ADT7462 Datasheet, PDF (22/81 Pages) Analog Devices – Flexible Temperature and Voltage Monitor and System Fan Controller

ADT7462
Table 11. Voltage Inputs
Pin
Voltage Measured
7
+12V1
8
+12V2
13
+3.3V
15
+2.5V / +1.8V
19
+1.25V / +0.9V
21
+5V
22
+12V3
23
V_CCP1 / +1.5V / +1.8V / +2.5V
24
V_CCP2 / +1.5V / +1.8V / +2.5V
25
+1.2V1 (G_BIT) / +3.3V
26
+1.2V2 (FSB_V_TT) / V_BATT
28
+1.5V1 (ICH)
29
+1.5V2 (3GIO)
Input Circuit
The internal structure for the voltage inputs is shown in
Figure 36. 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.
Voltages with full−scale values greater than the reference
are divided so that the full−scale value equals the reference
(2.25 V). All analog inputs are multiplexed into the on−chip,
successive approximation ADC. This ADC has a resolution
of ten bits. The basic input range is from 0 V to 2.25 V, but
the inputs have built−in attenuators to allow measurement of
larger and smaller voltages. To allow a tolerance for these
voltages, the ADC produces an output of 3/4 full scale
(decimal 768 or 0x300) for the nominal input voltage and so
has enough headroom to cope with overvoltages.
A list of corresponding LSB and full−scale values for each
input voltage is shown in Table 12.
Table 12. Input Range Code Conversion
Nominal Input
Voltage (3/4 Scale)
Pin No.
1 LSB
Value
Full
Scale
+12V
+5V
V_CCP1, V_CCP2
V_CCP1, when VIDs
are enabled
+3.3V
V_BATT
+2.5V
+1.8V
+1.5V
+1.25V
+1.2V
+0.9V
7, 8, 22
21
23, 24
23
13, 25
26
15, 23, 24
15, 23, 24
23, 24, 28, 29
19
25, 26
19
0.0625
0.026
0.00625
0.0125
16 V
6.67 V
1.6 V
3.2 V
0.0172
0.0156
0.013
0.0094
0.0078
0.0065
0.00625
0.00469
4.4 V
4.0 V
3.33 V
2.4 V
2.0 V
1.667 V
1.6 V
1.2 V
0.9V
G_BIT,
FSB_V_TT,
V_CCP1,
V_CCP2
1.25V
ICH,
3GIO,
1.5V
1.8V
2.5V
3.3V
5V
12V
8kΩ
92kΩ
32kΩ
77kΩ
30kΩ
72kΩ
51kΩ
66kΩ
8kΩ
91kΩ
30kΩ
72kΩ
68kΩ
71kΩ
76kΩ
39kΩ
100kΩ
16kΩ
35pF
10pF
10pF
8pF
35pF
MUX
10pF
5pF
5pF
5pF
Figure 36. Voltage Input Structures
Example Calculations
Given the LSB value for each channel, the corresponding
code for each voltage (or vice versa) can be calculated.
Code
+
Voltage
1 LSB
Example:
The code for 1.8 V in a 1.8 V channel is:
Code +
1.8
0.0094
+
192
(that is,
3ń4
scale)
Similarly, the voltage, given the code in a particular
channel, is calculated as follows:
Voltage + Code 1 LSB
where:
10 V is connected to the 12 V channel.
1 LSB = 0.0625.
Code = 160 decimal.
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