Hi Walter,
As per datasheet mentioned Reverse Breakdown Voltage Options = 1.225 V. But as simulation shows 2.8085V. Vref should be 18.475V if consider 1.225V.
Please correct me where i am doing mistake.
Kindly find attached screenshots.
Truly,
Krunal
Hello Krunal,
The vref voltage for the adjustable part is 1.212V as measured between the FB pin and the cathode. According to your simulation, 1.212V + 17.796V =19V
The maximum output voltage for this 10V and the simulated circuit will damage the device if the output is set to 18.475V. If this output voltage is required please consider using the TL431 device that can handle up to 36V.
Thanks,
Walter
Hello Krunal,
What further questions do you have? The simulation model works correctly but I recommend using this circuit layout and equation to set the output. Please do not set the output voltage to be greater than 10V.
Thanks,
Walter
Hello Walter,
As per suggested part number LM4051AIM3X-1.2/NOPB has maximum output voltage capacity = 15V. As per requirement, output voltage can withstand 18.475V.
Please check if any other solution possible.
Truly,
Krunal
Hello Walter,
As per TL431 datasheet it's adjustable part is 2.5V and during simulation it is achieve as it is showing V(Vref3, V_tp3). However, Vref should come 18.475V by resistor pair of R1=5.1K and R2=19.1K. But it isn't increase more than 18.334V even if increase resistance value of R2.
Although TL431 can handle up to 36V.
Please rectify me if something missed and find attached screenshot for reference.
Truly,
Krunal
Hello Krunal,
For the TL431, please use this schematic configuration. VKA is the output voltage =18.475V that is set by R1 and R2. Vref = 2.495V. For an input voltage of 19V and an output voltage of 18.475V, please use an Rin value between 525 and 6 ohms. This is because the TL431 needs a minimum IKA current of 1mA.
