TLK2501 driven from 3.3V data source

Adrian Fiergolski

Other Parts Discussed in Thread: TLK2501

Hello,

I would like to drive the TLK2501 chip by a source operating at 3.3V LVTTL voltage level. According to the specification, the maximum ratings for the TXD inputs are between -0.3V to Vdd+0.3V. It gives the upper limit equal to 2.8 V which is much below 3.3 V (+reflections). Has anybody faced with that problem ? Do I have to use voltage level transators ? Or maybe an active parallel termination is the possible, resonable way (prevents against reflections and reduces the output voltage level) ? Since I am rather a beginner, what would you reccomend ? Thanks in advance.

Best regards,

Adrian

over 12 years ago

0 Max Robertson over 12 years ago

TI__Guru 62910 points

Hi Adrian,

I wouldn't recommend driving the TXD pins directly with a 3.3-V source. Exceeding the absolute maximum ratings may result in permanent damage to the device. Instead, there are a few options:

You could use a voltage level translator to step down the voltages to the range supported by the TLK2501. TI's family of voltage level translators can be found here: http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?familyId=705&family=analog&uiTemplateId=NODE_STRY_PGE_T&familyAliasId=1100705. They are supported through the "Logic" forum, so if you have any questions you can ask them there.
You could use passive termination (e.g., resistive voltage dividers) on each input to attenuate the signaling amplitude.
You may want to look at using the TLK2711A instead. It supports a similar data rate range, but also supports I/O voltages up to 3.6 V (4 V absolute maximum).

I hope this helps.

Regards,
Max Robertson
Analog Applications Engineer
Texas Instruments
m-robertson@ti.com

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TLK2501 driven from 3.3V data source