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LP5009: LP50xx Driving external mosfets in 12bit PWM resolution

Dainius Mazuika
Prodigy 30 points
Part Number: LP5009
Other Parts Discussed in Thread: LP5036

I am willing to use LP5009 as I2C programmable PWM controller with these key parameters:

1) Open drain 2Amp outputs, is the proposed schematic valid?

2) 3-phase channels to reduce current spikes. Does LP5009 outputs "OUT0/1/2" are working in 3-phase mode? Asking this because chapter 8.3.1.4 of "SLVSEH2A rev 2019 July" mentions "LED 0 .. 11", not OUT 0..11 (1 RGB LED occupies 3 output channels OUT0..2, could be a typo mistake if copied from LP5036 part's datasheet..);

2) 12 bit resolution. How to operate with LED0_BRIGHTNESS and OUT0_COLOR registers to get 12 bit resolution accuracy for single output? For example, I would like to get 12bit value 0xBCD (0b101111001101) in the output. Should I write 0xBC to LED0_BRIGHTNESS register and 0xD0 to OUT0_COLOR register? 4 LSB's (0xD0 .. 0xDF) in OUT0_COLOR is automatically discarded?

 

  • 0
    TI__Genius 11836 points

    Hi,

    1) Open drain 2Amp outputs, is the proposed schematic valid?

        How to get 2A according to your circuit?

    2) 3-phase channels to reduce current spikes. Does LP5009 outputs "OUT0/1/2" are working in 3-phase mode? Asking this because chapter 8.3.1.4 of "SLVSEH2A rev 2019 July" mentions "LED 0 .. 11", not OUT 0..11 (1 RGB LED occupies 3 output channels OUT0..2, could be a typo mistake if copied from LP5036 part's datasheet..);

      Working in 3-phase mode.

    2) 12 bit resolution. How to operate with LED0_BRIGHTNESS and OUT0_COLOR registers to get 12 bit resolution accuracy for single output? For example, I would like to get 12bit value 0xBCD (0b101111001101) in the output. Should I write 0xBC to LED0_BRIGHTNESS register and 0xD0 to OUT0_COLOR register? 4 LSB's (0xD0 .. 0xDF) in OUT0_COLOR is automatically discarded?

      Write A(8bit) to LED0_BRIGHTNESS register and B(8bit) to OUT0_COLOR register, where A*B=0XBCD. The remaining process is done automatically.

  • 0 in reply to Charles-Chen
    Prodigy 30 points

    Charles-Chen said:
        How to get 2A according to your circuit?

    LP5009 open drain outputs with help of R1 .. R3 pullups drive 3.3V CMOS inputs of mosfet gate drivers U2 .. U4. U2 .. U4 are driving power mosfets Q1 .. Q3, which can handle 2A of current. Is this a valid way to use LP5009 "current sink" outputs to drive CMOS inputs of an external IC?

  • 0 in reply to Dainius Mazuika
    TI__Genius 11836 points

    Hi,

      It's OK.

      Besides, I have updated my answer in previous posts.

      Please note that "Write A(8bit) to LED0_BRIGHTNESS register and B(8bit) to OUT0_COLOR register, where A*B=0XBCD. The remaining process is done automatically".

  • 0 in reply to Charles-Chen
    Prodigy 30 points

    Thank you for quick support. I cannot get 0xA0 * 0xB0 (or some combinations of this) equal to 0xBCD with my calculator, but lets leave it to the programmer. Case closed.