ADT7421ARMZ-RL7 ON Semiconductor, ADT7421ARMZ-RL7 Datasheet - Page 8

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

Specifications of ADT7421ARMZ-RL7

• 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

time. Switching the range likewise switches the data format.
The next temperature result following the switching is
reported back to the register in the new format. However, the
contents of the limit registers do not change. It is up to the
user to ensure that when the data format changes, the limit
registers are reprogrammed as necessary. More information
on this is found in the Limit Registers section.
ADT7421 Registers
registers store the results of remote and local temperature
measurements, high and low temperature limits, and
configure and control the device. See the section through the
Consecutive ALERT Register section of this data sheet for
more information on the ADT7421 registers. Additional
details are shown in Table 3 through Table 7. The entire
register map is available in Table 8.
Address Pointer Register
it require, an address because the first byte of every write
operation is automatically written to this register. The data
in this first byte always contains the address of another
register on the ADT7421 that is stored in the address pointer
register. It is to this register address that the second byte of
a write operation is written, or to which a subsequent read
operation is performed.
is 0x00. Therefore, if a read operation is performed
immediately after power−on, without first writing to the
address pointer, the value of the local temperature is returned
because its register address is 0x00.
Temperature Value Registers
local and remote temperature measurements. These
registers can only be written to by the ADC and can be read
by the user over the SMBus. The local temperature value
register is at Address 0x00.
Address 0x01, with the low byte register at Address 0x10.
The power−on default for all three registers is 0x00.
Configuration Register
Address 0x09 at write. Its power−on default is 0x08. Only
five bits of the configuration register are used. Bit 0, Bit 1,
and Bit 3 are reserved; the user does not write to them.
output. If Bit 7 is 0, the ALERT output is enabled. This is the
power−on default. If Bit 7 is set to 1, the ALERT output is
disabled. This applies only if Pin 6 is configured as ALERT.
If Pin 6 is configured as THERM2, then the value of Bit 7
has no effect.
is in operating mode with ADC converting. If Bit 6 is set to
The user can switch between measurement ranges at any
The ADT7421 contains 22, 8−bit registers in total. These
The address pointer register itself does not have, nor does
The power−on default value of the address pointer register
The ADT7421 has three registers to store the results of
The external temperature value high byte register is at
The configuration register is Address 0x03 at read and
Bit 7 of the configuration register masks the ALERT
If Bit 6 is set to 0, which is power−on default, the device
http://onsemi.com
8
1, the device is in standby mode and the ADC does not
convert. The SMBus does, however, remain active in standby
mode; therefore, values can be read from or written to the
ADT7421 via the SMBus. The ALERT and THERM outputs
are also active in standby mode. Changes made to the
registers in standby mode that affect the THERM or ALERT
outputs cause these signals to be updated.
to zero beta cancellation is set on. If using a discrete
transistor as the sensing element, Beta Cancellation should
be switched off by setting Bit 4 to 1.
ADT7421. If Bit 5 is 0 (default), then Pin 6 is configured as
an ALERT output. If Bit 5 is 1, then Pin 6 is configured as
a THERM2 output. Bit 7, the ALERT mask bit, is only active
when Pin 6 is configured as an ALERT output. If Pin 6 is set
up as a THERM2 output, then Bit 7 has no effect.
0 (default value), the temperature measurement range is set
between 0°C to +125°C. Setting Bit 2 to 1 sets the
measurement range to the extended temperature range
(−40°C to +125°C).
Table 3. Configuration Register Bit Assignments
Conversion Rate Register
Address 0x0A at write. The lowest four bits of this register
are used to program the conversion rate. For example, a
conversion rate of five conversions per second means that
beginning at 200 ms intervals, the device performs a
conversion on the internal and the external temperature
channels.
back over the SMBus. The higher four bits of this register are
unused and must be set to 0. The default value of this register
is 0x06, giving a rate of 4 conversions per second. Use of
slower conversion times greatly reduces the device power
consumption.
Bit
Bit 4 switches beta cancellation on and off. With Bit 4 set
Bit 5 determines the configuration of Pin 6 on the
Bit 2 sets the temperature measurement range. If Bit 2 is
The conversion rate register is Address 0x04 at read and
The conversion rate register can be written to and read
7
6
5
4
3
2
1
0
MASK1
RUN/STOP
ALERT/
THERM2
Beta Enable
Reserved
Temperature
Range Select
Reserved
Reserved
Name
0 = ALERT Enabled
1 = ALERT Masked
0 = Run
1 = Standby
0 = ALERT
1 = THERM2
0 = Beta Compensation
On
1 = Beta Compensation
Off
Reserved
0 = 0°C to 125°C
1 = Extended Range
Reserved
Reserved
Function
Power−On
Default
0
0
0
0
1
0
0
0