MAX9526 datasheet(18/38 Pages) MAXIM

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Low-Power, High-Performance

NTSC/PAL Video Decoder

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PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Frequency

Fundamental mode only

27.000

MHz

Maximum Crystal ESR

Room temperature

Ω

Line-locked mode

±50

Accuracy

Async mode with multiple decoders

±50

ppm

Table 3. Recommended Crystal Parameters

SMBus is a trademark of Intel Corp.

Applications Information

Multiple Decoder Operation

Multiple asynchronous video input signals can be

decoded synchronously using multiple MAX9526s in

asynchronous (async) sampling mode. Figure 7 shows

an example of decoding four video input signals.

The MAX9526 is configured for async sampling mode

by writing the following registers:

crystal oscillator)

sampling to async mode)

When the MAX9526 is in async sampling mode, the

data outputs, D9–D0, of all decoders are synchronous

with the input clock (XTAL/OSC). The video content in

the data outputs is not frame aligned because the video

sources into each MAX9526 is asynchronous. A small

FPGA can be implemented to multiplex all four chan-

nels into a single 8- or 10-bit bus. This FPGA can also

format the outputs to be compatible for input into a

compression processor, which is commonly used in

digital video recorders (DVRs).

The crystal oscillator (external or internal) must have

better than ±50ppm accuracy for acceptable decoding

in this mode. An accuracy of ±10ppm is recommended

for optimal performance.

Recommended Crystal Parameters

Recommended crystal parameters are shown in Table 3.

Power-Supply Decoupling

For systems where additional power-supply isolation is

required, the circuit shown in Figure 8 can be used.

Additional supply decoupling is added and analog

power (AVDD) isolation is increased with the use of a fer-

rite bead (FB). The analog ground connection (AGND)

should be connected to a separate ground plane that

has a small bridge to the main ground plane of the sys-

tem. The video input termination (VIN1/VIN2), video refer-

ence (VREF) decoupling, and AVDD supply decoupling

should also be connected to the AGND ground plane.

I2C Serial Interface

The MAX9526 features an I2C/SMBus™-compatible,

2-wire serial interface consisting of a serial-data line

(SDA) and a serial-clock line (SCL). SDA and SCL facili-

tate communication between the MAX9526 and the

master at clock rates up to 400kHz. Figure 9 shows the

2-wire interface timing diagram. The master generates

SCL and initiates data transfer on the bus. The master

device writes data to the MAX9526 by transmitting the

proper slave address followed by the register address

and then the data word. Each transmit sequence is

framed by a START (S) or REPEATED START (Sr) con-

dition and a STOP (P) condition. Each word transmitted

to the MAX9526 is 8 bits long and is followed by an

acknowledge clock pulse. A master reading data from

the MAX9526 transmits the proper slave address fol-

lowed by a series of nine SCL pulses. The MAX9526

transmits data on SDA in sync with the master-generat-

ed SCL pulses. The master acknowledges receipt of

each byte of data. Each read sequence is framed by a

START or REPEATED START condition, a not acknowl-

edge, and a STOP condition. SDA operates as both an

input and an open-drain output. A pullup resistor, typi-

cally greater than 500Ω, is required on SDA. SCL oper-

ates only as an input. A pullup resistor, typically greater

than 500Ω, is required on SCL if there are multiple mas-

ters on the bus, or if the single master has an open-

drain SCL output. Series resistors in line with SDA and

SCL are optional. Series resistors protect the digital

inputs of the MAX9526 from high-voltage spikes on the

bus lines, as well as minimize crosstalk and undershoot

of the bus signals.

Bit Transfer

One data bit is transferred during each SCL cycle. The

data on SDA must remain stable during the high period

of the SCL pulse. Changes in SDA while SCL is high

are control signals (see the

START and STOP

Conditions section).

START and STOP Conditions

SDA and SCL idle high when the bus is not in use. A

master initiates communication by issuing a START con-

dition. A START condition is a high-to-low transition on

SDA with SCL high. A STOP condition is a low-to-high

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