PM6675 datasheet(41/47 Pages) STMICROELECTRONICS

Il numero della parte	PM6675

Spiegazioni elettronici	Very fast load transient response using constant on-time control loop

PDF	47 Pages

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Produttore elettronici	STMICROELECTRONICS [STMicroelectronics]

Homepage	http://www.st.com

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PM6675

Application information

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7.1.7

All ceramic capacitors application

Design of external feedback network depends on the output voltage ripple across the output

capacitors' ESR. If the ripple is great enough (at least 20mV), the compensation network

simply consists of a CINT capacitor.

Figure 21. Integrative compensation

The stability of the system firstly depends on the output capacitor zero frequency. It must be

verified that:

Equation 49

where k is a free design parameter greater than unity (k > 3) . It determines the minimum

integrator capacitor value CINT:

Equation 50

If the ripple on the COMP pin is greater than the integrator output dynamic (150mV), an

additional capacitor Cfilt could be added in order to reduce its amplitude. If q is the desired

attenuation factor of the output ripple, select:

CFILT

CINT

RINT

VREF

VSNS

Ton One-shot

generator

Vr=0.9

PWM

Comparator

COMP

VOUT

Integrator

out

Zout

⋅

Vref

Zout

INT

⋅

⎟

⎠

⎞

⎜

⎝

⎛

−

⋅

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