Re: Updated website

--- In CAD_CAM_EDM_DRO@y..., Steve Blackmore <steve@p...> wrote:

> On Fri, 19 Apr 2002 20:48:41 -0000, you wrote:

[snip]

> Yea - the L297 to 298 works OK. I've not built the L6203,
> the PCB's done, I've got all the bits, but the H Bridge
> design caught up with it
> :)

I'm sorry, I misunderstood the question. I thought you
were asking about connecting L297's to L298's.

> It's the L297 to H bridge I'm not sure of - I think
> I got it right, the sense pins go to the high side
> of the current sense resistor, the inh pins to low
> side (in this case ground) ??? Just like someone to
> confirm before I do another PCB.

I'm not real comfortable with FET's, but the transister
portion of your H-bridge does not look right to me.

The outputs of the L297 are TTL voltage levels between
0 and Vcc (5 volts.) When the output A of the L297 is
high, Q13 turns on, but Q1 is likely to be on as well.
In order turn Q13 off, the output would have to get
awfully close to Vs, which is likely greater than 20
volts. With the current bridge design, I think you
will have "shoot through" where both FET's turn on at
the same time and let all the magic smoke out.

The INH1* and INH2* pins on the L297 are outputs and
should not be grounded. I doubt you really need to
bother with either of these pins.

Lastly, I can't figure out what condition the diodes
D2-D9 are trying to protect against.

I hate to say it, but I think there is some more design work
needed. Unfortunately don't have enough experience to
propose alternative solutions.

[snip rest of message]

-Wayne