TPS65279V datasheet(23/46 Pages) TI

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ENFALLING

STOP

ENFALLING

1 h

R (I

I )

ENFALLING

START

STOP

ENRISING

ENFALLING

ENRISING

(

)

I (1

) I

TPS65279V

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SLVSBW1B – FEBRUARY 2013 – REVISED JANUARY 2014

Figure 42. Adjustable VIN Under-Voltage Lockout

(2)

(3)

Where Ih = 3 µA, IP = 3 µA, VENRISING = 1.21 V, VENFALLING = 1.17 V.

Adjustable Switching Frequency and Synchronization

The ROSC pin can be used to set the switching frequency of the device in two mode. The resistor mode is to

connect a resistor between ROSC pin and GND. The switching frequency of the device is adjustable from 200

kHz to 1600 kHz. The other mode called synchronization mode is to connect an external clock signal directly to

the ROSC pin. The device is synchronized to the external clock frequency with PLL.

Synchronization mode overrides the resistor mode. The device is able to detect the proper mode automatically

and switch from synchronization mode to resistor mode.

Adjustable Switching Frequency (Resistor Mode)

To determine the ROSC resistance for a given switching frequency, use Equation 4 or the curve in Figure 43. To

reduce the solution size one would set the switching frequency as high as possible, but tradeoffs of the supply

efficiency and minimum controllable on time should be considered.

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