0

schematic

simulate this circuit – Schematic created using CircuitLab

Here is a thought (hopefully) to my grounding/shorting problem (Multiple ground).

Would this circuit work being fed by the li-ion cells to obtain an isolated +-3.7V? What kind of transformer should I look for? Like key parameters. (please don`t mind the values)

NOTE: I realized that i drow the two ground connections the same, please refer to those as two separate GND connections

Status Re
  • 121
  • 6
  • 1
    What is the question? Reading the datasheet for the LT3436 doesn't look like you should be connecting the NC pins to ground... – Ron Beyer Nov 14 '21 at 16:21
  • 1
    You should also really use named nets instead of running lines all over the place. For example, U5 has "VIN" pin 8 connected directly to GND if you trace it back up to CN2 pin 3. And for some reason you have TS from U2 skipping over a bunch of ground connections to connect to GND from CN2 as well... – Ron Beyer Nov 14 '21 at 16:27
  • Ok, about the NC pins I don't think makes difference if they are connected to gnd. If you look at the suggested layout they are indeed grounded. About the TS running all the way I guess you are right, but it is for me to remember that the NTC is to be place underneath, or as close to, the battery pack. Then I am having hard time trying to get the "virtual ground" right in order to split my battery voltage in two – Status Re Nov 14 '21 at 16:57
  • With respect to "different" Ground nodes, if you are looking for a general procedure I suggest this: 1) Make all grounds a single net GND. 2) analyze if this leads to any problems. 3) determine specific solutions to these problems. Specifically, are you sure you need galvanic isolation ? – tobalt Nov 14 '21 at 18:05
  • 1
    This appears to be an addendum to a previous question, and should be an edit to that question. Posting extra information as a new question just makes things confusing for people trying to help. – Hearth Nov 14 '21 at 18:08
  • @Hearth: got it – Status Re Nov 14 '21 at 18:20
  • @tobalt: thanks I will try to proceed step by step from single gnd net – Status Re Nov 14 '21 at 18:23
  • @Hearth - Agreed, *but* making substantial updates to the schematics in the [original question](/questions/594167) could render the existing answers there to be obsolete - or at least confusing, as older answers would address the original schematic & newer answers would address new schematics. This is one reason why broad design review-type questions are not well-suited to the Stack Exchange Q&A format, as the questions can change after initial answers are given. So I can see both sides - we don't want to invalidate previous answers, but yes, this is only a "next stage" on a journey. Thoughts? – SamGibson Nov 14 '21 at 18:29
  • [continued] If there were no answers on the original question, then this would definitely be better as an edit to that question. However that isn't the situation in this case :-( – SamGibson Nov 14 '21 at 18:30
  • the `do not populate` directive does not indicate which components are affected – jsotola Nov 14 '21 at 19:19
  • 1
    What is the point of isolating from a battery? If it is battery powered, why not make ground the mid point between the batteries and then run the LDOs directly from the battery? – user1850479 Nov 25 '21 at 06:52
  • Because they need to get charged. And they get charged from usb – Status Re Nov 25 '21 at 10:33
  • Disconnect the batteries from the LDOs when you charge them. Or do you need to be to run off of USB power (without batteries) too? – user1850479 Nov 26 '21 at 06:11
  • I gave for granted that it would have worked also during charge. I never thought about power also from usb (which sounds interesting:). But in case that when it charges does only that, how would you disconnect them? – Status Re Nov 26 '21 at 06:17
  • Take the batteries out and put them in a charger or add a transistor that disconnects on USB insertion. This is common, lots of hardware cannot be used while charging. – user1850479 Nov 26 '21 at 07:03
  • Yeah taking batteries out is a no go. I don't like it. Not considering it. Add a transistor that disconnects on USB insertion: could you be a little bit more specific? – Status Re Nov 26 '21 at 07:12

0 Answers0