Line Regulation
For calculating Line regulation, ratio of change in output
voltage to the corresponding change in input voltage expressed in Percentage.
Here are a few notes on calculating Line regulation:
The output should be measured immediately at the IC pins.
If there are ferrites put at the input and output of the
regulator, measure the input voltage at the input Pin after the ferrite, and
before ferrite at the output pin. Ferrites have ohmic losses which should be
isolated from regulation calculation.
For best cases, connect the worst case load to the regulator
is going to observe during actual operation.
Set the input voltage to an expected maximum, may be even
slightly higher, and measure the output voltage right across the output
capacitor, before ferrites. Note down the input and output voltages
Set the input voltage to an expected minimum, may be slightly
lower, and measure the output voltage right across the output pin of the IC,
before ferrite. Note down the input and output voltages.
Calculate the Line regulation as follows:
((Output voltage at
maximum input – Output voltage at minimum input)/(Maximum input – Minimum
input))
Line regulation is also expressed in many other units:
%/V : Percentage change in output
voltage to the expected voltage for a unit change in input value
mV : Directly expressed in mV,
for the entire range of input and specified maximum load current
µV/V : Change in output voltage in
µV for corresponding change in input voltage
Depending on the datasheet parameter, for comparison with
actual measurements, we need to calculate the regulation accordingly.
Let me know your suggestion and comments about the post
Load Regulation
For calculating Load regulation, ratio of change in output
voltage to the corresponding change in output load current expressed in
Percentage.
Here are a few notes on calculating Load regulation:
The output should be measured immediately at the IC pins.
If there are ferrites put at the input and output of the
regulator, measure the input voltage at the input Pin after the ferrite, and
before ferrite at the output pin. Ferrites have ohmic losses which should be
isolated from regulation calculation.
For best cases, feed the worst case voltage input to the
regulator is going to observe during actual operation.
Set the load current to a minimum value (may be no load at
all, output ferrites can be made open in the circuit to get best value, if
possible) and measure the output voltage right across the output capacitor,
before ferrites. Note down the output voltage and output load current.
Set the load current to a maximum value (rheostat at the
output, and the value set to a value, which is slightly expected maximum load
current) and measure the output voltage right across the output capacitor,
before ferrites. Note down the output voltage and output load current.
Calculate the load regulation as follows:
((Output voltage at minimum
load – Output voltage at maximum load)/(Maximum load – Minimum load))
Load regulation is also expressed in many other units:
%/A : Percentage change in output
voltage to the expected voltage for a unit change in load current value
mV : Directly expressed in mV,
for the entire range of load current
µV/A : Change in output voltage in
µV for corresponding change in load current
Depending on the datasheet parameter, for comparison with
actual measurements, we need to calculate the regulation accordingly.
Hope, I have answered the question of how to calculate the
line and load regulation for a given voltage regulation section.
Also, there are specific guidelines and tips for measuring
proper line and load regulation by vendors such as TI, NI and ST.
Let me know your suggestion and comments about the post.
