LM85 National Semiconductor, LM85 Datasheet
LM85
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LM85 Summary of contents
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... CCP nal scaling resistors). To set fan speed, the LM85 has three PWM outputs that are each controlled by one of three temperature zones. The LM85 includes a digital filter that can be invoked to smooth temperature readings for better control of fan speed. The LM85 has four tachometer inputs to measure fan speed ...
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... Connection Diagram LM85BIMQX or LM85CIMQX (2500 units per tape and reel) Information on the differences between the LM85BIMQ and LM85CIMQ can be found in Section 6. highly recommended that all new designs use the LM85BIMQ. Pin Descriptions Symbol Pin SMBDAT 1 SMBCLK 2 VID0 5 VID1 6 VID2 7 VID3 ...
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... Digital Input Input for monitoring tachometer output of fan 3. Digital Input Input for monitoring tachometer output of fan Address Select Mode, determines the SMBus address of the LM85. Digital Open-Drain Fan speed control 1. When in XOR tree test mode, functions as Output XOR Tree output. ...
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... Power Supply Sensitivity Total Monitoring Cycle Time (Note 13) www.national.com (Notes 1, Machine Model Soldering Temperature, Infrared, 10 seconds (Note 6) Storage Temperature Operating Ratings −0.5V to 6.0V −0.5V to 6.0V LM85 Operating Temperature Range Remote Diode Temperature Range −0.5V to 16V Supply Voltage (3.3V nominal) −0.5V to 6.66V V Voltage Range IN +12V V IN ± ...
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... Time Interval Range (Continued all other limits T A MIN MAX Conditions LM85CIMQ V =0.55V OL LM85BIMQ V =0.4V OL LM85CIMQ OUT OUT LM85BIMQ OUT OUT OUT GND IN Conditions 5 = 50Ω unless otherwise S = 25˚C. A Typical Limits Units ...
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... Quiescent current will not increase substantially with an SMBus transaction. Note 10: The accuracy of the LM85CIMQA is guaranteed when using the thermal diode of Intel Pentium 4 processors in 423 pin or 478 pin packages or any thermal diode with a typical non-ideality factor of 1.0045. The accuracy of the LM85BIMQA is guaranteed when using the thermal diode of an Intel Pentium 4 processors or any thermal diode with a typical non-ideality of 1.0021 and series resistance of 3.64Ω ...
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... If the theoretical input voltage was applied to an LM85 that has positive error, the LM85’s reading would be less than the theoretical. Note 13: This specification is provided only to indicate how often temperature and voltage data is updated. The LM85 can be read at any time without regard to conversion state (and will yield last conversion result) ...
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... AUTO FAN CONTROL OPERATING MODE The LM85 includes the circuitry for automatic fan control. In Auto Fan Mode, the LM85 will automatically adjust the PWM duty cycle of the PWM outputs. PWM outputs are assigned to a thermal zone based on the fan configuration registers possible to have more than one PWM output assigned to a thermal zone ...
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Functional Description Register Read/ Register Address Write Name 49h R/W 3.3V High Limit 4Ah R/W 5V Low Limit 4Bh R/W 5V High Limit 4Ch R/W 12V Low Limit 4Dh R/W 12V High Limit 4Eh R/W Processor (Zone1) Low Temp 4Fh ...
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... This reading will cause the zone limit bit(s) (bits 6 and 4) in the Interrupt Status Register (41h) and the remote diode fault status bit(s) (bit the Interrupt Status Register 2 (42h set. The Temperature Reading registers are updated automatically by the LM85 at a minimum frequency of 4 Hz. These registers are read only — a write to these registers has no effect. ...
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... LSByte read. Therefore, reading the MSByte register twice in a row will yield the same data. When the LSByte of the LM85B 16-bit register is read, the other byte (MSByte) is latched at the current value until it is read. At the end of the MSByte read the Fan Tachometer Reading registers are updated. ...
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... The four least significant bits of the Version/Stepping register [3.0] contain the current stepping of the LM85 silicon. The four most significant bits [7.4] reflect the LM85 base device number when set to a value of 0110b. All LM85 revisions will have a base number of 6. For the LM85C, this register will read 01100000b (60h). The LM85B will read 01100010b (62h).If new revisions of the LM85C or LM85B are released the last 4 bits of this register will change ...
