Products > Test Equipment
MS05000 Budget Logic Analyzer Probe Set Design
electricMN:
How about option 1 but just offer the board blanks for sale if someone wants to assemble the boards themselves.
thmjpr:
AZ23C3V6 seems to have a capacitance in the ~100pF range, which is not too high but definitely much lower capacitance diodes are available.
Its hard for me to see why you wouldn't want the high value pulldown resistors. If the pins are floating in the air and reading 0V thats one thing, but what if you are probing a broken trace or similar? It could give misleading levels if its not lightly loaded.
Input clamp current is stated as 50mA max, so if you can stay under that it would be good. 5V -> 200R -> (3.3V + 0.6V) = 6mA, seems alright.
You might consider a 3.3V TVS on the supply rail so the ICs ESD diodes have something to dump to (I'm assuming here they are present, but datasheet only mentioned Vi < 0 so not sure). If the individual line zeners are not used. I know I've said it before, but I fully expect 5V to be applied on those inputs.
Gandalf_Sr:
I'm struggling to pick the right voltage for a TVS diode to protect the 3.3V supply rail (Vccb). I found the PESD4V0Y1BSF but, although the min breakdown voltage is 4.2V, the typical is 6.2V, and the max is 8V.
Any comments on what a suitable TVS diode should be?
MarkL:
--- Quote from: Gandalf_Sr on March 16, 2020, 10:33:27 pm ---...
One thing I haven't found yet is where in the menus I can align the analog and digital signals in time - I thought that was somewhere in the menus?
--- End quote ---
I don't have this scope, but according to the User Manual it's in the channel menu. Their example for Channel 1:
--- Quote from: Rigol Feb 2019 User Manual, pg. 2-8, section Channel Delay: ---Press 1 --> More --> Ch-Ch Skew, rotate the multifunction knob or use the numeric keypad to set the desired delay calibration time. The available range of the delay calibration time is from -100 ns to 100 ns.
--- End quote ---
Gandalf_Sr:
OK, I'm close to ready to order the new PCBs although the Connector PCB is unchanged. Attached are new pictures and I'll follow up with another post with the BOM and schematics for both PCBs.
I took out the pesky protection diodes on the input lines and placed new 10k \$\Omega\$ resistors to ground on each input line.
[EDIT] I added a protection diode on the 3.3V side of the voltage level translator as requested.
I have 4 people who've asked me for PCBs, tv84, lodkolven, and electricMN - you guys will each need a Connector PCB but let me know if you want something different from the basic just 2 probe PCBs; you will need 2 to have 16 channels and you may want 3 so you can have 2 x 3.3V versions and 1 x 5.5V version. Let me know by PM. To cover my costs is going to be something like $20 for 3 PCBs including shipping - have ordered extras to cover the inevitable late-comers.
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