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Constant current power supply

Sainer Siagian
Intellectual 370 points
Other Parts Discussed in Thread: LM3407, TLC5960, TLC5954

Hi,

I am designing a constant current power supply to Load that can change the Vout dynamically in range 10-15V.Is TI has IC that satisfy this requirement?. The maximum Iout is 50mA. Boost Converter with Vin=5V plusminus 5% is welcome, but if not possible Buck Converter with Vin up to 15V also OK.
So here is the requirements.
1. Dynamical Vout in range 9-15V
2. Iout range up to 60mA
3. Small package size with integrated inductor. (Example: LMZ21700SILR)

To make it possible to change Vout dynamically I am thinking to use DAC/digital potentiometer as shown on attached file. Other ideas/suggestions are welcome.

4048.Adjustable constant current Source.pdf

  • 0
    TI__Genius 16025 points
    Hi Sainer,

    Give me a day to review your design and provide feedback.

    Thanks,
    Anston
  • 0
    TI__Mastermind 23845 points
    Conceptually the graph that you showed me seems to be ok. I would put the CS resistor on the GND side of the load because the OP AMP VCC is lower than VOUT. Send me your draft schematic and we can definitely check for you

    Thanks
    -Arief
  • 0 in reply to Arief Hernadi
    Intellectual 370 points
    Thanks Arief and Anston. I have 3 option of architectures on my hand right now. 1 is as I showed on my previous post, using LMZ235003 as Current Supply. But the price is to expensive to use them on each channel of 32 channels of Load. Btw, in the past I actually used LMZ21700SILR with the same architecture to Supply up to 5V and it worked pretty well. Now, I am thinking if TI might be has such kind of LMZ21700SILR with Vout up to 15V and same price as it for my new system? :-)

    2 is using LED driver such as TLC5960 or LM3407 but seems not realistic because in case of TLC5960 the number of PWM signals are less than the number of Load channels which implies it can not control each channel independently. Besides, I still need 15V output of DC/DC Converter to supply current to 32 channels of my Load. While, in case LM3407 I need 32 independent PWM bus lines from my microcontroller to control all my 32 channels Loads independently.

    3 is using the conventional OPAMP-FET V-I converter, with DAC as the input but the drawback is the power/thermal dissipation from 32 FETs, which makes power consumption of the system becomes bigger.
  • 0 in reply to Sainer Siagian
    TI__Mastermind 23845 points
    Hi Sainer,

    We also have more channels LED driver such as TLC5954.
    www.ti.com/.../tlc5954.pdf
    But like you said you need to supply the 15V for the LED from another converter.
    I still think the multi-channel LED driver makes sense because you want to control the individual channel of the load. Instead of multiple DC-DC converter being used as current source. Then you only need 2 ICs one for LED driver and one for the supply of the LED
    What is your constraint on your design? Cost? Size?

    Thanks
    -Arief
  • 0 in reply to Arief Hernadi
    Intellectual 370 points
    Hi Arief,

    The Load are not LEDs by the way. Besides, the maximum Vout of TLC5954 is only 10V, and the maximum Iout is around 35mA, which don't satisfy my Spec. My constraint is cost and size. I can discuss the details offline if you don't mind to give me your email address.
  • 0 in reply to Sainer Siagian
    TI__Mastermind 23845 points

    Sure my email is arief.hernadi[at]ti.com

    Thanks

    -Arief