BD6581GU-E2 Rohm Semiconductor, BD6581GU-E2 Datasheet - Page 14

• Manufacturer Part Number: BD6581GU-E2
• Description: IC LED DVR WHT BCKLGHT VCSP85H2
• Manufacturer: Rohm Semiconductor
• Series: -r

Specifications of BD6581GU-E2

• Constant Current: -
• Constant Voltage: -
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 800kHz ~ 1.2MHz
• Voltage - Supply: 2.7 V ~ 22 V
• Voltage - Output: 44.7 V
• Mounting Type: *
• Package / Case: *
• Operating Temperature: -30°C ~ 85°C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

●Brightness Control
BD6581GU
© 2010 ROHM Co., Ltd. All rights reserved.
www.rohm.com
There are two dimming method is available, first method is analog dimming that apply analog voltage to ISET terminal, and
second method is PWM control via digital dimming of PWMPOW or PWMDRV. Because each method has the different merit,
please choose a suitable method for the application of use.
Two techniques can be used as digital dimming by the PWM control One is PWM control of current driver, the other is PWM
control of power control.
As these two characteristics are shown in the below, selects to PWM control process comply with application.
・Efficiency emphasis in the low brightness which has an influence with the battery life
・LED current dispersion emphasis in the PWM brightness control
(Reference)
1) Current driver PWM control is controlled by providing PWM signal to PWMDRV, as it is shown Fig.25.
2) Power control PWM control is controlled by providing PWM signal to PWMPOW, as it is shown Fig.27. The current setting
The current set up with ISETH is chosen as the Hi section of PWMDRV and the current is off as the Lo section. Therefore,
the average LED current is increasing in proportion to duty cycle of PWMDRV signal. This method that it lets internal
circuit and DC/DC to work, because it becomes to switch the driver, the current tolerance is a few when the PWM
brightness is adjusted, it makes it possible to brightness control until 50µs (MIN1% at 200Hz). And, don't use for the
brightness control, because effect of ISETH, ISETL changeover is big under 50µs ON time and under 50µs OFF time.
Typical PWM frequency is 100Hz~10kHz. When RSTB sets H → L, so the starting current may be effective, after RSTB
sets L→ H, it becomes PWM of the starting current and PWM of ISETH setting current to PWM two times.
set up with PWMDRV logic is chosen as the Hi section and the current is off as the Lo section. Therefore, the average LED
current is increasing in proportion to duty cycle of PWMPOW signal. This method is, because IC can be power-off at
off-time, the consumption current can be suppress, and the high efficiency can be available, so it makes it possible to
brightness control until 50µs (MIN1% at 200Hz). And, don't use for the brightness control, because effect of power
ON/OFF time changeover is big under 50µs ON time and under 50µs OFF time.
Typical PWM frequency is 100Hz~1kHz. Also, PWM can't control RSTB and PWMPOW at the same time.
After RSTB sets H, control PWM only PWMPOW.
PWM regulation process
Current driver
Power control
PWMPOW
LED current
Coil current
IC’s active current
PWMDRV
LED current
Coil current
IC’s active current
Efficiency of LED current 0.5mA
(PWM Duty=2.5%)
70%
93%
ON
ON
ON
ON
ON
ON
ON
Fig.40
Fig.41
14/26
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
Limit dispersion capability of low duty
PWM frequency 200Hz
0.2%
0.5%
→ 2) Power control PWM control
→ 1) Current driver PWM control
2010.03 - Rev.A
Technical Note