Use ST VB325SP as ignition driver?

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HotCat
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Use ST VB325SP as ignition driver?

Post by HotCat »

I want to use VB325SP integrated circuit to drive my coil, it is high integrated, TTL compatible and can drive coil directly with saturation current 4.2A, no extra MOSFET required. I post this thread to let us discuss the possibility to replace the vague 74LS86 on PUMA board

I include an attachment of VB325SP datasheet, here is a short description about this chip

The VB325SP is a high voltage power integrated
circuit made using the STMicroelectronics
VIPower™ M1-3 technology, with vertical current
flow power darlington and logic level compatible
driving circuit. The enable pin allows to externally
block the switch when the input is on. Built-in
protection circuit for coil current limiting and
collector voltage clamping allows the device to be
used as smart, high voltage, high current interface
in advanced electronic ignition system. If the input
signal from the micro happens to remain high, the
device protects itself against over-heating by
forcing collector current to smooth decrease (low
voltage clamp feature) and no undesidered spark
occurs
Attachments
VB325SP.pdf
(191.68 KiB) Downloaded 802 times
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jharvey
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Re: Use ST VB325SP as ignition driver?

Post by jharvey »

There are a great many devices that can directly drive the ignition. I like the diagnostics feed back from this one. I'm a fan of closing the feed back loop. Do you know the value, or approx value or Rsense?

The reason why Puma and DFH use the external drivers is to limit the RF and high voltage loops. The on board MOSFET's are mostly to increase the drive capabilities of the MCU and drive polarity. Direct drive hasn't really been in the plan because it typically requires longer routes of the high voltage. However, I seem to recall that there are some 300V OVP MOSFET's that can fit in the existing vias, and they can direct drive. We don't really need those large MOSFET's for the mA required to drive the external ignitors.
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nitrousnrg
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Re: Use ST VB325SP as ignition driver?

Post by nitrousnrg »

Hi there, welcome along

Nice chip, but keep in mind availability. There are many ICs out there that I'd put on Puma but were not available by any supplier. VB325SP seems to be stocked only at futureelectronics, and I feel like they won't get more of them once their stock is zero. Even in ST's website they are shown as non-stocked. Also, it would be the only ROHS non-compliant component of Puma.

Puma is ready to test some internal ign drivers, though, so if you know a way to have a reliable stock of those chips I can consider using it.

About the 74HC86, it is there to invert (or not invert) the signal. Is just to help the firmware, not the hardware :-)
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Re: Use ST VB325SP as ignition driver?

Post by Fred »

I'd also like to note that 4 amp saturation current doesn't provide a very good spark on the coils that I've tested... possibly good enough for some setups, but the Puma, I thought, was supposed to be for high performance setups. You have to remember that these chips are aimed firmly at OEMs where a mild setup that is only just good enough is the norm. Just look at the debacle that is the VB921, it's borderline useless.

+1 on limited suppliers and unique nature of the thing.

Additionally, you must allow for external ignitors to be driven properly, many people (those with good sense :-p :-) ) will not want to drive their coils from inside their ECU, and as such ignitor driving is, or should be, a high priority.

Fred.
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HotCat
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Re: Use ST VB325SP as ignition driver?

Post by HotCat »

nitrousnrg wrote:Puma is ready to test some internal ign drivers, though, so if you know a way to have a reliable stock of those chips I can consider using it.
I am from China, VB325SP is available on many online electronic store or local electronic market. I got two from local market, but the price was a little hight, 35 RMB.
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nitrousnrg
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Re: Use ST VB325SP as ignition driver?

Post by nitrousnrg »

wow, and I had to check all the electronic stores of my city to get a damn 1N4148.

Good to know you have those there, but honestly, that IC would make the production more difficult than already is. I'm a bit worried about those MAX9924 getting out of stock everywhere.

Thanks for the input anyway!
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HotCat
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Re: Use ST VB325SP as ignition driver?

Post by HotCat »

jharvey wrote:The reason why Puma and DFH use the external drivers is to limit the RF and high voltage loops.
I am so confused, stock ECU always use the build-in drivers to drive the coil. At least my Bosch MP5.2 and ME 7.4.4 had this design. RF can be shield by metal box,the voltage inducted from secondary coil winding is between 40-100V, my stock ECU does not have any special isolation on PCB layout but thicken the wire to allow more current
jharvey wrote:Direct drive hasn't really been in the plan because it typically requires longer routes of the high voltage.
Long route is really not a problem, the wiring harness is twisted around the engine. We can use shield wire to overcome this issue
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HotCat
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Re: Use ST VB325SP as ignition driver?

Post by HotCat »

Fred wrote:I'd also like to note that 4 amp saturation current doesn't provide a very good spark on the coils that I've tested. You have to remember that these chips are aimed firmly at OEMs where a mild setup that is only just good enough is the norm
Thanks for your reply, l've learn a lot from you. Mainsteam Chinese cars don't have big cylinder capacity, usually between 1.3-2.0 Litre with wasted spark and sequential injection(Europe III pollution standard compliant). Also the price of gas is extremely high and the quality is so poor. So the primary goal of designing a ECU is economy and reliable not performance. So I decide to try VB325SP on my prototype board which is based on PUMA board.

Also I would like FreeEMS to be a Linux-like project, we port it to different kind of vehicle rather than have a extremely complex configurations like MegaSquirt
Last edited by HotCat on Fri Apr 15, 2011 8:54 am, edited 1 time in total.
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HotCat
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Re: Use ST VB325SP as ignition driver?

Post by HotCat »

nitrousnrg wrote:Good to know you have those there, but honestly, that IC would make the production more difficult than already is. I'm a bit worried about those MAX9924 getting out of stock
China is a supernatural nation, I don't have this issue, I can even find the proprietary automobile ICs on my stock ECU just two decades ago.
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Re: Use ST VB325SP as ignition driver?

Post by Fred »

HotCat wrote:So the primary goal of designing a ECU is economy and reliable not performance. So I decide to try VB325SP on my prototype board which is based on PUMA board.
When does it end up on github.com for us to play with? I'm curious about what you've done with it :-)
HotCat wrote:Also I would like FreeEMS to be a Linux-like project, we port it to different kind of vehicle rather than have a extremely complex configurations like MegaSquirt
This is under control! :-) Trust me, software is my bag, baby! :-) (austin powers reference...)
HotCat-Edited-By-Fred wrote:China is the nation best at copying others work and reducing the quality in the process, I don't have this issue, I can even find the proprietary automobile ICs on my stock ECU just two decades ago.
Fixed! :-) It's amazing what you can get in shen zhen, but, much of it is rip off stuff, and when only genuine will do, you can be out of luck. The amount and well-matched-ness of the produce in China is remarkable. As Marcos says, it also doesn't help the rest of us find such parts. However, do as you please with your design, the more the merrier.

Fred.
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