MAX6697_09 Datasheet, PDF (16/18 Pages) Maxim Integrated Products – 7-Channel Precision Temperature Monitor

7-Channel Precision Temperature Monitor
Table 10. Remote-Sensors Transistor
Manufacturer
MANUFACTURER
Central Semiconductor (USA)
Rohm Semiconductor (USA)
Samsung (Korea)
Siemens (Germany)
Zetex (England)
MODEL NO.
CMPT3904
SST3904
KST3904-TF
SMBT3904
FMMT3904CT-ND
Note: Discrete transistors must be diode connected (base
shorted to collector).
Slave Address
Table 11 shows the MAX6697 slave addresses.
Table 11. Slave Address
PART
MAX6697EP34
MAX6697EP38
MAX6697EP99
MAX6697EP9C
MAX6697UP34
MAX6697UP38
MAX6697UP99
MAX6697UP9C
SMBus SLAVE ID
0011 010
0011 100
1001 100
1001 110
0011 010
0011 100
1001 100
1001 110
PIN-PACKAGE
20 QSOP
20 QSOP
20 QSOP
20 QSOP
20 TSSOP
20 TSSOP
20 TSSOP
20 TSSOP
ADC Noise Filtering
The integrating ADC has good noise rejection for low-
frequency signals such as power-supply hum. In envi-
ronments with significant high-frequency EMI, connect
an external 2200pF capacitor between DXP_ and
DXN_. Larger capacitor values can be used for added
filtering, but do not exceed 3300pF because it can
introduce errors due to the rise time of the switched
current source. High-frequency noise reduction is
needed for high-accuracy remote measurements.
Noise can be reduced with careful PCB layout as dis-
cussed in the PCB Layout section.
PCB Layout
Follow these guidelines to reduce the measurement
error when measuring remote temperature:
1) Place the MAX6697 as close as is practical to the
remote diode. In noisy environments, such as a
computer motherboard, this distance can be 4in to
8in (typ). This length can be increased if the worst
noise sources are avoided. Noise sources include
CRTs, clock generators, memory buses, and PCI
buses.
2) Do not route the DXP-DXN lines next to the deflec-
tion coils of a CRT. Also, do not route the traces
across fast digital signals, which can easily intro-
duce +30°C error, even with good filtering.
3) Route the DXP and DXN traces in parallel and in
close proximity to each other. Each parallel pair of
traces should go to a remote diode. Route these
traces away from any higher voltage traces, such as
+12VDC. Leakage currents from PCB contamination
must be dealt with carefully since a 20MΩ leakage
path from DXP to ground causes about +1°C error.
If high-voltage traces are unavoidable, connect
guard traces to GND on either side of the DXP-DXN
traces (Figure 5).
4) Route through as few vias and crossunders as pos-
sible to minimize copper/solder thermocouple
effects.
5) Use wide traces when practical.
6) When the power supply is noisy, add a resistor (up
to 47Ω) in series with V_CC.
GND
10 mils
DXP
10 mils
DXN
GND
10 mils
MINIMUM
10 mils
Figure 5. Recommended DXP-DXN PCB Traces
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