LM96163C NSC [National Semiconductor], LM96163C Datasheet - Page 39

• Manufacturer Part Number: LM96163C
• Manufacturer: NSC [National Semiconductor]

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Noise coupling into the digital lines greater than 400 mVp-p
(typical hysteresis) and undershoot less than 500 mV below
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 2 cm 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 LM96163's GND pin is as
close as possible to the Processor's GND associated
with the sense diode.
Leakage current between D+ and GND 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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GND, may prevent successful SMBus communication with
the LM96163. 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 LM96163'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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