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TPS61161A: Change in characteristics is found according to the diodes

TS Yang
Genius 4800 points
Part Number: TPS61161A

Hi,

We applied the TPS61161A to a new project, and the following symptoms occurred during the test.

1. LCD Drive IC: TPS61161A
2. Test Diode:
     A. PSBD1DF40V2L
     B. CRS01
3. Symptoms and Conditions:
     A. Condition: PWM frequency: 9.3 KHz, Duty: 96.3%, LED: 8 (series)
     B. Symptom: Using PSBD1DF40V2L increases current consumption by about 5mA compared to using CRS01.

Below attached files are the datasheet of diodes and waveformswhen the symptom appears.

As a symptom, there seems to be something to consider when using the Schottky diode at the end, and I want to know the exact reason.

PSBD1DF40V2L.PDF

thanks,

TS

  • 0
    TI__Mastermind 22745 points

    Hi，TS,

        When we choose schottky diode in backlight application, we usually consider those parameters: reverse voltage, current rating(DC current and peak current), forward voltage, diode capacitance, and reverse leakage current.

       I have carefully compared those two diode' parameters. Most parameters are similar,  and PSBD1DF40V2L has lower leakage current than CRS01. But the main difference is the diode capacitance. PSBD1DF40V2L has larger capacitance than CRS01(almost 8 times), which means PSBD1DF40V2L needs larger amount of charge to take the schottky diode from the blocking state to the on state.

      You can read out application note for more information:http://www.ti.com.cn/cn/lit/an/snva762/snva762.pdf

      The PSBD1DF40V2L capacitance is show as below:

      

     The CRS01 capacitance is show as below: