Analog Input Common-Mode Voltage Range

Hi mcoopwood 

Thanks for your interest in AD6641.

The AD6641 input structure includes internal buffers and biasing optimized for a common-mode voltage of approximately 1.8 V. While the absolute maximum rating specifies AVDD + 0.2 V (≈ 2.1 V), this limit applies to sustained DC levels. The brief signal peaks during normal operation are accounted for in the design and do not damage the device. Here’s why this works:

• The Vicm = 1.8 V is the recommended operating point for best linearity and performance.
• The input buffer can tolerate small excursions beyond AVDD without functional issues because of internal protection mechanisms.
• Lowering Vicm would reduce headroom and degrade performance, so the datasheet specifies 1.8 V as typical.

In short, the ADC is designed to handle this swing safely. The absolute maximum rating is a conservative limit for continuous voltage, not transient signal peaks.

Hello JAlipio,

Thank you for providing that context.  My application is DC coupled.  My max input signal level is 1.6Vpp (differential).  What input common mode voltage do you recommend?  Can you provide a recommended input common mode voltage range?