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Looking for a boost controller for driving HB LED

Other Parts Discussed in Thread: TPS40211Need: 1. upto 60V Vin 2. 1.4A output current (constant) 3. Output current can be changed using analog voltage setting from a pin 4. Can dim LED via PWM 5. Prefer controller only. Looked at TPS40211, but the output current cannot be set by an analog voltage input. Any idea? Thanks!
  • If you are willing to add a little circuitry, the output voltage can be programmed through an analog voltage.

    The simple way (produces an inversed relationship between control signal and output current)

    Add a non-inverting buffer with a series resistor between the analog current signal and the FB pin of the TPS40211.

    Add a resistor from FB to GND

    Size these two resistors such that when the analog control signal is at its minimum, they require 1.4A of current through the current sense resistor to maintain 260mV on the FB pin.

    Size the resistor from the buffer to the FB pin such that when the analog dimming voltage is at its maximum the FB pin is at 260mV with 0A through the current sense. - The attached PDF shows the circuit and linearity based on a 0-3.3V Analog dimming source.  The resistor values could be modified for alternate ranges.

    This circuit could be modified to use an inverting amplifier to provide a direct relationship between analog dimming voltage and load current.  Tie the non-inverting input pin of the op-amp to the full-scale voltage from the analog dimming source (3.3V from the example circuit) and use a unit-gain inverting amplifier (same resistor values into inverting input and between inverting input and output) - It would be recommended to add a matched resistor in series with the non-inverting pin as well to cancel any input bias currents on the Op-Amp input pins.

    Inverted.pdf
  • Thanks Nancy! I guess the buffer can be eliminated when the analog voltage is generated from the DAC. Best regards!