TC1130_08 Datasheet, PDF (74/114 Pages) Infineon Technologies AG – 32-Bit Single-Chip Microcontroller

TC1130
Functional Description
The oscillator circuit, which is designed to work with an external crystal oscillator or an
external stable clock source, consists of an inverting amplifier with XTAL1 as input and
XTAL2 as output.
Figure 3-17 shows the recommended external oscillator circuitries for both operating
modes, i.e. external crystal mode and external input clock mode.
V_DDOSC V_DDOSC3
V_DDOSC V_DDOSC3
XTAL1
f_OSC
External Clock Signal
XTAL1
f_OSC
4 - 25
MHz
TC1130
Oscillator
TC1130
Oscillator
XTAL2
C₁
C₂
XTAL2
Fundamental
Mode Crystal
V_SSOSC
V_SSOSC
Figure 3-17 Oscillator Circuitries
When using an external clock signal, it must be connected to XTAL1 and XTAL2 is left
open (unconnected). When supplying the clock signal directly, not using a crystal and
the oscillator, the input frequency can be in the range of 0 - 40 MHz if the PLL is not used,
4 - 40 MHz in case the PLL is used.
When using a crystal, its frequency can be within the range of 4 MHz to 25 MHz. An
external oscillator load circuitry must be used, connected to both pins, XTAL1 and
XTAL2. It consists normally of the two load capacitances, C1 and C2. For some crystals,
a series damp resistor may be necessary. The exact values and related operating range
are dependant on the crystal and have to be determined and optimized together with the
crystal vendor using the negative resistance method. As starting point for the evaluation
and for non-productive systems, the following load capacitor values might be used.
Table 3-5 Load Capacitors Select
Fundamental Mode Crystal Frequency
(approx., MHz)
4
8
12
16
Load Capacitors
C1, C2 (pF)
33
18
12
10
Data Sheet
68
V1.1, 2008-12