ADS54J60: input overdrive

Richard Mountain51

Part Number: ADS54J60

The ADS54J60 data sheet specifies a full scale input of 1.9Vp-p differential, The Absolute maximum DC voltage allowed on the INA or INB_P/N pins is -0.3 to +3.0V, There is also the input de-rating curve for frequencies above 400MHz in figure 3.7, one of my customers is concerned about damage occurring form over-driving the ADC inputs. He expects the overdrive condition to be at a ~10% duty cycle.

Question: is there a maximum safe input value for the ADC input, somewhere between the 0dBFS input and the 3VDC absolute maximum upper limit?

Question, is so, is this value impacted by table 3.7 in the data sheet?

Question: Is table 3.7 implying that there will be performance degradation when operating above the curve, i.e. the slew rate is to fast, or that damage will occur?

Question: Assuming there is an acceptable amplitude higher than full scale, is there any recovery time associated with over-driving the input amplifier / ADC ?

Thanks

Respectfully

Richard

over 3 years ago

0 jim s over 3 years ago

TI__Guru* 91947 points

Richard,

We are looking into this. Why would they want to operate this device in saturation mode? The data will be seriously distorted.

Regards,

Jim

0 Richard Mountain51 over 3 years ago in reply to jim s

Prodigy 70 points

Hi Jim,

They don't,

Their signal of interest a fairly low amplitude, but it contains a high amplitude burst with a 10% duty cycle. They want to attenuate the signal just enough to protect the ADC from the high amplitude burst while maximizing the SNR on the wanted signal.

Thanks

Respectfully

Richard

0 jim s over 3 years ago in reply to Richard Mountain51

TI__Guru* 91947 points

Richard,

I am checking with the design team. It may take a few days before I get an answer.

Regards,

Jim

0 jim s over 3 years ago in reply to jim s

TI__Guru* 91947 points

Richard,

What will the current drive be on these inputs?

Regards,

Jim

0 Richard Mountain51 over 3 years ago in reply to jim s

Prodigy 70 points

Hi Jim,

If the DC input resistance looking into the ADC pin is 600-ohms to VCM, as shown in the data sheet Figure 58, Analog Input Network, then the maximum current would be limited to +/- 1.5mA

If the DC input resistance to VCM were 0-ohms, the maximum drive current would be limited to +/-7.9mA

Respectfully

Richard

0 jim s over 3 years ago in reply to Richard Mountain51

TI__Guru* 91947 points

Richard,

For a band limited signal, there is peak to average. Do you know what this peak power is and also what duration it is in lifetime?

Regards,

Jim

0 Richard Mountain51 over 3 years ago in reply to jim s

Prodigy 70 points

Hi Jim,

I still have not heard back from my customer,All I have is their questions, They wanted the damage point to know how much attenuation to dial in and whether the damage point is average power or peak power? The loud signals that they may see are probably <10% duty.

Richard

0 jim s over 3 years ago in reply to Richard Mountain51

TI__Guru* 91947 points

Richard,

I have not received any new info regarding this from design. I would suggest never exceeding the data sheet limits if you want to guarantee not damaging the device.

Regards,

Jim

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ADS54J60: input overdrive