This is a caravel that has an LDO Design implemented on Skywaters 130nm technology.
We have an enable switch so all the following analysis when the enable signal is high.
We used dc analysis for displaying the operating point for proper biasing of transistors and also dc sweep of output voltage against variations in supply and temprature to calculate dropout voltage,line regulation,temperature coefficient.
We made dc sweep on the supply and plotted voltage of the output node and vdd node overlaid on the same plot @Load current = 0.1mA
@Load current = 10mA
@Load current = 100mA
We made dc sweep on temperature from 0 to 85°C and plotted the output voltage vs temperature from which we found temperature coeffiecient in ppm/°C. @Load current = 100uA
@Load current = 10mA
We used AC analysis by injecting small ac signal over the supply and plotted the output voltage in dB which refers to the PSRR vs Frequency.
We made the above testbench to cut the feedback loop of the ldo and inject ac signal and then measure the loop gain and phase to find phase margin.
We used transient analysis to show the line transient by varying the supply from 0 to vdd where the nominal supply voltage is 2.3v. When VDD varies from 0 to 2.3v When VDD varies from 2 to 3v
The load is varied from 0.1mA to 10mA where the load is modeled as current source varied as PWL source where the output voltage suffers from under shoot of 40mV due to change of load current from 0.1mA to 10mA in 10uS then it settles back to its original value so we used this analysis to measure the load regulation.
The plot includes load current variation and ac-coupled ldo_output overlaid on the same plot.
We have an enable signal so we varied it from 0 to Vin in 0.1uS and plotted the ldo_out. The start up time is less than 10uS.
The typical conditions are tt corner ,load of 50uA, T=27°C , VDD=2.3V , We have a script to automate running process corners then getting their statistical distribution where the variation of the load from 50uA till 100mA is included in the corners
|Dropout Voltage @IL=0.1mA
|Dropout Voltage @IL=10mA
|Dropout Voltage @IL=100mA
|0.06mV IL=0.1mA till IL=10mA
|PSRR @ 100Hz
|PSRR @ 100kHz
|50uA -> 100mA
The implementation of the LDO is as follows.
Refer to README for this sample project documentation.