• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 2208 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Part Selection Help: MCU adjustable buck/boost converter

Matt Lang
Intellectual 560 points
Other Parts Discussed in Thread: LM25118, LM34936, LM3481

I have an application that need a buck/boost converter. But I need to be able to change the output voltage via a microcontroller. PWM, SPI, DAC, etc.

Input voltage Range: 5V-12.6V

Output Voltage Range: 9-12.6V

Output Current Max @50 degrees C: 2.5Amps continuous

Application use case examples.

Worst case #1 boost 5V to 12.6V @ 500mA (Battery charging algorithms)

Worst case #2 boost 9V to 12V @2.5Amps (Supply current to a load, (9V is minimum input voltage that will require an output current greater than 500mA)

Normal case: Keeping an output voltage >= 12V with a minimum input voltage of 9V. (Supply current to a load)

The application: I need to be able to use this to output a constant voltage or a constant current. Constant voltage will be the output voltage setting of the buck/boost. The constant current I will use the MCU to monitor the load current and adjust the buck/boost output to maintain the correct current.

I also need an enable pin on the converter to go into a low power state. It would also be fine to have two separate converters, use a boost to always go to the max 12.6V and use a second stage MCU adjustable buck converter. I want low cost so which ever ends up cheaper.

Battery charging has similar needs, maybe there are chips in that area that meet my requirements.

  • 0
    TI__Guru* 78070 points
    Hi Matt,

    Thank you for posting. We can offer three options the controller:
    (1) the LM25118, which is a two switch, non-synchronous buck-boost controller,
    (2) the LM34936, a four-switch synchronous buck-boost controller,
    (3) the LM3481, a boost controller which can implement a SEPIC.

    Please take a look of these devices, and choose one that fit our need: cost, efficiency, solution size, etc.

    Regarding Vout adjustment, You can use PWM or DAC to control these devices. The method is to feed your control voltage through a resistor into the FB pin. If you use PWM, you should use a RC filter to converter it into a dc voltage. Note that the DAC output or the PWM duty is in the inverse logic: the higher the control voltage the lower the Vout voltage setting.

    Thanks,
    Youhao Xi, Applications Engineering