VB923

[Rich M]

It may be worth having a look at the data for other devices in the VBxxx
series, search for VB? to get a list. eg. VB024/025/026/027 show some
application/test circuits, although they are slightly different devices with
a status flag output, the principles are similar.
I think the connection for the VB923 should be fairly straight forward -
connect coil -ve to HVc terminal, ground to GND and a control signal which
is able to provide 4V at 10mA (minimum) to Vin.

The device actively clamps excess voltage when the coil turns off, and more
importantly if a plug lead becomes disconnected, so no additional protection
should be required at the HVc terminal. It may be prudent to clamp the input
signal to ensure the Vin terminal does not see excess voltage. It's unclear
from the datasheet exactly what the value of Vin(max) is, but I would think
that a 5V1 zener between Vin and GND should keep it happy.

The minimum pulse-width of the input signal will be determined by the
minimum supply voltage to the coil and the coil characteristics (resistance
and inductance). The minimum input pulse width must ensure that the coil
current reaches its design max. or current limit of the device when the
battery voltage is at minimum. (maybe a bit of experiment required?). A
pulse width that exceeds this requirement will push the device into current
limit (a safe condition provided sufficient heatsink is available) for the
duration of the pulse which exceeds the onset of current limit.
Hope this helps, if I'm stating the **** obvious then I apologise.

Rich.

> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of steve ravet
> Sent: 29 May 2000 19:57
> To: diy_efi at diy-efi.org
> Subject: Re: VB923
>
>
> There's a data sheet on the ST WWW page, www.st.com, type vb923 into the
> search box.  It sucks, though, there's no sample circuit.  Only 5
> pages.  I can't find anything else.  sounds like it might be
> interesting, though
>
> --steve
>

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