ADT7476ARQZ-R7 datasheet(14/67 Pages) ONSEMI

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ADT7476

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When the ADC is running, it samples and converts a

voltage input in 0.7 ms and averages 16 conversions to

reduce noise; a measurement takes nominally 11 ms.

Extended Resolution Registers

Voltage measurements can be made with higher accuracy

using the extended resolution registers (0x76 and 0x77).

Whenever the extended resolution registers are read, the

corresponding data in the voltage measurement registers

(0x20 to 0x24) is locked until their data is read. That is, if

extended resolution is required, then the extended resolution

appropriate voltage measurement register.

Additional ADC Functions for Voltage Measurements

A number of other functions are available on the

ADT7476 to offer the system designer increased flexibility.

Turn−Off Averaging

For each voltage/temperature measurement read from a

value register, 16 readings have been made internally and the

results averaged before being placed into the value register.

When faster conversions are needed, setting Bit 4 of

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

effectively gives a reading 16 times faster but the reading

can be noisier. The default round robin cycle time takes

146.5 ms.

Table 2. Conversion Time with Averaging Disabled

Channel

Measurement Time (ms)

Voltage Channels

0.7

Remote Temperature 1

Remote Temperature 2

Local Temperature

1.3

When Bit 7 of Configuration Register 6 (0x10) is set, the

default round robin cycle time increases to 240 ms.

Bypass All Voltage Input Attenuators

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

the attenuation circuitry from the 2.5 V, VCCP, VCC, 5.0 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.

Bypass Individual Voltage Input Attenuators

Bits [7:4] of Configuration Register 4 (0x7D) can be used

to bypass individual voltage channel attenuators.

Table 3. Bypassing Individual Voltage Input

Attenuators

Configuration Register 4 (0x7D)

Bit No.

Channel Attenuated

Bypass 2.5 V attenuator

Bypass VCCP attenuator

Bypass 5.0 V attenuator

Bypass 12 V attenuator

Configuration Register 2 (0x73)

[4] = 1, averaging off.

[5] = 1, bypass input attenuators.

[6] = 1, single−channel convert mode.

TACH1 Minimum High Byte (0x55)

[7:5] Selects ADC channel for single−channel convert mode.

Single−Channel ADC Conversion

While single−channel mode is intended as a test mode that

can be used to increase sampling times for a specific

channel, and therefore helps to analyze that channel’s

performance in greater detail, it can also have other

applications.

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

ADT7476 into single−channel ADC conversion mode. In

this mode, the ADT7476 can only read a single voltage

channel. The selected voltage 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).

Table 4. Programming Single−Channel ADC Mode

Bits [7:4], Register 0x55

Channel Selected (Note 1)

000

2.5 V

001

VCCP

010

VCC

011

5.0 V

100

12 V

101

Remote 1 temperature

110

Local temperature

111

Remote 2 temperature

1. In the process of configuring single−channel ADC conversion

mode, the TACH1 minimum high byte is also changed, possibly

trading off TACH1 minimum high byte functionality with

single−channel mode functionality.

ADT7476ARQZ-R7 Datasheet(PDF) 14 Page - ON Semiconductor

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