User's Manual l MBa7x UM 0101 l © 2020, TQ-Systems GmbH
Page 16
4.1.4
RTC backup
A CR2032 lithium battery with very low self-discharge is populated on the MBa7x to back-up the RTC on the TQMa7x.
The TQMa7x provides an i.MX7-internal RTC and an optional, discrete RTC.
Both RTCs are supplied by the lithium battery via pin LICELL of the TQMa7x.
Figure 5:
Position of RTC backup battery
The increased current consumption must be considered, if the RTC in the i.MX7 is used. This leads to a fast discharge of the
battery. More information can be found in the TQMa7x User's Manual.
The following tables show details of the RTC backup supply.
Table 12:
Electrical characteristics RTC backup supply
Parameter
Value
Remark
Coin cell voltage
2.1 V to 3.7 V
3.0 V typical
Current consumption i.MX7 RTC
7.1 µA typical
10 µA maximal @ T
amb
= +25 °C
Current consumption discrete RTC DS1339U-33
440 nA typical
7 µA maximal @ T
amb
= +25 °C
Table 13:
RTC backup supply, components
Manufacturer / Number
Description
Sony / CR2032
Lithium battery 3.0 V, 220 mAh
RENATA / SMTU2032
CR2032 battery holder
