TS1431_08 Datasheet, PDF (3/10 Pages) Taiwan Semiconductor Company, Ltd – Adjustable Precision Shunt Regulator

Test Circuits
TS1431
Adjustable Precision Shunt Regulator
Figure 1: V_KA = V_REF
Figure 2: V_KA > V_REF
Figure 3: Off-State Current
Additional Information – Stability
When The TS1431/1431A/1431B is used as a shunt regulator, there are two options for selection of C_L, are
recommended for optional 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 TS1431/1431A/1431B 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 TS1431/1431A/1431B 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
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Version: C07