AN2526

Evaluation board

3/10

1

Evaluation board

The evaluation board was designed with trouble-free customer evaluation in mind. Instead

of having two sets of RGB (VGA connector) and YPbPr (RCA connector) as inputs and

branching the output to the VGA and RCA connectors, two VGA RGB inputs are connected

and the outputs go directly to single VGA connector to a display unit.

For the evaluation, the customer can connect the two sets of inputs to two VGA port of PC,

while the output can be directly connected to the VGA port of the display unit.

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Power supply

The board can be powered either directly from a DC power supply or from a DC adaptor. If it

and the ground is connected to the power socket labeled GND. The board can also be

powered from a DC adaptor having output voltage of 7 V to 15 V. The DC adaptor voltage is

regulated to 5 V by the on board regulator. The DC adaptor can be center positive or

negative and it should be connected to the DC JACK.

To prevent the digital lines switching from coupling to the analog lines, the power distribution

is separated from digital and analog sections. Although STMAV340 has also two digital

lines, which are OE and SEL, it should still be powered from the analog supply because its

main function is to switch analog signals and those two digital lines are mostly static during

operation. Hence the analog lines are not disturbed by the digital part and, as such, there is

no need to have a separate analog and digital supply for STMAV340.

The analog and digital sections on the board are isolated by ferrite beads.

Note:

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Video input & output ports

There are four video input ports: VGA1, VGA2, CVBS1, and CVBS2. STMAV340 performs

the switching of these video inputs. Depending on the SEL control line, either VGA1 or

VGA2 input is directed to VGA_OUT and either CVBS1 or CVBS2 is directed to

CVBS_OUT.

Since STMAV340 does not perform the switching of VGA synchronization signals, two

STG719 are incorporated to switch both horizontal and vertical synchronization.

VGA port also has some ID signals. To prevent clashing between ID signals from VGA input

1 and 2, the ID lines are isolated by jumpers. If VGA1 is active and to be directed to

VGA_OUT, JP1 to JP4 should be closed whereas JP5 to JP8 should be opened. If VGA2 is

active and to be directed to VGA_OUT, JP5 to JP8 should be closed whereas JP1 to JP4

should be opened.

Table 1.

STMAV340 Demo board power supply

Designator

Notes

Connect to 5 V of external power supply.

GND

Connect to ground of external power supply.

DC JACK

Connect to DC adaptor output if the board is to be powered from DC

adaptor. Input voltage: 7 to 15 V