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TLC59116F PWM

Giorgio Bonesu
Prodigy 70 points
Other Parts Discussed in Thread: TLC59116F, TLC59116

Hi I have a problem with an your product TLC59116F

 I would like to use mosfet to drive high currents with this IC but if I use pwm output (value between 1 and 254)

 leds connected on mosfet are only turn on or turn off but not dimmered.

 I have seen with oscilloscope the output of TLC but I do not see pwm signal.

If I use leds directly connected to the TLC they are dimmered.

TLC drive a pnp transistor that drive a N-ch mosfet.

I attach schematics.

  • 0
    TI__Genius 14890 points

    Girogio,

    Attached is an example of the GRPPWM (set to 0000 1000) for OUT0.

    Can you let me know the values in these registers:  0x00, 0x01, 0x12, 0x13, 0x14, 0x15, 0x16 and 0x17?

    The TLC59116 PWM signals are based on an internal 97kHz signal.  Is your external circuit quick enough to respond?

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 70 points

    Dear Dick,

    I don't see the attachment.

    I'm using TLC59116F (open collector not constant current).

    I have attached the schematics of my circuit in previous form. (I think that transistor e mosfet are enough fast)

    Registers have correct value infact (I have written in previous form) if I connect directly to TLC59116F outputs leds they dimming (so is enabled individual brightness and can be controlled through its PWMx register).

    registers 0x00=0x80  0x01=0   0x12=0xFF   0x13=0  0x14= 0xAA  0x15= 0xAA  0x16= 0xAA  0x17= 0xAA

    I have checked with oscilloscope (350MHz I think is enough fast to view 97KHz PWM signal) but I see constant voltage.

    I think that TLC59116F works with constant voltage and variable current.

    Regards,

    Giorgio

  • 0 in reply to Giorgio Bonesu
    TI__Genius 14890 points

    Giorgio,

    I missed the "F" part.  The attached plot shows the TLC59116F

    For the GRPPWM to have an impact, you need to set resisters 0x14-0x17 to 0xFF.  0xAA would use the individual PWM channels (registers 0x02-0x11) for dimming. 

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 70 points

    Hi Dick,

    I have set registers 0x14-0x17 to 0xAA because I' working on individual brightness using registers 0x02-0x011 I don't use group dimming/blinking so I think is correct 0xAA value.

    Each output have a different brightness, is more correct value 0xFF or the 0xAA value?

    Regards,

    Giorgio 

  • 0 in reply to Giorgio Bonesu
    TI__Genius 14890 points

    Giorgio,

    You are correct if you are using individual brightness per output (0xAA).  The 0xFF would only be for Group Dimming.

    The EVM I am using for verification does not have the ability to change the individual registers so I will have to change setups to investigate more.

    To answer a question from an earlier post, the TLC59116F is an open-drain output device while the TLC59116 is a constant current device.  

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 70 points

    Dick,

    I know the differences between tlc59116i and tlc59116f indeed I have tested first TLC59116 and this IC goes  in overheating with 20ma on 8 channel instead TLC59116F hasn't the problem of overheating so I have decided to use the second.

    Now there is this problem that I cant drive an external mosfet with a PWM signal so I think that I shall have to choose another driver of competitior that meets my requirements (for example PCA9635... have you a xref of this IC?).

    I think that the functional description of TLC59116I/F isn't too much accurate.

    So I look forward a good news or a solution to my problem (if exists).

    Regards,

    Giorgio