ATL431: Load capacitance requirements for series regulator circuit

Michael Farrugia Magro

Part Number: ATL431

Hi,

I want to implement a precision series regulator (as shown in the figure attached) using the ATL431. In this configuration, is the ATL431 still subject to stability issues due to CKA capacitance? If so are the capacitance values in Figures 14 through figure 21 still valid? Should there be a capacitor between cathode and anode of ATL431 or across the output or both?

Thanks in advance for any insight provided,

MIchael

over 7 years ago

0 Diego Lewis over 7 years ago

TI__Intellectual 1540 points

Hi Michael,

Welcome to the TI E2E Community.

The CKA plots no longer apply for this application. I would, however, suggest using some output capacitance (1uF or larger).

It is also common to have a small (less then 10nF, greater then 200pF) feed-forward capacitor between the REF and Cathode pins to help with stability.

The specific values will depend on the NPN transistor that you use. I'd recommend bench testing the gain and phase of the system in order to check for stability.

Regards, Diego Lewis

0 Michael Farrugia Magro over 7 years ago in reply to Diego Lewis

Prodigy 20 points

Hi Diego,

Thanks for the reply. Is the gain and phase testing carried out using a network analyzer? Could you point me to some information where this type of testing is explained?

Regards,

Michael

0 Diego Lewis over 7 years ago in reply to Michael Farrugia Magro

TI__Intellectual 1540 points

Hi Michael,

A network analyzer is indeed one way to run a stability test.

Below is a link to an Application Report that discusses stability tests:

www.ti.com/.../slva381b.pdf

Regards, Diego

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ATL431: Load capacitance requirements for series regulator circuit