8.2.2.2 Connecting the REFIN Pin

The reference input has a finite input impedance as shown in the Functional Block Diagram . Consider this

impedance when driving the REFIN pin from a high-impedance source. Connect a 100nF capacitor from

REFIN to GND2 to filter out high-frequency noise at the reference input. Figure 8-3 shows different options

for connecting the REFIN pin.

VDD2

OUT

REFIN

GND2

100nF

Reference voltage

RSOURCE

VDD2 supply

(3.3V or 5V)

VDD2

OUT

REFIN

GND2

100nF

VDD2 supply

(3.3V or 5V)

Consider finite

input impedance

VDD2

OUT

REFIN

GND2

R1

R2

+

–

Figure 8-3. Connecting the REFIN Pin

In the first example, REFIN is shorted to VDD2. In the second example, VREFIN is derived from VDD2 through a

buffered resistive divider. In the third example, an external voltage source drives the reference input pin.

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