SH7018 Datasheet, PDF (62/431 Pages) Renesas Technology Corp – SuperH™ RISC engine

Notes on Duty Adjustment: Duty adjustment circuit is performed on an input clock of 5 MHz or
higher. With a frequency of less than 5 MHz, duty adjustment may not be performed, but AC
characteristics t_CH (clock high-level width) and t_CL (clock low-level width) are satisfied, and there
is no problem with SH7018 internal operation. Figure 4.6 shows the basic characteristics of the
duty adjustment circuit.
The duty adjustment circuit does not correct for transient fluctuations or jitter in the input clock.
Thus, several tens of µs are required until duty adjustment is performed and a stable clock is
obtained.
70
Input duty
70
60
60
50
50
40
40
30
30
1
2
5
10
20
Input frequency (MHz)
Figure 4.6 Duty Adjustment Circuit Characteristics
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