ADT7475 datasheet(2/68 Pages) AD

2 / 68 page

ADT7475

Rev. A | Page 2 of 68

TABLE OF CONTENTS

Features .............................................................................................. 1

General Description ......................................................................... 1

Functional Block Diagram .............................................................. 1

Specifications..................................................................................... 3

Timing Diagram ........................................................................... 4

Absolute Maximum Ratings............................................................ 5

Thermal Characteristics .............................................................. 5

ESD Caution.................................................................................. 5

Pin Configuration and Function Descriptions............................. 6

Typical Performance Characteristics ............................................. 7

Product Description......................................................................... 9

Quick Comparison Between ADT7473 and ADT7475 .......... 9

Recommended Implementation................................................. 9

Serial Bus Interface......................................................................... 10

Write Operations ........................................................................ 11

Read Operations ......................................................................... 12

Alert Response Address............................................................. 12

SMBus Timeout .......................................................................... 12

Virus Protection.......................................................................... 12

Voltage Measurement Input...................................................... 12

Analog-to-Digital Converter .................................................... 12

Input Circuitry............................................................................ 13

Voltage Measurement Registers................................................ 13

VCCP Limit Registers ................................................................... 13

Extended Resolution Registers ................................................. 13

Additional ADC Functions for Voltage Measurements ........ 13

Temperature Measurement Method ........................................ 15

Factors Affecting Diode Accuracy........................................... 17

Additional ADC Functions for Temperature Measurement 18

Limits, Status Registers, and Interrupts....................................... 20

Limit Values ................................................................................ 20

Interrupt Status Registers .......................................................... 21

THERM Timer ........................................................................... 23

Fan Drive Using PWM Control ............................................... 26

Operating from 3.3 V Standby ................................................. 31

Standby Mode ............................................................................. 31

XNOR Tree Test Mode .............................................................. 31

Power-On Default ...................................................................... 32

Programming the Automatic Fan Speed Control Loop ............ 33

Automatic Fan Control Overview............................................ 33

Step 1: Hardware Configuration .............................................. 34

Step 2: Configuring the Mux .................................................... 37

Step 3: TMIN Settings for Thermal Calibration Channels ...... 39

Step 4: PWM

for Each PWM (Fan) Output

MIN

...................... 40

Step 5: PWM

for PWM (Fan) Outputs

MAX

.............................. 40

Step 6: T

for Temperature Channels

RANGE

................................ 41

Step 7: T

THERM for Temperature Channels ............................... 44

Step 8: T

for Temperature Channels

HYST

.................................. 45

Outline Dimensions ....................................................................... 65

Ordering Guide .......................................................................... 65

REVISION HISTORY

2/06—Rev. 0 to Rev. A

Changes to Table 1............................................................................ 3

Changes to Quick Comparison Between ADT7473 and

ADT7475 Section ............................................................................. 9

Changes to Analog-to-Digital Converter section ...................... 13

Changes to TACH Inputs Section ................................................ 27

Changes to Fan Speed Measurement Section ............................. 28

Inserted Figure 42........................................................................... 32

Changes to Power-On Default Section........................................ 32

Changes to Step 5: PMWMAX For PWM (Fan)

Outputs Section .............................................................................. 40

Changes to Table 14 ....................................................................... 48

Changes to Table 23 ....................................................................... 53

Changes to Table 43 ....................................................................... 60

7/05—Revision 0: Initial Version

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