ADS8699IPWR datasheet(27/74 Pages) TI2

27 / 74 page

7.3.7.1 Internal Reference

The device features an internal reference source with a nominal output value of 4.096 V. In order to select the

internal reference, the INTREF_DIS bit of the RANGE_SEL_REG register must be programmed to logic 0. When

the internal reference is used, the REFIO pin becomes an output with the internal reference value. A 4.7-µF

(minimum) decoupling capacitor is recommended to be placed between the REFIO pin and REFGND, as shown

in Figure 7-7. The capacitor must be placed as close to the REFIO pin as possible. The output impedance of the

internal band-gap circuit creates a low-pass filter with this capacitor to band-limit the noise of the reference. The

use of a smaller capacitor value allows higher reference noise in the system that can potentially degrade SNR

and SINAD performance. The REFIO pin must not be used to drive external ac or dc loads because of limited

current output capability. The REFIO pin can be used as a source if followed by a suitable op amp buffer (such

as the OPA320).

ADC

4.096 VREF

REFCAP

REFIO

AGND

10 PF

REFGND

4.7 PF

AVDD

1 PF

RANGE_SEL_REG[6] = 0

(INTREF_DIS)

Figure 7-7. Device Connections for Using an Internal 4.096-V Reference

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ADS8691, ADS8695, ADS8699

SBAS777B – DECEMBER 2016 – REVISED MARCH 2021

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ADS8699IPWR Datasheet(PDF) 27 Page - Texas Instruments