AN2623 Freescale Semiconductor / Motorola, AN2623 Datasheet - Page 3

• Manufacturer Part Number: AN2623
• Description: LIN Temperature Sensor Using the MC68HC908QY/QY MCU
• Manufacturer: Freescale Semiconductor / Motorola

Temperature Sensor
Limitation
Hardware
MOTOROLA
Temp. Sensitivity
DC Offset
[mV/°C]
[mV]
LIN Temperature Sensor Using the MC68HC908QT/QY MCU
Note that the 8-bit A/D converter resolution is limited to 19.6 mV, so the
temperature sensitivity of the sensor must be comparable to this value. Of the
mentioned temperature sensors, only MAX6610 and MAX6611 meet this
requirement (see
how the accuracy of the temperature measurement can be degraded if the
temperature sensor not sensitive enough.
Table 2. Temperature Sensor Sensitivity and DC Offset
The common equation suitable to determine the temperature sensor output
voltage is:
The target MCU for the simple temperature sensor is the MC68HC908QY4,
which is one of the MCUs used in the LIN evaluation board described in
AN2573/D: LINkits Evaluation Boards. These boards were developed to
accelerate the creation of new LIN-based applications. LINkits contain all the
necessary components: LIN interface MC33399, voltage stabilizer LT1121,
and discreet elements.
The simplified circuit diagram of a simple temperature sensor can be seen in
Figure
The pin functions are shown in
•
•
•
Freescale Semiconductor, Inc.
MAX6610
For More Information On This Product,
Maxim
MCU
LIN interface (in this case the MC33399)
Two chips (these can be replaced by a single chip, such as the LIN SBC
MC33689)
–
–
1. The distinct components to implement a simple LIN node are:
750
10
V
5-volt regulator (LT1121 or 7805)
Temperature sensor (in this case the MAX6611) — has three pins
(not including those used for power supply)
temp
Go to: www.freescale.com
= DCoffset + Temperature × TempSensitivity
Table
2). The other types are mentioned only to demonstrate
MAX6611
Maxim
Temperature Sensor Type
1200
16
Table
3.
Semiconductor
National
LM66
400
6.2
Semiconductor
National
LM56
395
6.2
AN2623/D
Hardware
(EQ 3)
3