bd9202efs ROHM Co. Ltd., bd9202efs Datasheet - Page 6

• Manufacturer Part Number: bd9202efs
• Description: White Backlight Led Drivers For Medium To Large Lcd Panels Swreg Type
• Manufacturer: ROHM Co. Ltd.

●Functional explanation
© 2009 ROHM Co., Ltd. All rights reserved.
BD9202EFS
www.rohm.com
○ VREG
○ UVLO (Under Voltage Lock Out)
○ Fixed electric current driver
The fixed voltage of 5V is generated from VCC. It starts when it becomes EN=H.
UVLO (Under Voltage LOCK Out) is built in by VREG, When it is below 2.9V (typ)，the internal circuit stops.
When it is above 3.0V (typ), the internal circuit operation starts.
Please connect Creg=2.2 μ F to the VREG terminal, as a capacity for phase compensation.
In order to make IC heat generation decrease, impressing voltage into the VREG terminal from outside, it is possible
to decrease the loss with the regulator inside IC.
In this case, as for the impressing voltage, please impress that of above output voltage (5.25V5.5V) of the internal
regulator.
There are UVLO (REG) which detects VREG voltage① and UVLO (VCC) ② which detects VCC voltage in UVLO.
When each UVLO is below specified value, the internal circuit is made to stop. (The logic section is reset.)
Please do not connect VCC terminal (> 5.25V) to the UVLO terminal (for VCC detection) directly. Because there is a
possibility of destruction, please be sure to input with partial pressure.
Fixed current value of the fixed electric current driver can be got by constant doubling the standard electric current
which is decided by the resistance (RSET) of being connected to ISET and the voltage which are input into the VSET
terminal. In addition continual electric current variable (analog modulated light) is possible by changing VSET voltage
from outside.
In addition, it is possible to do PWM modulated light by the fact that the data is input to the internal register from the
serial interface section. It is possible to set the Duty value of PWM for each channel.
・ VREF normal output
・Setting of fixed current value
In VREG block, VREF (1.6V (typ.)of reference voltage output is provided.
The necessity of doing the voltage impression from outside by the fact that this terminal is connected to the VSET terminal is gone.
However, because the voltage variation of VREF is to be reflected on the variation of LED fixed electric current directly, so that
please pay attention to it.
However, when VSET voltage is above 2V, it reaches the point where it is clamped with 2V inside IC, fixed
current value above that does not increase.
In addition, please input VSET in the range of 0.6V-2.4V.
Fixed current value (DC value) of the LED driver is a relational expression below.
160
140
120
100
80
60
40
20
0
Detecting circuit
0
UVLO (VREG)
UVLO (VCC)
Survey value
(
Marker)
( マ ーカー）
I
LED
実 測 値
=｛VSET/(RSET[kΩ]+20[kΩ]) ｝×7980－8 [mA]
100
VCC partial pressure input Below1.9V(typ)
200
Detection object
Calculated value
Solid line
VREG
計 算 値
( 実 線 ）
RSET- ILE D特 性
300
6/19
R S E T[kΩ ]
400
Characteristic
Below2.9V(typ)
Detection
500
600
Above 3.0V(typ)
Above 2.0V(typ)
Cancellation
700
Technical Note
2009.04 - Rev.A
800