DS32EL0421/0124 - Pull down/up resistor for logic input pins

Kawai

Guru 19785 points

Other Parts Discussed in Thread: DS32EL0421, DS32EL0124

Hi Team,

Please tell me the recommended pull down and pull up resistor value for the logic inputs of DS32EL0421 and DS32EL0124.

I am reviewing customer's schematic and found 47kohm pull down resistor at DE_EMPHx , DC_B and /RS pins. As I do not know the internal circuit, I thought it may be too high. What is your opinion ?

I also have one more question.
Do you have a recommended schematic and PCB layout for DS32EL0421 and 0124 ?

Best Regards,
Kawai

over 11 years ago

0 Nasser Mohammadi over 11 years ago

TI__Guru* 93670 points

Hi Kawai-San,

47K Ohm R maybe good enough. Normally i would use lower value like 4.7K Ohm to create a lower impedance to ground(i.e better noise immunity) but 47K Ohm may work as well. We have up to 100K Ohm internal weak pull up or pull down on some devices. Please recommend 4.7K Ohm.

This evaluation board is obsolete but i believe Altera or it's representative sells this evaluation board. I believe it is called ELXLEV101.

Regards,,nasser

0 Nasser Mohammadi over 11 years ago in reply to Nasser Mohammadi

TI__Guru* 93670 points

Kawai-San,

Please attached find Altera EVK Schematic for DS32EL0124/0421. You can use this to compare with the customer schematic.

Regards,,nasser5430.exp_easylink_reva.pdf

0 Kawai over 11 years ago in reply to Nasser Mohammadi

Guru 19785 points

Hi Nasser-san,

Thanks for the answer and the reference schematic information.

Best Regards,
Kawai

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DS32EL0421/0124 - Pull down/up resistor for logic input pins