LM46002PWPR datasheet(19/52 Pages) TI

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100

150

200

250

500

1000

1500

2000

2500

Switching Frequency (kHz)

C008

Enable

Internal SS Ramp

Ext Tracking Signal to SS pin

VOUT

LM46002

www.ti.com

SNVSA13B – APRIL 2014 – REVISED SEPTEMBER 2014

Feature Description (continued)

Figure 39. Tracking with Shorter Start-up Time Than The Internal Ramp

8.3.7 Switching Frequency (RT) and Synchronization (SYNC)

The switching frequency of the LM46002 can be programmed by the impedance RT from the RT pin to ground.

The frequency is inversely proportional to the RT resistance. The RT pin can be left floating and the LM46002 will

operate at 500 kHz default switching frequency. The RT pin is not designed to be shorted to ground.

For a desired frequency, typical RT resistance can be found by Equation 3.

RT(kΩ) = 40200 / Freq (kHz) - 0.6

(3)

Figure 40 shows RT resistance vs switching frequency FS curve.

Figure 40. RT Resistance vs Switching Frequency

Table 1 provides typical RT values for a given FS.

Table 1. Typical Frequency Setting RT Resistance

FS (kHz)

RT (kΩ)

200

350

115

500

80.6

750

53.6

1000

39.2

1500

26.1

2000

19.6

2200

17.8

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