Re: Any beefy coil driver chips?

On a sunny day (Fri, 31 Jul 2009 07:34:43 -0700) it happened Joerg
<invalid@xxxxxxxxxxxxxxx> wrote in <7dgdohF2bq1uuU1@xxxxxxxxxxxxxxxxxx>:

Jan Panteltje wrote:
On a sunny day (Fri, 31 Jul 2009 06:26:18 -0700) it happened Joerg
<invalid@xxxxxxxxxxxxxxx> wrote in <7dg9o8F29sqa2U1@xxxxxxxxxxxxxxxxxx>:

Jan Panteltje wrote:
On a sunny day (Thu, 30 Jul 2009 20:49:35 -0700) it happened Joerg
<invalid@xxxxxxxxxxxxxxx> wrote in <7df7utF2bp6jvU2@xxxxxxxxxxxxxxxxxx>:

Yes, that plus an opamp for the PWM, plus a SVS so the FET doesn't go
*PHUT* when the control voltage is sluggish, numerous resistors, and so
on.
Since I did the PWM SEPIC with one PIC and one power MOSFET,
I would have a go with a PIC and maybe 3 resistors...
decoupling cap too.
Maybe the PIC can take over functons of other things on the board too.
That is usually where the advantage is,

Forgot to mention one "minor" detail. I also do not have a supply
voltage, just the on/off control signal with lots of amps (think
industrial control gear). This excludes many uC and also stepper driver
chips because they need several msec to boot, reset or prime a charge pump.

That is easy to solve, drive the MOSFET gate from the incoming voltage,
and while the PIC starts up in *microseconds* have it do the pulldown
thing on the gate,
As the PIC is high impedance output while not initialized, all you need is a pullup
resistor on thte PIC output.
You need a resistor to ground otherwise... for the same reason:
intintial floating ouput pins.


I don't know PICs, mainly just MSP430 and some 8051 variants. Don't they
have a POR/BOR in there that takes its time after VCC gets applied?

Yes there is, it all depends on how you program it, there are a number
of flags you can set.
There is a power up timer that will delay 72 ms (16F648A as an example),
but it can be disabled.
It is recommended to be enabled when brown out reset is enabled.
Perhaps in this situation you need neither.
.

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