PM6686 datasheet(30/50 Pages) STMICROELECTRONICS

30 / 50 page

Device description

PM6686

30/50

Doc ID 15281 Rev 4

Figure 49.

Inductor current and output voltage in NA SKIP mode

8.1.6

Gate drivers and logic supply

The integrated high-current drivers allow the use of different power MOSFET.

high-side driver is supplied with a bootstrap circuit with an integrated bootstrap diode. The

BOOT and the PHASE pins work respectively as supply and return rails for the HS driver.

The PVCC pin is the input for the supply of the low-side driver and PGND is the pin used as

return rail.

The PM6686 implements an anti-cross conduction protection which prevents high-side and

low-side MOSFET from being on at the same time.

The power dissipation of each driver can be calculated as:

Equation 5

Where VPVCC is the voltage applied to PVCC pin (+5 V) and fSW is the switching frequency.

The power dissipated by the drivers can be reduced lowering the sections switching

frequencies and mounting MOSFET with smaller QG.

VCC pin is the input voltage rail to supply the internal logic circuit. This pin is connected

internally with a resistor to PVCC. As usual analog supply should be divided by the power

supply with a low pass filter to reduce the noise for the analog supply of the logic. Being the

resistor integrated it is enough to put a decoupling capacitor near VCC pin to realize the

filter with a components count reduction.

Output

Inductor

current

Vreg

TMAX

TON TOFF

TIDLE

PVCC

DISS

⋅

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