Technical Note

15/26

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2011.06 - Rev.C

© 2011 ROHM Co., Ltd. All rights reserved.

BD6583MUV-A

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LED current setting range

LED current can set up Normal and Starting setting current.

LED current can set up Normal current by resistance value (RISETH) connecting to ISETH voltage and LED current can set

Starting current by resistance value (RISETL) connecting to ISETL voltage.

Setting of each LED current is given as shown below.

Normal current = 20mA(24kΩ/RISETH)

Starting constant current = 0.6/RISET L

Also, Normal current setting range is 10mA~25mA, Starting current setting range is OFF setting or 1µA~100µA.

LED current can set OFF setting by open setting ISETL pin.

LED current becomes a leak current MAX 1µA at OFF setting.

ISETH Normal current setting example

ISETL Starting current setting example

RISETH

LED current

RISETL

LED current

24kΩ (E24)

20mA

6.2kΩ (E24)

97µA

25.5 kΩ (E96)

18.8mA

10kΩ (E6)

60µA

27 kΩ (E12)

17.8mA

47kΩ (E6)

13µA

28kΩ (E96)

17.1mA

100 kΩ (E6)

6µA

30kΩ (E24)

16.0mA

560 kΩ (E12)

1.1µA

33kΩ (E6)

14.5mA

Connect to VREG pin

0mA

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The separations of the IC Power supply and coil Power supply

This IC can work in separating the power source in both IC power supply and coil power supply. With this application, it can

obtain that decrease of IC power consumption, and the applied voltage exceeds IC rating 22V.

That application is shown in below Fig 42. The higher voltage source is applied to the power source of coil that is connected

from an adapter etc. Next, the IC power supply is connected with a different coil power supply. Under the conditions for

inputting from 2.7V to 5.5V into IC VBAT, please follow the recommend design in Fig 38. It connects VBAT terminal and

VREG terminal together at IC outside.

When the coil power supply is applied, it is no any problem even though IC power supply is the state of 0V. Although IC

power supply is set to 0V, pull-down resistance is arranged for the power off which cuts off the leak route from coil power

supply in IC inside, the leak route is cut off. And, there is no power on-off sequence of coil power supply and IC power supply.

Fig.42 Application at the time of power supply isolation

10μF

Battery

VDET

SW

LED1

LED2

LED3

4.7μH

10LED x 6

SENSP

SENSN

LED4

20mA each

100mΩ

RTR020N05

2.2μF

RSTB

PWMDRV

PWMPOW

Power

ON/OFF

200Hz

PWM

VBAT

LED5

LED6

FAILSEL

VREG

1μF

2.7V to 5.5V

GND

24kΩ

TEST

GND

ISETH ISETL

GND

GND

IC Power supply

Coil Power supply

7V to 28V