LV5768M Просмотр технического описания (PDF) - ON Semiconductor

Номер в каталоге

Компоненты Описание

производитель

LV5768M

1-channel Step-down Switching Regulator

ON Semiconductor 

LV5768M

• Part selection and set

1) Output voltage set

Output voltage (VOUT) is shown the equation (1).

VOUT

=

(1

+

R4

R3

)×VREF

=

(1

+

22kΩ

1.3kΩ

)×0.67

(typ)

[V]

(1)

Ex) To set output voltage of 12V, set resistors as follows: R3=1.3kΩ and R4=22kΩ.

2) Soft start set

Soft start capacitor (C5) is obtained by the equation (2).

ISS×TSS 5µ×TSS

C5 = VREF = 0.67V [µF]

(2)

ISS: Charge current value, TSS: soft start time

Ex) To set soft start time of 15ms (approx.), set C5=0.1µF.

3) Overcurrent protector set

Overcurrent limit setting resistor (R5) is obtained by the equation (3).

R5

=

Rdson×IL

IIlim

max

=

Rdson×IL

18.5µ

max

[Ω]

(3)

IIlim: ILIM current value,

ILmax: the maximum value of coil current,

Rdson: Ron between drain and source of Q1 (upper Nch MOS FET).

Ron of ATP201 ≈ 23mΩ (when VGS=4.5V at 25°C)

Ex) To set current limit operation point to 11.3A (load current) where coil peak current value is 12A

(approx.), set R5 = 15kΩ. Set an optimum resistor taking variation of ON resistor into consideration due

to temperature change and make sure to confirm it with the user's specific board. For C6, connect a

capacitor of 1000pF to filter unwanted noise for the proper operation of current limiting.

ON resistor of FET

* Rdson of FET has its own temperature coefficient and the resistor becomes higher in proportion to the

temperature.

* To set Rdson value within the range of operating temperature, it is advisable that the user confirm the data sheet

by the FET supplier.

4) How to set oscillation frequency

Oscillation frequency Fosc is adjustable by RT resistor as

shown in the correlation chart as follows:

SW frequency setting range: 80kHz to 500kHz

500

450

400

350

300

250

200

150

100

50

0

0

FOSC -- RT

50 100 150 200 250 300 350 400 450 500

Resistance, RT - kΩ

5) Boot strap capacitor set

For boot strap capacitor C2, use capacitor 100 times larger than Ciss of power MOSFET.

PS No.A1988-9/15

Share Link: