LM3488MM datasheet(13/24 Pages) NSC

部件名	LM3488MM

功能描述	High Efficiency Low-Side N-Channel Controller for Switching Regulators

PDF	24 Pages

Scroll/Zoom	100%

制造商	NSC [National Semiconductor (TI)]

网页	http://www.national.com

标志

13 / 24 page

Functional Description (Continued)

FREQUENCY

ADJUST/SYNCHRONIZATION/SHUTDOWN

The switching frequency of LM3488 can be adjusted be-

tween 100kHz and 1MHz using a single external resistor.

This resistor must be connected between FA/SYNC/SD pin

and ground, as shown in Figure 6. Please refer to the typical

performance characteristics to determine the value of the

resistor required for a desired switching frequency.

The LM3488 can be synchronized to an external clock. The

external clock must be connected to the FA/SYNC/SD pin

through a resistor, R

SYNC as shown in Figure 7. The value of

this resistor is dependent on the off time of the synchroniza-

tion pulse, T

OFF(SYNC). Table 1 shows the range of resistors

to be used for a given T

OFF(SYNC).

TABLE 1.

OFF(SYNC) (µsec)

SYNC range (k

Ω)

5 to 13

20to40

40to65

10138813

FIGURE 4. Increasing the Slope of the Compensation Ramp

10138851

FIGURE 5.

∆V

SL vs RSL

LM3488MM 数据表(PDF) 13 Page - National Semiconductor (TI)