SN65HVD1474: Pulse Duration

JDJ

Part Number: SN65HVD1474
Other Parts Discussed in Thread: TLC5973, , THVD1451, THVD1551

Hello!

We are using the pulse generator within the TLC5973 to create the SDO signal. The range of the pulse is rather large (15ns to 45ns) due the variance of the internal oscillator.

We originally thought to have a multivibrator to stretch the pulse to 100ns to convert the SDO pulse to RS485 to run to another PCB further away. The pulse stretcher would make the pulse width complaint with the 20Mbps transceiver

Do you have any application notes or suggestions on how condition the signal to make it acceptable for the SN65HVD1474? Or any other general suggestions.

We also have another iteration with the a 50Mbps transceiver THVD1451.

Thanks!

over 3 years ago

0 Ravi Singh over 3 years ago

TI__Mastermind 22965 points

Hi JDJ,

Can you please share more details (perhaps a block diagram) to describe what you are trying to accomplish at system level?

0 JDJ over 3 years ago in reply to Ravi Singh

TI__Expert 3171 points

Hi Ravi,

I am trying to create a block diagram now but was making this post for help.

We have a TLC5973 creating an SDO pulse that needs to convert to RS485 to run to another far away PCB.

We are trying to use the following but the SDO pulse is 15ns to 45ns which I believe is too short.

SN65HVD1474DGKR 20Mbps

THVD1451DR 50Mbps

Have you seen any applications like this before and what is the recommended way to solve this.

Regards

0 Hao L over 3 years ago in reply to JDJ

TI__Mastermind 25705 points

Hi,

We haven't seen similar applications. THVD1451 and THVD1551 are the fastest RS485 TI has. Even the device could take the SDO pulse, the drive might not work due to the bus load. I cannot think of any solution other than stretching the pulses.

Regards,

Hao

0 JDJ over 3 years ago in reply to Hao L

TI__Expert 3171 points

Do you have a recommended part or solution that can be used for stretching the pulses.

Thanks

0 Hao L over 3 years ago in reply to JDJ

TI__Mastermind 25705 points

Unfortunately I'm not the expert. There are some ideas online.

Regards,

Hao

0 JDJ over 3 years ago in reply to Hao L

TI__Expert 3171 points

What is the minimum pulse requirement for each of the above transceivers?

Thanks,

JDJ

0 Hao L over 3 years ago in reply to JDJ

TI__Mastermind 25705 points

JDJ,

To meet the minimum bit width of 50Mpbs data rate, the minimum pulse width should be larger than 20ns. Surely it's better to have wider width for jitter margins.

Regards,

Hao

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SN65HVD1474: Pulse Duration