Datasheet
Preliminary Technical Data EVAL-AD5371EB
Rev. Pr A| Page 3 of 12
GENERAL DESCRIPTION
FUNCTIONALITY OVERVIEW
The evaluation board for the AD5371 is designed to allow the
user to fully evaluate all the functions and performance of the
AD5371 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 AD5371 with ease. The
software operation is described later in this document.
POWER SUPPLIES
The evaluation board requires a +5V supply for DV
CC
. The V
DD
and V
SS
supplies can be any value within the power supply
limits as specified in the AD5371 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 AD5371 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 AD5371 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 AD5371, VREF0,
VREF1 and VREF2, all 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 R16 T62
VREF1 R17 T63
VREF2 R18 T64
USING THE USB INTERFACE
The software provided with the evaluation board kit allows the
user to program the registers of the AD5371 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 AD5371. To use the interface LK1, LK3 and LK8
should be in place. The function of these links is described in
Table 4. LK2 should be in position A to select the SPI interface
which is required for USB operation.
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 AD5371 to their own DSP or micro-
controller thus allowing them to write code to operate the
AD5371 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 AD5371 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
DIN
10
CLR
3 SCLK 12
BUSY
4
SCLK
14
RESET
5 SYNC 16 TEST_IP
1
6
SYNC
18 TEST_OP
1
7,9,11,13,
15,17,19,20
DGND
1
These are test pins and should not be used