MAX9526ATJ(2011) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX9526ATJ
(Rev.:2011)

Low-Power, High-Performance NTSC/PAL Video Decoder

Maxim Integrated 

MAX9526

Low-Power, High-Performance

NTSC/PAL Video Decoder

Detailed Description

The MAX9526 is a simple, low-power video decoder

that converts all modes of NTSC and PAL composite

video signals to 10-bit YCbCr component video com-

patible with the ITU-R BT.656 standard. The device

powers up in fully operational mode and automatically

configures itself to standard NTSC or standard PAL.

An internal 10-bit, 54MHz ADC samples at four times

the sampling rate specified in ITU-R BT.601. The ana-

log front-end of the MAX9526 features a DC restoration

circuit, automatic gain control, and automatic offset cor-

rection. These blocks are controlled with digital pro-

cessing to accurately optimize the full-scale range of

the ADC. An integrated analog anti-aliasing filter elimi-

nates the need for off-chip filtering. The device includes

a 2:1 input multiplexer that can be configured to auto-

matically select the input based on activity.

The system clock is generated with an external 27MHz

crystal and an internal oscillator. Optionally, a 27MHz or

54MHz external clock can be connected to the

XTAL/OSC input. An internal line-locked digital PLL is

used to generate the 54MHz ADC sample clock that is

synchronous to the incoming video signal with up to

±5% variation in horizontal line length. The digital out-

put data and LLC clock are line locked to the video

input and provide a standard ITU output. The PLL can

also be configured to asynchronously sample the input

using the crystal oscillator or external clock.

The MAX9526 provides a 5-line adaptive comb filter to

separate the luminance (Y) and chrominance (C) video

components and reduce cross-chrominance and cross-

luminance artifacts. The MAX9526 operates with any

type of standard composite video signal source includ-

ing DVD players, video cameras, navigation systems,

and VCRs.

The device powers up in fully operational video

decoder mode. An I2C register interface monitors status

and enables programming of many decoder functions

including brightness, contrast, saturation, and hue. The

10-bit output can be reconfigured to provide 8-bit data

with separate horizontal and vertical syncs.

Analog Front-End (AFE)

The MAX9526 AFE implements DC restoration, auto-

matic gain control (AGC), analog anti-aliasing filter

(LPF), activity detection, channel selection, and analog-

to-digital conversion. A block diagram of the AFE is

shown in Figure 1.

Activity Detect and Automatic Channel Selection

The MAX9526 continuously monitors activity at both

video inputs, VIN1 and VIN2. Activity on the selected

channel is detected using the ADC output. On the

unselected channel an analog sync-tip clamp and sync

slicer are used to detect sync amplitudes greater than

50mV. In sleep mode, the analog sync-tip clamps and

sync slicers are used to detect activity on both inputs,

while the rest of the AFE is in a shutdown state.

The output of the activity detect circuit is reported

through the Status register 0x00. The user must manu-

ally select which video input to process by setting

INSEL in register 0x09 appropriately.

The MAX9526 can optionally be configured to automati-

cally select the video input that indicates the presence

of activity by setting AUTOSEL = 1 in register 0x09.

When activity is present on both VIN1 and VIN2 at

power-up or when there is no activity on either input

channel, VIN1 is selected. When there is activity on VIN2

and there is no activity on VIN1, then VIN2 is selected.

When VIN2 is automatically selected with the presence

of activity, the input only switches to VIN1 when activity

goes away on VIN2.

ACTIVITY

DETECT

DC RESTORATION

DAC

DIGITAL

CONTROL

VIN1

VIN2

ANALOG

AGC

ANALOG

LPF

10-BIT 10

DIGITAL

10

ADC

FILTERING

TO DECODER

VREF

INTERNAL

BIAS

Figure 1. Analog Front-End

10

Maxim Integrated

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