LMH0394: Bypass Mode

Mark Heh

Part Number: LMH0394

When the LMH0394 is in the bypass mode (bypassing the equalizer), what is the "minimum input sensitivity" of the part? Specifically, if the frequency of the input matters, for a 200 MHz Nyquist signal input requirement when bypassing the EQ of the LMH0394. We would like to use this part as a buffer without taking advantage of the equalization capability.

over 7 years ago

0 Nasser Mohammadi over 7 years ago

TI__Guru* 93670 points

Hi Mark,

Since you want to use LMH0394 as a buffer only, you can leave MUTE pin not connected(this pin has internal pull down) and pull BYPASS high. This way there is no dependency on carrier detect signal.

Regards,,nasser

0 Mark Heh over 7 years ago in reply to Nasser Mohammadi

Intellectual 270 points

Hi Nasser,

To use the LMH0394 as a buffer only, MUST the MUTE pin be left unconnected (in addition to pulling the BYPASS high)?

How would the IC's operation change if the MUTE pin was grounded and the BYPASS pulled high?

What is the requirement (min. input sensitivity or other parameter) at the input of the LMH0394 when the IC is acting as a buffer only?

Thanks,
Mark

0 Nasser Mohammadi over 7 years ago in reply to Mark Heh

TI__Guru* 93670 points

Hi Mark,

MUTE pin has internal pull down resistor so you do not need to ground this pin. It should be ok if you put external pull down on this pin as well.

This device - in normal mode - has very high gain so the signal could be as low as 10mV peak to peak.

Regards,,nasser

0 Mark Heh over 7 years ago in reply to Nasser Mohammadi

Intellectual 270 points

Hi Nasser,

What do you mean by the input signal "could" be as low as 10 mV peak to peak?
Where is this parameter specified in the datasheet?
What input differential is this part GUARANTEED to work at (over temperature, end of life of part, etc.)?

Thank you,
Mark Heh

0 Mark Heh over 7 years ago in reply to Mark Heh

Intellectual 270 points

Nasser,

We need to come up with a resolution in the next day or two if you could respond to my previous questions.

Thanks,
Mark

0 Nasser Mohammadi over 7 years ago in reply to Mark Heh

TI__Guru* 93670 points

Hi Mark,

My earlier comment was based on gain of this device and nominal launch amplitude. This is not guarantee.

We have minimum and maximum for some parameters within the data sheet under condition noted in the data sheet.

Regards,,nasser

0 Mark Heh over 7 years ago in reply to Nasser Mohammadi

Intellectual 270 points

Hi Nasser,

I looked through the datasheet again, but was not sure which parameters you are referencing.
Could you explain in more detail?

Thanks,
Mark

0 Mark Heh over 7 years ago in reply to Mark Heh

Intellectual 270 points

Hi Nasser,

Also, the datasheet says that the input must resemble a 75 Ω network. How does the device respond when the input traces are 50 ohms single ended / 100 ohm differential? Specifically for the application of when the device is in bypass mode. Does it matter then or only for equalization?

Thanks,
Mark

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LMH0394: Bypass Mode