Datasheet
Analog Integrated Circuit Device Data
Freescale Semiconductor 28
MC34708
Functional Block Description
7.3.1.2 Oscillator Specifications
The crystal oscillator has been optimized for use in conjunction with the Micro Crystal CC7V-T1A32.768 kHz-9.0 pF-30 ppm or
equivalent (such as Micro Crystal CC5V-T1A or Epson FC135) and is capable of handling its parametric variations.
The electrical characteristics of the 32 kHz Crystal oscillator are given in the following table, taking into account the crystal
characteristics noted above. The oscillator accuracy depends largely on the temperature characteristics of the crystal. Application
circuits can be optimized for required accuracy by adapting the external crystal oscillator network (via component accuracy and/
or tuning). Additionally, a clock calibration system is provided to adjust the 32.768 cycle counter that generates the 1.0
Hz timer
and RTC registers; see SRTC Support for more detail.
Table 15. Oscillator and Clock Main Electrical Specifications
Characteristics noted under conditions BP = 3.6 V, V
BUS
= 5.0 V, - 40 C T
A
85 C, unless otherwise noted. Typical values
at BP = 3.6 V and T
A
= 25 °C under nominal conditions, unless otherwise noted.
Symbol Characteristic Min Typ Max Unit Notes
OSCILLATOR AND CLOCK OUTPUT
V
INRTC
Operating Voltage
• Oscillator and RTC Block from BP
• Oscillator and RTC Block from LICELL
1.8
1.8
-
-
4.5
3.6
V
I
INRTC
Operating Current Crystal Oscillator and RTC Module
• All blocks disabled, no main battery attached, coin cell is attached
to LICELL
- 2.0 5.0
A
t
START-RTC
RTC oscillator startup time
• Upon application of power
- - 1.0
sec
V
RTCLO
Output Low
• CLK32K Output sink 100 A
• CLK32KMCU Output source 50 A
0.0 - 0.2
V
V
RTCHI
Output High
• CLK32K Output source 100 A
• CLK32KMCU Output sink 50 A
CLK32K
VCC -0.2
VSRTC-0.2
-
-
CLK32K
VCC
VSRTC
V
t
CLK32KET
CLK32K Rise and Fall Time, CL = 50 pF
• CLK32KDRV [1:0] = 00
• CLK32KDRV [1:0] = 01 (default)
• CLK32KDRV [1:0] = 10
• CLK32KDRV [1:0] = 11
-
-
-
-
6.0
2.5
3.0
2.0
-
-
-
-
ns
t
CKL32K
MCUET
CLK32KMCU Rise and Fall Time
•CL = 12 pF
- 22 -
ns
CLK32K
DC/
CLK32K
MCU
DC
CLK32K and CLK32KMCU Output Duty Cycle
• Crystal on XTAL1, XTAL2 pins
45 - 55
%
RMS Output Jitter
• 1 Sigma for Gaussian distribution
- - 30
ns
RMS