FDMF6840C datasheet(15/19 Pages) ONSEMI

15 / 19 page

www.onsemi.com

Application Information

Supply Capacitor Selection

For the supply inputs (VCIN), a local ceramic bypass

capacitor is recommended to reduce noise and to

supply the peak current. Use at least a 1 µF X7R or X5R

capacitor. Keep this capacitor close to the VCIN pin and

connect it to the GND plane w ith vias.

Bootstrap Circuit

The bootstrap circuit uses a charge storage capacitor

(CBOOT), as show n in Figure 30. A bootstrap capacitance

of 100 nF X7R or X5R capacitor is usually adequate. A

series bootstrap resistor may be needed for specific

applications to improve sw itching noise immunity. The

boot resistor may be required w hen operating above

15 VIN and is effective at controlling the high-side

MOSFET turn-on s lew rate and VSHW overshoot. RBOOT

values from 0.5 to 3.0

Ω are typically effective in

reducing VSWH overshoot.

VCIN Filter

The V DRV pin provides pow er to the gate drive of the

high-side and low -side pow er MOSFET. In most cases,

it can be connected directly to V CIN, the pin that

provides pow er to the logic section of the driver. For

additional noise immunity, an RC filter can be inserted

betw een the VDRV and V CIN pins. Recommended

values w ould be 10

Ω and 1 µF.

Power Loss and Efficiency

Measurement and Calculation

Refer to Figure 30 for pow er loss testing method.

Pow er loss calculations are:

PIN=(VIN x IIN) + (V5V x I5V) (W)

(1)

PSW=VSW x IOUT (W)

(2)

POUT=VOUT x IOUT (W)

(3)

PLOSS_MODULE=PIN - PSW (W)

(4)

PLOSS_BOARD=PIN - POUT (W)

(5)

EFFMODULE=100 x PSW/PIN (%)

(6)

EFFBOARD=100 x POUT/PIN (%)

(7)

Figure 29.

Block Diagram With VCIN Filter

Figure 30.

Pow er Loss Measurem ent

VDRV

VCIN

VIN

PWM

V5V

DISB#

PWM

Input

OFF

CVDRV

CVIN

CBOOT

RBOOT

LOUT

COUT

I5V

IIN

VIN

V VSW

IOUT

THWN#

BOOT

VSWH

CGND

PGND

DISB#

FDM 67 5

Open-

Drain

Output

PHASE

SMOD#

CVCIN

RVCIN

FDMF6840C

VDRV

VCIN

VIN

PWM

V5V

DISB#

PWM

Input

OFF

CVDRV

CVIN

CBOOT

RBOOT

LOUT

COUT

I5V

IIN

VIN

V VSW

IOUT

THWN#

BOOT

VSWH

CGND

PGND

DISB#

FDM

Open-

Drain

Output

PHASE

SMOD#

FDMF6840C

VOUT

FDMF6840C Scheda tecnica(PDF) 15 Page - ON Semiconductor

FDMF6840C Scheda tecnica(HTML) 15 Page - ON Semiconductor

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Scheda tecnica Scarica

Link URL