EVAL-AD7124-4SDZ User Guide

UG-855

Rev. 0 | Page 7 of 29

POWER SUPPLIES

The evaluation board requires that an external power supply—

either a bench top supply or a wall wart (dc plug) supply—be

applied to J3 or J5 (see Table 3 for more information). Linear

regulators generate the required power supply levels from the

applied VIN rail. The regulators used are the ADP1720-3.3 (U7)

and the ADP1720 (U4), which supply 3.3 V and 1.8 V,

respectively, to AVDD of the ADC. The 3.3 V ADP1720 (U10)

delivers 3.3 V to the IOVDD pin of the AD7124-4.

When a split power supply is used, the AVSS voltage must be

applied from an external source via Connector J9. AVDD and

IOVDD can also be provided via Connector J9. However, the 7 V

to 9 V supply is still required because the on-board reference

(ADR4525) is supplied from this power supply.

Each supply is decoupled at the point where it enters the board

and again at the point where it connects to each device (see the

schematics shown in Figure 26 to Figure 29 to identify

decoupling points).

SERIAL INTERFACE

The EVAL-AD7124-4SDZ evaluation board connects via the

serial peripheral interface (SPI) to the Blackfin® ADSP-BF527

on the EVAL-SDP-CB1Z. There are four primary signals: CS,

SCLK, DIN, and DOUT/RDY (all are inputs, except for

DOUT/RDY, which is an output).

To operate the EVAL-AD7124-4SDZ in standalone mode, the

AD7124-4 serial interface lines can be disconnected from the

120-pin header by removing the 0 Ω links, R9 through R13. The

test points can then be used to fly-wire the signals to an alternative

digital capture setup.

ANALOG INPUTS

The EVAL-AD7124-4SDZ primary analog inputs can be applied

in two ways:

•

Using J6 and J11, the green screw in terminal connectors

•

Using the A0 and A1 SMB/SMA footprints on the

evaluation board, which connect to the AIN4 and AIN5

analog inputs.

The AD7124-4 EVAL+ Software is set up to analyze dc inputs to

the ADC.

Table 3. Required External Power Supply1

Power Supply

(VIN) Applied To

Voltage Range

Function

J3

7 V to 9 V

Bench top supply to the evaluation board. Supplies LDOs that create the 3.3 V and 1.8 V rails. It also

supplies the ADR4525 external reference. Ensure that LK2 is set to Position A when the external

power supply is applied to this connector.

J5

7 V to 9 V

Wall wart (dc plug) supply to the evaluation board. Supplies LDOs that create the 3.3 V and 1.8 V rails.

It also supplies the ADR4525 external reference. Ensure that LK2 is set to Position B when the external

power supply is applied to this connector.

1

Only a single supply is required, either J3 or J5. This supply can be selected using LK2.