PM6675 datasheet(42/47 Pages) STMICROELECTRONICS

No. de pieza	PM6675

Descripción Electrónicos	Very fast load transient response using constant on-time control loop

PDF	47 Pages

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Fabricante Electrónico	STMICROELECTRONICS [STMicroelectronics]

Página de inicio	http://www.st.com

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42 / 47 page

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Application information

PM6675

42/47

Equation 51

In order to reduce noise on the COMP pin, it's possible to introduce a resistor RINT that,

together with CINT and Cfilt, becomes a low pas filter. The cutoff frequency fCUT must be

much greater (10 or more times) than the switching frequency:

Equation 52

For most applications both RINT and Cfilt are unnecessary.

If the ripple is very small (e.g. such as with ceramic capacitors), a further compensation

network, called "Virtual ESR" network, is needed. This additional part generates a triangular

ripple that substitutes the ESR output voltage ripple. The complete compensation scheme is

represented in Figure 22.

Figure 22. Virtual ESR network

Select C as shown:

Equation 53

)

(

INT

filt

−

⋅

FILT

INT

FILT

INT

CUT

INT

⋅

CFILT

CINT

RINT

PWM Comparator

1.237V

VOUT

Ton

Generation

Block

Integrator

INT

⋅

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