LM82

SNIS113D – JANUARY 2000 – REVISED MARCH 2013

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Figure 15. Ideal Diode Trace Layout

Noise coupling into the digital lines greater than 300mVp-p (typical hysteresis), overshoot greater than 500mV

above VCC, and undershoot less than 500mV below GND, may prevent successful SMBus communication with

the LM82. 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 R/C lowpass filter with a 3db corner frequency of about 40MHz has been included on the LM82'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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