MAX6691MUB+ Maxim Integrated Products, MAX6691MUB+ Datasheet - Page 5

• Manufacturer Part Number: MAX6691MUB+
• Description: IC TEMP-TO-PULSE WIDTH 10-UMAX
• Manufacturer: Maxim Integrated Products
• Type: Temperature Sensorr

Specifications of MAX6691MUB+

• Input Type: Logic
• Output Type: Voltage
• Interface: 1-Wire
• Current - Supply: 600µA
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Full Temp Accuracy: +/- 1 C
• Digital Output - Bus Interface: Serial (1-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 55 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 2. Thermistor Resistance vs. Temperature
Figure 3. T
The relationship between temperature and resistance
of an NTC thermistor is highly nonlinear. However, by
connecting the thermistors in series with a properly
chosen resistor (R
sure the voltage across the resistor, a reasonably linear
transfer function can be obtained over a limited temper-
ature range. Linearity improves for smaller temperature
ranges.
Figures 3 and 4 show typical T
standard thermistor in conjunction with values of R
chosen to optimize linearity over two series resistors
chosen to optimize linearity over two different tempera-
ture ranges.
Four-Channel Thermistor Temperature-to-Pulse-
HIGH
T
120
100
1.2
1.0
0.8
0.6
0.4
0.2
HIGH
80
60
40
20
0
0
10K3A1 THERMISTOR WITH R
/T
-40
0
/T
LOW
LOW
-20
20
EXT
_______________________________________________________________________________________
THERMISTOR RESISTANCE
vs. TEMPERATURE FOR BETATHERM
vs. Temperature, R
0
) and using the MAX6691 to mea-
vs. TEMPERATURE
40
TEMPERATURE ( C)
TEMPERATURE ( C)
20
60
40
80
HIGH
60
100
EXT
80
EXT
/T
= 5110
120
LOW
100 120
= 5110
140
curves for a
EXT
NTC thermistors are often described by the resistance
at +25°C. Therefore, a 10k
tance of 10k
ensure that the thermistor’s minimum resistance (which
occurs at the maximum expected operating tempera-
ture) in series with R
erence output current to exceed about 1mA. Some
standard 10k
are listed in Table 1.
Choose R
thermistor:
1) Decide on the temperature range of interest (for
2) Find the thermistor values at the limits of the tem-
3) Find R
The MAX6691 accuracy is relatively unaffected by
power-supply coupled noise. In most applications,
Figure 4. T
example 0°C to +70°C).
perature range. R
value (at the maximum temperature) and R
the maximum thermistor value (at the minimum tem-
perature). Also find R
in the middle of the temperature range (+35°C for
the 0°C to +70°C range).
R
EXT
HIGH
EXT
EXT
T
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
=
HIGH
0
10K3A1 THERMISTOR WITH R
/T
-40
using the equation below:
R
to minimize nonlinearity errors from the
/T
LOW
at +25°C. When choosing a thermistor,
MID
Width Converter
thermistors with similar characteristics
LOW
-20
Power-Supply Considerations
vs. Temperature, R
vs. TEMPERATURE FOR BETATHERM
EXT
R
0
R
MIN
MIN
MIN
TEMPERATURE ( C)
does not cause the voltage ref-
20
MID
is the minimum thermistor
R
40
, the thermistor resistance
R
MAX
MAX
thermistor has a resis-
60
EXT
80
Choosing R
EXT
2
2
R
R
= 7680
100
MIN
= 7680
MID
120
R
MAX
MAX
EXT
is
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