PM6686 STMicroelectronics, PM6686 Datasheet - Page 44

• Manufacturer Part Number: PM6686
• Description: Dual Step-down Controller With Adjustable Voltages, Adjustable Ldo And Auxiliary Charge Pump Controller For Notebook
• Manufacturer: STMicroelectronics

Diode selection
11.3.3
11.3.4
11.3.5
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Typical components values are: C1 = 1 µF and C2 = 1 µF.
VREF2 and VREF3 capacitors
A 10 nF to 100 nF ceramic capacitor on VREF2 pin must be added to ensure noise
rejection. If VREF3 voltage is not used the pin can be left floating, otherwise a 10 nF to 100
nF bypass ceramic capacitor should be mounted.
LDO output capacitors
Bypass the output of the linear regulator with 4,7 µF ceramic capacitor closer to the LDO
pin. In most applicative conditions the ceramic output capacitor can be enough to ensure
stability.
Bootstrap circuit
The external bootstrap circuit is represented in the next figure:
Figure 57. 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 100 nF.
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. A typical value is R
L
CBOOT
BOOT
Doc ID 15281 Rev 4
= 1 Ω.
RBOOT
RBOOT
PHASE
PM6686