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STMAV335 evaluation board & PCB layout recommendation
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Last Updated: 27/03/2007
Pages: 12
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AN2471 Application note
STMAV335 evaluation board & PCB layout recommendation
Introduction
STMAV335 has three sets of 3 to 1 switches that are well suited for switching analog video signals on the back panel of television sets or monitors. Below is a diagram of an STMAV335 typical application configuration:
Typical display unit back panel video input
V ID E O R E C E IV E R
Y P b P r O R R G B O R C V B S & S -V ID E O
STM A V 335
RGB C V B S & S -V ID E O
Y PbPr
As illustrated above, STMAV335 is used to switch one of the three video input sets to the video receiver. Depending on the SEL inputs, YPbPr, RGB, or CVBS&S-VIDEO signals will be directed to the video receiver. Hence less IO is required at the video receiver to handle the many different video signal inputs on the display unit back panel. Ultimately, integrating STMAV335 to the system will result in a straightforward system design and overall cost reduction.
March 2007
Rev 1
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Contents
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Contents
1 Evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Video input & output ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Video input conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 4
PCB layout recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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Evaluation board
1
Evaluation board
The STMAV335 evaluation board provides the customer with straightforward evaluation on the performance and the typical use of the switch in the real system. The boards include an STMAV335 switch, video input and output connectors, jumper for setting the control lines status, and a power supply portion.
1.1
Power supply
The board can be powered either directly from a DC power supply or from a DC adaptor. If it is powered from a DC power supply, 5VDC is connected to the power socket labeled VCC5V 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 will be 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 digital noise from coupling to the analog lines, the power distribution is separated from digital and analog sections. Though STMAV335 has also two digital lines, which are SEL1 and SEL2, it should still be powered from the analog supply. The reason is because its main function is to switch analog signals and those two digital lines are mostly static during operation. Hence the analog lines will not be disturbed by the digital part and as such, there is no need to have a separate analog and digital supply for STMAV335. The analog and digital sections on the board are isolated by ferrite beads. Table 1. Power connector
Designator VCC5V GND DC JACK Notes Connect to 5 V of external power supply. Connect to ground of external power supply. Connect to DC adaptor output if the board is to be powered from DC adaptor. Input Voltage: 7 to 15 V
Note:
External power can be applied to either VCC5V/GND or DC JACK, but not to both.
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Video input & output ports
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2
Video input & output ports
STMAV335 can switch three sets of video input to a single set of video output. On the evaluation board, the three sets of video input are: 1. 2. 3. RGB (VGA port) YPbPr (3 RCA connector) CVBS (RCA connector) & S-VIDEO ( S-connector)
In the real system, the outputs of STMAV335 are directly connected to the video receiver. However for the STMAV335 evaluation board, each output line branches to three signal lines. The reason for this is because each set of different video signal has a different type of connector. During evaluation, each output line should be branched and be connected to a different video connector on the display unit back panel by a cable. To avoid any PCB trace stub, the 1 to 3 branching of each output line cannot be shorted on the board. The branching of the output line is done by a zero ohm resistor. Depending on which particular set of video signal is active, the zero ohm resistors should be soldered such that the output of STMAV335 is connected to the right video output connector. Table 2. Evaluation board video input & output
Input Output SEL SEL1 = `1' SEL2 = `0' SEL1 = `0' SEL2 = `1' SEL1 = `0' SEL2 = `0' 0 Jumper output J11 = `R' J12 = `G' J13 = `B' J11 = `Y' J12 = `Pb' J13 = `Pr' J11 = `CVBS' J12 = `Y(S)' J13 = `C'
RGB (VGA_IN) Y (Y_IN) Pb (Pb_IN) Pr (Pr_IN) CVBS (CVBS_IN) S-VIDEO (S VIDEO_IN)
RGB (VGA_OUT) Y (Y_OUT) Pb (Pb_OUT) Pr (Pr_OUT) CVBS (CVBS_OUT) S-VIDEO (S VIDEO_OUT)
Note:
SEL1 JP9, SEL2 JP10, OPEN = '1' & CLOSE = '0'
2.1
Video input conditioning
The blanking level might vary between different video transmitters. This STMAV335 evaluation board can handle video signals with blanking level of 0V to 2.5 V. If video signal blanking levels are outside the above range, some input conditioning should be done to modify the blanking level to the range specified.
