ADM1024ARUZ ON Semiconductor, ADM1024ARUZ Datasheet - Page 12

• Manufacturer Part Number: ADM1024ARUZ
• Description: IC MONITOR SYS TEMP/VOLT 24TSSOP
• Manufacturer: ON Semiconductor

Specifications of ADM1024ARUZ

• Applications: PC's, PDA's
• Interface: Serial
• Voltage - Supply: 2.8 V ~ 5.5 V
• Package / Case: 24-TSSOP
• Mounting Type: Surface Mount
• Temperature Sensor Function: Temp Sensor
• Output Type: Digital
• Package Type: TSSOP
• Operating Temperature (min): 0C
• Operating Temperature (max): 100C
• Operating Temperature Classification: Commercial
• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (max): 5.5V
• Full Temp Accuracy: +/- 2 C , +/- 3 C
• Digital Output - Bus Interface: SMBus
• Digital Output - Number Of Bits: 10 bit
• Supply Voltage (max): 12 V
• Supply Voltage (min): 2.5 V
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: 0 C
• Supply Current: 1.4 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

voltage, and so has adequate headroom to cope with
overvoltages. Table 3 shows the input ranges of the analog
inputs and output codes of the ADC.
every 748 ms, except for the external temperature (D1 and
D2) inputs. These have special input signal conditioning and
are averaged over 16 conversions to reduce noise, and a
measurement on one of these inputs takes nominally 9.6 ms.
Input Circuits
Figure 13. Each input circuit consists of an input protection
diode, an attenuator, plus a capacitor to form a first−order
low−pass filter that gives the input immunity to high
frequency noise.
2.5 V Input Precautions
should be noted. There is a parasitic diode between Pin 18
and V
(which is used when Pin 18 is configured as a temperature
input). This will become forward biased if Pin 18 is more
than 0.3 V above V
powered off with a 2.5 V input connected.
Setting Other Input Ranges
2.5 V. If the input voltage range is zero to some positive
voltage, all that is required is an input attenuator, as shown
in Figure 14.
by using a positive reference voltage to offset the input
voltage range so it is always positive.
When the ADC is running, it samples and converts an input
The internal structure for the analog inputs is shown in
When using the 2.5 V input, the following precautions
A
Negative and bipolar input ranges can be accommodated
IN1
CC
and A
+V
Figure 13. Structure of Analog Inputs
due to the presence of a PMOS current source
(SEE TEXT)
CCP1
AIN1–AIN2
R1
R2
+5.0V
+2.5V
IN2
+12V
/V
+
CCP2
Figure 14. Scaling A
IN
IN
IN
can easily be scaled to voltages other than
V
IN
V
f s
CC
2.5
* 2.5
. Therefore, V
122.2k
91.6k
36.7k
42.7k
111.2k
80kW
22.7k
55.2k
97.3k
R1
W
W
W
W
W
W
W
W
AIN(1–2)
R2
IN(1−2)
10pF
35pF
25pF
25pF
50pF
CC
should never be
MUX
http://onsemi.com
(eq. 1)
12
used as shown in Figure 15.
point should be noted. Since the input signal is offset but not
inverted, the input range is transposed. An increase in the
magnitude of the −12 V supply (going more negative) will
cause the input voltage to fall and give a lower output code
from the ADC. Conversely, a decrease in the magnitude of
the −12 V supply will cause the ADC code to increase. The
maximum negative voltage corresponds to zero output from
the ADC. This means that the upper and lower limits will be
transposed.
making R1 equal to R2 and V
±2.5 V. Other input ranges can be accommodated by adding
a third resistor to set the positive full−scale input voltage.
(R3 has no effect as the input voltage at the device pin is zero
when V
(R2 has no effect as the input voltage at the device pin is
2.5 V when V
calculation becomes more complicated.
Temperature Measurement System
Local Temperature Measurement
sensor, whose output is digitized by the on−chip ADC. The
temperature data is stored in the Temperature Value Register
(address 27h) and the LSB from Bits 6 and 7 of the
Temperature Configuration Register (address 4Bh). As both
To measure a negative input voltage, an attenuator can be
This is a simple and cheap solution, but the following
Bipolar input ranges can easily be accommodated. By
Offset voltages other than 2.5 V can be used, but the
The ADM1024 contains an on−chip band gap temperature
Figure 15. Scaling and Offsetting A
Figure 16. Scaling and Offsetting A
IN
= minus full scale.)
R1
R2
R1
R3
R1
R2
IN
+
+
V
+
= plus full scale).
IN
V
V
IN
for Negative Inputs
V
f s
for Bipolar Inputs
V
V
OS
f s
R2
*
f s)
*
R1
2.5
R1
* 2.5
+V
OS
OS
R2
+V
AIN(1–2)
= 2.5 V, the input range is
OS
R2
AIN(1–2)
R3
IN(1−2)
IN(1−2)
(eq. 3)
(eq. 2)
(eq. 4)