User's Manual l TQMa8MxML UM 0103 l © 2022, TQ-Systems GmbH
Page 26
3.2.4
RTC
The TQMa8MxML provides an i.MX 8M Mini-internal RTC or a discrete RTC PCF85063A.
3.2.4.1
i.MX 8M Mini-internal RTC
The i.MX 8M Mini provides an RTC, which has its own power domain (V_0V8_SNVS). The RTC power domain SNVS of the
i.MX 8M Mini is supplied by the PMIC. The PMIC is supplied by the TQMa8MxML input voltage of V_5V_IN.
The quartz used to clock the RTC has a standard frequency tolerance of ±20 ppm @ +25 °C.
LGA
PMIC
i.MX 8M Mini / Nano
LDO
VDD_SNVS_0P8
V_5V_IN
5 V
INL1
Figure 8:
Block diagram RTC supply (TQMa8MxML without discrete RTC)
Note: RTC power supply
The CPU internal RTC can be used in regular operation. If the TQMa8MxML supply (5 V) fails,
it is no longer available, since the i.MX 8M Mini's SNVS rail is no longer supplied.
3.2.4.2
Discrete RTC PCF85063A
In addition to the i.MX 8M Mini-internal RTC the TQMa8MxML provides a discrete RTC PCF85063A, which is connected to I2C1.
The quartz used to clock the RTC has a standard frequency tolerance of ±20 ppm @ +25 °C.
The discrete RTC has an interrupt output which provides the open-drain signal at LGA pad E14 (RTC_EVENT#).
This pad requires a pull-up to 3.3 V on the carrier board.
The RTC PCF85063A is only directly supplied by V_LICELL when the PMIC or the TQMa8MxML supply is switched off.
During normal operation of the TQMa8MxML, the PMIC supplies 3.3 V.
LGA
V_5V_IN
VDD
Power
supply
V_LICELL
PCF85063ATL
VDD
PMIC
INL
Protection
Protection
BUCK
Coin Cell
(typ. 3 V)
Figure 9:
Block diagram RTC supply (TQMa8MxML with discrete RTC)
The discrete RTC has I
2
C address
Note: RTC power supply
The SNVS functions of the i.MX 8M Mini can only be used if the TQMa8MxML is supplied with 5 V.
It is not possible to obtain these functions by a separate supply during a reset.
Since the SNVS rail is not supplied when the TQMa8MxML is not powered-up, it is recommended to
use the optional RTC PCF85063A.
