Accel Instruments TS200 User Manual
Also see for TS200: Quick start guide
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Contents
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10LDO PSRR MeasurementPower supply rejection ratio (PSRR) or some time called power supply ripplerejection measurement are often difficult to measure, especially when thedevice under test (DUT) is heavily loaded. Because most network analyzercannot drive a heavy load, the TS200 modulated power supply is very usefulfor PSRR measurement for such devices as LDOs (low dropout regulators) andpower amplifiers. PSRR measurement is easy with the aid of the TS200. Figure3 shows how to measure PSRR. PSRR measurement technique involves anetwork analyzer, TS200 power amplifier, and device under test (DUT).LDOSourceABNetworkAnanyzer TS200ModInput OutputDUT LoadLDOSourceABNetworkAnanyzer TS200ModInput OutputDUT Load(a)(b)Figure 3. LDO PSRR measurement setup. (a) Calibration setup, (b) PSRR setup.Figure 3 shows the LDO PSRR measurement setup. Using a network analyzer,the source is connected to the TS200 modulation input. The TS200 output isconnected to the LDO supply input. It is recommended to reduce the LDO inputcapacitance to minimum. Since the TS200 can drive a heavy load, thus theLDO output can be loaded with the desired loading resistor (i.e. maximumspecified load).Set the TS200 modulation input to AC-coupled. Adjust the DC Offset knobuntil the output DC voltage reaches the desired voltage (i.e. 3.3V). Typicallyfor PSRR measurement, the supply ripple amplitude is 200mVpp. If you areusing the A-version, set the network analyzer output to 200mV. If you areusing the B-version and consider the modulation gain is 20dB, set the networkanalyzer output amplitude to 20mVpp.First the network analyzer and the TS200 need to be calibrated. Figure 3ashows the calibration setup. The network analyzer input-A and input-B areconnected together at one point on the DUT board near the LDO supply input.Set the network analyzer to calibration mode and sweep over the frequency |
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