BD6067GU_11 ROHM [Rohm], BD6067GU_11 Datasheet - Page 15

• Manufacturer Part Number: BD6067GU_11
• Description: White Backlight LED Drivers for Small to Medium LCD Panels (Switching Regulator Type)
• Manufacturer: ROHM [Rohm]

© 2011 ROHM Co., Ltd. All rights reserved.
BD6067GU, BD6069GUT, BD6071HFN, BD6072HFN
►BD6071HFN
●Setting range of LED current
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2-2) The brightness adjustment of below is done in adjusting of R2 ON time by R1 and Duty cycle of PWM.
Fig.43 The brightness adjustment example of VFB terminal by PWM
LED current is determined by the voltage of VFB
and the resistor connected to VFB terminal.
I
The current in the standard application is as shown below.
The shaded portion in the figure below is the setting range of LED current to become the standard. In case of using 2LED,
LED current might increase due to over boosting when VOUT is less than 5.5V. Therefore some ICs may not be used at
desired currents. Consequently, for the proper setting of LED current, thoroughly check it for the suitability under use
conditions including applicable power supply voltage and temperature.
LED
The minimum value of the LED current is decided by VFB / R1 at the PWM 0%, the maximum value of the LED current is
decided by VFB / R2 at the PWM 100%.
I
Standard PWM frequency is 100Hz~1kHz. And please don’t use duty less than 5% or more than 95% of current setting for
the brightness adjustment.
LED
VIN
is given as shown below.
I
V
I
is given as shown below.
LED
LED
FB
ILED=VFB / R1 + VFB / R2 × HI Duty
=0.5V, R
=V
=20.8mA
(f
FB
PWM
/R
=100Hz ~ 1kHz)
FB
FB
80
70
60
50
40
30
20
10
0
=24Ω
VIN
TEST
7
EN
GNDA
2LED
8
9
GND
VIN=5.5V
22μH
3LED
VOUT [V]
10
VOUT
PWM
1kHz
VFB
11
SW
12
Fig.46 LED Setting range of LED current
13
47Ω
R2
1μF
14
47Ω
R1
15/29
VIN
80
70
60
50
40
30
20
10
0
PWM
5.5
1μF
Fig.45 Recommended circuit diagram
2LED
7
VIN=3.1V ~ 4.2V
8.5
25
20
15
10
5
0
VIN
TEST
EN
0
VOUT [V]
Fig.44 VFB PWM Control
GNDA
3LED
10 20 30 40 50 60 70 80 90 100
10
11.5
GND
22μH
HI Duty [%]
13
VOUT
VFB
SW
14
2011.01 - Rev.C
Technical Note
1μF
RFB
24Ω
ILED