bd6581gu ROHM Co. Ltd., bd6581gu Datasheet - Page 15

• Manufacturer Part Number: bd6581gu
• Description: White Backlight Led Driver
• Manufacturer: ROHM Co. Ltd.

●LED Current Setting Range
●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 figure 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 figure 38. It connects VBAT terminal and VREG terminal
together at IC outside.
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.
BD6581GU
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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
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.
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
25.5 kΩ (E96)
27 kΩ (E12)
24kΩ (E24)
28kΩ (E96)
30kΩ (E24)
33kΩ (E6)
Normal current = 20mA(24kΩ/RISETH)
RISETH
IC Power supply
LED current
2.7V to 5.5V
RTR020N05
18.8mA
17.8mA
17.1mA
16.0mA
14.5mA
100mΩ
20mA
Coil Power supply
7V to 28V
10μF
200Hz
PWM
ON/OFF
Power
Fig.42 Application at the time of power supply isolation
Battery
1μF
4.7μH
2.2μF
GND
SENSP
SENSN
PWMPOW
SW
RSTB
PWMDRV
VREG
VBAT
GND
GND
GND
ISETL Starting current setting example
TEST
Connect to VREG pin
FAILSEL
ISETH ISETL
15/26
560 kΩ (E12)
24kΩ
6.2kΩ (E24)
100 kΩ (E6)
Starting constant current = 0.6/RISET L
10kΩ (E6)
47kΩ (E6)
RISETL
LED5
LED6
VDET
LED1
LED2
LED3
LED4
20mA each
10LED x 6
LED current
1.1µA
97µA
60µA
13µA
0mA
6µA
2010.03 - Rev.A
Technical Note