ADT7466 查看數據表（PDF） - ON Semiconductor

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ADT7466

dBCool® Remote Thermal Controller and Voltage Monitor

ON Semiconductor 

ADT7466

FUNCTIONAL DESCRIPTION

The ADT7466 is a complete thermal monitor and dual fan

controller for any system requiring monitoring and cooling.

The device communicates with the system via a serial system

management bus (SMBus). The serial data line (SDA, Pin 15) is

used for reading and writing addresses and data. The input line,

(SCL, Pin 16) is the serial clock. All control and programming

functions of the ADT7466 are performed over the serial bus. In

addition, an ALERT output is provided to indicate out-of-limit

conditions.

MEASUREMENT INPUTS

The device has three measurement inputs, two for voltage and

one for temperature. It can also measure its own supply voltage

and can measure ambient temperature with its on-chip

temperature sensor.

Pin 11 and Pin 12 are analog inputs with an input range of 0 V

to 2.25 V. They can easily be scaled for other input ranges by

using external attenuators. These pins can also be configured

for temperature monitoring by using thermistors or a second

remote diode temperature measurement.

The ADT7466 can simultaneously monitor the local

temperature, the remote temperature by using a discrete

transistor, and two thermistor temperatures.

Remote temperature sensing is provided by the D+ and D−

inputs, to which diode connected, remote temperature sensing

transistors such as a 2N3904 or CPU thermal diode can be

connected.

The device also accepts input from an on-chip band gap

temperature sensor that monitors system ambient temperature.

Power is supplied to the chip via Pin 6. The system also

monitors VCC through this pin. It is normally connected to a

3.3 V supply. It can, however, be connected to a 5 V supply and

monitored without going over range.

SEQUENTIAL MEASUREMENT

When the ADT7466 monitoring sequence is started, it

sequentially cycles through the measurement of analog inputs

and the temperature sensors. Measured values from these

inputs are stored in value registers, which can be read out over

the serial bus, or can be compared with programmed limits

stored in the limit registers. The results of out of limit

comparisons are stored in the status registers, which can be read

over the serial bus to flag out-of-limit conditions.

FAN SPEED MEASUREMENT AND CONTROL

The ADT7466 has two tachometer inputs for measuring the

speed of 3-wire fans, and it has two 8-bit DACs to control the

speed of two fans. The temperature measurement and fan speed

control can be linked in an automatic control loop, which can

operate without CPU intervention to maintain system operating

temperature within acceptable limits. The enhanced acoustics

feature ensures that fans operate at the minimum possible speed

consistent with temperature control, and change speed

gradually. This reduces the user’s perception of changing fan

speed.

Temperature sensing using thermistors is carried out by placing

the thermistor in series with a resistor. The excitation voltage is

provided by the REFOUT pin.

INTERNAL REGISTERS OF THE ADT7466

Table 4 provides brief descriptions of the ADT7466’s principal

internal registers. More detailed information on the function of

each register is given in Table 30 to Table 72.

Table 4. Internal Register Summary

Register

Description

Configuration

Address Pointer

Status

These registers provide control and configuration of the ADT7466 including alternate pinout functionality.

This register contains the address that selects one of the other internal registers. When writing to the ADT7466, the

first byte of data is always a register address, which is written to the address pointer register.

These registers provide status of each limit comparison and are used to signal out-of-limit conditions on the

temperature, voltage, or fan speed channels. Whenever a status bit is set, the ALERT output (Pin 14) goes low.

Interrupt Mask

These registers allow interrupt sources to be masked so that they do not affect the ALERT output.

Value and Limit

Offset

PROCHOT Status

The results of analog voltage inputs, temperature, and fan speed measurements are stored in these registers, along

with their limit values.

These registers allow each temperature channel reading to be offset by a twos complement value written to these

registers.

This register allows the ADT7466 to monitor and time any PROCHOT events gauging system performance.

TMIN

TRANGE

Enhance Acoustics

These registers program the starting temperature for each fan under automatic fan speed control.

These registers program the temperature-to-fan speed control slope in automatic fan speed control mode for each

fan drive output.

This register sets the step size for fan drive changes in AFC mode to minimize acoustic noise.

Rev. 3 | Page 11 of 48 | www.onsemi.com

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