GX500 Operational Description Revision A
LG Electronics 55/143 LGE Property
3.9 LCD back-light illumination
The SC654 is a high efficiency charge pump LED driver using Analogic-tech’s proprietary charge pump
technology. Performance is optimized for use in single-cell Li-ion battery applications.
Figure 3-17 LCD Back light unit and Flash LED charge pump IC
The LED current magnitude is controlled by the EN/SET pin using the S2Cwire interface. The interface records
rising edges of the EN/SET pin and decodes them into 32 individual current level settings. Code 1 is full scale
(31mA), and Code 32 is 0.5mA. The modulo 32 interface wraps states back to state 1 after the 32nd clock. The
counter can be clocked at speeds up to 1MHz, so intermediate states are not visible. The first rising edge of
EN/SET enables the IC and initially sets the output LED current to full scale, the lowest setting equal to 0.5mA.
Once the final clock cycle is input for the desired brightness level, the EN/SET pin should be held high to
maintain the device output current at the programmed level.
Figure 3-18 control method
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