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... This register will hold a set bit(s) until the event is read by software. The contents of this register will be cleared (set to 0) automatically by the LM85 after it is read by software, if the fault condition is no longer exists. Once set, the Interrupt Status Register 1 bits will remain set until a read event occurs, even if the fault condition no longer exists This register is read only — ...
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... Interrupt Status Register 2 will hold a set bit until the event is read by software. The contents of this register will be cleared (set to 0) automatically by the LM85 after it is ready by software, if fault condition no longer exists. Once set, the Interrupt Status Register 2 bits will remain set until a read event occurs, even if the fault no longer exists This register is read only — ...
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... LM85 in the Interrupt Status Register 1 (41h). For example, if the temperature read from the Remote1− and Remote1+ inputs exceeds the Processor (Zone1) High Temp register limit setting, Interrupt Status Register 1 ZN1 bit will be set. The temperature limits in these registers are represented as 8 bit, 2’ ...
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Functional Description 4.13 Registers 54-5Bh: Fan Tachometer Low Limit Register Read/ Register Address Write Name 54h R/W Tach1 Minimum LSB 55h R/W Tach1 Minimum MSB 56h R/W Tach2 Minimum LSB 57h R/W Tach2 Minimum MSB 58h R/W Tach3 Minimum LSB ...
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Functional Description This register becomes Read Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect. After power up the default value is used whenever the Ready/Lock/Start/Override register Start ...
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Functional Description In Auto Fan Mode, when the temperature for a zone is above the Temperature Limit (Registers 67-69h) and below its Absolute Temperature Limit (Registers 6A-6Ch), the speed of a fan assigned to that zone is determined as follows. ...
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... If the Remote1 or Remote2 pins are connected to a processor or chipset, instantaneous temperature spikes may be sampled by the LM85. If these spikes are not ignored, the CPU fan (if connected to LM85) may turn on prematurely and produce unpleasant noise. For this reason, any zone that is connected to a chipset or processor should have spike smoothing enabled. ...
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... Functional Description FIGURE 2. What LM85 Auto Fan Control Sees With and Without Spike Smoothing ZN-X[2:0] 000 001 010 011 100 101 110 111 TABLE 8. PWM Output Below Limit Depending on Value of Off/Min Off/Min 0 1 4.17 Registers 64-66h: Minimum PWM Duty Cycle Register Read/ Register ...
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Functional Description Current Duty 4.18 Registers 67-69h: Temperature Limit Register Read/ Register Address Write Name 67h R/W Zone1 Fan Temp Limit 68h R/W Zone2 Fan Temp Limit 69h R/W Zone3 Fan Temp Limit These are the temperature limits for the ...
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... Zone3 Absolute Temp Limit For the LM85B in the Auto Fan mode zone exceeds the temperature set in the Absolute Temperature Limit register, all of the PWM outputs will incresase its duty cycle to 100%. This is a safety feature that attempts to cool the system if there is a potentially catastrophic thermal event. If set to 80h (-128˚ ...
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... PWM1 output must control the fan that has it’s tachometer output connected to the TACH1 LM85 input. PWM2 output must control the fan that has it’s tachometer output connected to the TACH2 LM85 input. PWM3 output must control the fans that have their tachometer outputs connected to the TACH3 or TACH4 LM85 inputs. Setting (Tn[1:0]) Mode Function ...
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... XOR TEST MODE The LM85 incorporates a XOR tree test mode. When the test mode is enabled by setting the “XEN” bit high in the Test Register at address 6Fh via the SMBus, the part will enter XOR test mode. Since the test mode an XOR tree, the order of the signals in the tree is not important. SMBDAT and SMBCLK are not to be included in the test tree ...
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... Temperature Limit function 6 Register 3Fh Device ID default Revision History Date Revision 8/2002 Added LM85BIMQ functional differences and specifications. 3/2003 Updated Register 74h, Tachometer Monitor Mode description. (Continued) LM85CIMQ The override bit has no effect when the PWM output is disabled. Only the PWM output associated ...
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... Physical Dimensions unless otherwise noted Order Number LM85BIMQ, LM86BIMQX, LM85CIMQ or LM85CIMQX LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1 ...