At 07:49 AM 8/17/2004, Olin Lathrop wrote:

>Dave VanHorn wrote:
>> there's another fun thing that happens, when you're using two pins to
>> differential-drive.
>> You charge the capacitor (piezo), then take the low pin high, and
>> you've just discharged a 10V capacitor into your protection diodes!
>> (5v on the piezo, plus the 5V on the output pin.)
>>
>> Not good.
>>
>> If you take the high pin low, before taking the low pin high, then
>> you're safe.
>
>No, then you've got the same problem except that it drains the capacitor
>thru the low side diode of the low pin.

Not quite the same. The high side is usually where the problem happens.
That, and the effect of dumping a 10V 0.1uF cap into the VCC through the protection diodes.. If the supply impedance is large, the result can be ugly.

Point being, capacitive loads aren't as nice to drive, as they appear at first glance.

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