LED drivers for tablet LCD backlighting

Overview | Key Features Key Feature 1 | Key Feature 2 | Key Feature 3 | Key Feature 4 | Key Feature 5 |
Lineup

High efficiency and dimming possible, even at low duty (1%)

Overview

Tablet PCs, which are becoming increasingly mainstream, possess several key requirements, including the need for lighter weight, longer operating time, decreased thickness, and improved viewability. In response, ROHM offers a broad lineup of LED driver ICs that meets the needs of tablet PCs and similar devices.

Key Features

  • White LED drive (72 lamps max.) enabled from 2.7V
  • High efficiency PWM dimming enabled from 1% duty.
  • High efficiency thermal dissipation ensured with low EMI

Key Feature 1 : Operation enabled from a single li-ion battery

Operation is enabled from a supply voltage of 2.7V, enabling driving using a single li-ion battery, contributing to increased set miniaturization. A total of 72 lamps (12 units/line × 6 lines) can be powered, with a maximum current of 25mA per line (set via external resistor). In addition, automatic PWM-based backlight dimming is possible when used with ROHM's BD6092GU controller IC. The result is optimized screen visibility with minimal power consumption, increasing operating time for battery-driven applications.
Application-optimized system

Key Feature 2 : PWM dimming possible from 1% duty

PWM dimming from 1-100% duty is possible, enabling LCD backlight brightness adjustments over a wide range. Conventional DC dimming methods perform dimming by adjusting the current value. However, this results in significant differences in luminous intensity and brightness fluctuations. In contrast, ROHM utilizes PWM dimming that minimizes fluctuations at low brightness. In addition, constant current supply is ensured for each line, eliminating brightness variations between lines due to differences in VF.

PWM dimming minimizes fluctuations at low brightness
Constant current LED driver improves the brightness of each line

Key Feature 3 : Wide duty range provided for high efficiency operation

PWM dimming is utilized featuring a wide duty range, from 1-100%, resulting in high efficiency operation. For example, BD6581GU provides a power efficiency of 90% through 1-100% duty.
This is in contrast with conventional systems where the LED backlight power consumption exceeds LCD power consumption during low duty, making lower power consumption even at low brightness difficult to achieve.
ROHM LED driver ICs are equipped with a precision power supply control system synchronized with the PWM signal, ensuring high efficiency even during low brightness.

High efficiency throughout the entire brightness range

Key Feature 4 : Easy EMI protection

Only one resistor is required for EMI protection even in LED backlight systems with the largest step-up voltage circuits, preventing unwanted interference to the wireless communication systems in tablet applications.

EMI protection possible with just one resistor

Key Feature 5 : No countermeasures against output capacitor noise required

The system automatically reduces LED current ramp-up during PWM control, minimizing voltage changes to the output capacitor. Output Capacitor Noise Mechanism

Lineup

Part No. Power Supply
Voltage
(V)
No. of LEDs Output
Voltage
(V)
Current
(mA)
Switching
Frequency
(MHz)
Primary
Brightness
Control Method
Package
(mm)
RoHS
compliant
BD6586MUV 2.7 to 5.5 24.0
max.
6 units/line
× 4 lines
24.0
max.
25
(Per line)
1.0 Control
analog dimming ISET
terminal resistance
switching via PWM signal
at PWM terminal
VQFN024V4040 Yes
BD6581GU 2.7 to 22 72 max.
12 units/line
× 6 lines
(VFlimits exist)
43.0
max.
25
(Per line)
1.0 Control
analog dimming ISET
terminal resistance
switching via PWM signal
at PWMPOW PWMDRV terminals
VCSP85H2
(2.6×2.6),
H=1.0Max.
Yes
BD6583MUV-A 2.7 to 22 72max.
12 units/line
× 6 lines
(VFlimits exist)
43.0
max.
25
(Per line)
1.0 Control
analog dimming ISET
terminal resistance
switching via PWM signal
at PWMPOW
PWMDRV terminals
VQFN024V4040 Yes
BD6592MUV 2.7 to 22 72max.
12 units/line
× 6 lines
(VFlimits exist)
43.0
max.
40
(Per line)
1.0 Control
analog dimming ISET
terminal resistance
switching via PWM signal
at PWMPOW
PWMDRV terminals
VQFN024V4040 Yes

ROHM utilizes the most advanced technologies to develop cutting-edge solutions for current and next-generation devices. 
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