MAX6581TG9A+ Maxim Integrated Products, MAX6581TG9A+ Datasheet - Page 21

• Manufacturer Part Number: MAX6581TG9A+
• Description: Board Mount Temperature Sensors 1 C ACCUR 8-CH TEMP SENSR
• Manufacturer: Maxim Integrated Products

Specifications of MAX6581TG9A+

• Full Temp Accuracy: +/- 1 C
• Package / Case: TQFN-24
• Digital Output - Bus Interface: I2C
• Digital Output - Number Of Bits: 11 bit
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 3 V
• Description/function: Multichannel Temperature Sensor
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Supply Current: 4 uA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 13. Remote Sensors Transistor Suppliers (for Channels 1–7)
Note: Discrete transistors must be diode connected (base shorted to collector).
If one or more of the remote-diode channels is not
needed, disconnect the DXP_ and DXN_ inputs for
that channel, or connect the DXP_ to the correspond-
ing DXN_. The status register indicates a diode “fault”
for this channel and the channel is ignored during the
temperature-measurement sequence. It is also good
practice to mask any unused channels immediately upon
power-up by setting the appropriate bits in the ALERT
Mask and OVERT Mask registers. This prevents unused
channels from causing ALERT or OVERT to assert.
When sensing local temperature, the MAX6581 mea-
sures the temperature of the PCB to which it is soldered.
The leads provide a good thermal path between the PCB
traces and the die. As with all IC temperature sensors,
thermal conductivity between the die and the ambient
air is poor by comparison, making air-temperature mea-
surements impractical. Since the thermal mass of the
PCB is far greater than that of the MAX6581, the device
follows temperature changes on the PCB with little or no
perceivable delay. When measuring the temperature of a
CPU, or other IC with an on-chip sense junction, thermal
mass has virtually no effect; the measured temperature
of the junction tracks the actual temperature within a
conversion cycle. When measuring temperature with
discrete remote transistors, the best thermal-response
Siemens (Germany)
Zetex (England)
Central Semiconductor Corp. (USA)
Fairchild Semiconductor (USA)
Infineon (Germany)
ON Semiconductor (USA)
ROHM Semiconductor (USA)
Samsung (Korea)
±1°C Accurate 8-Channel Temperature Sensor
SUPPLIER
Thermal Mass and Self-Heating
______________________________________________________________________________________
Unused Diode Channels
CMPT3906
2N3906
MMBT3906
2N3906
SMBT3906
MMBT3906
2N3906
SST3906
KST3906-TF
SMBT3906
FMMT3906CT-ND
PNP
Table 14. Slave Address
times are obtained with transistors in small packages
(i.e., SOT23 or SC70). Take care to account for thermal
gradients between the heat source and the sensor,
and ensure that stray air currents across the sensor
package do not interfere with measurement accuracy.
Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible.
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 100pF capacitor between DXP_ and DXN_.
Larger capacitor values can be used for added filter-
ing; however, it can introduce errors due to the rise time
of the switched current source. High-frequency noise
reduction is needed for high-accuracy remote measure-
ments. Noise can be reduced with careful PCB layout as
discussed in the PCB Layout section.
The slave address for the MAX6581 is shown in Table 14.
A7
1
A6
0
MODEL NO.
A5
0
DEVICE ADDRESS
CMPT3904
2N3904
2N3904
—
2N3904
SST3904
KST3904-TF
SMBT3904
FMMT3904CT-ND
A4
1
A3
1
ADC Noise Filtering
NPN
A2
0
Slave Address
A1
1
R/W
A0
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