ADT7462ACPZ-R7 datasheet(22/81 Pages) ONSEMI

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ADT7462

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Table 11. Voltage Inputs

Voltage Measured

+12V1

+12V2

+3.3V

+2.5V / +1.8V

+1.25V / +0.9V

+5V

+12V3

VCCP1 / +1.5V / +1.8V / +2.5V

VCCP2 / +1.5V / +1.8V / +2.5V

+1.2V1 (GBIT) / +3.3V

+1.2V2 (FSB_VTT) / VBATT

+1.5V1 (ICH)

+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

7, 8, 22

0.0625

16 V

+5V

0.026

6.67 V

VCCP1, VCCP2

23, 24

0.00625

1.6 V

VCCP1, when VIDs

are enabled

0.0125

3.2 V

+3.3V

13, 25

0.0172

4.4 V

VBATT

0.0156

4.0 V

+2.5V

15, 23, 24

0.013

3.33 V

+1.8V

15, 23, 24

0.0094

2.4 V

+1.5V

23, 24, 28, 29

0.0078

2.0 V

+1.25V

0.0065

1.667 V

+1.2V

25, 26

0.00625

1.6 V

+0.9V

0.00469

1.2 V

Figure 36. Voltage Input Structures

0.9V

8kΩ

92kΩ

35pF

1.25V

30kΩ

72kΩ

10pF

32kΩ

77kΩ

10pF

51kΩ

66kΩ

8pF

1.8V

8kΩ

91kΩ

35pF

2.5V

30kΩ

72kΩ

10pF

3.3V

68kΩ

71kΩ

5pF

76kΩ

39kΩ

5pF

12V

100kΩ

16kΩ

5pF

MUX

GBIT,

FSB_VTT,

VCCP1,

VCCP2

ICH,

3GIO,

1.5V

Example Calculations

Given the LSB value for each channel, the corresponding

code for each voltage (or vice versa) can be calculated.

Code +

Voltage

1LSB

Example:

The code for 1.8 V in a 1.8 V channel is:

Code + 1.8

0.0094 +

192 (that is, 3 4scale)

Similarly, the voltage, given the code in a particular

channel, is calculated as follows:

Voltage + Code

1LSB

where:

10 V is connected to the 12 V channel.

1 LSB = 0.0625.

Code = 160 decimal.

ADT7462ACPZ-R7 Datasheet(PDF) 22 Page - ON Semiconductor

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