BD6581GU-E2 Rohm Semiconductor, BD6581GU-E2 Datasheet - Page 11

• 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

●How to Select the Number of LED Lines of the Current Driver
●Start Control and Select LED Current Driver
●Attendance Point of the Restriction Resistance Input to RSTB
BD6581GU
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www.rohm.com
When the number of LED lines of the current driver is reduced, the un-select can be set the matter that the unnecessary
LED1 ~ 6 terminal is connected to GND. When it uses with 4 lines and so on, it can correspond to it by connecting 2
unnecessary lines to GND.
RSTB is used as a power supply of this decision circuit. The select of the terminal is judged, It has no relation to the logic of
PWMPOW and PWMDRV and it isn't judged an unnecessary LED line even if it is connected to GND when it is judged a
necessary terminal once. This information can be reset by setting RSTB at 0V.
BD6581GU can control the IC system by RSTB, and IC can power off compulsory by setting 0.2V or below. Also, It powers
on PWMPOW is at more than 1.4V and RSTB is at more than 2.25V.
When RSTB=PWMPOW=H, ISETH current is selected at PWMDRV=H and ISETL current is selected at PWMDRV=L.
The starting current in PWMDRV=L sets OFF second time rise of PWMDRV and it becomes 0mA setting after that.
After RSTB sets L once, the starting current can be flowed again by changing it to H.
When the restriction resistance is input to RSTB, it is necessary to consider the input current of RSTB.
The input current of RSTB changes that depending on the power-supply voltage and the temperature reference to fig.33.
Because the temperature characteristic of the input current is shown in fig.33, please choose resistance for which the
voltage of the terminal can be guaranteed to 2.1V or more.
And, it has the margin in the decision of resistance, and please confirm and make sure it is no problem in a real application.
The decision example of restriction resistance
1. When use the current driver of 6 parallel
2. When use the current driver of 3 parallel
In addition, the selection number of parallel number of the current driver is changed, the power-supply current of RSTB will
be increased.Because the maximum value of the consumption current at the RSTB=2.1V is indicated in the following Table 1,
be careful enough when you calculate the restriction resistance.
Table. the use parallel number of current driver at RSTB=2.1V , 100℃ vs. RSTB input current
2.9V(to RSTB power-supply) - restriction resistance value×124µA(100℃ input current) ＞ 2.1V
restriction resistance value＜(2.9-2.1)/124μA=6.45kΩ
2.9V(to RSTB power-supply) - restriction resistance value×430μA(100℃ input current) ＞ 2.1V
restriction resistance value＜(2.9-2.1)/430μA=1.86kΩ
RSTB
Power supply
Parallel numbers used for current driver
1
1
1
1
0
for RSTB
RSTB inflow current
PWMPOW
0, 1
0
1
0
1
Limit resistor
Fig .33
6
5
4
3
2
1
0
PWMDRV
0, 1
0
0
1
1
RSTB
terminal
BD6581GU
Off
On
Off
On
Off
IC
OFF
Starting current decided with ISETL
OFF
Current decided with ISETH
OFF
RSTB input current
11/26
0.12mA
0.23mA
0.33mA
0.43mA
0.53mA
0.63mA
0.74mA
LED current
250
200
150
100
50
2.1
Fig .34 RSTB terminal voltage-RSTB inflow current
2.4
(At the time of the current driver six lines use)
2.7
RSTB[V]
3
3.3
2010.03 - Rev.A
Technical Note
3.6
+100℃
+80℃
+25℃
-30℃