Patent Publication Number: US-2010128177-A1

Title: Signal processing units capable of providing plug-in detection

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to plug-in detection, and more particularly, to signal processing units capable of providing plug-in detection without an external circuit occupying GPIO resource. 
     2. Description of the Related Art 
     As is known, audio signals are processed by a wide variety of electronic equipment, including portable, or handheld, devices. Such devices include laptop, notebook and other personal computers, personal digital assistants (PDA), CD players, MP3 players, DVD players, AM/FM radio, satellite radio systems, in-band on channel digital radios, cellular telephones, consumer audio equipment such as stereo systems, home theater systems, cable and satellite tuners and set-top boxes, digital video recorders and other systems that support the processing of audio and video, etc. Each of these devices includes one or more integrated circuits to provide the functionality of the device. As an example, a computer may include an audio codec or other audio input-output modules to support the processing of audio signals in order to produce an audio output that is delivered to the user through speakers, headphones or the like and/or to receive audio signals from an external device such as a microphone, CD player or other source of analog or digital audio signals. 
     A problem common for many of these devices is that many are equipped with multiple jacks for coupling signals such as audio input/output signals to and from the device. A user of the device may connect or disconnect these jacks while the device is in operation, either to discontinue the use of a connection or to couple a new peripheral or signal to the device. It is desirable to detect that a device or signal has been coupled or decoupled from each of the plurality of jacks in a manner that can be efficiently implemented in an electronic device. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of a signal processing unit with plug-in detection are provided, in which a switching element is coupled to a television signal output pad, a terminal resistor is coupled between the switching element and a ground voltage, and an interrupt signal generator generates an interrupt signal when a receiving port of a television signal receiver is coupled to the television signal pad. A control unit turns on the switching element to connect the terminal resistor to the television signal output pad when receiving the interrupt signal, wherein the switching element, the terminal resistor, the interrupt signal generator and the control unit are integrated in a chip. 
     The invention provides an embodiment of an electronic device, in which a signal processing chip interacts with a television signal receiver, and the signal processing chip comprises a switching element coupled to a television signal output pad, a terminal resistor coupled between the switching element and a ground voltage, an interrupt signal generator generating an interrupt signal when a receiving port of the television signal receiver is coupled to the television signal pad, and a control unit turning on the switching element to connect the terminal resistor to the television signal output pad when receiving the interrupt signal. 
     The invention provides an embodiment of a plug-in detection method, in which a voltage level on a television signal output pad of a chip is detected by an interrupt signal generator in the chip to determine whether the television signal output pad is coupled to a receiving port of a television signal receiver, and a switching element in the chip is turned on when the television signal output pad is coupled to the receiving port of the television signal receiver, such that the television signal output pad is coupled to a ground voltage through a terminal resistor in the chip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  shows an embodiment of an electronic device; 
         FIG. 2  shows another embodiment of the signal processing chip; and 
         FIG. 3  shows another embodiment of the signal processing chip. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     Certain terms are used throughout the description and claims to refer to particular system components. As one skilled in the art will appreciate, consumer electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. 
       FIG. 1  shows an embodiment of an electronic device. As shown, the electronic device  100  comprises a signal processing chip (also called signal processing unit)  10  capable of interacting with a television signal receiver  20 . For example, the electronic device  100  can be a mobile phone, a smart phone, a digital camera, a personal digital assistant (PDA), a notebook computer, a desktop computer, a tablet personal computer (PC) or a portable DVD player, but is not limited thereto. 
     The signal processing chip  10  comprises a micro processing unit  12 , a television digital-to-analog converter (TV DAC)  14 , an inverter INV, resistors RH and RT, switching elements SWH and SWL, and a television signal output pad POUT. The signal processing chip  10  performs a plug-in detection before transmitting television signals, and transmits television signals to the television signal receiver  20  after a receiving port RP of the television signal receiver  20  is coupled to the television signal output pad POUT. The television signal receiver  20  can, for example, be a display, such as a television, a car display, a monitor and the like. 
     The resistor RH comprises a first terminal coupled to a power voltage VDD, and a second terminal coupled to the switching element SWH. The switching element SWH comprises a first terminal coupled to the resistor RH, and a second terminal coupled to the television signal output pad POUT. The switching element SWL comprises a first terminal coupled to the television signal output pad POUT, and a second terminal coupled to the resistor RT, and the switching elements SWH and SWL are controlled by the micro processing unit  12 . The resistor RT is coupled between the second terminal of the switching element SWL and a ground voltage. 
     The inverter INV is coupled between the television signal output pad POUT to serve as an interrupt signal generator. The inverter INV comprises an input terminal coupled to the television signal output pad POUT, and an output terminal coupled to the micro processing unit  12 . The inverter INV generates an interrupt signal S 2  according to a voltage level VOUT on the television signal output pad POUT. For example, the inverter INV generates the interrupt signal S 2  with a logic low when the voltage level VOUT on the television signal output pad POUT is at a logic high. On the contrary, the inverter INV generates the interrupt signal S 2  with a logic high when the voltage level VOUT on the television signal output pad POUT is at a logic low. 
     The micro processing unit  12  controls operations of the TV DAC  14  and the switching elements SWH and SWL. For example, the micro processing unit  12  switches the switching elements SWH and SWL according to the interrupt signal S 2  and transmits a television signal S 3  to the television signal receiver  20  through the TV DAC  14  after the television signal receiver  20  is coupled to the television signal output pad POUT. The television signal S 3  can be a digital television signal. The TV DAC  14  converts the television signal S 3  from the micro processing unit  12  to an analog television signal and output to the television signal receiver  20 . 
