11
range (i.e. 100Hz to 100kHz) to be measured. Save the calibration data for later
use. Refer the network analyzer manual for detailed calibration setup.
After calibration, LDO PSRR measurement setup is shown Figure 3b. The
network analyzer input-B is moved to the LDO output near the capacitor while
keeping input-A at the LDO input. Again sweep the network analyzer over the
desired frequency range. You may refer to the network analyzer manual for
details. After subtracting the calibration data, PSRR data is plotted. Figure 4
shows an example of PSRR plot. Table 1 shows a list of network analyzers can
be used with TS200.
P
S
R
R
(
d
B
)
Frequency (Hz)
Figure 4. Example of PSRR plot. Table 1. List of network analyzers
LDO PSRR Measurement with Oscilloscope
Alternatively, PSRR measurement can be done using an oscilloscope. Place the
oscilloscope probes as shown in Figure 5. CH1 probe is connected to the LDO
supply input near the capacitor and CH2 probe is connected to the LDO output
near the capacitor. 1x probe is recommended due high oscilloscope noise floor.
Connect a function generator to the TS200 Modulation input. Set the function
generator output to 200mVpp sinewave or 20mV if B-version is used. Set the
frequency to the frequency of interest (i.e. 1kHz). Then set the TS200
modulation to AC-couple. Adjust the DC Offset knob until the TS200 output
voltage reaches the desired voltage (i.e. 3.3V).
Manufacturer
Model
AP Instruments
Model 300
Omicron
Bode 100
Agilent
4395A
Audio Precision
SYS2722
