BL0200C datasheet(13/26 Pages) SANKEN

13 / 26 page

BL0200 Series

BL0200-DS Rev.2.1

SANKEN ELECTRIC CO.,LTD.

Feb. 25, 2014

8.4 PWM Dimming Function

Figure 8-9 shows the peripheral circuit of PWM pin

and SW pin.

The PWM pin is used for the PWM dimming signal

input. The SW pin drives the gate of external dimming

MOSFET (Q2, Q4). The SW pin voltage is turned on /

off by PWM signal and thus the dimming of LED is

controlled by PWM signal input.

As shown in Figure 8-10, when the PWM pin voltage

becomes

the

PWM

Threshold

Voltage,

VPWM(ON) = 1.5 V or more, the SW pin voltage becomes

VCC. When the PWM pin voltage becomes the PWM Pin

OFF Threshold Voltage, VPWM(OFF) = 1.0 V or less, the

SW pin voltage becomes 0.1 V or less. The PWM pin has

the absolute maximum voltage of −0.3 V to 5 V, and the

input impedance, RPWM, of 200 kΩ.

The

PWM

dimming

signal

should

meet

these

specifications and threshold voltages of VPWM(ON) and

VPWM(OFF).

SW1

R15

Drive

PWM OSC

Main Logic

PWM1

PWM_IN

PWM Pulse

Detector

VCC

LED

LED_OUT1(+)

LED_OUT1(

−)

Figure 8-9 The peripheral circuit of PWM pin

and SW pin.

PWM pin voltage

SW pin voltaege

VPWM(ON)

VPWM(OFF)

VCC

Time

０

≤ 0.1V

Figure 8-10 The waveform of PWM pin and SW pin

8.5 Gate Drive

Figure 8-11 shows the peripheral circuit of DRV pin

and SW pin and FSET pin. The DRV pin is for boost

MOSFET, Q1 and Q3. The SW pin is for dimming

MOSFET, Q2 and Q4.

Table 8-1 shows drive voltages

and currents of DRV pin and SW pin.

● Power MOSFET should be selected so that these

VGS(th) threshold voltages are less than VDRV enough

over entire operating temperature range.

● Peripheral components of Power MOSFET, gate

resistors and diode, affect losses of power MOSFET,

gate waveform (ringing caused by the printed circuit

board trace layout), EMI noise, and so forth, these

values should be adjusted based on actual operation in

the application.

● The resistors between gate and source (R19, R24, R47

and R63) are used to prevent malfunctions due to steep

dv/dt at turn-off of the power MOSFET, and these

resistors are connected near each the gate of the power

MOSFETs and the ground line side of the current

detection resistance. The reference value of them is

from 10 kΩ to 100 kΩ.

Table 8-1 Drive voltage and current

Pins

Drive voltage, VDRV

Drive current, IDRV

High

Low

Source

Sink

DRV

VCC

≤ 0.1 V

−0.36 A

0.85 A

VCC

≤ 0.1 V

−85 mA

220 mA

R15

LED_OUT1(+)

R16

R17

R19

R20

R21

R22

R24

DRV1

SW1

PWM OSC

Main Logoc

Drive

VCC

GND 9

Figure 8-11 The peripheral circuit of DRV pin,

SW pin and FSET pin

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