SNAS207B May   2004  – January 2024 LM64

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 Operating Ratings
    3. 5.3 DC Electrical Characteristics
    4. 5.4 Operating Electrical Characteristics
    5. 5.5 AC Electrical Characteristics
    6. 5.6 Digital Electrical Characteristics
    7. 5.7 SMBus Logical Electrical Characteristics
    8. 5.8 SMBus Digital Switching Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Conversion Sequence
      2. 6.3.2  The ALERT Output
        1. 6.3.2.1 ALERT Output as a Temperature Comparator
        2. 6.3.2.2 ALERT Output as an Interrupt
        3. 6.3.2.3 ALERT Output as an SMBus ALERT
      3. 6.3.3  SMBus Interface
      4. 6.3.4  Power-On Reset (POR) Default States
      5. 6.3.5  Temperature Data Format
      6. 6.3.6  Open-Drain Outputs, Inputs, and Pull-Up Resistors
      7. 6.3.7  Diode Fault Detection
      8. 6.3.8  Communicating with the LM64
      9. 6.3.9  Digital Filter
      10. 6.3.10 Fault Queue
      11. 6.3.11 One-Shot Register
      12. 6.3.12 Serial Interface Reset
  8. 7 Registers
    1. 7.1 LM64 Registers
      1. 7.1.1 LM64 Register Map in Hexadecimal Order
      2. 7.1.2 LM64 Register Map in Functional Order
      3. 7.1.3 LM64 Initial Register Sequence and Register Descriptions in Functional Order
        1. 7.1.3.1 LM64 Required Initial Fan Control Register Sequence
      4. 7.1.4 LM64 Register Descriptions in Functional Order
        1. 7.1.4.1 Fan Control Registers
        2. 7.1.4.2 Configuration Register
        3. 7.1.4.3 Tachometer Count And Limit Registers
        4. 7.1.4.4 Local Temperature And Local High Setpoint Registers
        5. 7.1.4.5 Remote Diode Temperature, Offset And Setpoint Registers
        6. 7.1.4.6 ALERT Status And Mask Registers
        7. 7.1.4.7 Conversion Rate And One-Shot Registers
        8. 7.1.4.8 ID Registers
    2. 7.2 General Purpose Registers
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Fan Control Duty Cycle VS. Register Settings and Frequency
        1. 8.1.1.1 Computing Duty Cycles for a Given Frequency
      2. 8.1.2 Use of the Lookup Table for Non-Linear PWM Values VS Temperature
      3. 8.1.3 NON-Ideality Factor and Temperature Accuracy
        1. 8.1.3.1 Diode Non_Ideality
        2. 8.1.3.2 Compensating for Diode Non-Ideality
      4. 8.1.4 Computing RPM of the Fan from the TACH Count
    2. 8.2 Typical Application
  10. 9 Layout
    1. 9.1 PCB Layout for Minimizing Noise
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.1.4.1 Fan Control Registers

Address
Hex		Read/
Write		BitsPOR
Value		NameDescription
4AHEX PWM AND RPM REGISTER
4AR/W7:600PWM
Program		These bits are unused and always set to 0.
510: the PWM Value (register 4C) and the Lookup Table (50–5F) are read-only. The PWM value (0 to 100%) is determined by the current remote diode temperature and the Lookup Table, and can be read from the PWM value register.
1: the PWM value (register 4C) and the Lookup Table (Register 50–5F) are read/write enabled. Writing the PWM Value register will set the PWM output. This is also the state during which the Lookup Table can be written.
40PWM
Output
Polarity		0: the PWM output pin will be 0 V for fan OFF and open for fan ON.
1: the PWM output pin will be open for fan OFF and 0 V for fan ON.
30PWM Clock
Select		if 0, the master PWM clock is 360 kHz
if 1, the master PWM clock is 1.4 kHz.
20[Reserved]Always write 0 to this bit.
1:000Tachometer Mode00: Traditional tach input monitor, false readings when under minimum detectable RPM.
01: Traditional tach input monitor, FFFF reading when under minimum detectable RPM.
10: Most accurate readings, FFFF reading when under minimum detectable RPM.
11: Least effort on programmed PWM of fan, FFFF reading when under minimum detectable RPM.
