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AN469 APPLICATION NOTE

(8)

Looking at equation 4 it can easily be seen that the minimum pulse width of T2 will occur when the value of Ri

is at its minimum and the value of R1 at its maximum.

Therefore, when evaluating equation 7 the minimum value for Ri of 700

Ω (1 KΩ –30 %) should be used to guar-

antee the required pulse width.

For a typical application using the L298, which has a maximum turn on delay of 2.5

µs, with the L6506 consider

the following operating points:

f = 20 KHz

T1 + T2 = 50

µs

T2 min = 3

µs

From equation 6:

From equation 7:

From equation 8:

C1

T1

0.69R1

--------------------

=

DC

3

µs

50

µs

--------------

0.06

==

R1

1

0.06

----------- 2



 700 10.3KΩ

=

=

C1

47

µs

0.69

() 10.3K

()

--------------------------------------

6.6nF

==

Figure 6. Load Current and Sync Pulse.

Figure 7. Oscillator Circuit and Waveforms.