JAJSF96C April 2018 – October 2021 LM5036
PRODUCTION DATA
The two feedback resistors are selected to set the primary output voltage VAUX1 of the auxiliary supply. The internal reference for the off-state and on-state auxiliary output voltage levels are VAUX-OFF (1.4-V typical) and VAUX-ON (1-V typical). The feedback resistors are calculated such that both of the off-state and on-state auxiliary output voltage fall into the recommended operating range (8.5-V to 14-V). In this design example, the off-state and on-state auxiliary output voltages are set to 11.9-V and 8.5-V, respectively. RFB2 is selected to be 1-kΩ and RFB1 is calculated to be 7.5-kΩ according to Equation 89. Note that it is the valley of the output voltage that is regulated at the reference value. Therefore the average output voltage is greater than the reference value due to the ripple injected to the feedback node.