ISL59450 Datasheet, PDF(21/37 Page) Intersil Corporation – Multiformat Video Crosspoint with Integrated Sync Separator

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ISL59450 Datasheet, PDF (21/37 Pages) Intersil Corporation – Multiformat Video Crosspoint with Integrated Sync Separator

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ISL59450

Functional Description

Signal Muxes

The ISL59450 accepts 6 composite, 4 S-video and 4

component video sources. Each signal type is routed into a

crosspoint mux with two outputs. The 6 composite signals

are routed into a 6:2 mux, the S-video inputs are routed into

a double 4:2 mux and the component video signals are

routed into a triple 4:2 mux. Each mux is controlled through

the I2C interface.

Each signal type has two dedicated outputs, A and B. Signal

types cannot be routed to different signal type outputs. For

example, an S-video signal (Y, C) cannot be routed to the

composite outputs.

For the luma (Y and CVBS) channels, the DC-restore

function is either a standard sync-tip clamp (Master Mode) or

slaved to a clamp signal generated from the sync separator

(Slave Mode).

For the chroma (C and Pr/Pb) channels, the DC-restore

function is a keyed clamp timed to the luma channel (Master

Mode) or timed to a clamp signal generated from the sync

separator (Slave Mode).

The clamping circuit restores the AC-coupled video signal to

a fixed DC level (VTIP, or VLUMA). The clamping circuit

provides line-by-line restoration of the video sync level to a

the selected DC reference voltage during the sync tip.

Clamp Modes

The ISL59450 has two clamp modes: master and slave. Each

output group can operate in either mode. In master mode, sync

timing is derived directly from the video signal and video levels

are clamped using this internal sync signal. In slave mode,

video sync is derived from the input groups corresponding sync

separator (A or B) or an external source connected to the

corresponding sync separator. In the slave mode, the sync

timing can come from HSYNCIN and VSYNCIN or it can be

derived from the sync timing on the active video on the

composite, S-video, or component channels (see âSync

Separator Block Diagramâ on page 9). In the slave mode,

clamping occurs during the sync tip of the selected video signal

or the HSYNC signal (external HSYNC input).

Filters

The ISL59450 has integrated anti-aliasing/smoothing filters

for SD and HD video signals. For the Composite Video

signals, the user can use a 7MHz low pass filter or bypass it

(40MHz bandwidth). S-video signals have an 10MHz filter

with bypass (43MHz). Component Video signals have a

user-selectable 36MHz, 20MHz, or 10MHz filter, or bypass

(275MHz). All filters selections are made via the I2C host

interface.

Clamps

The clamps for all the luma and composite channels can be

sync tip clamps (master mode) or timed keyed clamps (slave

mode) driven off the sync separator. The clamps for the

chroma channels (C/Pr/Pb) are keyed clamps timed to either

the luma (master mode) or the sync separator (slave mode).

Clamp Disable

The clamp can be disabled for each channel by setting the

appropriate bit high in the Miscellaneous 2 register (0x16).

For the S-video and component channels, additional action

needs to be taken in order to completely disable the clamps.

For S-video, setting the bit in the Miscellaneous 2 register

disables the pull-down 1ÂµA pull-down current for both the

luma and chroma channel along with the clamp pull-up

current for the luma channel. However, it does not disable

the clamp pull-up current for the chroma channel unless the

sync separator for that channel is set to 0x25.

For component, setting the bit in the Miscellaneous 2

three channels, along with the clamp pull-up current for the

luma channel. However, it does not disable the clamp pull-up

current for the Pr and Pb channels unless the sync separator

for that channel is set to 0x24.

Low Offset Mode

Setting bit 6 in the Composite and S-Video Channel registers

increases the maximum amount of pull-up clamp current

available from 130ÂµA to 270ÂµA, which slightly reduces the

offset between the reference and the output when the clamp

is enabled.

For the component channels, this setting can be enabled by

setting Bit 7 in the Miscellaneous 2 register for Channel A and

Bit 3 for Channel B. This mode increases the maximum amount

of pull-up clamp current available from 270ÂµA to 500ÂµA.

References

Table 1 shows the references used for clamping depending

on the mode and video input being used. VSLICE should

usually be set to 70mV to 100mV above the selected

reference level for luma.

TABLE 1. CHANNEL REFERENCE LEVELS

VIDEO

OUTPUT

MASTER MODE

GAIN 1

GAIN 2

SLAVE MODE

GAIN 1

GAIN 2

Composite

S-Video

Luma

VTIP

VLUMAx1

VLUMAx2

S-Video

Chroma

VCHROMAx1 VCHROMAx2 VCHROMAx1 VCHROMAx2

Component:

Luma/Green

(YPrPb Mode)

VTIP

VLUMAx1 VLUMAx2

Component:

Luma/Green

(RGB Mode)

VTIP

VLUMAx1 VLUMAx2

FN7510.0

February 14, 2008

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