ADT7490ARQZ-R7 datasheet(14/75 Pages) ONSEMI

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ADT7490

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is the dedicated reference voltage for the PECI circuitry. The

IMON input on Pin 19 can be used to monitor the IMON output

of ON Semiconductor’s VR11.1 controllers. IMON is a

voltage representation of the CPU current.

Analog−to−Digital Converter

All analog inputs are multiplexed into the on−chip,

successive approximation, analog−to−digital converter.

This ADC has a resolution of 10 bits. The basic input range

is 0 V to 2.25 V, but the inputs have built−in attenuators to

allow measurement of 2.5 V, 3.3 V, 5.0 V, 12 V, and the

processor core voltage VCCP without any external

components. To allow the tolerance of these supply

voltages, the ADC produces an output of 3/4 full scale

(768 decimal or 0x300 hexadecimal) for the nominal input

voltage, and therefore, has adequate headroom to cope with

overvoltages.

Input Circuitry

The internal structure for the analog inputs is shown in

Figure 24 . The input circuit consists of an input protection

diode, an attenuator, plus a capacitor to form a first−order

low−pass filter that gives input immunity to high frequency

noise.

Voltage Measurement Registers

Figure 24. Analog Inputs Structure

VTT

45k

30pF

IMON

45k

94k

30pF

VCCP

17.5k

52.5k

35pF

+2.5VIN

45k

94k

30pF

VCC

68k

71k

30pF

+5VIN

93k

47k

30pF

+12VIN

20k

30pF

MUX

120kW

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.

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 (0x1F, 0x76, and

0x77). Whenever the extended resolution registers are read,

the corresponding data in the voltage measurement registers

(0x1D, 0x1E, and 0x20 to 0x24) is locked until their data is

read. That is, if extended resolution is required, the extended

resolution register must be read first, immediately followed

by the appropriate voltage measurement register.

Additional ADC Functions for Voltage Measurements

A number of other functions are available on the

ADT7490 to offer the system designer increased flexibility.

The functions described in the following sections are

enabled by setting the appropriate bit in Configuration

Configuration Register 2 (Register 0x73)

Bit 4 (AVG) = 1, averaging off.

Bit 5 (ATTN) = 1, bypass input attenuators.

Bit 6 (CONV) = 1, single−channel convert mode.

Turn−Off Averaging

For each voltage/temperature measurement read from a

value register, 16 readings have actually been made

internally and the results averaged before being placed into

the value register. When faster conversions are needed,

setting Bit 4 (AVG) of Configuration Register 2 (0x73) turns

averaging off. This effectively gives a reading that is

16 times faster, but the reading can be noisier. The default

round−robin cycle time takes 146.5 ms.

ADT7490ARQZ-R7 Datasheet(PDF) 14 Page - ON Semiconductor

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