Preventing power-on audio output noise in a wireless telephone handset
US7084701B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 17, 2002 |
| Grant date | Aug 1, 2006 |
| Priority date | — |
| Expiry date | Sep 27, 2024 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02D30/70
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A wireless telephone (10) including audio amplifier circuitry (20) that produces reduced “pop” noise in speakers such as in handsfree headsets (HS) is disclosed. The audio amplifier circuitry (20) includes an audio amplifier (22) that drives the headset speaker (HSS). A first transistor (26) has its source-drain path connected between an output (HSO) of the audio amplifier (22) and a power supply voltage (Vdd), and a second transistor (28) has its source-drain path connected between the amplifier output (HSO) and a reference voltage such as ground. The first and second transistors (26, 28) are controlled by control logic (24), in response to the state of various register locations (30) that indicate the powered-up and enabled state of the audio amplifier circuitry (20). Normal and automatic modes for the precharge control are available, with the automatic mode eliminating the need for the precharge enable register location (30d) being written during operation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.