The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 25, 2002
Filed:
Jun. 10, 1998
John Patrick Purcell, Dooradoyle, IE;
Vincent James Troy, Raheen, IE;
Kieran Heffernan, Patrickswell, IE;
Analog Devices, Inc., Norwood, MA (US);
Abstract
A detector circuit ( ) for detecting the presence or absence of a television ( ) on an output ( ) of a video DAC ( ) comprises a comparator ( ) for comparing a voltage developed by the video signal on a control resistor R with a reference voltage of 0.5 volts. The resistor R is of 75 ohms and matches the internal impedance R of 75 ohms of the television ( ). A latch ( ) latches the output from the comparator ( ) onto an output pin Q when the voltage developed across the control resistor R is developed by an equalisation pulse of the vertical blanking interval of the video signal. In the presence of a television ( ) the voltage developed across the control resistor R is 0.35 volts, which pulls the output of the comparator ( ) low, while in the absence of a television ( ) the voltage developed across the control resistor R is 0.7 volts which pulls the output of the comparator ( ) high. A control logic control circuit ( ) reads the output pin Q of the latch ( ) for powering up or powering down the video DAC ( ) as appropriate.