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LT8640S tracking/soft-start as servo control

vidpix
on Oct 18, 2018

Hello,

I´m trying to dynamically adjust the LT8640S output voltage with an external control voltage (let´s say from a DAC).

Could this be done using the TR/SS pin?

The LT8640S output voltage refers to its resistor devider:

Vout = 0,97V * (R1/R2 + 1)

Varying the input voltage to TR/SS (0...0,97V), however should change the output voltage (0V to Vout) accordingly,

kind of superimposing the closed-loop:

Is my assumption correct?

Thank you so much ;)

  • 0
    •  Analog Employees 
    on Oct 21, 2018 8:33 PM over 2 years ago

    Hello,

    A more common (recommended) method to adjust the output voltage is to add a resistor (R3 as below) at the FB node. V_DAC can control the Vout value through this resistor.

    LT8640S TR/SS pin voltage can be used to adjust the output voltage, as long as TR/SS is less than 0.97V. However, the FCM (forced continuous mode) is disabled when TR/SS is less than 0.97V.