Differential Video Receiver Using the ADA4851 Amplifier and the ADV7180 Video Decoder
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To introduce a differential video receiver reference design from ADI
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Differential Video Receiver Using the ADA4851 Amplifier and the ADV7180 Video Decoder
- 4. Differential Video Receiver Reference Design
- 6. Differential to Single-ended Conversion DC offset to prevent the incoming signal from violating the input and output voltage range. AC-coupled capacitors to protect the input to the amplifier from a short to a voltage higher than its supply voltage.
- 10. Video Decoder Configuration Single ended video signal
Notes de l'éditeur
- Welcome to the training module on Differential Video Receiver Using the ADA4851 Amplifier and the ADV7180 Video Decoder . This training module introduces a differential video receiver reference design from ADI.
- All cables, no matter what their length or quality, produce problems when used for the transmission of video signals - a loss of signal is dependent primarily on the frequency, the higher the frequency, the higher the loss. Traditionally, coaxial cable is used to transmit video signal, such as the camera’s video signal to the display. However, in many cases it’s better to transmit this signal on twisted-pair wire, twisted-pair wire is smaller and lighter than coaxial cable. These systems utilize differential signals and can lower costs because they use lower cost cables, connectors, and termination methods. They also have the ability to lower crosstalk and reject common-mode signals, which can be important for equipment that operates in noisy environments, or where common-mode voltages are present between transmitting and receiving equipment. In such systems, the video signals are differential; there are positive and negative (or inverted) versions of the signals. Here we will introduce a low cost differential video receiver design from ADI.
- ADI provides a low cost solution for differential video receiver using the ADA4851 amplifier and ADV7180 video decoder. In the front end of the video receiver circuit, the differential input signal from the twisted-pair is converted into a single-ended output signal by ADA4851. The ADV7180 video decoder is used to digitize the analog video signal. This circuit is able to eliminate common mode noise and phase noise caused by ground potential difference from an incoming video signal and is well suited for automotive and vision safety systems. The ADA4851 family of amplifiers along with the ADV7180 are all AECQ100 qualified which makes both products ideal for automotive applications.
- The ADA4851 amplifier family is low cost, high speed, voltage feedback rail-to-rail output operational amplifier. The 130 MHz, −3 dB bandwidth and high slew rate make these amplifiers well suited for many general-purpose, high speed applications. The ADA4851 family is designed to operate at supply voltages as low as +3 V and up to ±5 V. These parts provide true single-supply capability, allowing input signals to extend 200mV below the negative rail and to within 2.2V of the positive rail. On the output, the amplifiers can swing within 60mV of either supply rail. With the excellent differential gain (0.08%), differential phase (0.09º), and 0.1 dB flatness out to 11 MHz, these amplifiers are ideal for consumer video applications.
- In this differential video receive circuit, the ADA4851 performs the differential to single-ended conversion for video signals. This configuration is a standard 4-resistor difference amplifier optimized for composite video frequencies, with a differential to single-ended gain of 1. The amplifier only amplifies the difference between the two inputs while eliminating the common mode noise between the incoming signals and allowing the reconstruction of the original signal. Using low value, high accuracy resistors and a high CMRR amplifier provides the exceptional performance. A critical design consideration that is important to note about this architecture is its dependence on resistor matching for the Common Mode Rejection (CMR) of this circuit design. The Common Mode Rejection CMR can be calculated using the formula as shown. In this expression, the term “Kr” is a single resistor tolerance in fractional form (1% = 0.01 etc), and it is assumed that the amplifier has significantly higher Common Mode Rejection performance. Using this formula, it shows that if 54dB or better Common Mode Rejection is desired, then R1, R2, R3 and R4 need to have a matching tolerance of 0.1% or better.
- The ADV7180 automatically detects and converts standard analog baseband television signals compatible with worldwide NTSC, PAL, and SECAM standards into component video data compatible with the 8-bit interface standard. The simple digital output interface can connect gluelessly to a wide range of MPEG encoders, and mobile video processors. The accurate 10-bit analog-to-digital conversion provides professional quality video performance for consumer applications with true 8-bit data resolution. Three analog video input channels accept standard composite, S-video, or component video signals, supporting a wide range of consumer video sources.
- The ADV7180 analog front end comprises a single high speed, 10-bit, analog-to-digital converter (ADC) that digitizes the analog video signal before applying it to the standard definition processor. The analog front end employs differential channels to the ADC to ensure high performance in mixed-signal applications. The front end also includes a 3-channel input mux that enables multiple composite video signals to be applied to the ADV7180. In this application, only A IN 1 is used, as a single-ended video signal is converted by the ADA4851. The ADV7180 has optional on-chip antialiasing filters on each of the three channels that are multiplexed to the ADC. The antialiasing filters can be disabled or bypassed using the Antialiasing Filter Override control.
- The ADV7180 is capable of decoding a large selection of baseband video signals in composite, S-video, and component formats. The ADV7180 can automatically detect the video standard and process it accordingly. The ADV7180 has a five-line, superadaptive, 2D comb filter that gives superior chrominance and luminance separation when decoding a composite video signal. Video user controls such as brightness, contrast, saturation, and hue are also available with the ADV7180. The ADV7180 implements an Adaptive Digital Line Length Tracking ™ algorithm to track varying video line lengths from sources. Adaptive Digital Line Length Tracking enables the ADV7180 to track and decode poor quality video sources such as VCRs and noisy sources from tuner outputs, VCD players, and camcorders.
- Our last slide illustrates a configuration of the ADV7180 video decoder for the differential video receiver. The analog video input channel accepts standard composite, S-video, or component video signals, supporting a wide range of consumer video sources. AGC and clamp-restore circuitry allow an input video signal peak-to-peak range of up to 1.0 V.
- Thank you for taking the time to view this presentation on “ Differential Video Receiver Using the ADA4851 Amplifier and the ADV7180 Video Decoder ” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the ADI site – link shown, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility.