AD7367 datasheet(18/28 Pages) AD

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AD7366/AD7367

Rev. 0 | Page 18 of 28

Unlike other bipolar ADCs, the AD7366/AD7367 do not have

a resistive analog input structure. On the AD73667/AD7366,

the bipolar analog signal is sampled directly onto the sampling

capacitor. This gives the AD7366/AD7367 high analog input

impedance. The analog input impedance can be calculated from

the following formula:

Z = 1/(fS × CS)

where:

fS is the sampling frequency.

CS is the sampling capacitor value.

CS depends on the analog input range chosen (see the Analog

Inputs section). When operating at 1 MSPS, the analog input

impedance is typically 260 kΩ for the ±10 V range. As the

sampling frequency is reduced, the analog input impedance

further increases. As the analog input impedance increases, the

current required to drive the analog input therefore decreases

(see Figure 7 for more information).

TYPICAL CONNECTION DIAGRAM

Figure 20 shows a typical connection diagram for the AD7366/

AD7367. In this configuration, the AGND pin is connected

to the analog ground plane of the system, and the DGND pin

is connected to the digital ground plane of the system. The

analog inputs on the AD7366/AD7367 accept bipolar single-

ended signals. The AD7366/AD7367 can operate with either

an internal or an external reference. In Figure 20, the AD7366/

AD7367 is configured to operate with the internal 2.5 V reference.

A 680 nF decoupling capacitor is required when operating with

the internal reference.

The AVDD and DVDD pins are connected to a 5 V supply voltage.

The VDD and VSS are the dual supplies for the high voltage analog

input structures. The voltage on these pins must be equal to

or greater than ±11.5 V (see Table 8 for more information). The

VDRIVE pin is connected to the supply voltage of the micro-

processor. The voltage applied to the VDRIVE input controls the

voltage of the serial interface. VDRIVE can be set to 3 V or 5 V.

AD7366/

AD7367

VDRIVE

10µF

0.1µF

+3V OR +5V SUPPLY

+11.5V TO +16.5V

SUPPLY

–16.5V TO –11.5V

SUPPLY

+5V SUPPLY

DVCC AVCC

BUSY

CNVST

REFSEL

VDRIVE

DCAPA

DCAPB

ADDR

ANALOG INPUTS ±10V,

±5V, AND 0V TO +10V

680nF

SCLK

DOUTA

DOUTB

DGND

AGND

VSS

VB1

VB2

VA1

VDD

VA2

10µF

0.1µF

10µF

0.1µF

SERIAL

INTERFACE

10µF

0.1µF

Figure 20. Typical Connection Diagram Using Internal Reference

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