PM6680 datasheet(41/49 Pages) STMICROELECTRONICS

No de pièce	PM6680

Description	No Rsense dual step-down controller with adjustable voltages for notebook system power

PDF	49 Pages

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Fabricant	STMICROELECTRONICS [STMicroelectronics]

Site Internet	http://www.st.com

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41 / 49 page

PM6680

Device description

41/49

Figure 39.

Inductor current waveforms

Typical components values are: R=47

Ω and C = 1uF.

●

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 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.

●

Bootstrap circuit

The external bootstrap circuit is represented in the next figure:

Figure 40.

Bootstrap circuit

The bootstrap circuit capacitor value CBOOT must provide the total gate charge to the high

side MOSFET during turn on phase. A typical value is 100nF.

The bootstrap diode D must charge the capacitor during the off time phases. The maximum

rated voltage must be higher than VINmax.

A resistor RBOOT on the BOOT pin could be added in order to reduce noise when the phase

node rises up, working like a gate resistor for the turn on phase of the high side MOSFET.

CBBOOOOTT

RBBOOOOTT

PM6680 Fiches technique(PDF) 41 Page - STMicroelectronics