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TPS61194: Can TPS61194-Q1 drive 20mA per channel?

Kazuya Nakai59
Guru 21545 points
Part Number: TPS61194

 Hello guys,

 One of my customers is designing LED lighting board for their next products with TPS61194-Q1. They want to set TPS61194 constant current output oer channel to 20mA. According to Figure 5, LED Current vs Riset graph on page 9 of the device datasheet, Riset should be set to 120kohm for 20mA. But according to Equation 3 on page 15, Riset should be set to 133kohm. The pin function table on page 4 says that LED current setting resistor placeed between ISET pin and GND must be from 24 kohm to 129kohm.

 The customer questions are the followings.

 Q1. Can TPS61194-Q1 constant current output be set to 20mA.

 Q2. If the answer of Q1 is yes, what is the Riset value for 20mA?

 Your reply would be much appreciated.

 Best regards,

 Kazuya Nakai.

  

  • 0
    TI__Expert 5475 points
    Hi,

    Yes the current of TPS61194-Q1 can be set to 20mA. Please use the Figure 5 in the datasheet to choose the resistance, which is 120kohm for 20mA. It seems the equation 3 is a fitted equation which is not very accurate at low current condition.
  • 0 in reply to Shirley He
    Guru 21545 points
    Hi Shirley,
    Thank you very much for your reply. I understood.
    Could I ask you an additional question?

    Q: The pin function table in the device datasheet says "LED current setting resistor; for normal operation, resistor value
    from 24 kΩ to 129 kΩ must beconnected between this pin and ground.". But the figure 5 graph shows IOUT current data
    for 150kohm as the maximum RISET. Can 150kohm be used for normal operation? The amximum RISET is 150kohm not 129kohm?

    Thank you again and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Expert 5475 points

    Hi,

    We do not recommend setting the current lower than 20mA. The accuracy may not be very good. What is the end equipment that customer is using this device in? Why so low current is needed?

  • 0 in reply to Shirley He
    Guru 21545 points
    Hi Shirly,

    Thank you for the reply. I asked the customer what their application is. But they didn't disclosed it. I'm sorry I couldn't get the information.

    Thank you and best regards,
    Kazuya Nakai.