Example Application (continued)

5 of 6

ELM304

ELM304DSC

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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 75

Ω load (so you may have to add one). If

Figure 2. Gray bar pattern output

Note: There is no colourburst on

the ‘back porch’, so this is

a monochrome signal