LM317HV: lm317hv variable high current variable power supply 53V

Hello Baskaran,

At the power levels in the diagram, you will want to give strong consideration to a switching converter which can provide the 53V * 4A = 212W of load.
This linear regulator solution is not a feasible design solution given the output voltage and load requirements.

Let's review the LM317HV first.  According to section 7.5 "Electrical Characteristics" in the datasheet, the reference tolerance is 4% and the load regulation is 1.5% for this component up to max load current.  The line regulation can be ignored because there will be very little change in the line to allow for 53V output.  We will see that in a moment.  This does not account for tolerances in the resistors you see in the schematic, and tolerance due to the ballast resistors.  Let's assume the total tolerance of the 53V output voltage is6.5% when accounting for reference tolerance, load regulation, resistor tolerance and ballast resistor tolerance. 

At 53V output nominal, and assuming 6.5% tolerance, you will have a maximum 56.445V and minimum 49.555V.  The specifications in section 7.5 "Electrical Characteristics" are given with 3V of headroom.  Therefore the input voltage Vin will need to be 3V higher than the output voltage to maintain the necessary headroom.  The input supply will therefore need to be at least 59.445V but not exceed 60V to prevent the maximum rating of the linear regulator from being exceeded.  This would require a very tight input voltage of 59.7225V with a tolerance of less than 0.5%.

Thanks,

- Stephen