PM6685 datasheet(43/52 Pages) STMICROELECTRONICS

Part #	PM6685

Description	Dual step-down main supply controller with auxilary voltages for notebook system power

PDF	52 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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43 / 52 page

PM6685

Other parts design

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Other parts design

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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=4.7uF.

●

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=1uF.

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VREF capacitor

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

rejection.

●

LDO3 and LDO5 output capacitors

Bypass the output of each linear regulator with 1uF ceramic capacitor closer to the LDO pin

and a 4.7uF tantalum capacitor (ESR=2

Ω). In most applicative conditions a 4.7uF ceramic

output capacitor can be enough to ensure stability.

VIIN

Input

voltage

PM6685 Datasheet(PDF) 43 Page - STMicroelectronics