Datasheet ADT7470 (Analog Devices) - 3

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Data Sheet ADT7470 SPECIFICATIONS
TA = −40oC to +125oC, VCC = 3.0 V to 5.5 V, unless otherwise noted.
Table 1. Parameter1, 2, 3, 4, 5 Min Typ Max Unit Test Conditions/Comments
POWER SUPPLY1 Supply Voltage 3.0 3.3 5.5 V Supply Current, ICC 0.5 0.8 mA Standby Current, ICC 4 µA FAN RPM-TO-DIGITAL CONVERTER Accuracy ±12 % Full-Scale Count 65,535 Nominal Input RPM 109 RPM Fan count = 0xBFFF 329 RPM Fan count = 0x3FFF 5,000 RPM Fan count = 0x0438 10,000 RPM Fan count = 0x021C OPEN-DRAIN DIGITAL OUTPUTS, PWM1 to PWM4, SMBALERT Output Low Voltage, VOL 0.4 V IOUT = –8.0 mA, VCC = +3.3 V High Level Output Current, IOH 0.1 1 µA VOUT = VCC OPEN-DRAIN SERIAL DATA BUS OUTPUT (SDA) Output Low Voltage, VOL 0.4 V IOUT = –4.0 mA, VCC = +3.3 V High Level Output Current, IOH 0.1 1 µA VOUT = VCC SMBus DIGITAL INPUTS (SCL, SDA) Input High Voltage, VIH 2.4 V Input Low Voltage, VIL 1.0 V VCC = 3.3 V Hysteresis 500 mV DIGITAL INPUT LOGIC LEVELS (TACH INPUTS, FULL_SPEED, GPIO) Input High Voltage, VIH 2.4 V Input Low Voltage, VIL 0.8 V Hysteresis 50 mV p-p DIGITAL INPUT LOGIC LEVELS (TMP_IN) Input High Voltage, VIH VDD – 0.3 V Input Low Voltage, VIL 0.4 V DIGITAL INPUT CURRENT Input High Current, IIH –5 µA VIN = VCC Input Low Current, IIL 5 µA VIN = 0 Input Capacitance, CIN 5 pF 1 VDD should never be floated in the presence of SCL/SDA activity. Charge injection can be sufficient to induce approximately 0.6 V on VDD. 2 All voltages are measured with respect to GND, unless otherwise specified. 3 Typical values are at %A = 25°C and represent the most likely parametric norm. 4 Logic inputs accept input high voltages up to 5 V even when the device is operating at supply voltages below 5 V. 5 Timing specifications are tested at logic levels of VIL = 0.8 V for a falling edge and VIH = 2.0 V for a rising edge. Rev. E | Page 3 of 40 Document Outline Features Applications General Description Functional Block Diagram Revision History Specifications Serial Bus Timing Specifications Absolute Maximum Ratings Thermal Characteristics ESD Caution Pin Configuration and Function Descriptions Functional Description General Description ADT7470 Monitoring Cycle Configuration Register 1 (Address 0x40) Configuration Register 2 (Address 0x74) ID Registers General-Purpose I/O Pins (Open Drain) SMBus/I2C Serial Interface Address Selection Serial Bus Protocol Write Operations Send Byte Write Byte Read Operations Receive Byte Alert Response Address SMBus Timeout Temperature Measurement Using TMP05/TMP06 Measuring Temperature TMP05/TMP06 Decoder Temperature ReadBack By the Host Temperature Data Format Temperature Measurement Limits Thermal Zones for Automatic Fan Control Thermal Zone TMIN Limit and Status Registers Limit Values Temperature Limits Fan Speed Limits Out-of-Limit Comparisons Status Registers SMBALERT Interrupt Handling SMBALERT Interrupts Masking Interrupt Sources Enabling the SMBALERT Interrupt Output Fan Drive Using PWM Control High Frequency Fan Drive Low Frequency Fan Drive Setting the Fan Drive Frequency Inverted PWM Output Fan Full Speed Function Fan Speed Measurement Tach Inputs Pulse Stretching Disabling Tach measurement Fan Speed Measurement Fan Speed Measurement Registers Reading Fan Speed from the ADT7470 Fan Tach Limit Registers Fan Speed Measurement Rate Calculating Fan Speed and Tachometer Limits Fan Pulses per Revolution Manual Fan Speed Control Setting the PWM Duty Cycle Example 1: For a PWM Duty Cycle of 50% Example 2: For a PWM Duty Cycle of 33% Automatic Fan Speed Control PWM Min Duty Cycle Example: For a PWM Min Duty Cycle of 30% PWN Max Duty Cycle PWM Current Duty Cycle Register Map Detailed Register Descriptions Outline Dimensions Ordering Guide