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TPS92515: question about analog dimming

TS Yang
Genius 4800 points
Part Number: TPS92515

Hi,

1. Analog dimming is different from picture on datasheet and picture on EVM User's guide.
On the datasheet, the LED current is 1A when the VIADJ voltage is 2.4V, and 2A is shown on the user's guide.
Which is right?
The actual test results show that the picture on the user's guide is correct.

* datasheet

* EVM user guide

2. What is the role of D1 in the picture below?
Why is the D1 100V / 3A product used? Can I use lower values? What value accepted?
Why is the voltage of D2 100V? Low value availability? What value is OK?

thanks,

TS

  • 0
    TI__Expert 3920 points
    Hi TS,

    Please note that we are showing the normalized current on the datasheet, the max current has been normalized as 1, not meaning that the absolute value is at 1.0 A.

    Thank you!
  • 0
    TI__Mastermind 25500 points

    Hello TS,

    Issac is correct. Regarding question 2, D1 conducts the current during the switch off time. It will see a maximum reverse voltage of VIN when the switch is on. So a 100V diode is used on the EVM to account for a maximum VIN of 65V. If the application has a maximum input voltage of 16V for example then a 20V schottky could be used. It should also be rated for a current at least as high as the maximum output current. If it is a 1A maximum output current application then a 1A diode could be used.

    D2 can be relatively low current (100mA or more), but it will see a maximum reverse voltage of VIN + 5V. So it needs a voltage rating of greater than VIN(max) + 5V.

    Regards,

    Clint