PM6680ATR datasheet(39/48 Pages) STMICROELECTRONICS

部件名	PM6680ATR

功能描述	Dual synchronous step-down controller with adjustable output voltages plus LDO

PDF	48 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

39 / 48 page

PM6680A

Design guidelines

39/48

9.7

Other parts design

●

VIN filter

A VIN pin low pass filter is suggested to reduce switching noise. The low pass filter is

shown in the next figure:

Figure 38.

VIN pin filter

Typical components values are: R = 3.9

Ω and C = 4.7 µF.

●

VCC filter

A VCC low pass filter helps to reject switching commutations noise:

Figure 39.

Inductor current waveforms

Typical components values are: R = 47

Ω and C = 1µF.

●

VREF capacitor

A 10nF to 100nF ceramic capacitor on VREF pin must be added to ensure noise

rejection.

●

LDO5 output capacitors

Bypass the output of each linear regulator with 1

µF ceramic capacitor closer to the

LDO pin and a 4.7

µF tantalum capacitor (ESR = 2 Ω). In most applicative conditions a

4.7

µF ceramic output capacitor can be enough to ensure stability.

●

Bootstrap circuit

The external bootstrap circuit is represented in the next figure:

VIIN

Input

voltage

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