Method for controlling the charging and discharging phases of a backup capacitor and a circuit configuration for carrying out the method
US6859011B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 6, 2003 |
| Grant date | Feb 22, 2005 |
| Priority date | — |
| Expiry date | Dec 18, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K19/073
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method for controlling the charging and discharging phases of a backup capacitor for a data storage medium has the step where the backup capacitor is first discharged to a defined voltage level before it is charged. The capacitor is discharged using a constant current. This ensures that the charging current for the backup capacitor cannot be used to identify what the charge-state of the capacitor was before discharging. Therefore, it is no longer possible to infer the currents that flowed during security-related arithmetic operations in a data processing unit. In one advantageous circuit configuration, a constant current source is formed by a current-mirror circuit, and a comparator is used to compare the voltage on the backup capacitor with a bandgap reference.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.