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| 型号： | LM89EVAL |
| 厂商： | National Semiconductor |
| 文件页数： | 13/32页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION LM89 |
| 标准包装： | 1 |
| 传感器类型： | 温度 |
| 传感范围： | 0°C ~ 125°C |
| 接口： | SMBus（2 线/I²C） |
| 灵敏度： | ±1°C |
| 电源电压： | 3 V ~ 3.6 V |
| 嵌入式： | 否 |
| 已供物品： | 板，CD |
| 已用 IC / 零件： | LM89 |
| 相关产品： | LM89CIM-ND - IC TEMP SENSOR DGTL 8-SOIC LM89CIMX-ND - IC TEMP SENSOR DGTL 8-SOIC LM89CIMM-ND - IC TEMP SENSOR DGTL 8-MSOP LM89CIMMX-ND - IC TEMP SENSOR DGTL 8-MSOP |
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Temperature
Digital Output
SNIS128C – AUGUST 2002 – REVISED MARCH 2013
Binary
Hex
+125°C
+25°C
+1°C
0°C
? 1°C
? 25°C
? 55°C
0111 1101
0001 1001
0000 0001
0000 0000
1111 1111
1110 0111
1100 1001
7Dh
19h
01h
00h
FFh
E7h
C9h
OPEN-DRAIN OUTPUTS
The SMBData, ALERT and T_CRIT_A outputs are open-drain outputs and do not have internal pull-ups. A “high”
level will not be observed on these pins until pull-up current is provided by some external source, typically a pull-
up resistor. Choice of resistor value depends on many system factors but, in general, the pull-up resistor should
be as large as possible. This will minimize any internal temperature reading errors due to internal heating of the
LM89. The maximum resistance of the pull-up to provide a 2.1V high level, based on LM89 specification for High
Level Output Current with the supply voltage at 3.0V, is 82k Ω (5%) or 88.7k Ω (1%).
DIODE FAULT DETECTION
The LM89 is equipped with operational circuitry designed to detect fault conditions concerning the remote diode.
In the event that the D+ pin is detected as shorted to V DD or floating, the Remote Temperature High Byte (RTHB)
register is loaded with +127°C, the Remote Temperature Low Byte (RTLB) register is loaded with 0, and the
OPEN bit (D2) in the status registe r is set. As a result, if the Remote T_CRIT setpoint register (RCS) is set to a
value less than +127°C the ALERT and T_Crit output pins will be pulled low, if the Alert Mask and T_Crit Mask
are disabled. If the Remote HIGH Setpoint High Byte Register (RHSHB) is set to a value less than +127°C then
ALERT will be pulled low, if the Alert Mask is disabled. The OPEN bit itself will not trigger and ALERT.
In the event that the D+ pin is shorted to ground or D ? , the Remote Temperature High Byte (RTHB) register is
loaded with ? 128°C (1000 0000) and the OPEN bit (D2) in the status register will not be set. Since operating the
LM89 at ? 128°C is beyond it's operational limits, this temperature reading represents this shorted fault condition.
If the value in the Remote Low Setpoint High Byte Register (RLSHB) is more than ? 128°C and the Alert Mask is
disabled, ALERT will be pulled low.
Remote diode temperature sensors that have been previously released and are competitive with the LM89 output
a code of 0°C if the external diode is short-circuited. This change is an improvement that allows a reading of 0°C
to be truly interpreted as a genuine 0°C reading and not a fault condition.
COMMUNICATING WITH THE LM89
The data registers in the LM89 are selected by the Command Register. At power-up the Command Register is
set to “00”, the location for the Read Local Temperature Register. The Command Register latches the last
location it was set to. Each data register in the LM89 falls into one of four types of user accessibility:
1. Read only
2. Write only
3. Read/Write same address
4. Read/Write different address
A Write to the LM89 will always include the address byte and the command byte. A write to any register requires
one data byte.
Reading the LM89 can take place either of two ways:
1. If the location latched in the Command Register is correct (most of the time it is expected that the Command
Register will point to one of the Read Temperature Registers because that will be the data most frequently
read from the LM89), then the read can simply consist of an address byte, followed by retrieving the data
byte.
2. If the Command Register needs to be set, then an address byte, command byte, repeat start, and another
address byte will accomplish a read.
Copyright ? 2002–2013, Texas Instruments Incorporated
Product Folder Links: LM89
13
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