ADC3561 datasheet(35/85 Pages) TI

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8.3.3.2 External voltage reference (VREF)

For highest accuracy and lowest temperature drift, the VREF input can be directly connected to an external 1.6V

reference. A 10 uF and a 0.1 uF ceramic bypass capacitor (CVREF) connected between the VREF and REFGND

pins and placed as close to the pins as possible is recommended. The load current from the external reference

is about 1mA.

Note: The internal reference is also used for other functions inside the device, therefore the reference amplifier

should only be powered down in power down state but not during normal operation.

xINP

xINM

VREF

(1.6V)

REFBUF

(1.2V)

REFGND

VREF1.2

VCM

0.95V

x1.33

CVREF

Reference

1.6V

Figure 8-19. External 1.6V reference

8.3.3.3 External voltage reference with internal buffer (REFBUF)

The ADC356x is equipped with an on-chip reference buffer that also includes gain to generate the 1.6V

reference voltage from an external 1.2V reference. A 10 uF and a 0.1 uF ceramic bypass capacitor (CVREF)

between the VREF and REFGND pins and a 10 uF and a 0.1 uF ceramic bypass capacitor between the

REFBUF and REFGND pins are recommended. Both capacitors should be placed as close to the pins as

possible. The load current from the external reference is less than 100uA.

xINP

xINM

VREF

(1.6V)

REFBUF

(1.2V)

REFGND

VREF1.2

VCM

0.95V

x1.33

CVREF

CREFBUF

Reference

1.2V

Figure 8-20. External 1.2V reference using internal reference buffer

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ADC3561, ADC3562, ADC3563

SBAS990B – FEBRUARY 2021 – REVISED OCTOBER 2022

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