MIC284-3BM TR Micrel Inc, MIC284-3BM TR Datasheet - Page 19

• Manufacturer Part Number: MIC284-3BM TR
• Description: IC SUPERVISOR THERM 2ZONE 8-SOIC
• Manufacturer: Micrel Inc
• Series: SilentSense™r

Specifications of MIC284-3BM TR

• Function: Temp Monitoring System (Sensor)
• Topology: ADC (Sigma Delta), Comparator, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -55°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: MIC284-3BMTR; MIC284-3BMTR

September 2005
MIC284
1. Place the MIC284 as close to the remote diode
2. Since any conductance from the various volt-
3. When using the MIC284 to sense the tempera-
4. Due to the small currents involved in the mea-
as possible, while taking care to avoid severe
noise sources such as high frequency power
transformers, CRTs, memory and data busses,
and the like.
ages on the PC Board and the T1 line can in-
duce serious errors, it is good practice to guard
the remote diode’s emitter trace with a pair of
ground traces. These ground traces should be
returned to the MIC284’s own ground pin. They
should not be grounded at any other part of their
run. However, it is highly desirable to use these
guard traces to carry the diode’s own ground
return back to the ground pin of the MIC284,
thereby providing a Kelvin connection for the
base of the diode. See Figure 6.
ture of a processor or other device which has an
integral thermal diode, e.g., Intel’s Pentium III,
connect the emitter and base of the remote sen-
sor to the MIC284 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
MIC284 has superb rejection of noise appearing
from collector to GND, as long as the base to
ground connection is relatively quiet.
surement of the remote diode’s ΔV
important to adequately clean the PC board after
soldering to prevent current leakage. This is
OVER-TEMP
SERIAL BUS
SHUTDOWN
FROM
HOST
10k pull-ups
3.3V
Figure 7. V
1
2
3
4
Figure 6. Guard Traces/Kelvin Ground Returns
DATA
CLK
/INT
GND
MIC284
BE
, it is
DATA
CLK
/INT
/CRIT
/CRIT
VDD
DD
A0
T1
MIC284
Decoupling for Very Noisy Supplies
100
8
7
6
5
GND
VDD
A0
T1
19
REMOTE DIODE (T1)
GUARD/RETURN
GUARD/RETURN
0.1F
5. In general, wider traces for the ground and T1
6. Always place a good quality power supply
7. When the MIC284 is being powered from par-
most likely to show up as an issue in situations
where water-soluble soldering fluxes are used.
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 MIC284 and under the connections from
the MIC284 to the remote diode. This will help
guard against stray noise pickup.
bypass capacitor directly adjacent to, or un-
derneath, the MIC284. This should be a 0.1µF
ceramic capacitor. Surface-mount parts provide
the best bypassing because of their low induc-
tance.
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 4.7µF, 6.3V electrolytic
capacitor from VDD to GND. See Figure 7.
4.7F
2200pF
Remote
Diode
Micrel, Inc.
MIC284