BD9206EFV Ver la hoja de datos (PDF) - ROHM Semiconductor

Número de pieza

componentes Descripción

Fabricante

BD9206EFV

LED Driver Series for LCD Backlight Simple Structure Constant Current Backlight Driver for LCD panels (Non-step type)

ROHM Semiconductor 

BD9206EFV

Technical Note

● Block functional descriptions

■PREREG, REF, 5VREG

PREREG is an circuit of constant voltage supplied to REF and 5VREG in which the voltage applied to VCC terminal is made

to be constant.

REF is a temperature-compensated reference voltage resource and used as reference voltage of TSD (Thermal Shutdown

Circuit).

5VREG is a 5V constant-voltage source and used as a power supply of constant-current driver.

The 5V constant voltage is output to VREG terminal. Moreover, it is recommended to attach a 1μF ceramic capacitor using

for phase correction, to VREG terminal.

■UVLO（Under Voltage Lock Out）

The LED driver is turned OFF when the VREG voltage is less than 2.9V(typ). The operation of lighting up is reset when

VREG becomes more than 3.0V(typ).

■ TSD（Thermal Shutdown Circuit）

TSD circuit protects the IC from thermo runaway or thermal damage.

TSD circuit detects the chip temperature and turns the circuit off if the chip temperature reaches 175℃. The hysteresis of

20℃ is set for TSD detection and release so as to prevent malfunction caused by temperature fluctuations.

■Current Driver（Constant-current driver）, Driver Current Setting

Current Driver(Constant-current driver) is an circuit that generates a constant current for lighting of LED.

Constant-current circuit of BD9206EFV consists of the constant current setting part and the constant current driver part.

The constant-current driver part operates in such a manner that the voltage of Point a is equal to the voltage of point b

because the part serves as a buffer, the input of which is the voltage VX that is set by the constant current setting part.

Therefore, the current ILED that flows into the VLED terminal is as follows:

ILED = Vb/RSET = Va/RSET = VX/RSET = VSET*A/RSET = VSET*B

（A and B are numerical constants）

For BD9206EFV, the numerical constants inside the IC are set in such a way that the following formula is brought into

existence:

ILED(mA) = VSET ＊10 (VSET=0.6～3.0V)

If VSET is fixed, then the Vb is fixed, therefore the current ILED always flows independent of the fixed voltage of VLED.

However, the constant current operation is stopped if the voltage of VLED terminal is less than 0.6V, so please ensure

VLED>0.6V.

Vo

VSET

[Constant【c定urre電nt s流etti設ng 定part部] 】

VX=VSET*A

Vo電ltag圧e

sh変ift c換ircuit

VX

回路

[Cons【ta定nt c電urre流nt dドrivラerイpaバrt] 部 】

Condenser for phase

compe位ns相atio補n 償 用 コ ン デ ン サ

a

+

IL E D

VLED

-

b

RSET

EN

Fig..5

www.rohm.com

© 2009 ROHM Co., Ltd. All rights reserved.

5/12

2009.07 - Rev.A

Share Link: