Cirrus-logic AN374 Manual de usuario descargar pdf (Pagina 13)

AN374

AN374REV2 13

Figure 5 illustrates the process used to select the second stage flyback mode using the CS1630/31 system

design utility.

The CS1630/31 has a minimum required T1 time that is dependent on leading edge blanking time T

LEB

Blanking time T

LEB

is programmable from 150ns to 800ns and is used to effectively disable the peak current

comparator from turning off the gate drive too early due to spurious switching noise. In applied systems, a good

rule of thumb is to target a minimum duty cycle of 10% or greater.

Step 3) General considerations for all topology

1. In the series configurations, the current in one string will always be higher than the current in the second

string across the entire dim and temperature range. There are specific advantages to using the series con-

figuration if the light engine specifications comply with the constraints. In Mode 1, the phase synchronizer

MOSFET is ‘OFF’ and the output power P

MODE1

delivered to the load in a series design is calculated using

Equation 7:

Figure 5. Selecting the Second Stage Mode Using the CS1630/31 System Design Utility

MODE1

CH1

CH2

+I

CH2

=

[Eq. 7]

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Cirrus-logic AN374 Manual de usuario Pagina 13