LM82CIMQA National Semiconductor, LM82CIMQA Datasheet - Page 16

• Manufacturer Part Number: LM82CIMQA
• Description: IC,SSOP,16PIN
• Manufacturer: National Semiconductor

Specifications of LM82CIMQA

• Rohs Compliant: NO

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4.0 Application Hints
3. Ideally, the LM82 should be placed within 10cm of the
4. Diode traces should be surrounded by a GND guard ring
5. Avoid routing diode traces in close proximity to power
6. Avoid running diode traces close to or parallel to high
7. If it is necessary to cross high speed digital traces, the
8. The ideal place to connect the LM82’s GND pin is as
9. Leakage current between D+ and GND should be kept
Processor diode pins with the traces being as straight,
short and identical as possible. Trace resistance of 1Ω
can cause as much as 1˚C of error.
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.(See Figure 10)
supply switching signals or filtering inductors.
speed digital and bus lines. Diode traces should be kept
at least 2cm. apart from the high speed digital traces.
diode traces and the high speed digital traces should
cross at a 90 degree angle.
close as possible to the Processors GND associated
with the sense diode.
to a minimum. One nano-ampere of leakage can cause
as much as 1˚C of error in the diode temperature read-
ing. Keeping the printed circuit board as clean as pos-
sible will minimize leakage current.
FIGURE 10. Ideal Diode Trace Layout
(Continued)
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16
Noise coupling into the digital lines greater than 300mVp-p
(typical hysteresis), overshoot greater than 500mV above
V
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 termina-
tion 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.
CC
, and undershoot less than 500mV below GND, may