Figure 5 graphs the relationship between inductor current

and current limit. Figure 6 plots ideal inductor current wave-

forms to illustrate inductor current behavior. Figure 7 gives

peak inductor current versus input voltage and shows the

two regions where the oscillator and current limit, respec-

tively, determine peak inductor current.

during the charge phase. Actual voltage across the inductor will be slightly

INCREASING CURRENT LIMIT AND PEAK INDUCTOR

CURRENT

It is possible to increase the current limit by placing an

external resistor between the V

Figure 8. With the addition of the external resistor, only a

fraction of the total inductor current passes through internal

sense resistor. Thus, it takes more inductor current for the

voltage across the internal sense resistor to become large

enough to trip the current limit comparator.

The addition of an external current limit resistor modifies the

associated peak inductor equation to:

R

20099231

FIGURE 5. Peak Inductor Current and Current Limit vs.

Input Voltage

20099232

FIGURE 6. Ideal Inductor Current Waveforms

20099252

FIGURE 7. Peak Inductor Current vs. Input Voltage.

L = 22µH, C

20099233

FIGURE 8. Increase Current Limit and Peak Inductor

Current by Adding R

EXT

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