ADT7462ACPZ-R7 datasheet(24/81 Pages) ONSEMI

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ADT7462

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Figure 37. Equivalent VBATT Input Protection Circuit

ADC

VBATT

4.5pF

DIGITAL

CONTROL

49.5kΩ

82.7kΩ

3kΩ

ADC Information

Round Robin

Both temperature and voltage measurements are analog

inputs that are digitized using the on−board ADC. An

internal multiplexer switches between the different analog

inputs and digitizes them, in turn, in a round−robin manner.

The total conversion time depends upon how the ADT7462

is configured. The conversion times for each measurement

channel are shown in Table 14. The complete conversion

time is the sum of the time for the voltage and temperature

measurements.

For example, if the ADT7462 is configured as Easy

Configuration Option 1, the round−robin conversion time is

calculated as follows:

Total Conversion Time =

× (Local Conversion Time) +

× (Remote Conversion Time) +

× (Voltage Measurement Time)

The TACH is not measured using the ADC and so is not

part of the round−robin monitoring cycle.

Table 14. Measurement Channel Conversion Times

Channel

Conversion Time (ms)

Local Temperature

9.01

Remote Temperature

38.36

Voltage

8.53

For each ADC temperature and voltage measurement read

from their value registers, 16 readings have actually been

made internally and the results averaged before being placed

in the value register.

Bypass Voltage Attenuators

There are up to 13 voltage measurement channels on the

ADT7462. Each of these voltage measurement channels has

an input structure (see Figure 36 for input structures for each

of the voltage channels). Because the ADC has a voltage

input range from 0 V to 2.25 V, these input circuits attenuate

the voltage input using a resistor divider network to match

the input range of the ADC. However, the user may

occasionally want to remove the attenuators and directly

apply a voltage of between 0 V and 2.25 V to the ADC.

These attenuators can be disabled by setting relevant bits in

the voltage attenuator configuration registers (see Table 15).

This feature also allows the user to rescale the voltage inputs

using an external attenuator circuit. However, when the

attenuators are disabled, the user should ensure that the

voltage on the pin never exceeds 2.25 V.

Table 15. Voltage Attenuator Configuration Registers

Voltage Attenuator

Configuration Register 1

0x18

Voltage Attenuator

Configuration Register 2

0x19

Single−Channel ADC Conversions

Setting Bit 2 of the EDO Enable register (0x16) places the

ADT7462 into single−channel mode. In this mode, the

ADT7462 can be made to convert on a single voltage or

temperature channel only. The channel to be converted on is

selected by writing to Bits [7:3] of the EDO

(single−channel) Enable register (0x16). When the device is

in single−channel mode, the pin configuration option should

not be changed.

Note that when the Pin 26 voltage, which includes the

VBATT option, is selected in single−channel mode, this

means that voltage measurements are continuously made in

this mode. If a battery is connected to this input, this results

in an excessive current drain on the battery. The

specification of >10 years of battery life is valid only when

the battery voltage is measured as part of the round robin and

not in single−channel mode.

Table 16. Single−Channel Mode Options

Bits [7:3]

ADC Channel Selected

0000 0

+1.2V2 voltage, Pin 26

0000 1

Remote 1 temperature

0001 0

Remote 2 temperature

0001 1

Remote 3 temperature

0010 0

Local temperature

0010 1

+12V1 voltage, Pin 7

0011 0

+12V2 voltage, Pin 8

0011 1

+12V3 voltage, Pin 22

0100 0

+3.3V voltage, Pin 13

0100 1

+2.5V/+1.8V voltage, Pin 15

0101 0

+1.25V/+0.9V voltage, Pin 19

0101 1

+5V voltage, Pin 21

0110 0

+1.5V/+1.8V/+2.5V voltage, Pin 23

0110 1

+1.5V/+1.8V/+2.5V voltage, Pin 24

0111 0

+1.2V1/+3.3V voltage, Pin 25

1000 0

+1.5V1 voltage, Pin 28

1000 1

+1.5V2 voltage, Pin 29

Dynamic VID Functionality

VID Code

The ADT7462 can be configured to monitor up to seven

VID inputs. The VID code is output on seven lines from the

CPU to tell the power controller what input voltage it

requires. The ADT7462 can monitor the VID code and the

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