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LP8860-Q1: EEPROM Configuration Support

Thamizh K
Prodigy 115 points
Part Number: LP8860-Q1

Hi 

VIN = 5V

VDD=5V

VO =21V

Iout =150mA(Ma).. 

I am trying to boost the 5V input for my LCD backlight.

I am using all the four strings. My LCD back-light requirement is 21V and 103mA.

I am using in following mode

- Extrenal PWM duty control

- No custer mode

- Charge pump disabled

- With adaptive brightness My Boost voltage jumping to 48V.

- Without adaptive brightness my Back-light is not working

Could any one help with EEPROM configuration?

Thanks!

Thamizh

  • 0
    TI__Intellectual 2180 points
    Hi Thamizh,

    Please find link below to app note which indicates all EEPROM versions already available for LP8860. From conditions provided, you could start by using D version EEPROM. Current can be scaled current down to 103mA with RISET resistor (by default 150mA). Also note that adaptive boost is enabled by default but can disabled using EN_ADAP register. When adaptive boost is disabled, vboost output voltage will be determined by BOOST_INITIAL_VOLTAGE[5:0] setting. D version has setting at 25V which should work for your application (21 Vf) but can be decreased to optimize efficiency.

    www.ti.com/.../snva757c.pdf


    Hope this helps.
  • 0 in reply to Salome Ramirez Carrion
    Prodigy 115 points
    Hi Salome Ramirez,

    I have configured the similar way which you have described above, But i could not able to make it working.

    Is there any other setting which i need to take care?

    Thanks!
    Thamizh
  • 0 in reply to Thamizh K
    Prodigy 115 points
    Here is my register setting below..
    0x60 0xEA
    0x61 0xFC
    0x62 0xDC
    0x63 0xF0
    0x64 0xDF
    0x65 0xE5
    0x66 0xF8
    0x67 0x77
    0x68 0x77
    0x69 0x71
    0x6A 0x3F
    0x6B 0xB7
    0x6C 0x17
    0x6D 0xEF
    0x6E 0xB0
    0x6F 0x87
    0x70 0xCE
    0x71 0xF3
    0x72 0xC5
    0x73 0x0A
    0x74 0x35
    0x75 0x06
    0x76 0xDC
    0x77 0xFF
    0x78 0x3E..

    I have read back and checked, all the programmed values are correct..

    My output voltage is coming as 21V.. When i connect my LCD back-light; After applying PWM input(Logic High) backlight is not turning on.

    Any suggestion??
  • 0 in reply to Thamizh K
    Prodigy 115 points

    I have Found the Issue.

    Actually my LCD typical voltage is 21V.  I said to Initial Boost of 21V with No adaptive  mode.. There is no headroom voltage, So no current flow.

    When i increase to 22V My LCD started working.

  • 0 in reply to Thamizh K
    TI__Intellectual 2180 points

    Hi Thamizh,

    Good to hear issue was solved! LED drivers do require some headroom voltage to allow proper function and to account for LED variation between the strings.