> Although the 1N914 has a book value of 4ns for recovery time, it won't
> take the current. The UF400x series are rated at 50ns (1N400x series
> are 400-1000ns depending on V rating) and are capable of taking that
> massive back emf power surge. It's essential to not allow that power
> near the output stage of the driver IC. In general any inductive
> device such as a relay, solenoid or motor must have diodes across it
> to spare the driver IC an early grave

In regards to the original question about the internal diodes - They
are rated for 600mA but have a Vf of 1.3V at that current. At the
very least, by using external diodes you move that power
dissipation out of the IC and into the breeze. If you are switching
the outputs at any reasonable rate, the diodes can be generating
as much heat as the transistors.

Steve.

======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: steveb@tla.co.nz      fax +64 9 820-1929
======================================================

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