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# ADC10080: Vcom variation and common mode input range

Other Parts Discussed in Thread: LMH6551,

Hi,

Earlier, I made a similar post. And I closed the thread and created a new one.

According to the data sheet,
Vcm = 0.5 to 1.5Vmax.
For 2Vpp differential input, each input signal is Vcom +/- 0.5V. In other words, is the limit of each analog input PIN 0 to 2.0V?

The customer wants to use the Vcom of the ADC to drive the VCM of the LMH6551.

Question
1. The maximum value of the analog input voltage is Abs maximam ratings = VDDA-0.3V. Does differential 2Vpp input work properly under these conditions?
Or is it limited to 0 to 2.0V?
According to Figure 39, the input voltage range might be 2.5Vmax. However, the condition of VDDA is unknown.

2. When Vcom of ADC10080 is connected to Vcm of LMH6551, is operation guaranteed in the temperature range of -40 to 85 ° C (2 Vpp differential)?
Or do you have any information about Vcom of ADC10080 such as histogram and temperature characteristics?

Customers are concerned that the Vcom of the ADC10080 will overrange the analog input due to environmental and variability.

Best regards,
Hiroshi

• Hiroshi,

We are looking  into this.

Regards,

Jim

• Hi Hiroshi,

In the datasheet, there is a difference between V_CM and V_COM. V_CM is the acceptable range of the common mode voltage (0.5 to 1.5V) on the analog input pins. V_COM is the output voltage (1.45) that is present on the V_COM pin that can be applied to the LMH6551.

For 2Vpp differential input, each input signal is Vcom +/- 0.5V. In other words, is the limit of each analog input PIN 0 to 2.0V?

With a differential input, each input (V_IN- and V_IN+) has a 1 Vpp swing which will sum to 2 Vpp differential. See table on page 3 (pin description) and figure 39 on page 17.

1.The maximum value of the analog input voltage is Abs maximam ratings = VDDA-0.3V. Does differential 2Vpp input work properly under these conditions?

Or is it limited to 0 to 2.0V?
According to Figure 39, the input voltage range might be 2.5Vmax. However, the condition of VDDA is unknown.

The 2.5V max for the analog input does not scale with the value of VDDA. This has more to do with the value of VREF (1.2V), not VDDA.

2. When Vcom of ADC10080 is connected to Vcm of LMH6551, is operation guaranteed in the temperature range of -40 to 85 ° C (2 Vpp differential)?
Or do you have any information about Vcom of ADC10080 such as histogram and temperature characteristics?

There are not any additional temperature resources for the ADC10080. The temperature plots that are available in the datasheet, shows how performance is effected across temperature with an external VREF. If temperature stability is critical for your application, I would suggest using a very stable external voltage reference.

Best Regards,

Dan

• Hi Dan,