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4.3.2. Guidelines: Connecting External Reference to the Agilex™ 5 Voltage Reference Pins
The Agilex™ 5 voltage sensor has two dedicated voltage reference pins, VREFP_ADC and VREFN_ADC. Follow these guidelines when you connect an external voltage reference to the VREFP_ADC and VREFN_ADC pins.
- To minimize noise coupling to the power rail, Altera recommends that you keep the external VREF source as close as possible to the VREFP_ADC and VREFN_ADC pins.
- Route the reference traces as a tightly-coupled differential pair to the package ball with ground shielding.
- You must place a 10 µF and a 1 µF board capacitors to decouple the VREFP_ADC and VREFN_ADC pins.
- Place the 1 µF board capacitor as close as possible to the package balls.
Figure 10. Board Capacitors to Decouple VREFP_ADC and VREFN_ADC Pins