AN-744
APPLICATION NOTE
One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106 • Tel: 781/329-4700 • Fax: 781/326-8703 •
www.analog.com
TABLE OF CONTENTS
Evaluation Board Overview.......................................... 1
Evaluation Board Features........................................... 1
DIP Switch Link Options............................................... 2
External Connectors.................................................... 3
External Memory Interface.......................................... 5
Potentiometer Demonstration Circuit ......................... 6
Schematic.................................................................... 7
Parts List ..................................................................... 9
OVERVIEW
The ADuC7026 evaluation board has the following
features:
• 2-Layer PCB (4”
5” form factor)
• 9 V power supply regulated to 3.3 V on board
• 4-pin UART header to connect to RS-232 interface
cable
• 20-pin standard JTAG connector to connect to ULINK
emulator
• Demonstration circuit
• 32.768 kHz watch crystal to drive the PLL clock
• ADR291 2.5 V external reference chip
• Reset/Download/IRQ0 push-buttons
• Power indicator/general-purpose LEDs
• Access to all ADC inputs and DAC output from external
header. All device ports are brought out to external
header pins.
• Surface-mount and through hole general-purpose
prototype area
• External memory and latch footprint
Notes
1. This document refers to the MicroConverter ADuC7026
Eval Board, Rev. A1.
2. All references in this document to physical orientation
of components on the board are made with respect to
a component side view of the board with the prototype
area appearing in the bottom of the board.
3. The board is laid out to minimize coupling between the
analog and digital sections of the board. To this end, the
ground plane is split with the analog section on the left-
ADuC7026 Evaluation Board Reference Guide
by Aude Richard
hand side and a digital plane on the right-hand side of
the board. The regulated 3.3 V power supply is routed
directly to the digital section and is filtered before being
routed into the analog section of the board.
FEATURES
Power Supply
The user should connect the 9 V power supply via the
2.1 mm input power socket (J5). The input connector
is configured as CENTER NEGATIVE, i.e., GND on the
center pin and +9 V on the outer shield.
This 9 V supply is regulated via a linear voltage regulator
(U5). The 3.3 V regulator output is used to drive the digital
side of the board directly. The 3.3 V supply is also filtered
and then used to supply the analog side of the board.
When on, the red LED (D3) indicates that a valid 3.3 V
supply is being driven from the regulator circuit. All
active components are decoupled with 0.1
F at device
supply pins to ground.
RS-232 Interface
The ADuC7026 (U1) P1.1 and P1.0 lines are connected to
the RS-232 interface cable via connector (J1). The interface
cable generates the required level shifting to allow direct
connection to a PC serial port. Ensure that the cable
supplied is connected to the board correctly, i.e., DVDD is
connected to DVDD and DGND is connected to DGND.
Emulation Interface
Nonintrusive emulation and download are possible on the
ADuC7026 via JTAG by connecting the ULINK emulator to
the J4 connector.
Crystal Circuit
The board is fitted with a 32.768 kHz crystal, from which
the on-chip PLL circuit can generate a 45 MHz clock.
External Reference (ADR291)
The external 2.5 V reference chip (U2) has two functions.
It is provided on the evaluation board to demonstrate the
external reference option of the ADuC7026, but its main
purpose is to generate the V
OCM
voltage of the differential
amplifier, if required.
Reset/Download/IRQ0 Push-buttons
A RESET push-button is provided to allow the user to
manually reset the part. When inserted, the RESET pin
of the ADuC7026 will be pulled to DGND. Because the
REV. 0
