LM2903B-Q1: common mode voltage question

Sherry Liang

Part Number: LM2903B-Q1
Other Parts Discussed in Thread: LM2903, LM339

Dear team,

In my understanding, Both IN+ and IN- can't exceed the VCM_max/(V+)-2, but I am a little confused for the note 1 description, which means one of two inputs can exceed VCM_max?

Thanks & Best Regards,

Sherry

over 1 year ago

+1 kai klaas69 over 1 year ago

Guru 140200 points

Hi Sherry,

this is explained in detail in section 5.2.2.1 of datasheet.

Keep in mind, though, that leaving the recommended common mode input voltage range will degrade the performance of LM2903 (speed, etc.) and is not recommended.

Kai

+1 Paul Grohe over 1 year ago

TI__Mastermind 49906 points

Hello Sherry,

Yes. Each input should be less than 2V below V+. The output will be correct as long as ONE input is within the legal range.

As Kai said, there will be changes in performance during that time.

Please see sections 2.4 and 2.5 of the LM339 family application note:

Application Design Guidelines for LM339, LM393, TL331 Family Comparators

0 Sherry Liang over 1 year ago in reply to Paul Grohe

TI__Genius 10255 points

Hi,

Thanks for your reply!

Our device can still work normally when there is only one input exceeds (V+)-2. But in the long term, our device's performance deteriorates and will no longer meet the data sheet specifications. Is my understanding right?

Thanks & Best Regards,

Sherry

+1 Clemens Ladisch over 1 year ago in reply to Sherry Liang

Guru 243220 points

No, there is no permanent damage, and the device will work correctly. But with an out-of-range input, the electrical characteristics (especially propagation delay) are no longer guaranteed.

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LM2903B-Q1: common mode voltage question