On Tue, 10 Jan 2012 21:57:49 +1300, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote:
>Hal Murray wrote: >> >> The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm >> resistor. Changing those resistors to 150 ohms should work. Maybe a bit >> lower to account for the impedance in the drivers. I'd probably check it >> with a scope. >> >That approach doesn't do anything for the Vcc and GND bounce exhibited >by the driver chip. >GND and Vcc bounce is the cause of the high frequency ringing exhibited >by the TADD-3 outputs. >This ringing can even be observed at the outputs of inverters whose >inputs are tied low or high in the same package > >Damping the crossover current induced transient in the supply leads >(bondwire and lead frame) inductance is one way to minimise this. >A small resistor in series with the Vcc pin often works well, the >resistor value being chosen for near critical damping. > >Another problem with the TADD-3 is the sharing of a driver chip by >different input frequencies which leads to intermodulation between the 2 >outputs. I have never seen that much ground bounce before so assumed it was a termination problem. Was the driver chip decoupling inadequate? That at least would be easy enough to fix. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
