LM95245CIMMX-1 NSC [National Semiconductor], LM95245CIMMX-1 Datasheet - Page 23

• Manufacturer Part Number: LM95245CIMMX-1
• Manufacturer: NSC [National Semiconductor]

7.
8.
9.
Noise coupling into the digital lines greater than 400 mVp-p
(typical hysteresis) and undershoot less than 500 mV below
GND, may prevent successful SMBus communication with
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 LM95245's GND pin is as
close as possible to the Processors GND associated with
the sense diode.
Leakage current between D+ and GND and between D+
and D− should be kept to a minimum. Thirteen nano-
amperes of leakage can cause as much as 0.2°C of error
in the diode temperature reading. Keeping the printed
circuit board as clean as possible will minimize leakage
current.
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the LM95245. SMBus no acknowledge is the most common
symptom, causing unnecessary traffic on the bus. Although
the SMBus maximum frequency of communication is rather
low (100 kHz 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 3 dB corner frequency of about 40 MHz is included on
the LM95245's SMBCLK input. Additional resistance can be
added in series with the SMBDAT and SMBCLK lines to fur-
ther 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 SMBDAT and
SMBCLK lines.
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