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VCC5V_A VCC5V VCC5V Y GND C GND Y C SHLD 5 R1 Y(S)_OUT C_OUT GND JP9 VCC5V_A R2 SEL2 JP10 AGND AGND ID0 ID1 H_SYNC V_SYNC ID3 AGND U1 2 1 AGND Pb STMAV335 AGND JP11 Pr CVBS/Y/R_OUT1 OUT1 IN OUT2 OUT3 JP12 Y(S)/Pb/G_OUT 1 AGND AGND L2 C/Pr/B_OUT 1 OUT1 IN OUT2 OUT3 JP13 OUT1 IN OUT2 OUT3 VCC5V VCC5V_A 2 B_OUT 3 Pr_OUT 4 C_OUT 1 TO 3 JUMPER CVBS_OUT 2 G_OUT 3 Pb_OUT 4 Y(S)_OUT 1 TO 3 JUMPER Pr_OUT 2 R_OUT 3 Y_OUT 4 CVBS_OUT 1 TO 3 JUMPER L1 CVBS Pb_OUT C Pr B SEL2 CVBS/Y/R_OUT Y(S)/Pb/G_OUT AGND Y_OUT 2 Y_OUT 1 RCA AGND Pb_OUT Y VCC5V_A R_OUT G_OUT B_OUT ID2 10K VGA_OUT C1 10uF C2 100nF SEL1 C3 100pF 10K 1 2 3 4 VCC5V_A AGND
S VIDEO_OUT
Figure 1.
VGA_IN R G B ID2 AGND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
RED_IN GREEN_IN BLUE_IN ID_2 GND RED_RTN GREEN_RTN BLUE_RTN NC SYNC_RTN ID0 ID1 H_SYNC V_SYNC ID3
Board schematic
VGA_CON
Y_IN
ID0 ID1 H_SYNC V_SYNC ID3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
RED_OUT GREEN_OUT BLUE_OUT ID_2 GND RED_RTN GREEN_RTN BLUE_RTN NC SYNC_RTN ID0 ID1 H_SYNC V_SYNC ID3 VGA_CON
RCA
Pb_IN
SEL1 CVBS Y R Y(S) Pb G C/Pr/B_OUT 1 2 3 4 5 6 7 8 SEL1VCC Y1 SEL2 Y2 Y/R R Pb/G Pb1 GND Pb2 Pr1 G Pr2 Pr/B B 16 15 14 13 12 11 10 9
RCA
Pr_IN
RCA AGND
CVBS_IN
RCA AGND Pr_OUT
RCA
RCA AGND CVBS_OUT
S VIDEO_IN 1 2 3 4 Y(S) C
SHLD
Y GND C GND Y C VCC5V 2 U5 VOUT VIN GND
RCA AGND
5
U4 3 +~ -~ 1 4 3 BRIDGE RECT 1 C4 10uF 2 1 2 3
DC JACK VCC GND GND Title DC PLUG Size Number Revision
LD1117V50
A Date: File: 4/17/2006 Sheet of C:\Documents and Settings\..\STMAV335.SCHDOC Drawn By:
Video input & output ports
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Video input & output ports Table 3.
No 1 2 3 4 5 6 7 8 8 9 10 11 12 13 14
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Bill of material
Component Designator U1 S VIDEO_IN, S VIDEO_OUT VGA_IN, VGA_OUT Y_IN, Pb_IN, Pr_IN,CVBS_IN, Y_OUT, Pb_OUT, Pr_OUT, CVBS_OUT U5 U4 DC JACK VCC5V, GND VCC5V, GND L1, L2 C2,C3 1206 0603 Cap7.62 mm HDR 2X1 0603 0603 TO-220 DFM STMicroelectronics GENERAL SEMI Package TSSOP16 Manufacturer STMicroelectronics
STMAV335 S-Video CON VGA FEMALE CON RCA CON LD1117V50 DF04M RECTIFIER DC JACK POWER SOCKET POWER SOCKET FERRITE BEAD 100 nF Cap
10 F Electrolytic Cap C1, C4 Jumper 10 k Resistor 0 Resistor JP9, JP10 R1, R2 JP11, JP12, JP13
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PCB layout recommendation
3
PCB layout recommendation
For the purpose of maintaining 75 track for all the analog lines, a 4-layer structure is recommended. All the analog tracks are routed on the top and bottom layers of the board. The middle two layers are used for both analog and digital ground. The middle two layers are identical and separated into two sections, analog and digital grounds. They are separated by a slot area and are only connected at the top layer through ferrite bead. This ensures the digital noise will not get coupled to the analog portion. All the analog tracks are referenced to the analog ground and all the digital tracks are referenced to the digital ground. In this evaluation board SEL1&SEL2, that in the actual system would come from the digital portion of the system, are included in the analog portion. Since these two select digital lines will be mostly static during operation, it will not cause any disruption to the analog portion. STMAV335 supply is connected to VCC5V analog and GND analog. To further guarantee the stability of STMAV335 supply, a 100 nF capacitor is used to decouple the VCC pin and should be placed as close as possible to the pin. The stability of the analog supply lines is of significant importance since the bias level of STMAV335 is referenced to it. Any instability on the analog supply will affect the switch characteristics. Each set of video signals, RGB, YPbPr, and YC (S-VIDEO) are routed with the same track length. This will guarantee minimum channel-to-channel delay that will lead to minimum display distortion. Figure 2. Recommended board stack-up for 75 impedance
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PCB layout recommendation Figure 3. PCB top layer
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PCB layout recommendation
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PCB layout recommendation Figure 5. PCB bottom layer
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Revision history
4
Revision history
Table 4.
Date 13-Mar-2007
Document revision history
Revision 1 Initial release Changes
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