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[FAQ] REF35: When do I need a reference buffer for my ADC?

Part Number: REF35
Other Parts Discussed in Thread: ADS127L21, REF54, REF4132, , REF70, REF6025, REF2025

It is unclear to me if I need a reference buffer on the output of my voltage reference before it connects to my ADC. How do I know when I may need to buffer the output of the voltage reference?

  • Hello,

    There are a couple reasons which may lead you to add a reference buffer on the output of an external voltage reference which attaches to your ADC:

    1. High ADC sampling rate. A high ADC sampling rate, especially with high resolution ADCs such as ADS127L21, typically leads to a higher current demand due to fast current transients as binary weighted bit decisions are made. A buffer with a low output impedance will help minimize voltage droop and settling errors that can occur between conversions. Generally, sampling rates that are several hundred kHz or above may need a buffer. There are voltage references available, like REF6025, which have an integrated reference buffer to help simplify your voltage reference drive topology. However, using any other voltage reference, such as REF54, REF35, REF34, REF33, REF4132, REF20, or REF70 with an external buffer can help maintain the high precision parameters of those voltage references so you don't have to sacrifice performance for functionality. 

    2. Driving multiple ADCs with one reference. The more ADCs that are sampling the reference pin, the more current will be needed to support the ADC sampling. Voltage references like REF2025 can source and sink up to 20 mA of current, but typically voltage references source up to 10 mA of current. Using a buffer to increase the amount of current that can be sourced can be important to maintaining a low gain error. 

    No matter the ADC, TI has multiple voltage reference options which can aid in your successful data acquisition design.