Introduction; Analog Front End - Analog Devices ADV7850 Hardware Manual

ADV7850

2 INTRODUCTION

The ADV7850 is a high quality, single chip, multiformat video decoder graphics digitizer with an integrated 4:1 multiplexed High-
Definition Multimedia Interface (HDMI™) receiver. The multiformat 3D comb filter decoder supports the conversion of PAL, NTSC, and
SECAM standards in the form of a composite or an S-Video input signal into a digital ITU-R BT.656 format. SCART and overlay functionality are
enabled by the ability of the ADV7850 to process simultaneously CVBS and standard definition RGB signals.
The ADV7850 contains one main component processor (CP), which processes YPrPb and RGB component formats, including RGB
graphics. The ADV7850 can operate in quad HDMI and analog input mode, thus allowing for fast switching between the ADCs and the
HDMI.
The ADV7850 supports the decoding of a component RGB/YPrPb video signal into a digital Transition Minimized Differential Signaling
(TMDS) output stream. The support for component video includes 525i, 625i, 525p, 625p, 720p, 1080i, 1080p, and 1250i standards, as well
as many other SMPTE and HD standards. The ADV7850 supports graphics digitization. The ADV7850 is capable of digitizing RGB
graphics signals from VGA to UXGA rates and converting them into a digital TMDS output stream. Internal EDID is available for one
graphics port.
The ADV7850 incorporates a quad input HDMI receiver that supports all HDTV formats up to 1080p and display resolutions up to UXGA
(1600 × 1200 at 60 Hz). The HDMI ARC feature is fully supported on all ports where audio is supplied via the SPDIF in interface.
The ADV7850 supports full HDCP de-encryption with internal key storage. The ADV7850 features HDCP authentification, sync
measurement and status monitoring for all non selected HDMI ports. These features allow for extremely fast switching between ports.
Each HDMI input port has a dedicated +5V Detect and Hot Plug Assert pin. The HDMI receiver also includes an integrated equalizer that
ensures the robust operation of the interface. The HDMI receiver has advanced audio functionality, such as a mute controller, that
prevents audible extraneous noise in the audio output. In addition, the HDMI receiver incorporates an internal EDID, which can be
available in power saving modes.
Fabricated in an advanced CMOS process, the ADV7850 is provided in a 19 mm × 19 mm, 425-ball, CSP_BGA, surface-mount, RoHS-
compliant package and is specified over the 0°C to +70°C temperature range.

2.1 ANALOG FRONT END

The ADV7850 analog front end comprises of four 170 MHz, 12-bit ADCs that digitize the analog video signal before applying it to the
SDP or CP. The analog front end uses differential channels to each ADC to ensure high performance in a mixed-signal application.
The front end also includes a 13-channel input mux that enables multiple video signals to be applied to the ADV7850 without the
requirement of an external mux. Current and voltage clamp control loops ensure that any DC offsets are removed from the video signal.
The clamps are positioned in front of each ADC to ensure that the video signal remains within the range of the converter. The ADV7850
can support two composite outputs for full SCART support. These two outputs can be connected to a selection of composite inputs
The ADCs are configured to run up to 4× oversampling mode when decoding composite or S-Video inputs. For component 525i, 625i,
525p, and 625p sources, 2× oversampling is performed. All other video standards are 1× oversampled. Oversampling the video signals
reduces the cost and complexity of external anti aliasing filters with the benefit of an increased signal to noise ratio (SNR).
Optional internal anti aliasing filters with programmable bandwidth are positioned in front of each ADC. These filters can be used to
band limit video signals, removing spurious and out-of-band noise.
The ADV7850 can support the simultaneous processing of CVBS and RGB standard definition signals to enable SCART compatibility and
overlay functionality. A combination of CVBS and RGB inputs can be mixed and the output is under the control of I C registers and the
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fast blank pin.
Rev. A May 2012 15