ADT7476AARQZ-R datasheet(13/69 Pages) ONSEMI

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ADT7476A

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Voltage Limit Registers

Associated with each voltage measurement channel is a

high and low limit register. Exceeding the programmed high

or low limit causes the appropriate status bit to be set.

Exceeding either limit can also generate SMBALERT

interrupts.

Table 8. VOLTAGE LIMIT REGISTERS

Description

Default

0x44

2.5 V Low Limit

0x00

0x45

2.5 V High Limit

0xFF

0x46

VCCP Low Limit

0x00

0x47

VCCP High Limit

0xFF

0x48

VCC Low Limit

0x00

0x49

VCC High Limit

0xFF

0x4A

5.0 V Low Limit

0x00

0x4B

5.0 V High Limit

0xFF

0x4C

12 V Low Limit

0x00

0x4D

12 V High Limit

0xFF

Table 13 shows the input ranges of the analog inputs and

output codes of the 10-bit ADC.

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

ADT7476A 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 9. 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 10. BYPASSING INDIVIDUAL VOLTAGE INPUT

ATTENUATORS

Configuration Register 4 (0x7D)

Bit No.

Channel Attenuated

[4]

Bypass 2.5 V Attenuator

[5]

Bypass VCCP Attenuator

[6]

Bypass 5.0 V Attenuator

[7]

Bypass 12 V Attenuator

Table 11. CONFIGURATION REGISTER 2 (REG. 0x73)

Bit

Description

[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 ADT7476A into single-channel ADC conversion mode.

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