L6756D datasheet(29/36 Pages) STMICROELECTRONICS

tên linh kiện	L6756D

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L6756D

Main oscillator

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Main oscillator

The internal oscillator generates the triangular waveform for the PWM charging and

discharging with a constant current an internal capacitor. The switching frequency for each

channel, FSW, is internally fixed at 200 kHz: the resulting switching frequency at the load

side results in being multiplied by N (number of configured phases).

The current delivered to the oscillator may be varied using an external resistor (ROSC)

typically connected between the OSC pin and SGND. Since the OSC pin is fixed at 1.24 V,

the frequency is varied proportionally to the current sunk from the pin considering the

internal gain of 10 kHz/

μA (See Figure 13).

Connecting ROSC to SGND the frequency is increased (current is sunk from the pin),

according to the following relationships:

Figure 13.

ROSC vs. switching frequency per phase

200kHz

1.240V

OSC kΩ

()

---------------------------- 10

kHz

μA

-----------

⋅

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