ELM304SM View Datasheet(PDF) - Elm Electronics

Part Name

Description

Manufacturer

ELM304SM

NTSC Video Generator

Elm Electronics 

Example Application (continued)

Note: There is no colourburst on

the ‘back porch’, so this is

a monochrome signal

ELM304

Figure 2. Gray bar pattern output

V1

V2

V3

Figure 3. ELM304 outputs to give gray bars

connections, and an adequate amount of power supply

filtering. Since this circuit switches voltages quite

rapidly, and it is of relatively low impedance, it will tend

to radiate rf signals. To reduce any effects, you should

keep your connections short, and possibly consider a

shielded enclosure.

Figure 2 shows an actual circuit output when

connected to a 5.00V supply, and a 75 Ω load. Note

that the slight noise and overshoot may be due to the

experimenter board setup, and would likely be

‘cleaned up’ quite a bit if a proper circuit board were

used, along with quality connectors, shorter supply

leads, and more power supply filtering.

Figure 3 should actually be considered to be an

extension of Figure 2. The dotted lines represent the

transition points in the signal displayed in Figure 2, so

that you can see how the three ELM304 output

voltages combine to make one signal. We are often

asked how the signals work, and this is meant to show

that. If you are testing your circuit and look at this

same waveform, don’t forget that the levels shown are

for with a 75Ω load (so you may have to add one). If

ELM304DSC

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