MAX6682MUA+ Maxim Integrated Products, MAX6682MUA+ Datasheet - Page 4

• Manufacturer Part Number: MAX6682MUA+
• Description: IC THERMISTOR TO DGTL 8UMAX
• Manufacturer: Maxim Integrated Products
• Type: Temperature Sensorr

Specifications of MAX6682MUA+

• Input Type: Logic
• Output Type: Logic
• Interface: 3-Wire SPI Serial
• Current - Supply: 29µA
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Full Temp Accuracy: +/- 0.5 C
• Digital Output - Bus Interface: 3-Wire, SPI
• Digital Output - Number Of Bits: 10 bit
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 3 V
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 55 C
• Supply Current: 21 uA
• Ic Output Type: Digital
• Sensing Accuracy Range: ± 0.5°C
• Temperature Sensing Range: -55°C To +125°C
• Supply Voltage Range: 3V To 5.5V
• Resolution (bits): 10bit
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX6682 is a sophisticated interface circuit that
energizes a low-cost thermistor and converts its tem-
perature-dependent resistance to 10-bit digital data.
The MAX6682 powers the thermistor only when a mea-
surement is being made; the power dissipated in the
thermistor is minimized. This virtually eliminates self-
heating, a major component of thermistor error. The
simple serial interface is compatible with common
microcontrollers.
The MAX6682 converts the voltage drop across the
resistor R
ADC. By measuring the voltage across R
code is directly related to temperature when using an
NTC thermistor.
Although the relationship between a thermistor’s resis-
tance and its temperature is very nonlinear, the voltage
across R
ature range, provided that R
example, over a +10°C to +40°C range, the relationship
between the voltage across R
linear to within approximately 0.2°C. Wider temperature
ranges result in larger errors.
The digital output is available as a 10-bit + sign word.
The relationship between the 11-bit digital word and the
voltage across R
where V
ized to the value of V
Thermistor-to-Digital Converter
4
_______________________________________________________________________________________
PIN
1
2
3
4
5
6
7
8
REXT
EXT
EXT
D
OUT
is reasonably linear over a limited temper-
/V
to a digital output using an internal 10-bit
R+
EXT
=
NAME
GND
SCK
V
I.C.
SO
R+
CS
is the voltage across R
R-



CC
V
(normalized to V
R+
REXT
V
Detailed Description
R
.
Temperature Conversion
+
0 010404
−
.
Internally Connected. Connect to GND or leave unconnected.
Reference Voltage Output. External resistor positive input.
External Resistor Negative Input. Connect R- to the junction of the external resistor and the
thermistor.
Ground. Ground connection for MAX6682 and ground return for external thermistor.
Chip Select. Drive CS low to enable the serial interface.
Serial Data Output
Serial Clock Input
Positive Supply. Bypass V
EXT
0 174387
.
EXT
is chosen properly. For
and temperature is
R+

 ×

) is given by:
EXT
8
EXT
, the output
normal-
CC
to GND with a 0.1µF capacitor.
Table 1 shows the relationship between the voltage
across R
also shows the temperature that would produce the list-
ed value of V
in conjunction with R
duces output codes scaled to the actual temperature
when used with the standard thermistor and R
7680Ω over the +10°C to +40°C temperature range.
Under these conditions, the nominal accuracy is about
0.2°C between +10° and +40°C, and about 1.5°C from
0°C to +50°C. In Table 1, the 3LSBs of the output code
represent fractional temperatures. The LSB has a value
of 0.125°C.
All table entries assume no errors in the values of R
or the thermistor resistance. Table 1 also assumes the
use of one of the following standard thermistors:
Betatherm 10K3A1, Dale 1M1002, or Thermometrics
C100Y103J. These thermistors have a nominal resis-
tance of 10kΩ at +25°C and very similar temperature-
to-resistance functions. They give the results shown in
Table 1.
Different temperature ranges can be accommodated as
well using different values of R
External Resistor). The MAX6682 works with thermistors
other than the ones listed above, but the transfer func-
tions vary somewhat.
NTC thermistors are resistive temperature sensors
whose resistance decreases with increasing tempera-
ture. They are available in a wide variety of packages
that are useful in difficult applications such as measure-
ment of air or liquid temperature. Some can operate
over temperature ranges beyond that of most ICs. The
relationship between temperature and resistance in an
FUNCTION
Thermistors and Thermistor Selection
EXT
and the MAX6682’s digital output code. It
REXT
Applications Information
when a standard thermistor is used
EXT
= 7680Ω. The MAX6682 pro-
Pin Description
EXT
(see Choosing the
EXT
EXT
=