Table of Contents
Advertisement
BAT-RTC (Backup Battery)
The BAT‐RTC (backup battery) pin is used as a back‐up power supply for the internal Real Time
Clock (RTC). VBATT provides the power supply to the RTC when VBATT is switched on but a
back‐up power supply is needed to save the date and hour when it is switched off.
If VBATT is available, the back‐up battery can be charged by the internal 3.0V power supply
regulator via a 2KΩ resistor implemented inside the WISMO228.
If the RTC is not used, this pin can be left open.
Electrical Characteristics
The following table describes the electrical characteristics of the BAT‐RTC signal.
Parameters
Input voltage
Input current consumption*
Output voltage
Max charging current (@VBATT=3.6V)
*
Provided by an RTC back-up battery when the WISMO228 is off and VBATT = 0V.
Pin Description
The following table provides the pin description of the BAT‐RTC voltage supply.
Pin #
Signal
6
BAT-RTC
Application
The backup power supply can be any of the following:
•
A super capacitor
WA_DEV_W228_PTS_002
Table 33. Electrical Characteristics of the BAT-RTC Signal
Table 34. BAT-RTC Pin Description
I/O
I/O Type
I/O
Supply
RTC Back-up supply
Rev 001
Product Technical Specification &
Customer Design Guidelines
Minimum
Typical
-
3.0
-
2.5
2.82
3.0
-
0.6
Description
Maximum
Unit
-
V
-
µA
3.18
V
-
mA
Page 78 of 108
Advertisement
Table of Contents
