ADG5404 cross talk?

Question

hello, 
 ive some problem with my designed multiplexer card, i attach the schematic, see adg5404.jpg. 
 the address is set to 0: 
 if i switch +24V on out_1 and measure the results on out_mplex_1 and out_mplex_2, 
 now i get some heavy spark on the out_mplex_2, see osci_1.jpg. 
 the address is set to 1: 
 if i switch +24V on out_1 and measure the results on out_mplex_2 and out_mplex_3, 
 now i get some little spark on the out_mplex_3, see osci_2.jpg.

is this an design error? 
 why is the spark on out_mplex_2 such high? 
 some hints for me? 
 
 thanks a lot

EricC · Accepted Answer

Hi Nico, 
 That's great that helped. I think this would point towards the speed of the logic transition when using the 100k compared to the 10k affecting the charge injection mechanism. The logic input is into a high impedance buffer with associated capacitance, see the equivalent circuit for the charge injection mechanism. If using pull up/down resistors I would typically use 10kohm resistors on our switch evaluation boards. 
 Regards, 
 Eric.)

Electronic Design Services - PartnerZone

Products Mentioned

ADG5404 cross talk?