
0010 0001
0100 0001
Undefined
Undefined
Binary
Power−On Default
5V OR 12V
0x08
0x06
0x01
0x21
0x41
Hex
Decimal
DD
pin. In