9

PS7012H

08/30/04

PI5A100

Precision, Wide-Bandwidth, Quad SPDT Analog Switch

Applications Information

Overvoltage Protection

Proper power-supply sequencing is recommended for all CMOS

devices. Do not exceed the absolute maximum ratings, because

stresses beyond the listed ratings may cause permanent damage

to the devices. Always sequence V+ on first, followed by V-, and

then logic inputs. If power-supply sequencing is not possible, add

two small signal diodes or two current limiting resistors in series

with the supply pins for overvoltage protection (Figure 8).Adding

diodes reduces the analog signal range, but low switch resistance

and low leakage characteristics are unaffected.

RGB Switch

Figure 9 illustrates a simple low cost RGB switch. The RGB -

to-Composite Decoder produces either NTSC or S-VHS video

from an RGB source. Asingle PI5A100 selects one of the two

video sources to produce either SVHS, Composite or RGB video

outputs. The low insertion loss of the PI5A100 eliminates the need

for expensive input/output buffers.

Figure 8: Overvoltage protection is accomplished using two ex-

ternal blocking diodes or two current limiting resistors.

Figure 9: The single PI5A100 is used to select SVHS, VGA or Composite video outputs.

V+

Positive Supply

COM

NO

Vg

V-

Select

C

Composite

Connector

S-Video

Connector

Composite

RGB to

Composite

Encoder

SVGA

R-G-B

Sync

R

B

+5V

G

Sync

4

Y

PI5A100

H-Sync-0.3V

G or Composite 0.714V

R or Luma 0.7V

B or Chroma 0.28V

VGA

Connect or