Coded data generation or conversion – Analog to or from digital conversion – Digital to analog conversion
Reexamination Certificate
1997-09-30
2001-08-28
JeanPierre, Peguy (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Digital to analog conversion
C341S135000
Reexamination Certificate
active
06281821
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to switched capacitor digital-to-analog converters, and, more particularly, to switched capacitor digital-to-analog converters with power-up/down transient suppression for use in audio systems.
2. Description of Related Art
A number of digital sources of audio information are known. These include compact disk players, digital audio tape, digital transmissions and the like. Stereo digital-to-analog converters are also known, which convert the output from such digital sources into analog information for playback. It is common, when dealing with such stereo digital-to-analog converters, that they have a single ended output ranging between a ground or return value and a supply voltage level with a nominal or quiescent value, V
q
, when no signal is applied. It is common in single ended output systems to use a D.C. blocking capacitor to provide a ground centered signal for subsequent processing.
Single-ended digital-to-analog converters (DACs) powered from a single supply can suffer from large transient signals appearing at the outputs when initially powered on. Such DACs present an analog output centered on a nominal quiescent operating voltage, V
q
. The transient occurs when power is applied to the part, and the analog outputs are required to move from ground to V
q
. If this transient occurs rapidly, it can be approximated as a step function, which has energy at all frequencies. On power-up, such a system can suffer an annoying “POP” at the speaker as the DAC initially charges the D.C. blocking capacitor to V
q
.
A similar click or pop can occur when the system is powered off. On entering the power-down state, the charge on the D.C. blocking capacitor remains. When power is removed, the residual charge on the D.C. blocking capacitor discharges rapidly across the load resister resulting in a loud pop.
SUMMARY OF THE INVENTION
In accordance with the invention, digital-to-analog converters provide power-up pop/click transient suppression utilizing a digital transient generator which operates to replace the pop or click, which would otherwise occur, with a smooth transition.
In accordance with another aspect of the invention, a digital-to-analog converter suppresses a pop or a click which would otherwise occur when the DAC is powered down using a current source and a positive feedback amplifier.
In accordance with another aspect of the invention, a digital-to-analog converter automatically switches from a base rate mode to a high rate mode by detecting the ratio of the master clock to the left/right clock.
REFERENCES:
patent: 3610953 (1971-10-01), Gordon et al.
patent: 3864624 (1975-02-01), Sugiyama et al.
patent: 4140960 (1979-02-01), Ohsawa
patent: 4653029 (1987-03-01), Sato
patent: 4673889 (1987-06-01), Cini et al.
patent: 4859955 (1989-08-01), Trethewey
patent: 4947140 (1990-08-01), Tateishi
patent: 5061925 (1991-10-01), Sooch et al.
patent: 5087914 (1992-02-01), Sooch et al.
patent: 5196850 (1993-03-01), Duffy et al.
patent: 5258758 (1993-11-01), Sooch
patent: 5594442 (1997-01-01), Paulos et al.
patent: 5740453 (1998-04-01), Lada, Jr.
patent: 5767722 (1998-06-01), Kasha et al.
patent: 5796276 (1998-08-01), Phillips et al.
patent: 5796851 (1998-08-01), Hewitt et al.
patent: 5818299 (1998-10-01), Tran
patent: 6064188 (2000-05-01), Takashima et al.
patent: 6127852 (2000-10-01), Ogawa et al.
Bocock Richard
Krone Andrew W.
Paulos John J.
Rhode Jason P.
Jean-Pierre Peguy
Musgrove Jack V.
Skjerven Morrill & MacPherson LLP
LandOfFree
Digital-to-analog converter with power up/down transient... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digital-to-analog converter with power up/down transient..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital-to-analog converter with power up/down transient... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2546485