ADM1023ARQZ ON Semiconductor, ADM1023ARQZ Datasheet - Page 14

• Manufacturer Part Number: ADM1023ARQZ
• Description: IC SENSOR TEMP DUAL PREC 16-QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1023ARQZ

• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 120°C, External Sensor
• Output Type: SMBus™
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: 0°C ~ 120°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 1 C, +/- 3 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Maximum Operating Temperature: + 120 C
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Low Power Standby Modes
using hardware or software, that is, by taking the STBY
input low or by setting Bit 6 of the configuration register.
When STBY is high or Bit 6 is low, the ADM1023 operates
normally. When STBY is pulled low or 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.
STBY is low, conversions are completely inhibited. When
Bit 6 is set, but STBY is high, a one−shot conversion of both
channels can be initiated by writing any data value to the
one−shot register (Address 0x0F).
Sensor Fault Detection
detects if the external sensor diode is open−circuit. This is a
simple voltage comparator that trips if the voltage at D+
exceeds V
is checked when a conversion is initiated and sets Bit 2 of the
status register if a fault is detected.
measuring range, for example, due to the diode being
short−circuited, the ADC outputs –128°C (1000 0000 000).
Because the normal operating temperature range of the
device extends only down to 0°C, this output code is never
seen in normal operation and can be interpreted as a fault
condition.
upon, competitive devices that output 0 if the external sensor
goes short−circuit. Unlike the ADM1023, these other
devices can misinterpret a genuine 0°C measurement as a
fault condition.
shorted out, the resulting ALERT may be cleared by writing
0x80 (−128°C) to the low limit register.
Applications
Factors Affecting Accuracy, Remote Sensing Diode
transistors built into processors or with discrete transistors.
Substrate transistors are generally PNP types with the
The ADM1023 can be put into a low power standby mode
The SMBus is still enabled. Power consumption in the
These two modes are similar but not identical. When
The ADM1023 has a fault detector at the D+ input that
If the remote sensor voltage falls below the normal
In this respect, the ADM1023 differs from, and improves
If the external diode channel is not being used and is
The ADM1023 is designed to work with substrate
4. If more than one device’s ALERT output is low,
5. Once the ADM1023 has responded to the ARA, it
the one with the lowest device address has priority,
in accordance with normal SMBus arbitration.
resets its ALERT output, provided that the error
condition that caused the ALERT no longer exists.
If the SMBALERT line remains low, the master
sends ARA again, and so on until all devices
whose ALERT outputs were low have responded.
CC
– 1.0 V (typical). The output of this comparator
http://onsemi.com
ADM1023
14
collector connected to the substrate. Discrete types can be
either PNP or NPN, connected as a diode (base−shorted to
collector). If an NPN transistor is used, the collector and
base are connected to D+ and the emitter to D−. If a PNP
transistor is used, the collector and base are connected to D−
and the emitter to D+.
discrete transistor is used, the best accuracy is achieved by
choosing devices according to the following criteria:
•
•
•
•
SOT−23 packages are suitable devices to use.
Thermal Inertia and Self−Heating
sensing diode and/or the internal temperature sensor being
at the same temperature as that being measured, and a
number of factors can affect this. Ideally, the sensor should
be in good thermal contact with the part of the system being
measured, such as the processor, for example. If it is not in
good thermal contact, the thermal inertia caused by the mass
of the sensor causes a lag in the response of the sensor to a
temperature change. With the remote sensor, this should not
be a problem, as it will be either a substrate transistor in the
processor or a small package device, such as SOT−23,
placed in close proximity to it.
processor and monitors only the general ambient
temperature around the package. The thermal time constant
of the QSOP−16 package is about 10 seconds.
connection to the printed circuit board. Therefore, the
temperature rise due to self−heating is negligible.
Layout Considerations
the ADM1023 is measuring very small voltages from the
remote sensor; therefore, care must be taken to minimize
noise induced at the sensor inputs. The following
precautions are needed:
•
•
The user has no choice with substrate transistors, but if a
Transistors such as 2N3904, 2N3906, or equivalents in
Accuracy depends on the temperature of the remote
The on−chip sensor, however, is often remote from the
In practice, the package has electrical, and hence thermal,
Digital boards can be electrically noisy environments, and
Base emitter voltage greater than 0.25 V at 6 mA, at the
highest operating temperature.
Base emitter voltage less than 0.95 V at 100 mA, at the
lowest operating temperature.
Base resistance less than 100 W.
Small variation in h
indicates tight control of V
Place the ADM1023 as close as possible to the remote
sensing diode. Provided that the worst noise sources,
such as clock generators, data/address buses, and CRTs,
are avoided, this distance can be 4 to 8 inches.
Route the D+ and D− tracks close together, in parallel,
with grounded guard tracks on each side. Provide a
ground plane under the tracks if possible (see Figure 19).
fe
(approximately 50 to 150), which
BE
characteristics.