TS431I

Adjustable Precision Shunt Regulator

3/13

Version: A07

Test Circuits

Figure 1: Vka = Vref

Figure 2: Vka > Vref

Figure 3: Off-State Current

Additional Information – Stability

stability:

A) No load capacitance across the device, decouple at the load.

B) Large capacitance across the device, optional decoupling at the load.

The reason for this is that TS431I/431AI/431BI exhibits instability with capacitances in the range of 10nF to 1uF (approx.) at light

cathode current up to 3mA (typ). The device is less stable the lower the cathode voltage has been set for. Therefore while the

device will be perfectly stable operating at a cathode current of 10mA (approx.) with a 0.1uF capacitor across it, it will oscillate

transiently during start up as the cathode current passes through the instability region. Select a very low capacitance, or alternatively

a high capacitance (10uF) will avoid this issue altogether. Since the user will probably wish to have local decoupling at the load

anyway, the most cost effective method is to use no capacitance at all directly across the device. PCB trace/via resistance and

inductance prevent the local load decoupling from causing the oscillation during the transient start up phase.

Note: if the TS431I/431AI/431BI is located right at the load, so the load decoupling capacitor is directly across it, then this capacitor

will have to be ≤1nF or ≥10uF.

Applications Examples

Figure 4: Voltage Monitor

Figure 5: Output Control for Three Terminal

Fixed Regulator