MAX6680MEE+T Maxim Integrated Products, MAX6680MEE+T Datasheet - Page 8

• Manufacturer Part Number: MAX6680MEE+T
• Description: IC TEMP SENSOR SMBUS 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX6680MEE+T

• Function: Thermometer, Thermostat
• Topology: ADC, Multiplexer, 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: 3 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 5 C, +/- 3 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 10 bit + Sign
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 55 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ply hum. In noisy environments, high-frequency noise
reduction is needed for high-accuracy remote mea-
surements. The noise can be reduced with careful PC
board 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 it 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 MAX6680/MAX6681 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
6) Use wide traces. Narrow traces are more inductive
7) Add a 200Ω resistor in series with V
±1°C Fail-Safe Remote/Local Temperature
Sensors with SMBus Interface
8
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 12VDC. Leakage currents
from PC board contamination must be dealt with care-
fully 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 2).
sible to minimize copper/solder thermocouple
effects.
both the DXP and the DXN paths have matching
thermocouples. A copper-solder thermocouple
exhibits 3µV/°C, and it 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 spacings that are recommended in Figure 2 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 the Typical Operating Circuit).
_______________________________________________________________________________________
PC Board Layout
CC
for best noise
Use a twisted-pair cable to connect the remote sensor
for remote-sensor distances 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 1/2°C error.
Standby mode reduces the supply current to less than
10µA by disabling the ADC. Enter hardware standby by
forcing the STBY pin low, or enter software standby by
setting the RUN/STOP bit to 1 in the Configuration Byte
register. Hardware and software standbys are very sim-
ilar: all data is retained in memory, and the SMB inter-
face is alive and listening for SMBus commands, but
the SMBus timeout is disabled. The only difference is
that in software standby mode, the One-Shot command
initiates a conversion. With hardware standby, the One-
Shot command is ignored. Activity on the SMBus caus-
es the device to draw extra supply current (see the
Typical Operating Characteristics).
Driving the STBY pin low overrides any software con-
version command. If a hardware or software standby
command is received while a conversion is in progress,
the conversion cycle is interrupted, and the tempera-
Figure 2. Recommended DXP-DXN PC Traces
10mils
10mils
Twisted-Pair and Shielded Cables
Low-Power Standby Mode
GND
GND
DXP
DXN
10mils
MINIMUM
10mils