B431LAK3 데이터 시트보기 (PDF) - Bay Linear

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B431LAK3

1.24V Adjustable Shunt Regulator

Bay Linear 

Application Notes:

B431

B431L

Stability: Selection of Load Capacitor

Selection of load capacitor for when B431L is used as a

shunt regulator, two options for selection of CL 1) No

load capacitance across the device, decouple at the load

2) Large capacitance across the device, optional

decoupling at the load.

The reason for this is that B431L exhibits instability

with capacitances in the range of 10nF to 1µF (approx.)

at light cathode currents (up to 3mA typical). 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

with a 0.1µF capacitor across it, it will oscillate

transiently during start-up as the cathode current passes

through the instability region. Selecting a very low (or

preferably, no) capacitance, or alternatively a high

capacitance such as 10µF will avoid this issue

altogether. Since the user 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 B431L is located right at the load, so the

load decoupling capacitor is directly across it, then this

capacitor will have to be ≤1nF or ≥ 10µF

Bay Linear, Inc 2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556

www.baylinear.com

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