MIC280 datasheet(22/23 Pages) MICREL

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MIC280

Micrel

MIC280

November 2004

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 ∆VBE, 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.

REMOTE DIODE (T1)

GUARD/RETURN

VDD

GND

/INT

DATA

CLK

GUARD/RETURN

MIC280

Figure 6. Guard Traces/Kelvin Ground Returns

DATA

SERIAL BUS

HOST

2N3906/�

CPU DIODE

1800pF

MIC280

CLK

/INT

3V to 3.6V

100Ω

3 ×

10k

VDD

GND

0.1µF

ceramic

4.7µF

Figure 7. VDD Decoupling for Very Noisy Supplies

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 VDD pin, and a 4.7 µF, 6.3V electrolytic

capacitor from VDD to GND. See Figure 7.

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