Difference between LM75A and LM75B?

Hi Al,

Sorry for the delay. Here is a summary of the differences:

1. LM75A has a product ID register - the LM75B does not support this.
2. LM75A has 1000V CDM (Charged Device Model) ESD rating - the LM75B is not rated for CDM ESD
3. LM75A abs max voltage is 6V - the LM75B is 6.5V
4. One order number for each package for the LM75A supports a power supply range of 2.7V to 5.5V - LM75B has two order numbers for each package option a -3 that supports a range of 3.0V to 3.6V and a -5 option with a range of 4.5V to 5.5V
5. When reading a 16-bit register for the LM75A the lower 7 unused bits will report "0" - LM75B the lowest 3 unused bits are zeros the next 4 bits are readable/writable
6. Fault queue behavior for the LM75A sets after n over-temperature events where n = 1, 2, 4, 6 and esets after n under-temperature events - LM75B sets after n over-temperature events where n = 1, 2, 4, 6 and resets after 1 under-temperature event.
7. LM75A is 7 years newer and was released in Feb of 2009 - LM75B was released in Sept. 2002.

Hope this answers your question. There is one other difference I will need a few days to investigate. Will update you when the investigation is complete.

Take care,

Emmy Denton
Precision Systems Applications
Silicon Valley Analog (formerly National Semiconductor)
Texas Instruments

Hi emmy,

In your post on the LM75A vs B/C you stated several factors that were different in the parts, but ended saying

"There is one other difference I will need a few days to investigate. Will update you when the investigation is complete"

Have you investigated that difference ?

We presently have several designs using LM75B that we want to transition to LM75A due to the lower Vcc tolerance of 2.75V.

Best Regards,

Paul O'Keefe

Hardware Engineer - Casa systems

100 Old River Road - Andover. Ma 01810

Hi Paul,

The LM75A and LM75B/C have a small difference in design, and they are also completely difference process; however, they have an equivalent behavior. As far as I know, LM75C does not have the timeout feature.  If the SDA of the LM75A or LM75B is held LOW for longer than the timeout specification, the device will reset to the idle state.

I hope that I have answered your question. Please let me know if you further question.

Aaron Heng

Hi Aaron,

Can you elaborate on the small design differences you mention between LM75A and B/C ?  or does it not effect the end use of the device ?

Regards,

-Paul

Hi Paul,

I'm sorry, but this is confidential. I cannot disclose any information. Like I said before, they are similar behavior.

Aaron Heng

Hi Aaron,

Not trying to pry into confidential info, just trying to understand if as a user we'd see any differences while using when swapping from a B to an A

Regards,

-Paul

Hi Paul,

After I spoke with my coworker, I finally got the answer that Emmy was referring to in this quote “There is one other difference I will need a few days to investigate. Will update you when the investigation is complete.” The difference is that the variation in accuracy for the LM75A that is caused by power supply variation less than in the LM75B and C. That is evidenced by the fact that there are no -3 and -5 options available for the LM75A as for the LM75B and C. She deleted a note that was included in the LM75A Electrical Characteristics that listed the power supply effect on accuracy the same as the LM75B and C, as this note does not apply.

Please let me know if you further question.

Aaron