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AD7380/AD7381

Data Sheet

Rev. 0 | Page 16 of 31

APPLICATIONS INFORMATION

Figure 31 shows an example of a typical application circuit for

the AD7380/AD7381. Decouple the VCC, VLOGIC, REGCAP, and

REFIO pins with suitable decoupling capacitors as shown.

The exposed pad is a ground reference point for circuitry on the

device and must be connected to the board ground.

A differential resistor capacitor (RC) filter must be placed on

the analog inputs to ensure performance is achieved.

The performance of the AD7380/AD7381 device may be

impacted by noise on the digital interface. This impact is

dependent on board layout and design. Keep a minimal

distance of the digital line to the digital interface or place a

100 Ω resistor in series and close to the SDOA pin and

SDOB pin to reduce noise from the digital interface coupling of

the AD7380/AD7381.

POWER SUPPLY

The AD7380/AD7381 have two independent power supplies,

VCC and VLOGIC, that supply the analog circuitry and digital

interface, respectively. Decouple both the VCC supply and the

VLOGIC supply separately with a 1 µF capacitor. Additionally,

there is an internal low dropout (LDO) regulator that supplies the

AD7380/AD7381. The on-chip regulator provides a 1.9 V

supply for internal use on the devices only. Decouple the

REGCAP pin with a 1 µF capacitor to GND.

Power-Up

The AD7380/AD7381 are robust to power supply sequencing.

VCC and VLOGIC can be applied in any sequence. An external

reference must be applied after VCC and VLOGIC are applied.

The AD7380/AD7381 require a tPOWERUP time from applying VCC

and VLOGIC until the ADC conversion results are stable.

Applying CS pulses or interfacing with the AD7380/AD7381

prior to the setup time elapsing does not have a negative impact

on ADC operation. Conversion results are not guaranteed to

meet data sheet specifications during this time, however, and

must be ignored.

AINA+

AINA–

AINB+

AINB–

VCC

VLOGIC

SDOB

SDOA

SDI

SCLK

GND

REFIO

3.3V

1µF

3Ω

330pF

68pF

330pF

68pF

3Ω

REGCAP

1µF

EXPOSED

PAD

1µF

REF

100Ω

AD7380/AD7381

Figure 31. Typical Application Circuit

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