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Shutdown Technique

330

Ω

1 k

Ω

500

Ω

To Current-Sense

Resistor

Shutdown

Shutdown

COMP

0.1

µF

R1

R2

C

TL284xB, TL384xB

HIGH-PERFORMANCE CURRENT-MODE PWM CONTROLLERS

SLVS610B – AUGUST 2006 – REVISED JULY 2007

APPLICATION INFORMATION (continued)

1 V or pull the COMP terminal 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

In one example, an externally latched shutdown can be accomplished by adding an SCR that resets by cycling

Figure 5. Shutdown Techniques

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

compensation for converters requiring duty cycles over 50% (see Figure 6). Note that capacitor C forms a filter

with R2 to suppress the leading-edge switch spikes.

Figure 6. Slope Compensation

13

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