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TDA9171 Datasheet(PDF) 4 Page - NXP Semiconductors |
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TDA9171 Datasheet(HTML) 4 Page - NXP Semiconductors |
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4 / 20 page  1996 Jun 17 4 Philips Semiconductors Preliminary specification YUV picture improvement processor based on histogram modification and blue stretch TDA9171 PINNING SYMBOL PIN DESCRIPTION BLG 1 blue stretch gain input UIN 2 U colour difference input −UIN VIN 3 V colour difference input −VIN NLC 4 non-linear gain control input SC 5 sandcastle input AMPSEL 6 amplitude select input YIN 7 luminance input TAUHM 8 time constant histogram input HM1 9 histogram segment memory 1 input HM2 10 histogram segment memory 2 input HM3 11 histogram segment memory 3 input HM4 12 histogram segment memory 4 input HM5 13 histogram segment memory 5 input YOUT 14 luminance output VEE 15 ground VCC 16 supply voltage Vref 17 reference voltage output VOUT 18 colour difference output −VOUT UOUT 19 colour difference output −UOUT BLM 20 activation level blue stretch input Fig.2 Pin configuration. handbook, halfpage TDA9171 MBE989 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 BLM UOUT VOUT Vref VCC VEE YOUT HM5 HM4 HM3 BLG UIN VIN NLC SC AMPSEL YIN TAUHM HM1 HM2 FUNCTIONAL DESCRIPTION Input selection and amplification The dynamic range of the luminance input amplifier is 0.3 or 1 V (excluding sync) typically, depending on the logic level at pin AMPSEL (pin 6). Amplitudes which extend the corresponding specified range will be clipped smoothly, however, the sync is processed to the output transparently. The non-linear gain setting will have minimum effect. Optionally, in the 1 V input mode, the Y output can be attenuated by a factor of 0.7 by means of an intermediate level at pin AMPSEL. This option is meant for correctly interfacing the combed CVBS signal to the video processor in a YC-application. The input is clamped during the logic HIGH period of the CLP, defined by the sandcastle reference, and should be DC-decoupled with an external capacitor. Histogram measurement For the luminance signal the histogram distribution is measured in real-time over five segments (HM1 to HM5) in each field. During the period that the luminance is in one segment, a corresponding external capacitor HMx is loaded via a current source. At the end of the field five segment voltages are stored from the external capacitors into on-board memories. The external capacitors are discharged and the measurements are repeated. Parts in the scene that do not contribute to the information in that scene should be omitted from the histogram measurement. No measurements are performed during the blanking period defined by the sandcastle. The miscount detector disables measurements until it detects changing parts. Additionally, luminance values close to full scale (or white) do not contribute as well in order to maintain the absolute light output. This procedure is allowed because the eye is less sensitive to detail in white. |
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