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TPS61196-Q1: TPS61196 design inquiry

Chun Youngsu
Expert 2485 points
Part Number: TPS61196-Q1
Other Parts Discussed in Thread: TPS61196, TPS61199

Hi.

Configure the circuit using TPS61196-Q1 and inquire for problems during TEST.

Design

1. We connected the TPS61196 in series with 23 LEDs per Ch.

2. The Ilim setting is set to 50mA and the PWM duty is set to 20mA output.

3. Vh is 90V.

Issue

1. I made 20 sets and I lost 3 ICs of TEST.

2. Even when the PWM is in the 0 state, the LED light is intermittent.

Question

1. I wonder if the above symptoms are caused by high voltage of VFB.

2. Can you check if there is a solution that can drive 23pcs RGB LEDs per Ch with 20mA using the TPS61196?


I will wait for your reply.

Thanks,

Regards,

Tyler

  • 0
    TI__Expert 4550 points
    Hi Tyler,
    What do you mean by "Vh=90V"? Is it the max output voltage?
    TPS61196 should support your application, please check the minimum input voltage, the maximun duty cycle is a limit.
    Could you please check the IFBx pin voltage when PWM is zero? We could calculate the leakage current then by VIFBx/R1( or R2 to R6), and we could see if the leakage current is higher enough and the LEDs are sensitive to that current.
  • 0 in reply to Caryss Li
    Expert 2485 points
    Hi. Caryss

    Yes. Vh is the max output voltage.

    IFB voltage is indicated on the data sheet up to 38V. However, we calculated it to use 20mA and it is about 40V.

    Does this result in the IC being dead?

    We should use 20mA per Ch with TPS61199. The LEDs are 23 serial connections.

    20mA should be adjusted 20mA by PWM duty adjustment after H / W phase 50mA setting.

    What we want to know is whether the TPS61199 IC can be implemented.

    The result of our testing is that the IC is dead and the LED does not turn off after PWM control.

    Is it possible to check if there is any problem in the attached circuit?

    Thanks,

    Best Regards
    Tyler
  • 0 in reply to Chun Youngsu
    TI__Expert 4550 points
    Hi Tyler,
    TPS61199 has only one PWM dimming signal input, but TPS61196 has 6, depending on your application, you can choose which one is suitable.
    And you said the max output voltage is 90V, but according to the resistor value, OVP voltage is set around 55V, that's lower than max output voltage.
    What is your input voltage? If the device is down, the Vin is lower than Vout, there is no current path for LED current.