EVAL-AD7793

Rev. 0 | Page 3 of 16

EVALUATION BOARD HARDWARE

POWER SUPPLIES

The AD7793 evaluation board is powered via the 5 V supply

from the USB connector, J1. This 5 V supply can be used to

power the AD7793 directly. A 3.3 V regulated voltage from the

on-board ADP3303 (a high precision, low power, 3.3 V output

voltage regulator) can also be used. Alternatively, the AD7793 can

be powered using an external 3 V or 5 V power supply via J3.

LINKS

Seven link options must be set for the required operating setup

before using the evaluation board. The functions of these link

options are outlined in Table 1.

SETUP CONDITIONS

Care should be taken before applying power and signals to the

evaluation board to ensure that all link positions are set per the

required operating mode. Table 2 shows the position in which

all the links are initially set.

SOCKETS

There are five sockets relevant to the operation of the AD7793

on this evaluation board. The functions of these sockets are

outlined in Table 3.

Table 1. Evaluation Board Link Settings

Table 2. Initial Link and Switch Positions

Link No.

Position

Function

LK1

In

AIN1(+) and AIN1(−) are shorted.

LK2 to LK3

Out

Internal reference is used.

LK4 to LK5

Out

AIN2(+) and AIN2(−) are not connected to the temperature demonstration circuit.

LK6

Out

IOUT2 is not connected to the temperature demonstration circuit.

LK7

B

The 3.3 V supply is used as AVDD for the AD7793.

Table 3. Socket Functions

Link

Default

Description

LK1

In

This link is used to externally short AIN1(+) to AIN1(−). If VBIAS is enabled and directed to AIN1(−), a noise analysis

can be performed in this configuration. With this link out, an external voltage can be applied to AIN1(+)/AIN(−)

using the SMB connectors.

LK2 to LK6

Out

These links are used to connect the on-board temperature demonstration circuit to the ADC and must all be in

place when attempting to measure the ambient temperature.

When the on-board temperature demonstration circuit is selected in software, LK6 allows current from the

on-chip current source of the AD7793 to flow through the temperature demonstration circuit. When LK4 and

LK5 are in place, the 1 kΩ thermistor is connected to AIN2(+)/AIN2(−). When LK2 and LK3 are in place, the

5 kΩ precision resistor is used to generate the reference for the AD7793 so that a ratiometric configuration of

the temperature demonstration circuit is achieved.

LK7

B

LK7 is used to select the power source for AVDD on the AD7793. LK7 in Position A selects an external power

supply, supplied via J3. LK7 in Position B selects the 3.3 V regulated output from the on-board ADP3303 voltage

regulator. LK7 in Position C selects the 5 V supply from the USB connector, J1.

Socket

Description

AIN1+

Subminiature BNC (SMB) Connector. The analog input signal for the AIN1(+) input of the AD7793 is applied to this socket.

AIN1−

Subminiature BNC (SMB) Connector. The analog input signal for the AIN1(−) input of the AD7793 is applied to this socket.

REFIN1+

Subminiature BNC (SMB) Connector. This socket is used in conjunction with REFIN1− to apply an external reference to the

AD7793. The voltage for the REFIN(+) input of the AD7793 is applied to this socket.

REFIN1−

Subminiature BNC (SMB) Connector. This socket is used in conjunction with REFIN1+ to apply an external reference to the

AD7793. The voltage for the REFIN(−) input of the AD7793 is applied to this socket.

J2

16-Pin (2 × 8) Straight Header. This socket is used in conjunction with the prototype area to interface any signal to the AD7793.