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ADS8380

REFM

REFIN

REFOUT

AGND

0.1 mF

1 mF

ADS8380

REFM

REFIN

REFOUT

AGND

0.1 mF

1 mF

External

Reference

ADS8380

AGND

+VA

_

+

53 W

53 W

40 pF

40 pF

+IN

−IN

AGND

ANALOG INPUT

ADS8380

SLAS387A – NOVEMBER 2004 – REVISED DECEMBER 2004

PRINCIPLES OF OPERATION (continued)

Figure 48. ADS8380 Using Internal Reference

The REFIN pin is also internally buffered. This eliminates the need to put a high bandwidth buffer on the board

to drive the ADC reference and saves system area and power. When an external reference is used, the

reference must be of low noise, which may be achieved by the addition of bypass capacitors from the REFIN pin

to the REFM pin. See Figure 49 for operation of the ADS8380 with an external reference. REFM must be

connected to the analog ground plane.

Figure 49. ADS8380 Using External Reference

Figure 50. Simplified Analog Input

When the converter enters hold mode, the voltage difference between the +IN and –IN inputs is captured on the

The input current on the analog inputs depends upon throughput and the frequency content of the analog input

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