TPS54341_15 datasheet(18/48 Pages) TI

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1.008

101756

(kHz)

RT (k )

0.991

92 417

RT (k )

(kHz)

W =

TPS54341

SLVSC61 – NOVEMBER 2013

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DETAILED DESCRIPTION (continued)

Figure 34. Ratiometric Startup With Tracking

Figure 35. Ratiometric Startup With Tracking

Resistors

Figure 36. Simultaneous Startup With Tracking Resistor

Constant Switching Frequency and Timing Resistor (RT/CLK) Pin)

The switching frequency of the TPS54341 device is adjustable over a wide range from 100 to 2500 kHz by

placing a resistor between the RT/CLK pin and GND pin. The RT/CLK pin voltage is typically 0.5 V and must

have a resistor to ground to set the switching frequency. To determine the timing resistance for a given switching

frequency, use Equation 10 or Equation 11 or the curves in Figure 5 and Figure 6. To reduce the solution size,

one typically sets the switching frequency as high as possible. Tradeoffs of the conversion efficiency, maximum

input voltage, and minimum controllable on time must be considered. The minimum controllable on time is

typically 135 ns which limits the maximum operating frequency in applications with high input-to-output step-down

ratios. The maximum switching frequency is also limited by the frequency-foldback circuit. A more detailed

discussion of the maximum switching frequency is provided in the next section.

(10)

(11)

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