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TPS92638-Q1: About using REFHI, PWM

Ömer Kalayci
Prodigy 175 points
Part Number: TPS92638-Q1

1-) I'm not using the REFHI pin, should I leave the float or pull it directly to GND?

2-) I pull the PWM pins (PWM2, PWM3, PWM4) that I do not use directly to GND.
I'm connecting the PWM pin I'm using to GND with 10k.
Is this true?

  • 0
    TI__Expert 4955 points

    Hello Omer, 

    Thank you for your questions, I will answer them in the order you presented them:

    1. It is perfectly alright not to use the REFHI pin, this is intended for applications with only a single level of brightness. However you must have a resistor in the REF pin to control the current regulation. Additionally, the signal applied to the STOP pin must be low in order to control the system uniquely with the REF reference resistor. This is explained in detail on section 9.3.1 of the datasheet on page 14. 

    Once you have ensured that the STOP pin is pulled low, please ensure that you have selected an appropriate resistor based on the following directions:

    Once you have done this it is alright to leave the REFHI pin floating. Figure 42 on page 24 showcases in detail the implementation:

    2. For the unused PWM channels it is appropriate to connect them to GND as shown, as they also work as the channel disable pin if pulled low. In your current setting you are going to be able to control OUT1, and OUT2. By ting PWM2-4 to GND Outputs 3-8 will be disabled according to the following figure in page 14 of the datasheet:

    If this response answers your question please check the box at the bottom right stating that this is the resolved your issue. If not I will be happy to provide more information. 


    Best,

    Pedro Arango Ramirez