     A method for plug-in detection in the signal processing chip  10  is illustrated hereinafter. Initially, the micro processing unit  12  outputs a control signal S 1  to turn on the switching element SWH and turn off the switching element SWL. As a result, the voltage level VOUT at television signal output pad POUT is electrically separated from the ground voltage and is pulled high by the power voltage VDD. Because the television signal output pad POUT is pulled high, the interrupt signal S 2  from the inverter INV is at a logic low. 
     When the receiving port RP of the television signal receiver  20  is plugged in (i.e., the receiving port RP is coupled to the television signal output pad POUT of the electronic device  100 ), the voltage level VOUT at television signal output pad POUT is pulled low by the resistor RTTV in the television signal receiver  20 . As a result, the interrupt signal S 2  from the inverter INV becomes a logic high. As the interrupt signal S 2  is at a logic high, the micro processing unit  12  turns the switching elements SWH and SWL off and on respectively by the control signal S 1 . Consequently, the television signal output pad POUT is electrically separated from the power voltage VDD and is coupled to the ground voltage through the terminal resistor RT. 
     After that, the micro processing unit  12  can provide the television signal S 3  to the TV DAC  14 , and then the TV DAC  14  converts the television signal S 3  into an analog television signal and outputs to the television signal receiver  20  through the television signal output pad POUT. After TV DAC  14  finishes its operations or the receiving port RP of the television signal receiver  20  is decoupled from the television signal output pad POUT, the micro processing unit  12  turns the switching elements SWH and SWL on and off, respectively. In embodiments of the invention, the terminal resistor RT can be a variable resistor, but is not limited thereto. 
     Because the inverter INV can enable the micro processing unit to switch the switching elements SWH and SWL according to the connection of the receiving port RP of the television signal receiver  20 , the plug-in detection is obtained without an external circuit occupying GPIO resource. 
       FIG. 2  shows another embodiment of the signal processing chip. As shown, the signal processing chip  10 ′ is similar to the signal processing chip  10  shown in  FIG. 1 , differing only, in that the terminal resistor RT in  FIG. 1  is replaced with a variable terminal resistor RT″, and a calibration circuit  16  is added for calibrating the variable terminal resistor RT″. Operations for Plug-in detection in the signal processing chip  10 ′ are similar to that in the signal processing chip  10  illustrated above, and thus, are omitted for simplification. 
     The calibration circuit  16  comprises a fixed current  17  and a comparator  18 . During a calibration period, the micro processing unit  12  turns the switching elements SWH and SWL off and on respectively by the control signal S 1  and the fixed current  17  provides an accurate reference current IC to the terminal resistor RT″. The comparator  18  compares the voltage level VOUT with a reference voltage VERF, and outputs a result signal S 4  to the control unit  12 . Because the voltage level VOUT at the television signal output pad POUT is in direct ratio to the product of the reference current IC and the terminal resistor RT″, the control unit  12  calibrates the terminal resistor RT″ according to the result signal S 4 . For example, the micro processing unit  12  outputs a signal S 5  to decrease the resistance of the terminal resistor RT″ when the voltage level VOUT exceeds the reference voltage VERF. On the contrary, the micro processing unit  12  outputs the signal S 5  to increase the resistance of the terminal resistor RT″ when the voltage level VOUT is lower than the reference voltage VERF. 
     It should be noted that, the current source  17  and the comparator  18  can be electrically separated from the television signal output pad POUT after calibration for the terminal resistor RT″ is accomplished. For example, two switching elements can be disposed between the current source  17  and the television signal output pad POUT and between the comparator  18  and the television signal output pad POUT respectively. When such calibration is accomplished, the micro processing unit  12  controls the switching elements to electrically separate the current source  17  and the comparator  18  from the television signal output pad POUT. 
       FIG. 3  shows another embodiment of the signal processing chip. As shown, the signal processing chip  10 ″ is similar to the signal processing chip  10 ′ shown in  FIG. 2 , differing only, in that the current source  17  is omitted. Operations for Plug-in detection in the signal processing chip  10 ″ are similar to that in the signal processing chip  10  illustrated in  FIG. 1 , and thus, are omitted for simplification. 
     During a calibration period, the micro processing unit  12  turns the switching elements SWH and SWL off and on respectively by the control signal S 1 , and then enables the TV DAC  14  to output a current signal (not shown) to the terminal resistor RT″. The comparator  18  compares the voltage level VOUT with a reference voltage VERF, and outputs a result signal S 4  to the control unit  12 . Because the voltage level VOUT at the television signal output pad POUT is in direct ratio to the product of the current signal from the TV DAC  14  and the terminal resistor RT″, the control unit  12  calibrates the terminal resistor RT″ according to the result signal S 4 . For example, the micro processing unit  12  outputs a signal S 5  to decrease the resistance of the terminal resistor RT″ when the voltage level VOUT exceeds the reference voltage VERF. On the contrary, the micro processing unit  12  outputs the signal S 5  to increase the resistance of the terminal resistor RT″ when the voltage level VOUT is lower than the reference voltage VERF. 
     It should be noted that, the comparator  18  can be electrically separated from the television signal output pad POUT after calibration for the terminal resistor RT″ is accomplished. For example, a switching element can be disposed between the comparator  18  and the television signal output pad POUT. When such calibration is accomplished, the micro processing unit  12  controls the switching element to electrically separate the comparator  18  from the television signal output pad POUT. 
     Although the invention has been described in terms of preferred embodiment, it is not limited thereto. Those skilled in the art can make various alterations and modifications without departing from the scope and spirit of the invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.