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Preliminary User's Manual l TQMa335x UM 002 l © 2013 TQ-Group
3.2.4
Page 11
Temperature sensor
A temperature sensor for supervision of the module temperature is provided on the TQMa335x.
The sensor is placed on the bottom side of the module (D8 in Illustration 17).
The temperature sensor is connected to the I2C bus 0 of the processor.
The overtemperature detection output of the sensor is not connected to the CPU.
The following block diagram shows how the temperature sensor is connected to the processor.
Illustration 8:
Block diagram temperature sensor connection
The following table shows the temperature sensor used.
Table 11:
Temperature sensor
Manufacturer
NXP
Part number
SE97BTP
Remark
11 bit ADC
Error
Max. ±1 °C
Temperature range
–40 °C to +125 °C
The I2C address of the temperature sensor is 0x1F / 0b001 1111.
3.2.5
RTC
Both the AM335x and the PMIC on the TQMa335x provide an RTC. The RTC pins of the PMIC are routed to the module connector
(VBACKUP_PMIC) to connect a backup supply. For the RTC to work reliably the voltage at pin “VBACKUP_PMIC” has to be in the
range of 2.3 V to 3.0 V.
The RTC used depends on the software implementation. More details are to be taken from the Texas Instruments Reference
Manual of the CPU and the PMIC. The accuracy of the RTC is mainly determined by the characteristics of the quartz used.
The type FC-135 used on the TQMa335x has a standard frequency tolerance of ±20 ppm @ 25 °C.
(Parabolic coefficient: max. –0.04 × 10–6 / °C2).
An optional RTC DS1339U-33 is also available. This optional RTC is supplied through pin VBACKUP_RTC.
The PMIC on the TQMa335x provides a backup supply voltage. It supports coin cells, Lithium coin cells or Supercapacitors.
Charging methods and electrical characteristics of the pin VBACKUP_RTC of the PMIC are to be taken from the User’s Guide of
the PMIC TPS65910 (6).
The typical current consumption of the different RTCs is shown in the following table:
Table 12:
Current consumption RTC
RTC
Typical current consumption
Remark
PMIC RTC
Approximately 6.0 µA
–
CPU RTC
>5 mA
Supply has to be configured in PMIC
DS1339U-33
400 nA to 700 nA
–