Product Info

Smart Module Series
SC600Y&SC600T Hardware Design
SC600Y&SC600T_Hardware_Design 42 / 134
3.6. VRTC Interface
The RTC (Real Time Clock) can be powered by an external power source through VRTC when the
module is powered down and there is no power supply for the VBAT. The external power source can be
rechargeable battery (such as coil cells) according to application demands. The following reference circuit
design when an external battery is utilized for powering RTC.
Figure 10: RTC Powered by Coin Cell
If RTC is ineffective, it can be synchronized through network after the module is powered on.
 2.0V~3.25V input voltage range and 3.0V typical value for VRTC, when VBAT is disconnected.
 When powered by VBAT, the RTC error is 50ppm. When powered by VRTC, the RTC error is about
200ppm.
 If the rechargeable battery is used, the ESR of battery should be less than 2KΩ, and it is
recommended to use the MS621FE FL11E of SEIKO.