MAX6692MUA Maxim Integrated Products, MAX6692MUA Datasheet - Page 13

• Manufacturer Part Number: MAX6692MUA
• Description: Board Mount Temperature Sensors
• Manufacturer: Maxim Integrated Products

Specifications of MAX6692MUA

• Full Temp Accuracy: +/- 3 C
• Package / Case: uSOP
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 10 bit + Sign
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: 0 C
• Output Type: Digital
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Temperature Sensors with Overtemperature Alarms
be low enough to alter the effective ideality factor.
Good results can be obtained if the process is consis-
tent and well behaved. For example, the curve shown
in the Remote Temperature Error vs. 45nm Remote
Diode Temperature graph in the Typical Operating
Characteristics section shows the temperature mea-
surement error of the MAX6648/MAX6692 when used
with a typical 45nm CPU thermal diode. Note that the
error is effectively a simple +4°C offset.
The integrating ADC used has good noise rejection for
low-frequency signals such as 60Hz/120Hz power-sup-
ply hum. In noisy environments, high-frequency noise
reduction is needed for high-accuracy remote mea-
surements. The noise can be reduced with careful PCB
layout and proper external noise filtering.
High-frequency EMI is best filtered at DXP and DXN with
an external 2200pF capacitor. Larger capacitor values
can be used for added filtering, but do not exceed
3300pF because larger values can introduce errors due
to the rise time of the switched current source.
Follow these guidelines to reduce the measurement
error of the temperature sensors:
1) Place the MAX6648/MAX6692 as close as is practi-
2) Do not route the DXP-DXN lines next to the deflec-
3) Route the DXP and DXN traces in parallel and in
4) Route through as few vias and crossunders as pos-
5) When introducing a thermocouple, make sure that
cal 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
ISA/PCI buses.
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.
close proximity to each other, away from any higher
voltage traces, such as 12V DC. 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 4).
sible to minimize copper/solder thermocouple
effects.
both the DXP and the DXN paths have matching
thermocouples. A copper-solder thermocouple
Precision SMBus-Compatible Remote/Local
______________________________________________________________________________________
ADC Noise Filtering
PCB Layout
6) Use wide traces. Narrow traces are more inductive
7) Add a 200Ω resistor in series with V
8) Copper cannot be used as an EMI shield; only fer-
Use a twisted-pair cable to connect the remote sensor
for remote-sensor distance longer than 8in, or in very
noisy environments. Twisted-pair cable lengths can be
between 6ft and 12ft before noise introduces excessive
errors. For longer distances, the best solution is a
shielded twisted pair like that used for audio micro-
phones. For example, Belden 8451 works well for dis-
tances up to 100ft in a noisy environment. At the
device, connect the twisted pair to DXP and DXN and
the shield to GND. Leave the shield unconnected at the
remote sensor.
For very long cable runs, the cable’s parasitic capaci-
tance often provides noise filtering, so the 2200pF
capacitor can often be removed or reduced in value.
Cable resistance also affects remote-sensor accuracy.
For every 1Ω of series resistance, the error is approxi-
mately 0.5°C.
Figure 4. Recommended DXP-DXN PC Traces
10MILS
10MILS
exhibits 3µV/°C, and takes about 200µV of voltage
error at DXP-DXN to cause a 1°C measurement
error. Adding a few thermocouples causes a negligi-
ble error.
and tend to pick up radiated noise. The 10mil widths
and spacing recommended in Figure 4 are not
absolutely necessary, as they offer only a minor
improvement in leakage and noise over narrow
traces. Use wider traces when practical.
filtering (see Typical Operating Circuit ).
rous materials such as steel work well. Placing a
copper ground plane between the DXP-DXN traces
and traces carrying high-frequency noise signals
does not help reduce EMI.
Twisted-Pair and Shielded Cables
GND
GND
DXP
DXN
CC
for best noise
10MILS
MINIMUM
10MILS
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