Sony Ericsson GM47 - Manual (Page 66)

GM47/GM48 INTEGRATOR’S MANUAL
66
LZT 123 7263 R1C
2.17 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
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.
Pin Signal Dir Description
25 VRTC - Voltage for the Real Time Clock
Parameter Min. Typ. Max. Units
RTC accuracy 20 (52) 40 (104) ppm (s/month)
Parameter Min. Typ. Max. Units
Supply Voltage RTC (normal mode -
charging the capacitor)
1.6 1.8 2.0 V
Supply Voltage RTC (back-up mode -
Capacitor provides the current)
1.0 1.8 2.0 V
Current drawn 5.0 10.0 µA