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TPS92512HV: Min/Max VOUT

Sepeedah Zadeh
Intellectual 2880 points
Other Parts Discussed in Thread: TPS92512HV, TPS92512, TPS92513

Hello team, 

Customer is needing to drive a single 1A (3W) LED with 2.5-3V working voltage and considering TPS92512HV for constant current source and PWM dimming. Would we have any other recommendation besides 512? I think 513 could work if current is set to 1A and not higher. Vin is at 24V. 

Another question that comes to mind, how are we setting Vout min and max bounds? For example how are the limits set in the EVM design? Is it just based on application? Reason to ask is to make sure 2.5V Vout can be supported with the right design.

Section 8.4.2 of datasheet discusses the Ton(min) limitation, but is there any other point to consider? Assuming equation 12 in datasheet and assuming 24V input and switching frequency 100kHz, then can we say Vout(min) = 24V*100kHz*140ns = 0.336V ?

Thanks!

*Post has been updated to reflect Vin info from customer.

  • 0
    TI__Mastermind 18550 points

    Hi Sepeedah,

    The TPS92512 is a 1.5A Buck LED driver so it should also work for your application of 1A or even up to 1.5A nothing is exceeding the data sheet specifications.

    The LED forward voltage determines the Vout since the TPS9512 is current driver.  So this is based on your application.

    Section 8.4.2:  This limitation is so that you do not have output voltage that is violates the minimum ON time (pulse width) of the part.  Your calculation is correct.  Thus the minimum output voltage you can have is 0.336V for 100Khz switching frequency.  So for your requirement of 2.5V-3V there should be no issue.  However if you go up to 1Mhz then the Vout(min) = 3.36V and it will not work for your application.

    Thanks Tuan

  • 0 in reply to Tuan Tran74
    TI__Intellectual 2880 points

    Hi Tuan, 

    Thanks for the response, I think 512 is 2.5A and 513 is 1.5A part, correct?  So could TPS92513 be an option as well?

    In the product page for the parts, we specify Vout(min) = 0.2V, where does that come from? It would be very helpful to understand any other conditions that bound the Vout min and max values. Thank you!

  • 0 in reply to Sepeedah Zadeh
    TI__Mastermind 18550 points

    Hi

    Sorry for the typo...I meant to sat TPS92513 is a 1.5A part and can be used for your application.

    Your questions can be answered with really understanding of how a buck regulator work in a current driver.  The maximum voltage cannot exceed VIN since it's Buck.  Vout minimum is limited by both the minimum ON time and the sense voltage to get circuit to sense properly.

    Thanks Tuan