Preliminary Technical Data

EVAL-AD5370/2/3EB

Rev. Pr

C | Page 3 of 12

GENERAL DESCRIPTION

FUNCTIONALITY OVERVIEW

The evaluation board for the AD537x is designed to allow the

user to fully evaluate all the functions and performance of the

AD537x prior to designing it into a system. The evaluation

board can be used in a stand-alone mode with the control

signals being provided through the 20 pin header J3 or it can be

connected to a PC using the USB cable supplied with the

evaluation board kit. Software is provided which allows the user

to program the various registers of the AD537x with ease. The

software operation is described later in this document.

POWER SUPPLIES

The evaluation board requires a +5V supply for DVCC. The VDD

and VSS supplies can be any value within the power supply

limits as specified in the AD537x data sheet. Power supply

connections are made to the screw terminals of J2. The USB

interface, if used, gets its power supply from the USB port of the

PC. This power supply is not used by the AD537x or any of its

associated circuitry. When connecting the power supply leads it

is recommended that the supplies are turned off and that the

ground leads are connected first.

REFERENCE SELECTION

The evaluation board includes two voltage references ICs, the

ADR435 and ADR423 which are 5V and 3V references

respectively. An SMB connector is provided to allow an external

voltage to be connected for use as a reference. Link LK4 is used

to select which reference source is used by the AD537x as

shown in Table 1.

Table 1. Reference Selection using LK4

LK4

Position

Description

A

The reference voltage is 3V (default)

B

The reference voltage is 5V

C

The voltage on the SMB, EXT_REF is used as the

reference voltage

By default the voltage reference pins of the AD537x, VREF0 and

VREF1, both use the same reference, i.e. that selected by LK4. If

it is required that the reference pins should use different voltage

references this can be achieved by removing the 0Ω resistor

associated with each VREF pin. The required reference can then

be connected to the testpoint associated with the VREF pin.

Table shows the 0Ω resistor and testpoint associated with each

VREF pin.

Table 2. 0Ω Resistor and Testpoints for VREF pins

VREF

Resistor

Testpoint

VREF0

R17

T63

VREF1

R18

T64

USING THE USB INTERFACE

The software provided with the evaluation board kit allows the

user to program the registers of the AD537x via the USB

interface. It is important that the software supplied is installed

on the PC before the board is connected. See the Using the USB

Software section for more information. The USB circuitry gets

its power from the USB port of the PC and will generate the

required interface signals, RESET, CLR, SYNC, SCLK etc. to

control the AD537x. To use the interface LK1, LK3 and LK8

should be in place. The function of these links is described in

Table 4.

STAND-ALONE OPERATION

The evaluation board can be used as a stand-alone device if

required. This has the advantage that it lets the user to connect

the interface pins of the AD537x to their own DSP or micro-

controller thus allowing them to write code to operate the

AD537x as their application requires. To use the board in stand-

alone mode the connection to the USB interface must be

removed. This is achieved by removing LK1, which will three-

state the connections to CLR, LDAC, SYNC, SCLK and DIN. LK3

should be removed to isolate the RESET pin from the USB

interface and the push-button. The interface signals required to

control the AD537x can then be provided through the 20 pin

header J3. The pinout of J3 is shown in Table 3

Table 3. J3 Header Pinout

Pin

Signal

Pin

Signal

1

DIN

8

LDAC

2

NC

10

CLR

3

SCLK

12

BUSY

4

NC

14

RESET

5

NC

16

NC

6

SYNC

18

NC

7,9,11,13,

15,17,19,20

DGND