ADM1021AARQ-REEL ON Semiconductor, ADM1021AARQ-REEL Datasheet - Page 8

• Manufacturer Part Number: ADM1021AARQ-REEL
• Description: IC SENSOR TEMP DUAL3/5.5V 16QSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1021AARQ-REEL

• Rohs Status: RoHS non-compliant
• 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

operating currents of I and N × I. The resulting waveform is
passed through a 65 kHz low−pass filter to remove noise,
and then to a chopper−stabilized amplifier that performs the
functions of amplification and rectification of the waveform
to produce a dc voltage proportional to DV
is measured by the ADC to give a temperature output in
8−bit, twos complement format. To reduce the effects of
noise further, digital filtering is performed by averaging the
results of 16 measurement cycles.
temperature sensor is performed in a similar manner.
Differences Between the ADM1021 and the ADM1021A
the ADM1021, there are some differences between the two
devices. Below is a summary of these differences and
reasons for the changes.
To measure DV
Signal conditioning and measurement of the internal
Although the ADM1021A is pin−for−pin compatible with
1. The ADM1021A forces a larger current through
2. As a result of the greater remote sensor source
3. The temperature measurement range of the
4. The power−on reset values of the remote and local
5. The four MSBs of the revision register can be used
6. The power−on default value of the address pointer
7. Setting the mask bit (Bit 7 Config Reg) on the
the remote temperature sensing diode, typically
205 mA vs. 90 mA for the ADM1021. The primary
reason for this is to improve the noise immunity of
the part.
current, the operating current of the ADM1021A is
higher than that of the ADM1021, typically
205 mA vs. 160 mA.
ADM1021A is 0°C to 127°C, compared with
−128°C to +127°C for the ADM1021. As a result,
the ADM1021 should be used if negative
temperature measurement is required.
temperature values are −128°C in the ADM1021A
as compared to 0°C in the ADM1021. As the part
is powered up converting (except when the part is
in standby mode, that is, Pin 15 is pulled low), the
part measures the actual values of remote and local
temperature and writes these to the registers.
to identify the part. The ADM1021 revision register
reads 0x0x, and the ADM1021A reads 0x3x.
register is undefined in the ADM1021A and is
equal to 0x00 in the ADM1021. As a result, a
value must be written to the address pointer
register before a read is performed in the
ADM1021A. The ADM1021 is capable of reading
back local temperature without writing to the
address pointer register, as it defaulted to the local
temperature measurement register at powerup.
ADM1021A masks current and future ALERTs.
On the ADM1021, the mask bit, masks only
ALERTs. Any current ALERT has to be cleared
using an ARA.
BE
, the sensor is switched between
BE
. This voltage
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ADM1021A
8
Temperature Data Format
theoretically measure from −128°C to +127°C, although the
device does not measure temperatures below 0°C; therefore,
the actual range is 0°C to 127°C. The temperature data
format is shown in Table 1.
measurements are stored in the local and remote temperature
value registers and are compared with limits programmed
into the local and remote high and low limit registers.
Registers
store the results of remote and local temperature
measurements, and high and low temperature limits, and to
configure and control the device. A description of these
registers follows, and further details are given in Table 2 to
Table 4. It should be noted that the ADM1021A’s registers
are dual port and have different addresses for read and write
operations. Attempting to write to a read address, or to read
from a write address, produces an invalid result. Register
addresses above 0x0F are reserved for future use or used for
factory test purposes and should not be written to.
Address Pointer Register
require an address, because it is the register to which the first
data byte of every write operation is written automatically.
This data byte is an address pointer that sets up one of the
other registers for the second byte of the write operation or
for a subsequent read operation.
Value Registers
local and remote temperature measurements. These registers
are written to by the ADC and can only be read over the
SMBus.
Status Register
ADC is busy converting. Bit 5 to Bit 3 are flags that indicate
the results of the limit comparisons.
above the corresponding high temperature limit or below the
Table 1. Temperature Data Format
One LSB of the ADC corresponds to 1°C so the ADC can
The results of the local and remote temperature
The ADM1021A contains nine registers that are used to
The address pointer register does not have and does not
The ADM1021A has two registers to store the results of
Bit 7 of the status register indicates when it is high that the
If the local and/or remote temperature measurement is
Temperature (5C)
100
125
127
10
25
50
75
0
1
Digital Output
0 000 0000
0 000 0001
0 000 1010
0 001 1001
0 011 0010
0 100 1011
0 110 0100
0 111 1101
0 111 1111