Hi,
Please tell me about channel switching delay time of SN74LV4051A.
Can anyone please let me know whether this part SN74LV4051A can support this switching speed
from one channel to next channel without any disturbances in applied voltage at the 8 analog channels.
For example:
I would like to know the delay time of Y2 to Y4 when A, B, and C are controlled with INH=L fixed.
best regards
Hello Cafain,
I did some tests on the SN74LV4051A for the delay between switching channels. The general test setup can be observed in Figure 1. For these tests, the input signal on the COM pin was just a constant voltage. In these tests the switching delay between channels Y0 and Y1 was assesed. Only these channels were assessed as we expect similar performance from the other channels in this particular device. Channel 1 (yellow) corresponds to the signal inputted at pin A to switch between channels Y0 and Y1, while channel 3 (magenta) corresponds to Y0 and channel 4 (green) corresponds to Y1. Figure 2 shows the delay observed when switching from channel Y0 to Y1 and this is ~19.6ns. Figures 3 and 4 show the delays for switching from Y1 to Y0. The maximum delay observed for this switch was ~12.4ns.
Figure 1
Figure 2
Figure 3
Figure 4
Hello Cafain-san,
In Figures 1 and 2 below are the results I get when switching A, B , and C all at the same time. For my results there is a noticeable drop (~600mV) from the input of COM to the output of Y0 and Y7. This is actually expected behavior due to the particular setup I have used as shown in Figure 3. The amount of voltage that drops across the SN74LV4051Aswitch hinges on the termination impedance of your input supply as well as the load seen at the Y pins. Another important factor is the parasitic Ron resistance of the internal FETs in SN74LV4051A. Essentially these FETS, which for the purposes of simplification can be treated as resistors (Figure 4), form a voltage divider with your load and source impedances (Figure 5). Upon looking at the Ron in the Electrical Characteristics section of the datasheet (Table 1), one can see that depending on the Vcc, temperature, and device variation, this parasitic resistance can range anywhere from less than 22 ohms to 600 ohms. Consequently if you have a small load impedance, it is quite likely you will observe inconsistent output voltages between different units. However, if your load is 10 to 100 times larger than Ron, you should expect to see a very negligible drop across the switch.
Figure 1
Figure 2
Table1
Hello Cafain-san,
According to the description from the datasheet, inputting the signal at Y7 and outputting at COM should not be a problem. Also inputting the signal from Y0 and outputting at COM should not be a problem. By setting the logic levels on pins A, B, and C, you essentially determine the signal path to or from COM. If you observe behavior that deviates from this, please let us know.
