Sony Ericsson GM48, GM47 manual Real Time Clock, Vrtc

GM47/GM48 INTEGRATOR’S MANUAL

2.17 Real Time Clock

Pin	Signal	Dir	Description
25	VRTC	-	Voltage for the Real Time Clock

The Real Time Clock (RTC) provides the main microprocessor with a time-of-day calendar and alarm, and a one-hundred-year calendar. It’s accuracy is shown in the table below

Parameter	Min.	Typ.	Max.	Units
RTC accuracy		20 (52)	40 (104)	ppm (s/month)

The Real Time Clock operates in two modes when connected to a separate power supply:

•RTC normal mode: the module is in ON or OFF mode and it is supplied with power (VCC is applied).

•RTC back-up mode: VCC is disconnected and the RTC is maintained by a separate backup power supply connected to the VRTC input (see Figure 2.10 below).

Backup power is provided by a capacitor, golden-capacitor or battery in your application and must be connected to the VRTC pin. During RTC normal operation, the back up source will be charged.

In back-up mode, the back-up source must provide enough power for RTC operation. Refer to the table for the amount of current required.

The following table shows voltage characteristics for both modes.

Parameter	Min.	Typ.	Max.	Units
Supply Voltage RTC (normal mode -	1.6	1.8	2.0	V
charging the capacitor)
Supply Voltage RTC (back-up mode -	1.0	1.8	2.0	V
Capacitor provides the current)
Current drawn		5.0	10.0	µA

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