LM239A: Common mode input voltage query

Art Mecina

Part Number: LM239A
Other Parts Discussed in Thread: LM339

Hello Guys,

Good day.

The common mode input voltage range states that the input voltage can go up to Vcc-2V, I'm assuming this means for both inputs per comparator and therefore one input of the comparator can go to the supply voltage if they other is not at the same voltage?

Is that correct or is there an issue if any input goes within 2V of the supply voltage?

Thanks in advance!

Art

over 3 years ago

0 Paul Grohe over 3 years ago

TI__Mastermind 49766 points

Hello Art,

We have a FAQ on this:

https://e2e.ti.com/support/amplifiers/f/amplifiers-forum/967541/faq-common-mode-voltage-range-vs-input-voltage-range-for-a-comparator

Please see the LM339 family application note, particularly section 2.2 and 2.5:

Application Design Guidelines for LM339, LM393, TL331 Family Comparators (Rev. A)

In short: The limit is PER INPUT, so neither input should go above Vcc-2. Section 2.5 will explain the "feature" if you bring one input up to Vcc.

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Art,

the dynamic performance of comparator (propagation delay time, etc.) may degrade when an input exceeds the positive common mode input voltage range or goes within 2V of the supply voltage, as you would say.

Kai

0 Chuck Sins over 3 years ago in reply to kai klaas69

TI__Mastermind 23395 points

Good point to add Kai, thanks for the excellent support.

Art

If you have any further questions, feel free to ask.

Chuck

Amplifiers

Amplifiers forum

LM239A: Common mode input voltage query