TSM102A: TSM102A Best Method for Connecting Unused Comparator and Op-Amps

BobL

Part Number: TSM102A
Other Parts Discussed in Thread: TSM102, TL431, LM339, LM358

Support, The TSM102 datasheet doesn't spell out how to connect unused Op-amps and Comparators. How should they be connected? I've read some datasheets that say to never connect inputs pins directly to ground, as they may draw high current. Are the following snip-it connections ok, or should they be connected differently. If differently, why exactly? Vcc- is grounded on the IC.

over 1 year ago

0 Chi Nguyen1 over 1 year ago

TI__Genius 11701 points

Hi BobL,

Thanks for your post. Please see Section 5.1 of this app note: Application Design Guidelines for LM339, LM393, TL331 Family Comparators (Rev. B). It explains best practices for unused inputs for comparators. In general, it is best to connect the inputs to known voltages such as VCC or GND with current limiting resistors to put the comparator into normal operation mode. For the op amp, i believe how you configured is fine. This article here explains what to do with unused op amps: (+) The Unused Op Amp—what to do? - The Signal - Archives - TI E2E support forums

0 BobL over 1 year ago

Intellectual 330 points

Yes! That's the document I referred to above.

0 Clemens Ladisch over 1 year ago

Guru 283830 points

For the op-amps, see section 7 of the Design Guidelines for Devices with LM324/LM358 Cores. (The PNP input architecture allows some things that would not be possible for a CMOS op-amp.)

0 BobL over 1 year ago in reply to Clemens Ladisch

Intellectual 330 points

I'm uncertain that either of these two documents actually apply to this part, as we have another similar device we use, the LM613WMX, that actually tells you to connect the unused op-amp and comparator per above. "Tying inverting input to output and non-inverting input to V− on unused amps is preferred. Unused comparators should have non-inverting input and output tied to V+, and inverting input tied to V−."

0 Clemens Ladisch over 1 year ago in reply to BobL

Guru 283830 points

The TSM102 integrates an LM358, an LM339, and a TL431 in a single chip. These app notes definitely apply.

0 BobL over 1 year ago in reply to Clemens Ladisch

Intellectual 330 points

Excellent! Thx!

+1 Chi Nguyen1 over 1 year ago in reply to BobL

TI__Genius 11701 points

Thank you Clemens.

I hope this helps you with your design BobL.

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TSM102A: TSM102A Best Method for Connecting Unused Comparator and Op-Amps