MV1012SC

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5.2 PWM dimming

5.2.1

PWM dimming in 100% and oscillation off regions

should be 1 kHz or less and 1% or more, respectively.

Figure 21 Example of PWM dimming operation

As shown in Figure 21, when a PWM signal with on-duty cycle of Don is applied to the REF pin, Io becomes an average

current Io (ave) = Don x Io (max) + (1 – Don) x Io (min). In actual use, Io (min) is very small, and the equation may be

rewritten to Io (ave) ≈ Don x Io (max).

In PWM dimming, if the first switching-on timing in the H-level period is irregular, the practical Don will also become

irregular and Io will become unstable. The effect is especially significant if Don is small. To avoid this problem, the first

H level and forcibly outputting an on-trigger. This function helps stabilize Io (ave), even if Don is small.

CAT.No.1A0602-1E