BD2802 データシートの表示（PDF） - ROHM Semiconductor

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BD2802

System LED Drivers for Mobile phones 6LEDs Illumination

ROHM Semiconductor 

BD2802GU

Technical Note

 RGB LED Driver Operation Description

- Two drivers “RGB1 (R1LED, G1LED, B1LED)” and “RGB2 (R2LED, G2LED, B2LED)” are mounted.

- A slope function is incorporated to control drivers independently.

- Refer to  RGB Waveform Setting for more information about output waveform setting.

- The LED current can be set via a resistance value (RISET) to be connected to the RGBISET terminal. The maximum

current value can be derived from the following expression:

ILEDmax [A] = 3.048 / RISET [kΩ] (Typ)

However, this setting must be made so that the maximum current value can be less than or equal to 30.48mA. In

addition, the RGBISET terminal has an overcurrent protection circuit to prevent the excessive LED current from flowing

for low impedance to the ground.

- Note that the setting voltage shall be higher than or equal to a saturation voltage (0.2V) in the constant current circuit.

When LED Vf is large, the LED destination shall be connected to another step-up circuit.

RGB*EN

または

RGBR*GEBN*OS

or

RFB*OS

Ton

(Max:20ms)

LED 電流

LED current

- The LED destination is fixed before on (RGB*EN=Hi or RGB*OS=Hi).

VLED

VLED

RGB*EN

Or

RGB*OS

RGB*EN

Or

RGB*OS

●The synchronism of RGB1/RGB2

The period of RGB1 and RGB2 and start, stop timing can be set up independently.

When synchronizes RGB1 and RGB2, You must start an internal counter at the same time under the state of resetting.

(Internal Counter are prepared for each of RGB1 and RGB2, so You must reset both.)

<How to reset internal Counter>

Inside Counter can be reset by carrying out one of following actions.

• Reset by hard reset (RSTB_IL). (RGB1, RGB2 is reset together.)

• Reset by soft reset. (RGB1, RGB2 is reset together.)

• It is written register of the current setup (I1・I2), the slope setup, the period setup and the pattern setup.

Internal Counter of RGB1 is reset when it is written between Address=0Bh from 02h.

Internal Counter of RGB2 is reset when it is written between Address=15h from 0Ch.

Counter is reset as to overwriting the same value.

Note)

Internal Counter isn't reset if write RGB1EN =L and RGB2EN =L. (Address=01h).

When it write RGB1EN=L (RGB2EN=L), inside Counter is held, and IC will operate from the held state at next restart.

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© 2011 ROHM Co., Ltd. All rights reserved.

17/27

2011.04 - Rev.A

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