pi6c3622 Pericom Semiconductor Corporation, pi6c3622 Datasheet - Page 3

• Manufacturer Part Number: pi6c3622
• Description: Low Power Spread Spectrum Frequency Multiplier
• Manufacturer: Pericom Semiconductor Corporation

Timing Diagram
The following diagrams demonstrate the characteristics of the output signals when SSON Pin is switched off
to disable the feature and switched on to enable to spread spectrum feature. The spreading ratio is set at ±1.0%,
and the input frequency is 27MHz when the diagrams are generated.
Figure 1 and 2 demonstrate the responses of the output signal when then SSON pin is switched from high to
low to disable the spread spectrum feature. When the feature is disabled, the output signal takes approximately
400us to re-lock from -1.0% to 0% frequency offset. When spread spectrum feature is disabled, the system
must wait 1ms before the output signal can be used in order to maintain maximal system stability. This delay
allows the output signal to settle properly to the required frequency.
Figure 1 and 3 demonstrates the responses of the output signal when then SSON pin is switched from low to
high to enable the spread spectrum feature. The spreading ratio is twice of the expected value immediately
after the switching. The spreading ratio then gradually settles to the expected value in approximately 400us.
Figure 1 shows that it takes 400us for the spreading ratio to settle from ±2.0% to the expected ±1.0%. System
designer should take this initial spreading ratio that is twice of the expected value into consideration when
designing the system when designing the system in order to maintain maximal system stability.
Figure 1. Frequency trend of the output signal when SSON is switched on and then off
3
Low Power Spread Spectrum Frequency Multiplier
SSCG-GP Family
PS8939A
PI6C3622
01/29/08