Analog Integrated Circuit Device Data
Freescale Semiconductor
100
PC34708
Functional Block Requirements and Behaviors
32.768 kHz Crystal Oscillator RTC Block Description and Application Information
7.9
32.768 kHz Crystal Oscillator RTC Block Description and
Application Information
7.9.1
Clock Generation
A system clock is generated for internal digital circuitry as well as for external applications utilizing the clock output pins. A crystal
oscillator is used for the 32.768 kHz time base and generation of related derivative clocks. If the crystal oscillator is not running
(for example, if the crystal is not present), an internal 32 kHz oscillator will be used instead.
Support is also provided for an external Secure Real Time Clock (SRTC) which may be integrated on a companion system
processor IC. For media protection in compliance with Digital Rights Management (DRM) system requirements, the
CLK32KMCU can be provided as a reference to the SRTC module where tamper protection is implemented.
7.9.1.1
Clocking Scheme
The internal 32 kHz oscillator is an integrated backup for the crystal oscillator, and provides a 32.768 kHz nominal frequency at
±60% accuracy, if running. The internal oscillator only runs if a valid supply is available at BP, and would not be used as long as
the crystal oscillator is active. In absence of a valid supply at the BP supply node (for instance due to a dead battery), the crystal
Table 104. Core Voltages Electrical Specifications
Characteristics noted under conditions BP = 3.6 V, VBUS = 5.0 V, -40°C ≤ TA ≤ 85°C, unless otherwise noted. Typical values at
BP = 3.6 V and TA = 25°C under nominal conditions, unless otherwise noted.
Symbol
Characteristic
Min
Typ
Max
Unit
Notes
VCOREDIG (DIGITAL CORE SUPPLY)
VCOREDIG Output voltage
ON mode and OFF with good battery mode, and charging
(66) RTC mode
VCOREDIG
-
1.5
0
1.0
-
V
μF
VDDLP (DIGITAL CORE SUPPLY - LOWER POWER)
VDDLP
Output voltage
ON mode with good battery
(67) OFF mode with good battery
RTC mode
VDDLP
-
1.5
1.2
100
-
V
pF
VCORE (ANALOG CORE SUPPLY)
VCORE
Output voltage
OFF and RTC mode
VCORE
-
2.775
0
1.0
-
V
μF
VREFCORE (BANDGAP / REGULATOR REFERENCE)
-
1.2
-
V
Absolute Accuracy
-
0.5
-
%
Temperature Drift
Bypass capacitor
-
0.25
100
-
%
nF
Notes
66.
3.0 V < BP < 4.5 V, no external loading on VCOREDIG, VDDLP, VCORE, or REFCORE. Extended operation down to UVDET, but no
system malfunction.
67.
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