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Replace LCD display on EVM AM3358

GeoD
Intellectual 325 points
Other Parts Discussed in Thread: AM3358, TPS61081

Hi,

I have an EVM with the AM3358 and want to disconnect the EVM LCD board and make my own pcb for connection to a new display and touchscreen (24-bit paraller RGB, white LED for backlight, interface mode for touchscreen: I2C, I do not have the touch-controller on my pcb, it is part of the display/touchscreen solution).

I am trying to establish what connections of the current EVM LCD board I should keep and what are not needed.

Can you answer the questions below please (my reference is the LCD board schematic) ?

1) Sheet 2 - VEXPD - Is this a 5V supply? I am going to generate this from a bench power supply. V5_0D will still come from the daughetrboard.

2) Sheet 2 - 'LCD_ENBKL' can you tell me the purpose of this pin and how it is used?can I use a GPIO of the AM3358 if needed?

3) Sheet 5 - Does this power control (U8) is needed? If I don't use it what are the implications?

Thanks,

Yu-Li

  • 0
    TI__Intellectual 2150 points

    Yes, VEXPD is a +5VDC power supply on the GP EVM.

    Yes, LCD_ENBKL is an enable signal for the white LED backlight.  You can use a GPIO for simple on/off function or a PWM for dimming capability.

    U8 is for expanding I2C to control some GPIO signals for the LCD.  You can replace as needed for your LCD.

  • 0 in reply to ddomke
    Intellectual 325 points

    Just to ensure I understand this correctly, if I connect the LCD_ENBKL signal to the EN pin of the TPS61081 it can be used as an on/off function.

    For using a PWM for dimming capability can I still connect my PWM signal to the EN pin or to the SS and FB pins as per figure 24 of datasheet?

    Thanks.

  • 0 in reply to GeoD
    TI__Intellectual 2150 points

    When using the TPS61081, you can use the EN pin or the SS pin for an enable signal when using the TPS61081 in constant current mode for white LED backlights.  The circuit schematic for the AM335x GP EVM LCD board is the preferred way to control the TPS61081 based on that operating mode.  In this connection, the same signal acts as the enable and PWM for dimming capability.

    -Please contact the power team for additional details on the TPS61081.