User's Manual l TQMa6x & TQMa6xP UM 0403 l © 2019, TQ-Systems GmbH
Page 15
3.2.3
RTC
The i.MX6 provides an RTC, which has its own power domain (SNVS). The accuracy of the RTC is mainly determined by the
characteristics of the quartz used. The type FC-135 used on the TQMa6x has a standard frequency tolerance of
±20 ppm @ +25 °C. The following block diagram shows the implementation on the TQMa6x.
Connector X2
TQMa6x
PMIC
CPU i.MX6
LICELL
LICELL
VSNVS
SNVS
Coin Cell
Li coin cell
SuperCap
Illustration 7:
Block diagram RTC
The RTC power domain SNVS of the i.MX6 is supplied by the PMIC-internal regulator VSNVS. This regulator is supplied either by
VIN (VDD4V2) or by LICELL. LICELL supports coin cells as well as Lithium coin cells or SuperCaps, which can also be charged by
the PMIC. Charging methods and electrical characteristics of the pin LICELL are to be taken from the PMIC data sheet (10).
A coin cell is not suitable for long term bridging because of the high current consumption. A Lithium coin cell or a SuperCap
might be an option depending on the use case. It is to be taken note of that the typical charging current is only 60 µA.
For long term bridging an external RTC connected at the I
2
C bus on the carrier board is recommended.
Table 16:
Current consumption RTC at pin LICELL
Coin Cell voltage
PMIC PF0100A, typical current consumption
2.4 V
85 µA
2.7 V
100 µA
3.0 V
115 µA
3.3 V
130 µA
3.2.4
Temperature sensor
A temperature sensor LM75ADP is assembled on the TQMa6x to monitor the temperature of the TQMa6x.
The LM75ADP is placed on the bottom side of the TQMa6x, (D2 in Illustration 22). Depending on the TQMa6x version,
the temperature sensor is connected to the I2C1 or the I2C3 bus of the i.MX6, see also 3.2.5.9.
The following block diagram shows how the temperature sensor is connected to the i.MX6.
i.MX6
Temperature sensor
I2C[1/3]_SCL
I2C[1/3]_SDA
SCL
SDA
Illustration 8:
Block diagram temperature sensor interface
The “OS”-output (over-temperature shutdown) of the sensor is not connected.
The following table shows the temperature sensor used.
Table 17:
Temperature sensor
Manufacturer
Part number
Resolution
Error
Temperature range
NXP
LM75ADP
11 bit ADC
Max. ±3 °C
–55 °C to +125 °C
The I
2
C address of the temperature sensor is
