Method for Calculating Output Voltage Tolerance in Adjustable Voltage Regulators

introduce

When designing a voltage regulator circuit, the designer is faced with the need to calculate the tolerance of the regulated output voltage. For fixed voltage regulators, this problem is easily solved because the required information is directly provided in the semiconductor manufacturer's data sheet.
Calculating the tolerance of an adjustable regulator is more complicated because of the introduction of the external feedback resistor network, the effect of the adjustment terminal current, and the difficulty in combining these conditions to calculate an estimate of the output voltage tolerance.

Traditional "worst case" analysis methods, although effective, can result in unrealistic and overly conservative estimates of the total tolerance, thereby adding unnecessary circuit cost.

The reduction in voltage of modern microprocessors has further increased the demand on the available voltage tolerance. As such, the tolerance issue needs to be understood in more detail.