I am working on duplicating a product according to the Microchip datasheet. http://ww1.microchip.com/downloads/en/appnotes/00857b.pdf
My question has to do with something I found in the schematic (page 29, and also inserted below). That is, the bypass circuitry at supply of each of the two main drivers appears to have a path straight to ground from +12V (see below). How will this power the drivers at all connected like this??? I figure I am just understanding this wrong and it is not a typo because its coming from Microchip and not some Joe-Schmo. Can someone explain this to me? Thanks in advance.
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1\$\begingroup\$ Yeah. That picture looks like no one reviewed it for sanity. \$\endgroup\$– jonkCommented Apr 13, 2019 at 19:52
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\$\begingroup\$ Some use straight path for ground. I used to use a slanted bar for voltage sources. Sometimes a box I would say you aren't reading the symbolic logic diagram properly. (artistic licence) Are IPC standards relevant with motors? i.sstatic.net/bU8FF.png No \$\endgroup\$– D.A.S.Commented Apr 13, 2019 at 19:53
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\$\begingroup\$ I'm not sure. I don't think it is an issue of standards though. \$\endgroup\$– thisissparzoCommented Apr 13, 2019 at 20:11
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\$\begingroup\$ Those capacitors should be between VDD and ground, the connection from the ground side of them to VDD is erroneous. The symbol is wrong too, pins 6 and 9 should be 3B and 4B respectively. Page 10 of ww1.microchip.com/downloads/en/DeviceDoc/21425C.pdf shows what they meant to draw. \$\endgroup\$– ColinCommented Apr 13, 2019 at 20:14
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\$\begingroup\$ What do you mean "straight path"? The net is the +12V power rail. \$\endgroup\$– Ale..chenskiCommented Apr 13, 2019 at 20:39
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3 Answers
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The connection from pin 14 to the bottom of cap C2 should not be there. Also, the link in the original post is to an Application note, and not a datasheet. The TC4469 datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/21425C.pdf has the 3B, 4B, pins labelled correctly and Figure 4-1 shows the proper GND connection for the caps.
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Yes, this is definitely wrong. You could try emailing Microchip with the correction, but it's a pretty old document so they probably won't bother doing it.
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1\$\begingroup\$ I really thought so. I guess I'll try emailing them. In the meantime I'll just take out that circuitry and do what that TC4469 datasheet suggests. \$\endgroup\$ Commented Apr 13, 2019 at 19:56
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\$\begingroup\$ Yeah - worth a try, and good citizenship. Well caught too :) \$\endgroup\$– awjloganCommented Apr 13, 2019 at 19:57
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There is nothing not much wrong with the schematics, if the attention is at the pointed arrow. Some schematics drawing tools do use the solid bar symbol as power rail:
The GND usually have striped shape, or triange, or other shapes that are meant to differentiate between signal ground, power ground, analog ground, and shields.
However, the OP marks wrong spot on the drawings. One wire is obviously wrong, I agree:
answered Apr 13, 2019 at 20:33
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\$\begingroup\$ @Colin, then the OP should point to the wrong wire, and not to +12V symbol. I appended my opinion. \$\endgroup\$ Commented Apr 13, 2019 at 20:45
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\$\begingroup\$ the OP may no be experienced enough to confidently guess where the error on the datasheet lies. \$\endgroup\$ Commented Apr 14, 2019 at 4:25