KA3842 Ver la hoja de datos (PDF) - Fairchild Semiconductor

Número de pieza

componentes Descripción

Fabricante

KA3842

SMPS Controller

Fairchild Semiconductor 

KA3842B/KA3843B/KA3844B/KA3845B

Shutdown of the KA3842B can be accomplished by two methods; either raise pin 3 above 1V or pull pin 1 below a voltage

two diode drops above ground. Either method causes the output of the PWM comparator to be high (refer to block diagram).

The PWM latch is reset dominant so that the output will remain low until the next clock cycle after the shutdown condition at

pins 1 and/or 3 is removed. In one example, an externally latched shutdown may be accomplished by adding an SOR which

will be reset by cycling Voc below the lower UVLO threshold. At this point the reference turns off, allowing the SCR to reset.

Figure 9. Slope Compensation

A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope compensation for

converters requiring duty cycles over 50%. Note that capacitor, C, forms a filter with R2 to suppress the leading edge switch

spikes.

TEMPERATURE (°C)

Figure 10. TEMPERATURE DRIFT (Vref)

TEMPERATURE (°C)

Figure 11. TEMPERATURE DRIFT (Ist)

TEMPERATURE (°C)

Figure 12. TEMPERATURE DRIFT (Icc)

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