MIC280_14 Datasheet, PDF (26/28 Pages) Micrel Semiconductor – Precision IttyBitty™ Thermal Supervisor

Micrel, Inc.
MIC280
providing a Kelvin connection for the base of the
diode. See Figure 6.
3. When using the MIC280 to sense the temperature of a
processor or other device which has an integral
thermal diode, e.g., Intel's Pentium II, III, IV, AMD
Athlon CPU, Xilinx Virtex FPGAs, connect the emitter
and base of the remote sensor to the MIC280 using
the guard traces and Kelvin return shown in Figure 6.
The collector of the remote diode is typically
inaccessible to the user on these devices. To allow for
this, the MIC280 has superb rejection of noise
appearing from collector to GND.
4. Due to the small currents involved in the measurement
of the remote diode’s ∆V_BE, it is important to
adequately clean the PC board after soldering to
prevent current leakage. This is most likely to show up
as an issue in situations where water-soluble soldering
fluxes are used.
5. In general, wider traces for the ground and T1 lines will
help reduce susceptibility to radiated noise (wider
traces are less inductive). Use trace widths and
spacing of 10mm wherever possible and provide a
ground plane under the MIC280 and under the
connections from the MIC280 to the remote diode.
This will help guard against stray noise pickup.
6. Always place a good quality power supply bypass
capacitor directly adjacent to, or underneath, the
MIC280. This should be a 0.1 µF ceramic capacitor.
Surface-mount parts provide the best bypassing
because of their low inductance.
7. When the MIC280 is being powered from particularly
noisy power supplies, or from supplies which may
have sudden high-amplitude spikes appearing on
them, it can be helpful to add additional power supply
filtering. This should be implemented as a 100Ω
resistor in series with the part’s VDD pin, and a 4.7µF,
6.3V electrolytic capacitor from VDD to GND. See
Figure 7.
Figure 6. Guard Traces/Kelvin Ground Returns
May 5, 2014
Figure 7. VDD Decoupling for Very Noisy Supplies
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Revision 2.0