MIC280_06 Datasheet, PDF (22/23 Pages) Micrel Semiconductor – Precision IttyBitty Thermal Supervisor

MIC280
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 mea-
surement 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 10 mils 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.
Micrel
6. Always place a good quality power supply
bypass capacitor directly adjacent to, or under-
neath, the MIC280. This should be a 0.1 µF ce-
ramic capacitor. Surface-mount parts provide the
best bypassing because of their low inductance.
7. When the MIC280 is being powered from par-
ticularly noisy power supplies, or from supplies
which may have sudden high-amplitude spikes
appearing on them, it can be helpful to add ad-
ditional power supply filtering. This should be
implemented as a 100Ω resistor in series with
the part’s V_DD pin, and a 4.7 µF, 6.3V electrolytic
capacitor from V_DD to GND. See Figure 7.
MIC280
1 VDD
2 GND
3 T1
/INT 6
DATA 5
CLK 4
GUARD/RETURN
REMOTE DIODE (T1)
GUARD/RETURN
Figure 6. Guard Traces/Kelvin Ground Returns
3V to 3.6V
3×
10k
TO
SERIAL BUS
HOST
100Ω
MIC280
5 _DATA
4 _CLK
6 _/INT
VDD ¹
T1 ³
GND ²
0.1µF 4.7µF
ceramic
1800pF
2N3906/�
CPU DIODE
Figure 7. V_DD Decoupling for Very Noisy Supplies
MIC280
22
May 2006