XC2288H_11 Datasheet, PDF (117/151 Pages) Infineon Technologies AG – 16/32-Bit Single-Chip Microcontroller with 32-Bit Performance

XC2288H, XC2289H
XC2000 Family / High Line
Electrical Parameters
The timing in the AC Characteristics refers to TCSs. Timing must be calculated using the
minimum TCS possible under the given circumstances.
The actual minimum value for TCS depends on the jitter of the PLL. Because the PLL is
constantly adjusting its output frequency to correspond to the input frequency (from
crystal or oscillator), the accumulated jitter is limited. This means that the relative
deviation for periods of more than one TCS is lower than for a single TCS (see formulas
and Figure 21).
This is especially important for bus cycles using waitstates and for the operation of
timers, serial interfaces, etc. For all slower operations and longer periods (e.g. pulse train
generation or measurement, lower baudrates, etc.) the deviation caused by the PLL jitter
is negligible.
The value of the accumulated PLL jitter depends on the number of consecutive VCO
output cycles within the respective timeframe. The VCO output clock is divided by the
output prescaler K2 to generate the system clock signal f_SYS. The number of VCO cycles
is K2 × T, where T is the number of consecutive f_SYS cycles (TCS).
The maximum accumulated jitter (long-term jitter) D_Tmax is defined by:
D_Tmax [ns] = ±(220 / (K2 × f_SYS) + 4.3)
This maximum value is applicable, if either the number of clock cycles T > (f_SYS / 1.2) or
the prescaler value K2 > 17.
In all other cases for a timeframe of T × TCS the accumulated jitter D_T is determined by:
D_T [ns] = D_Tmax × [(1 - 0.058 × K2) × (T - 1) / (0.83 × f_SYS - 1) + 0.058 × K2]
f_SYS in [MHz] in all formulas.
Example, for a period of 3 TCSs @ 33 MHz and K2 = 4:
D_max = ±(220 / (4 × 33) + 4.3) = 5.97 ns (Not applicable directly in this case!)
D₃ = 5.97 × [(1 - 0.058 × 4) × (3 - 1) / (0.83 × 33 - 1) + 0.058 × 4]
= 5.97 × [0.768 × 2 / 26.39 + 0.232]
= 1.7 ns
Example, for a period of 3 TCSs @ 33 MHz and K2 = 2:
D_max = ±(220 / (2 × 33) + 4.3) = 7.63 ns (Not applicable directly in this case!)
D₃ = 7.63 × [(1 - 0.058 × 2) × (3 - 1) / (0.83 × 33 - 1) + 0.058 × 2]
= 7.63 × [0.884 × 2 / 26.39 + 0.116]
= 1.4 ns
Data Sheet
117
V1.3, 2011-07