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LP8860-Q1: LP8860 application questions.

Chen Bogey8
Mastermind 9990 points
Part Number: LP8860-Q1

Hi Sir 

1.May we know how to set up Iset? is Iset = (Vbg/(50 * Riset))*1000 ? 

2.For Figure 61, may we konw what is Protection FETs function? May LP8860 can use in 63.9V application?

                                                          Bogey

  • 0
    TI__Intellectual 2180 points

    Hi Bogey,

    1. If RISET resistor is enabled (DRV_EN_EXT_LED_CUR_CTRL=1), then current is set by the below equation. LP8860 has the option of scaling current with both external resistor and also registers. Resistor can be enabled or disabled but register settings will always affect LED current.

    If only RSET resistor is needed for scaling then DISP_CL1_CURRENT[11: 0] could be set to  xFFF (4095) and DRV_LED_CURRENT_SCALE[2:0] = 150mA, therefore current could be calculated just by:

    2. Protection FETs for high voltage application are used to protect OUT pins in case of short/open condition. OUT pins absolute max rating is 52V, so if short condition happens where output voltage is greater than 52V, these pins would be damaged. By adding these protection FETs, the voltage at OUT pins will be limited to ~10V. If higher, the PFETs will turn off, protecting the device.

    Although there is nothing preventing 63.9V application from working, we only validate device up to 60V, so we don't recommend using LP8860 above above this level. Also note that components would have to be rated accordingly.