MIC384-3BMM Micrel Inc, MIC384-3BMM Datasheet - Page 19

• Manufacturer Part Number: MIC384-3BMM
• Description: IC SUPERVISR THERM LOC/REM 8MSOP
• Manufacturer: Micrel Inc

Specifications of MIC384-3BMM

• Function: Temp Monitoring System (Sensor)
• Topology: ADC (Sigma Delta), Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -55°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Layout Considerations
The following guidelines should be kept in mind when design-
ing and laying out circuits using the MIC384:
September 2005
MIC384
1. Place the MIC384 as close to the remote diodes
2. Since any conductance from the various volt-
3. When using the MIC384 to sense the tempera-
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 to the T1 or T2 line can
induce serious errors, it is good practice to guard
the remote diodes’ emitter traces with pairs of
ground traces. These ground traces should be
returned to the MIC384’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 diodes’ own ground
return back to the ground pin of the MIC384,
thereby providing a Kelvin connection for the
base of the diodes. 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 MIC384 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
MIC384 has superb rejection of noise appearing
from collector to GND, as long as the base to
ground connection is relatively quiet.
1
2
3
4
Figure 6. Guard Traces/Kelvin Ground Returns
DATA
CLK
/INT
GND
MIC384
VDD
A0
T1
T2
8
7
6
5
19
REMOTE DIODE (T1)
REMOTE DIODE (T2)
GUARD/RETURN
GUARD/RETURN
GUARD/RETURN
GUARD/RETURN
4. Due to the small currents involved in the mea-
5. In general, wider traces for the ground and
6. Always place a good quality 0.1µF power supply
7. When the MIC384 is being powered from par-
surement of the remote diode’s ΔV
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.
T1/T2 lines will help reduce susceptibility to
radiated noise (wider traces are less inductive).
Use trace widths and spacing of 10 mils wher-
ever possible and provide a ground plane under
the MIC384 and under the connections from
the MIC384 to the remote diodes. This will help
guard against stray noise pickup.
bypass capacitor directly adjacent to, or under-
neath, the MIC384. Surface-mount capacitors
are preferable because of their low inductance.
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 an additional 4.7µF,
6.3V electrolytic capacitor from VDD to GND.
See Figure 7.
BE
, it is
MIC384
Micrel