User's Manual l TQMa335xL UM 0101 l © 2019, TQ-Systems GmbH
Page 12
3.2.3
AM335x-RTC, PMIC-RTC
Both the AM335x and the PMIC on the TQMa335xL provide an RTC, which have their own power domain VRTC.
The RTC power domain VRTC of the CPU is supplied by the PMIC through an internal regulator.
The PMIC is either supplied by V
IN
(VCC3V3IN), or through the PMIC backup supply pin VBACKUP_PMIC,
which is routed to TQMa335xL pad C9.
The PMIC can charge a battery or a SuperCap connected through TQMa335xL pad C9.
Charging methods and electrical characteristics are to be taken from the PMIC User’s Guide (6).
The typical current consumption of the PMIC_RTC is approximately 20 µA @ 3 V.
The accuracy of the RTC is mainly determined by the characteristics of the quartz used. The 32.768 kHz crystal type FC-135 used
on the TQMa335xL has a standard frequency tolerance of ±20 ppm @ +25 °C. (Parabolic coefficient: max. –0.04 × 10
–6
/ °C
2
.)
Note: Current consumption
Long-term bridging with a coin cell is not possible due to the high current consumption
of the PMIC-RTC. Depending on the use case a Li coin cell or a SuperCap can be used.
