ASC7531A ETC2 [List of Unclassifed Manufacturers], ASC7531A Datasheet - Page 5

• Manufacturer Part Number: ASC7531A
• Description: LOW-VOLTAGE 1-WIRE DIGITAL TEMPERATURE SENSOR AND VOLTAGE MONITOR
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

Values that would represent temperatures below -273.15°C (0
K or absolute zero) are reserved and are not be returned
except as specifically noted.
For the aSC7531 the required resolution is 0.125°C. Bits [2:0]
will be defined but they are beyond the required resolution.
The sign bit will indicate a negative temperature except when
reporting an error condition (see
A to D Converter Resolution and Mapping
The mapping of the A-D converter bit values is a two’s
complement representation with the binary point between bits
5 and 6 of the 16-bit data word. Bit 15 is the sign, bits 14
through 6 are integer temperature in degrees, bits 5 down to
3 are the fractional part with 0.125°C as the LSB. The lowest
3 bits are set to zero.
Temperature Inputs
The aSC7531A has an internal thermal sensor plus an
external sensor using a remote diode. The remote sensor is
calibrated for a 2N3904 NPN transistor that has a non-
ideality (η) factor of approximately 1.0046. Use of the remote
diode is discussed in the Applications Information section.
The aSC7531B also has an internal thermal sensor plus an
external sensor using a remote diode however the remote
sensor is calibrated for an Intel CPU (Pentium 4, 65nM) that
has a non-ideality (η) factor of approximately 1.009. Use of
the remote diode is discussed in the Applications Information
section.
It is recommended that the actual transistor type and
manufacturers chosen for the remote sensor be
characterized for non-ideality as part of system qualification.
Sensor Error Condition
The aSC7531 has the capability to detect and report open or
shorted external diode inputs per Sensor Error Condition.
When an error or failure condition is detected, the sensor
device must return a large negative value in response to
either the GetIntTemp() or GetExtTemp() command. In this
manner software is provided with a means to determine
whether or not the sensor is working normally and that the
data returned is good.
© Andigilog, Inc. 2006
Sign
15
14
13
Integer Temperature 0°C to 512°C
Sensor Error
12
11
Condition).
Figure 2. Temperature Reading
10
9
www.andigilog.com
8
- 5 -
7
Temperature
80°C
79.875°C
1°C
0°C
-1°C
-5°C
The aSC7531 will write one of the values from the table
below to appropriate memory locations for GetIntTemp()
and/or GetExtTemp().
The aSC7531 uses the OEM defined values of 0x8102
(open) and 0x8103 (short) rather than the generic errors
defined for codes 0x8000 to 0x8003.
Voltage Data
Accuracy and Resolution
The aSC7531 measures the following voltages:
Voltage Data Format
The data format used to report voltage allows values in the
range of +/-32V. The voltage sensor data is returned as a 16-
bit 2’s complement binary value. It represents the number of
1/1024 volts in the reading if extended the full 16-bits. This
allows voltages to be represented with approximately a 1mV
resolution.
0x8000 to 0x80FF
0x8102
0x8103
0x8100-0x81FF
6
•
•
•
Error Code
Table 1. Temperature Representation
●
Measured voltages:
Measurement Error: +/- 2% of full scale
Resolution: 7.8 mV
aSC7531A / aSC7531B
o
o
o
o
o
5
LSB 0.125°C
Temperature
Fractional
12V
5V
3.3V
2.5V
V
Table 2. Error Codes
CCP
4
2’s complement representation
Reserved
Remote Diode Open
Remote Diode Short
Reserved
0001 0100 0000 0000
0001 0011 1111 1000
0000 0000 0100 0000
0000 0000 0000 0000
1111 1111 1100 0000
1111 1110 1100 0000
3
Description
2
December
Always Zero
1
2006 - 70A05012
0