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TPS54200: TPS54200

Mamzi Ghasemi
Prodigy 130 points
Part Number: TPS54200
Other Parts Discussed in Thread: LM3405A

Hi TI,

I'm trying to design a driver for a laser diode and in the chart below you see some test results with TPS54200 and LM3405A. I need to keep the current below 600mA.

Unfortunately the efficiency stays below %77, and as I reduce the current, the efficiency drops further. 

 
This is gonna be hand held device and power dissipation matters a lot.

So I was wondering if you recommend any solution or an alternative converter for a higher efficiency.   

540mA current:

Vin [V]  

Iin [mA]  

Pin [mW]  

Vo [V]  

Io [A]  

Po [mW]  

Eff. [%]  

8.4 

59.1 

496.44 

0.54 

0.54 

291.6 

58.7 

8.2 

60.2 

493.64 

0.54 

0.54 

291.6 

59.1 

8.0 

61.8 

494.40 

0.54 

0.54 

291.6 

59.0 

7.8 

63.2 

492.96 

0.54 

0.54 

291.6 

59.2 

7.6 

65.0 

494.00 

0.54 

0.54 

291.6 

59.0 

700mA:

Vin [V]   

Iin [mA]   

Pin [W]   

Vo [V]   

Io [A]   

Po [mW]   

Eff. [%]   

Laser Temp 

8.4 

285.8 

2.401 

2.676 

0.7 

1.873 

78.0 

30°C 

8.2 

294.8 

2.417 

2.677 

0.7 

1.874 

77.5 

30°C 

8.0 

305.4 

2.443 

2.677 

0.7 

1.874 

76.7 

30°C 

7.8 

311.9 

2.433 

2.677 

0.7 

1.874 

77.0 

30°C 

7.6 

321.8 

2.446 

2.678 

0.7 

1.875 

76.6 

30°C 

7.4 

334.7 

2.477 

2.679 

0.7 

1.875 

75.7 

30°C 

Mamzi

  • 0
    TI__Genius 9630 points

    hi Ghasemi

    you mentioned this will be used for hand hold device, is it a scanner application?

    For the result, do you test with EVM? if not, pls provide the schematic so that I can check if we can take some action to improve. Besides, how many LEDs are connected?

    For the result of 540mA, why output voltage is so small with 0.54V?  

  • 0 in reply to Mason Wang
    Prodigy 130 points

    Mason,

    This will be a laser device for phototherapy, driving red and infrared laser diodes.
    The tests are all done on EVM.
    only one laser diode was connected.
    0.54v is because we used a one ohm resistor as a load instead of diode. 

  • 0 in reply to Mamzi Ghasemi
    TI__Genius 9630 points

    hi Ghasemi

    From the result in the TPS54200EVM userguide, the efficiency under the condition Vin=12V, VLED=1.8V one IR LED, ILED=0.75A is roughly at 85%. under you operation condition, I think efficiency should be a little bit higher.

     

    1. so please double confirm your test methods and test points

    2. besides, would you mind providing some waveforms of PWM pin, SW, VLED, ILED

  • 0 in reply to Mason Wang
    TI__Genius 9630 points

    hi Ghasemi

    if this has been resolved, I would like to close this thread. thanks