Note: If the PWM Clock is 360 kHz, mode 00 is used regardless of the setting of these two bits.
4BHEX FAN SPIN-UP CONFIGURATION REGISTER
4BR/W7:60Fast
Tachometer
Spin-Up		These bits are unused and always set to 0
51If 0, the fan spin-up uses the duty cycle and spin-up time, bits 0–4.
If 1, the LM64 sets the PWM output to 100% until the spin-up times out (per bits 0–2) or the minimum desired RPM has been reached (per the Tachometer Setpoint setting) using the tachometer input, whichever happens first. This bit overrides the PWM Spin-Up Duty Cycle register (bits 4:3)—PWM output is always 100%.
If PWM Spin-Up Time (bits 2:0) = 000, the Spin-Up cycle is bypassed, regardless of the state of this bit.
4:311PWM
Spin-Up
Duty Cycle		00: Spin-Up cycle bypassed (no Spin-Up), unless Fast Tachometer Terminated Spin-Up (bit 5) is set.
01: 50%
10: 75%–81% Depends on PWM Frequency. See Applications Notes.
11: 100%
2:0111PWM
Spin-Up
Time		000: Spin-Up cycle bypassed (No Spin-Up)
001: 0.05 seconds
010: 0.1 s
011: 0.2 s
100: 0.4 s
101: 0.8 s
110: 1.6 s
111: 3.2 s
4DHEX FAN PWM FREQUENCY REGISTER
4DR/W7:5000PWM
Frequency		These bits are unused and always set to 0
4:010111The PWM Frequency = PWM_Clock / 2n, where PWM_Clock = 360 kHz or 1.4 kHz (per the PWM Clock Select bit in Register 4A), and n = value of the register. Note: n = 0 is mapped to n = 1. See the Applications Notes at the end of this datasheet.
4CHEX PWM VALUE REGISTER
4CRead (Write only if reg 4A bit 5 = 1.)7:600PWM
Value		These bits are unused and always set to 0
5:0000000If PWM Program (register 4A, bit 5) = 0 this register is read only and reflects the LM64’s current PWM value from the Lookup Table.
If PWM Program (register 4A, bit 5) = 1, this register is read/write and the desired PWM value is written directly to this register, instead of from the Lookup Table, for direct fan speed control.
This register will read 0 during the Spin-Up cycle.
See Application Notes section at the end of this datasheet for more information regarding the PWM Value and Duty Cycle in %.
50HEX to 5FHEX LOOKUP TABLE (7 Bits for Temperature and 6 Bits for PWM for each Temperature/PWM Pair)
50 Read. (Write only if reg 4A bit 5 = 1.) 7 0 Lookup Table
Temperature
Entry 1		 This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 51.
517:600Lookup Table
PWM Entry 1		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 50.
5270Lookup Table
Temperature
Entry 2		This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 53.
537:600Lookup Table
PWM Entry 2		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 52.
5470Lookup Table
Temperature
Entry 3		This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 55.
557:600Lookup Table
PWM Entry 3		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 54.
5670Lookup Table
Temperature
Entry 4		This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 57.
577:600Lookup Table
PWM Entry 4		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 56.
5870Lookup Table
Temperature
Entry 5		This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 59.
597:600Lookup Table
PWM Entry 5		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 58.
5A70Lookup Table
Temperature
Entry 6		This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 5B.
5B7:600Lookup Table
PWM Entry 6		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 5A.
5C70Lookup Table
Temperature
Entry 7		This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 5D.
5D7:600Lookup Table
PWM Entry 7		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 5C.
5E70Lookup Table
Temperature
Entry 8		This bit is unused and always set to 0.
6:00x7FIf the remote diode temperature exceeds this value, the PWM output will be the value in Register 5F.
5F7:600Lookup Table
PWM Entry 8		These bits are unused and always set to 0.
5:00x3FThe PWM value corresponding to the temperature limit in register 5E.
4FHEX LOOKUP TABLE HYSTERESIS
4FR/W7:5000Lookup
Table
Hysteresis		These bits are unused and always set to 0
4:000100The amount of hysteresis applied to the Lookup Table. (1 LSB = 1°C).