TPS65279V datasheet(24/46 Pages) TI

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ROSC

Mode

Selection

1.019

osc

(k )

45580 f

(kHz)

W =

TPS65279V

SLVSBW1B – FEBRUARY 2013 – REVISED JANUARY 2014

www.ti.com

Figure 43. ROSC vs Switching Frequency

(4)

Synchronization

An internal phase locked loop (PLL) has been implemented to allow synchronization between 200 kHz and 1600

kHz, and to easily switch from Resistor mode to Synchronization mode.

To implement the synchronization feature, connect a square wave clock signal to the ROSC pin with a duty cycle

between 20% to 80%. The clock signal amplitude must transition lower than 0.8 V and higher than 2 V. The start

of the switching cycle is synchronized to the falling edge of ROSC pin.

In applications where both Resistor mode and Synchronization mode are needed, the device can be configured

as shown in Figure 44. Before the external clock is present, the device works in Resistor mode and the switching

frequency is set by ROSC resistor. When the external clock is present, the Synchronization mode overrides the

Resistor mode. The first time the ROSC pin is pulled above the ROSC high threshold (2 V), the device switches

from the Resistor mode to the Synchronization mode and the ROSC pin becomes high impedance as the PLL

starts to lock onto the frequency of the external clock. It is not recommended to switch from the Synchronization

mode back to the Resistor mode because the internal switching frequency drops to 100 kHz first before returning

to the switching frequency set by ROSC resistor.

Figure 44. Resistor Mode and Synchronization Mode

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