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| 型号： | LM89EVAL |
| 厂商： | National Semiconductor |
| 文件页数： | 24/32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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SNIS128C – AUGUST 2002 – REVISED MARCH 2013
as possible to the LM89's D+ and D ? pins. Make sure the traces to the 2.2nF capacitor are matched.
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Ideally, the LM89 should be placed within 10cm of the Processor diode pins with the traces being as straight,
short and identical as possible. Trace resistance of 1 Ω can cause as much as 1°C of error. This error can be
compensated by using the Remote Temperature Offset Registers, since the value placed in these registers
will automatically be subtracted from or added to the remote temperature reading.
Diode traces should be surrounded by a GND guard ring to either side, above and below if possible. This
GND guard should not be between the D+ and D ? lines. In the event that noise does couple to the diode
lines it would be ideal if it is coupled common mode. That is equally to the D+ and D ? lines.
Avoid routing diode traces in close proximity to power supply switching or filtering inductors.
Avoid running diode traces close to or parallel to high speed digital and bus lines. Diode traces should be
kept at least 2cm apart from the high speed digital traces.
If it is necessary to cross high speed digital traces, the diode traces and the high speed digital traces should
cross at a 90 degree angle.
The ideal place to connect the LM89's GND pin is as close as possible to the Processors GND associated
with the sense diode.
Leakage current between D+ and GND should be kept to a minimum. One nano-ampere of leakage can
cause as much as 1°C of error in the diode temperature reading. Keeping the printed circuit board as clean
as possible will minimize leakage current.
Noise coupling into the digital lines greater than 400mVp-p (typical hysteresis) and undershoot less than 500mV
below GND, may prevent successful SMBus communication with the LM89. SMBus no acknowledge is the most
common symptom, causing unnecessary traffic on the bus. Although the SMBus maximum frequency of
communication is rather low (100kHz max), care still needs to be taken to ensure proper termination within a
system with multiple parts on the bus and long printed circuit board traces. An RC lowpass filter with a 3db
corner frequency of about 40MHz is included on the LM89's SMBCLK input. Additional resistance can be added
in series with the SMBData and SMBCLK lines to further help filter noise and ringing. Minimize noise coupling by
keeping digital traces out of switching power supply areas as well as ensuring that digital lines containing high
speed data communications cross at right angles to the SMBData and SMBCLK lines.
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Product Folder Links: LM89
Copyright ? 2002–2013, Texas Instruments Incorporated
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