Spread-spectrum clock buffer/driver that modulates clock period by switching loads
US6501307B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Nov 12, 2001 |
| Grant date | Dec 31, 2002 |
| Priority date | — |
| Expiry date | Nov 12, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B2215/067
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A clock modulator spreads the frequency spectrum of an input clock to generate an output clock. A capacitor is connected to an intermediate clock node by a load-switching transistor. When the transistor is turned on, the capacitor increases the loading on the intermediate clock node, increasing delay. When the transistor is turned off, the delay is reduced. Output clock cycle periods are extended when delay is added, and reduced when the transistor turns off. A counter or sequencer is clocked by the input clock and drives the load-switching transistor. The transistor is turned on and off for alternate cycles when the counter is a toggle flip-flop, spreading the frequency over two frequencies every two clock cycles. Two capacitors of different sizes, connected to the intermediate clock node by two transistors, can be switched by a 2-bit sequencer, spreading the output clock over 7 frequencies every 7 clock cycles.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.