SN74LVC4245APWR is a bus transceiver/level shifter not a gate driver

[rusefillc]

24-TSSOP

Rafael Matos says

50ma per output is definitely not plenty at all to drive an IGBT for ignition either inside or outside the coil doesn't really matter an ISL9v3040s might use around 70ma with 5v on the gate, I have no questions about it turning ON I know it will drive, but its not reliable, i never seen an ignition driver circuit like this straight from a level shifter, all the ECU's I have ever owned/repaired/designed use very similar ignition driver circuits with a few small differences but same concept, after the level shifter it's always good practice to have some gate driver that can handle more current. The SN74 is a bus transceiver/level shifter not a gate driver

[rusefillc]

@dron0gus @andreika-git any opinions? we use SN74 on all recent mega-module designs which has inherited it from https://github.com/andreika-git/hellen-one/tree/master/modules/ign8 where it was used since day one

[rusefillc]

originally reported at https://www.facebook.com/groups/rusEfi/permalink/1876919989409302/

[rusefillc]

I am tracking this as a hellen-one ticket https://github.com/andreika-git/hellen-one/issues/378 not as an uaEFI ticket because same exact design was used on all hellen-one units. Some of them are driving for YEARS! Obviously the fact that we might have got lucky for a few years does not mean that the design is correct thus the ticket is open and will be open until we have a clear resolution.

We have a ton of https://github.com/rusefi/alphax-4chan boards in the wild

We have https://github.com/rusefi/hellen154hyundai used on daily driven vehicles for over a year

We have https://github.com/rusefi/rusefi/wiki/Hellen-128-Mercedes used on daily driven vehicle for over a year

[rusefillc]

The coil is golf mk3 from the distributor versions. Theres only one, and its VW 6N0905104. Mine's an aftermarket replacement from meyle

This is scope trace of trigger input and ign output . Does anyone know how big the pullup is on the ign output? Edit: this was WITH coil connected. Volt is same scale, red reaches 5v, blue only 2,5v.

[rusefillc]

huh

https://www.nxp.com/docs/en/data-sheet/MC33810.pdf

[dron0gus]

Do we sure that all smart coils have IGBTs as power switch? May be some have bipolar transistors or even darlington? Looking at oscilogram from https://github.com/andreika-git/hellen-one/issues/378#issuecomment-2045234004 I suspect bipolar or gate protection. Fronts are sharp I see no other reason to stop on 2.5V, does not look like output stage overload.

Another note. MC33810 is good for on-board IGBTs and dump (two-wire) coils. Definitely not the best choice for driving smart coils - no feedback benefits, no diagnostic.

[dron0gus]

High voltage NPN for ignition coil https://www.st.com/en/power-transistors/std901t.html

[rusefillc]

Some suggestions at https://rusefi.com/forum/viewtopic.php?p=49945#p49945