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LM2733

SNVS209E – NOVEMBER 2002 – REVISED APRIL 2013

www.ti.com

Figure 27. 10 µH Inductor Current,

5V–12V Boost (LM2733X)

During the 0.390 µs ON time, the inductor current ramps up 0.176A and ramps down an equal amount during the

OFF time. This is defined as the inductor “ripple current”. It can also be seen that if the load current drops to

about 33 mA, the inductor current will begin touching the zero axis which means it will be in discontinuous mode.

A similar analysis can be performed on any boost converter, to make sure the ripple current is reasonable and

continuous operation will be maintained at the typical load current values.

MAXIMUM SWITCH CURRENT

The maximum FET swtch current available before the current limiter cuts in is dependent on duty cycle of the

application. This is illustrated in the graphs below which show both the typical and specified values of switch

current for both the "X" and "Y" versions as a function of effective (actual) duty cycle:

Figure 28. Switch Current Limit vs Duty Cycle - "X"

Figure 29. Switch Current Limit vs Duty Cycle - "Y"

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