Buck converter for the ISL8117 track an external voltage level

Hello community, I'm working on a project about Buck Converter using ISL8117.

I'm using it with
Input voltage  Vin = 24V.
Output voltage Vout is adjustable. 
Vout_min = 3V.   Vout_max = 21V.      

The ISL8117 will be set up to track an external voltage level Vmaster.
Voltage level Vmaster is the output of external DAC.  
Vmaster_min = 0V.  Vmaster_max = 10V.
A resistive divider is connected between the Vmaster and ground.
The center point of the divider will be connected to the SS/TRK pin of the ISL8117.
The voltage at SS/TRK pin (Vtrk) is greater than 0.6V when the master rail reaches regulation.
Output voltage Vout = Vout_min =    3V, when Vtrk = 0,6V. 
Output voltage Vout = Vout_max = 21V, when Vtrk = 4,2V. 

What is the maximum voltage Vtrk at SS/TRK pin for tracking control mode ISL8117?
Does value Vtrk = 4,2V is legal level for tracking control mode ISL8117?

Thank you.

Parents Reply
  • Hi,

    Looks like you purpose is to use controller’s SPI signal to control ISL8117’s output to track a voltage rail. For same  the Vmaster signal should adjust the FB pin voltage not SS/TRK to adjust ISL8117’s Vout..SS/TRK pin is not for this purpose . Kindly find below diagram as reference .R value deepends on the controller DA signal. maybe start with 10k,




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