LT4294

     Hello! Please explain to me how the resistance in the upper arm is 174k, in the lower arm 52.3 K on the example of the DC2583A debugging Board circuit.

Parents
  • Hello,

    Please see Figure 7. in the LT4294 datasheet. The top resistor sets the auxiliary mode hysteresis, the difference between when the LT4294 enters and exits auxiliary mode. Rtop x IAUXH = VAUXHYS, with IAUXH = 5uA typical. Rtop should also be sized so that the auxiliary pin does not sink too much current at the max auxiliary voltage. AUX pin max current sink is 1.4mA, and the VAUXT threshold is 6.3V typical, so Rtop < (VAUX_MAX - VAUXT) / 1.4mA. The bottom resistor sets the turn off threshold, which is Rbottom = Rtop / [(VAUX_OFF / VAUXT) - 1]. The turn on voltage is VAUX_OFF + VUAXHYS.

    Best Regards,
    Eric

Reply
  • Hello,

    Please see Figure 7. in the LT4294 datasheet. The top resistor sets the auxiliary mode hysteresis, the difference between when the LT4294 enters and exits auxiliary mode. Rtop x IAUXH = VAUXHYS, with IAUXH = 5uA typical. Rtop should also be sized so that the auxiliary pin does not sink too much current at the max auxiliary voltage. AUX pin max current sink is 1.4mA, and the VAUXT threshold is 6.3V typical, so Rtop < (VAUX_MAX - VAUXT) / 1.4mA. The bottom resistor sets the turn off threshold, which is Rbottom = Rtop / [(VAUX_OFF / VAUXT) - 1]. The turn on voltage is VAUX_OFF + VUAXHYS.

    Best Regards,
    Eric

Children