TC1762 Datasheet, PDF (65/114 Pages) Infineon Technologies AG – 32-Bit Single-Chip Microcontroller TriCore

TC1762
Preliminary
Functional Description
are derived from f_VCO only by the K-Divider. In this mode, the system clock f_SYS is
equal to f_CPU.
XTAL1
XTAL2
Oscillator ^fOSC
Circuit
Osc. Run
Detect.
P
Divi-
der
Clock Generation Unit (CGU)
1
M
≥1
Phase
Detect.
VCO
f_VCO
U
X
0
N
Divider
PLL
1:1
Divider
K:1
Divider
M
f_SYS
U
X
f_CPU
Lock
Detector
BYPASS ^{OGC MOSC OSCR PDIV OSC PLL_}
[2:0] DISC LOCK
NDIV VCO_ VCO_ KDIV SYS PLL_
[6:0] SEL[1:0] BYPASS [3:0] FSL BYPASS
OSC_
BYPASS
Register
OSC_CON
Register PLL_CLC
System Control Unit (SCU)
MCA06083
Figure 3-14 Clock Generation Unit
Recommended Oscillator Circuits
The oscillator circuit, a Pierce oscillator, is designed to work with both, an external crystal
oscillator or an external stable clock source. It basically consists of an inverting amplifier
and a feedback element with XTAL1 as input, and XTAL2 as output.
When using a crystal, a proper external oscillator circuitry must be connected to both
pins, XTAL1 and XTAL2. The crystal frequency can be within the range of 4 MHz
to 25 MHz. Additionally, it is necessary to have two load capacitances C_X1 and C_X2, and
depending on the crystal type, a series resistor R_X2, to limit the current. A test resistor R_Q
may be temporarily inserted to measure the oscillation allowance (negative resistance)
of the oscillator circuitry. R_Q values are typically specified by the crystal vendor. The C_X1
and C_X2 values shown in Figure 3-15 can be used as starting points for the negative
resistance evaluation and for non-productive systems. The exact values and related
operating range are dependent on the crystal frequency and have to be determined and
optimized together with the crystal vendor using the negative resistance method.
Data Sheet
61
V1.0, 2008-04