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SM72441

Steven Paul
Prodigy 10 points
Other Parts Discussed in Thread: SM72441, SM72442

having some difficulty with the documentation on the SM72441  -- can't figure out how to  setup the resistance networks for A0, A2, A4, A6.  Is there other documentation than in the data-sheet -- perhaps a worked example somewhere ?    /Steven

  • 0
    TI__Intellectual 2010 points

    Hi Steven,

    The maximum output voltage of SM72441 is set by A0 and use the following equation to calculate your Vout

    RT1 to RT4 can be scaled to 20k ohms. 

    Use 2kohm for RFB2 where the value of  RFB1 depends on your output voltage. You want to set the AVOUT to be close to the maximum allowed A/D input/output 4V. So choose an appropriate value for RFB1 based on your output voltage where AVOUT is ~4V. 

    A2 voltage range is listed in Table 1 of the datasheet. The RT2 value can be set to 20kohm. You can choose the RB2 value based on what voltage you want on this pin based on Vfs voltage (refer to Table 1)

    A4 is used to set the over current threshold. RT3 can be 20kohm and set RB3 to set the voltage at A4. When the voltage at AIOUT hits this value, the overcurrent will be activated. "Overcurrent at the output is detected when the voltage on AIOUT (pin 21) equals to the voltage on A4 (pin 18). The voltage on A4 can be set by a resistor divider connected to 5V whereas a current sense amplifier output can be used to set the voltage on AIOUT." If you don't want to implement OCP, try shorting A4 to GRN to that the voltage on A4 never reaches AIOUT voltage level

    A6 sets the slew rate for the output voltage. Datasheet mentions an example for A6 is you want a fast slew rate like 125V/sec use 9:1 ratio for RT4 and RB4.

    Please visit the following link where SM72442 is used in charge controller system.

    www.ti.com/.../snosb76c.pdf