MPC506 vs HCT4067

Almerindo Paiva

Other Parts Discussed in Thread: OPA2170, ADS1018, MPC506

Hi,

I'm developing a 32 channel PLC analog interface with signal ranges from 0-10V or 4-20mA that will be converted to 0-5V trough a 250ohms sense resistor.

I'm planning to use a resistor voltage divider (factor 1/2) for each channel, a 16:1 mux, an buffer and a ADC.

For the ADC I choose ADS1018, and OPA2170, operating at 5V.

I would like to ask, if someone, for any reason, would advise me to not use HCT4067 and to use MPC506, and why? There is a factor of 10 in price costs.

MPC506 is protected to input over-voltage until 70Vpp by it's internal 1kOhms resistance. HCT4067 has any over-voltage protection, but I could put a resistor in series. I'm also planning to introduce TVS in each input. Will this solve anything?

I've not much experience with industrial environment, so I would like to get more information if this over-voltage protection is a requirement.

Best regards,

A. Paiva

over 12 years ago

0 Bob Benjamin over 12 years ago

TI__Guru** 113765 points

Hi Almerindo,

I think you have covered the differences. With extra features you end up paying more. One thing to consider is the overall BOM costs and space savings.

You should be able to use the 4067 as long as you have protected the inputs so that they do not go above the supply. The same is true for the ADS1018.

Best regards,

Bob B

0 Almerindo Paiva over 12 years ago in reply to Bob Benjamin

Intellectual 410 points

Hi,

Thanks for your reply.

16 resistors plus 16 TVS diodes, won't cost 1/6 of MPC506. And space I have enough.

Is there any other feature? Or need I use other kind of protections?

Best regards,

A. Paiva

0 Bob Benjamin over 12 years ago in reply to Almerindo Paiva

TI__Guru** 113765 points

Hi Almerindo,

You may have other filtering needs such as anti-aliasing, and EMI/RFI filtering. This will depend on operating conditions and the level of filtering required due to the environment in which your system is operating. This may be as simple as RC filters, but may also require ferrites or inductance as well.

Best regards,

Bob B

0 Almerindo Paiva over 12 years ago in reply to Bob Benjamin

Intellectual 410 points

Dear Mr. Bob.

Certainly i need to introduce anti-aliasing and EMI/RFI filtering, on both parts. I found that, there are some hct4067 with ~1Kohms. What are the main difference with this parts having 1Kohms and MPC506, in terms of input protection?

Best regards,

A. Paiva

0 Bob Benjamin over 12 years ago in reply to Almerindo Paiva

TI__Guru** 113765 points

Hi Almerindo,

Anytime you add series resistance it will be a part of your RC filter combination and added resistance to the input of the ADC.

Best regards,

Bob B

0 Almerindo Paiva over 12 years ago in reply to Bob Benjamin

Intellectual 410 points

Dear Mr. Benjamin,

What can happen when a remote sensor is connected to HCT4067 and the board where this device is connected isn't be powered? How can I prevent this device from being demaged in this case?

Is there any channel active when there is no power?

Best regards,

Almerindo Paiva

0 Bob Benjamin over 12 years ago in reply to Almerindo Paiva

TI__Guru** 113765 points

Almerindo,

Unfortunately I know very little about the part except for what is in the datasheet. You might try posting your question in the Logic forum. I would assume that the ESD protection would conduct current and could potentially damage the device if the current is too high.

Best regards,

Bob B

0 Almerindo Paiva over 12 years ago in reply to Bob Benjamin

Intellectual 410 points

Mr. Benjamin,

Ok. Thank you very much!

Best regards,

Almerindo Paiva

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MPC506 vs HCT4067