LM25122-Q1: startup waveform - VOUT flat region

Ella KIM

Expert 4212 points

Part Number: LM25122-Q1

Hello,

May I have a quick question on LM25122-Q1 startup waveform?

1. Why there appears a flat region in VOUT when VOUT=VIN?

2. Can I assume how long it would last?

Thanks,

over 3 years ago

0 Haroon Wardak over 3 years ago

TI__Genius 10385 points

Hi Ella,

Thank you for using E2E forums, May I know the purpose of this question in order to better understand and answer your question? Why do you need to know the delay time during which the Vout is flat? maybe you could give me your design specs and/or schematics?

BR,

Haroon

+1 Haroon Wardak over 3 years ago

TI__Genius 10385 points

Hi Elia,

This delay consists of two parts:

- Standby time – basically the time to startup the device and settle the internal Vcc and logic signals.

- the Startup delay – see the SS signal. For a Boost this time also allows the output cap to already charge up to Vin

As to why it is flat is to help the regulator to gradually reach the steady state operating point, thus reducing startup stresses and surges.

Hope this helps. Let me know if you have further questions regarding this.

BR,

Haroon

0 Ella KIM over 3 years ago in reply to Haroon Wardak

TI__Expert 4212 points

Haroon, It greatly helps to understand the basic operation. Thanks a lot.

0 Haroon Wardak over 3 years ago in reply to Ella KIM

TI__Genius 10385 points

Hi Ella,

You are welcome.

BR,

Haroon

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LM25122-Q1: startup waveform - VOUT flat region