LM324: About unused pin processing

Tsukui Yusuke

Guru 21930 points

Part Number: LM324

Hi,

Could you tell me the recommended unused pin processing?
My customer is going to pin processing method described below.

・IN+ connect to GND
・Short the OUT and IN- pin
(voltage follower)

Is this all right?

Best Regards,
Yusuke/Japan Disty

over 8 years ago

0 Tim Claycomb over 8 years ago

TI__Genius 15410 points

Hello,

I recommend reading "The Unused Op Amp - what to do?" for an explanation on how to configure your unused op amp.

Thank you,

Tim Claycomb

0 Tsukui Yusuke over 8 years ago in reply to Tim Claycomb

Guru 21930 points

Tim-san,

Thank you for your information.
Customers want to know the recommended pin processing in this device (LM324).

As background,
Currently, customer use the processing method described below.
・IN+,IN-,OUT：Connect to GND

Cusutomer want to change to the processing method TI's recommended in timing of design change.
Could you tell me LM324 specific information?

Best Regards,
Yusuke/Japan Disty

0 Tim Claycomb over 8 years ago in reply to Tsukui Yusuke

TI__Genius 15410 points

Hello Yusuke-san,

What supply voltage is the customer using to power the LM324?

Thank you,

Tim Claycomb

0 Tsukui Yusuke over 8 years ago in reply to Tim Claycomb

Guru 21930 points

Tim-san,

Thank you for your response.
Supply voltage is +5V (single power source).

There is one more questions that I would like to ask you.

The following information is included in the materials you sent.

In case of single power supply:IN+ connect to Vref

However,
Common-Mode Voltage Range is 0 to V+ -1.5V in the case of LM324
Do you have a problem with this?

Best Regards,
Yusuke/Japan Disty

0 Tim Claycomb over 8 years ago in reply to Tsukui Yusuke

TI__Genius 15410 points

Hello Yusuke-san,

Using a +5V single supply I recommend to connect 2.5V to IN+ (Vref) and place the amplifier in a buffer configuration. With a common mode voltage range of 0 to (V+)-1.5V applying 2.5V to the IN+ pin with a +5V supply will place the amplifier in a linear operating region. Please let me know if there is anything else I can do to help.

Thank you,

Tim Claycomb

0 Tsukui Yusuke over 8 years ago in reply to Tim Claycomb

Guru 21930 points

Tim-san,

Thank you for your kind support.
I understood your explanation.

By the way,
Is the current customer pin processing problematic?

----
・IN+,IN-,OUT：Connect to GND
----

Best Regards,
Yusuke/Japan Disty

0 Ron Michallick over 8 years ago in reply to Tsukui Yusuke

TI__Guru**** 164456 points

Tsukui-san,

IN+ at GND and IN- connect to OUT is not harmful for LM324 single supply operation.

0 Ron Michallick over 8 years ago in reply to Ron Michallick

TI__Guru**** 164456 points

As a final note; it is never acceptable to short OUT pin to ground.

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LM324: About unused pin processing