ADT7468 datasheet(16/80 Pages) AD

16 / 80 page

ADT7468

Rev. 0 | Page 16 of 80

VID Code Register (Reg. 0x43)

<7> VIDSEL = 0,

Pin 21 functions as a 12 V measurement

input. Software can read this bit to determine that there are five

VID inputs being monitored. Bit 5 of Register 0x43 (VID5)

always reads back 0. Bit 0 of Status Register 2 (Reg. 0x42)

reflects 12 V out-of-limit measurements.

VIDSEL = 1,

Pin 21 functions as the sixth VID code input

(VID5). Software can read this bit to determine that there are

six VID inputs being monitored. Bit 5 of Register 0x43 reflects

the logic state of Pin 21. Bit 0 of Status Register 2 (Reg. 0x42)

reflects VID code changes.

VID CODE CHANGE DETECT FUNCTION

The ADT7468 has a VID code change detect function. When

Pin 21 is configured as the VID5 input, VID code changes can

be detected and reported back by the ADT7468. Bit 0 of Status

change when set. The VID code change bit is set when the logic

states on the VID inputs are different than they were 11 µs

previously. The change of VID code can be used to generate an

SMBALERT interrupt. If an SMBALERT interrupt is not

required, Bit 0 of Interrupt Mask Register 2 (Reg. 0x75), when

set, prevents SMBALERTs from occurring on VID code

changes.

Status Register 2 (Reg. 0x42)

<0> 12V/VC = 0,

if Pin 21 is configured as VID5, then Logic 0

denotes no change in VID code within the last 11 µs.

<0> 12V/VC = 1,

if Pin 21 is configured as VID5, then Logic 1

means that a change has occurred on the VID code inputs

within the last 11 µs. An SMBALERT is generated, if this

function is enabled.

ADDITIONAL ADC FUNCTIONS FOR VOLTAGE

MEASUREMENTS

A number of other functions are available on the ADT7468 to

offer the system designer increased flexibility.

Turn-Off Averaging

For each voltage measurement read from a value register,

16 readings have actually been made internally and the results

averaged before being placed into the value register. For

instances where faster conversions are needed, setting Bit 4 of

Configuration Register 2 (Reg. 0x73) turns averaging off. This

effectively gives a reading 16 times faster (0.7 ms), but the

reading may be noisier.

Bypass Voltage Input Attenuator

Setting Bit 5 of Configuration Register 2 (Reg. 0x73) removes

the attenuation circuitry from the 2.5 V, VCCP, VCC, 5 V, and 12 V

inputs. This allows the user to directly connect external sensors

or rescale the analog voltage measurement inputs for other

applications. The input range of the ADC without the

attenuators is 0 V to 2.25 V.

Single-Channel ADC Conversion

Setting Bit 6 of Configuration Register 2 (Reg. 0x73) places the

ADT7468 into single-channel ADC conversion mode. In this

mode, the ADT7468 can be made to read a single voltage

channel only. If the internal ADT7468 clock is used, the selected

input is read every 0.7 ms. The appropriate ADC channel is

selected by writing to Bits <7:5> of the TACH1 minimum high

byte register (0x55).

Bits <7:5> Reg. 0x55

Channel Selected

000

2.5 V

001

VCCP

010

VCC

011

5 V

100

12 V

101

Remote 1 Temperature

110

Local Temperature

111

Remote 2 Temperature

Configuration Register 2 (Reg. 0x73)

<4> = 1,

averaging off.

<5> = 1,

bypass input attenuators.

<6> = 1,

single-channel convert mode.

TACH1 Minimum High Byte (Reg. 0x55)

<7:5>

Selects ADC channel for single-channel convert mode.

ADT7468 Datasheet(PDF) 16 Page - Analog Devices

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