[SOLVED] Application Note Explanation for DG408DJ

[sammy-e]

Hello,

1. Why does the test circuit within the app note for the DG408DJ specify a 50 ohm pull down on the enable line? A current of 50 mA would leak to ground 2.5V high signal, which seems inefficient.

2. Why is a 300 ohm pull down specified on Vo? Same as #1, this would end up with 30 mA of current being leaked to ground.

I would think a higher ohm resistor would be warranted for each. Thanks.

Info:
The DG408 is an 8 channel single-ended analog multiplexer
designed to connect one of eight inputs to a common output
as determined by a 3-bit binary address (A0, A1, A2).

https://www.mouser.com/ds/2/427/dg408-240041.pdf

 

[FvM]

As indicated in the datasheet, the test circuit has the purpose of testing specific dynamic parameters like switching speed. All special circuit elements, e.g. termination resistors, must be understood related to this measurements.

The test circuit isn't an application circuit for normal switch operation, you can simply ignore it.

 

[sammy-e]

Thanks for the tip, especially for clarifying the use of test vs. application circuits.

As indicated in the datasheet, the test circuit has the purpose of testing specific dynamic parameters like switching speed. All special circuit elements, e.g. termination resistors, must be understood related to this measurements.

The test circuit isn't an application circuit for normal switch operation, you can simply ignore it.