AN-718 APPLICATION NOTE One Technology Way P.O. Box 9106 Norwood, MA 02062-9106 Tel: 781/329-4700 Fax: 781/326-8703 www.analog.com ADuC7020 Evaluation Board Reference Guide MicroConverter ADuC7020 Development System by Aude Richard TABLE OF CONTENTS FEATURES Evaluation Board Overview ............................................. 1 Power Supply Evaluation Board Features............................................... 1 The user should connect the 9 V power supply via the DIP Switch Link Options................................................... 2 2.1 mm input power socket (J5). The input connector is External Connectors ......................................................... 3 configured as CENTER NEGATIVE, i.e., GND on the cen - Demonstration Circuit ...................................................... 4 ter pin and 9 V on the outer shield. Parts List ............................................................................ 5 This 9 V supply is regulated via a linear voltage regula- tor (U5). The 3.3 V regulator output is used to directly OVERVIEW drive the digital side of the board. The 3.3 V supply is The ADuC7020 evaluation board has the following also filtered, and is then used to supply the analog side features: of the board. 2-layer PCB (4 5 form factor) When on, the red LED (D3) indicates that a valid 3.3 V 9 V power supply regulated to 3.3 V on board supply is being driven from the regulator circuit. All active components are decoupled with 0.1 F at device 4-pin UART header to connect to RS232 interface supply pins to ground. cable RS232 Interface 20-pin standard JTAG connector to connect to ULINK The ADuC7020 (U1) P1.1 and P1.0 lines are connected emulator to the RS232 interface cable via connector (J1). The Demonstration circuit interface cable generates the required level shifting to 32.768 kHz watch crystal to drive the PLL clock allow direct connection to a PC serial port. Ensure that the cable supplied is connected to the board correctly, ADR291 2.5 V external reference chip i.e., DV is connected to DV , and DGND is connected DD DD Reset/Download/IRQ0 push-buttons to DGND. Power indicator/general-purpose LEDs Emulation Interface Access to all ADC inputs and DAC outputs from Nonintrusive emulation and download are possible on external header. All device ports are brought out to the ADuC7020 via JTAG by connecting the ULINK emula- external header pins. tor to the J4 connector. Surface-mount and through-hole general-purpose Crystal Circuit prototype area The board is fitted with a 32.768 kHz crystal from which the on-chip PLL circuit can generate a 45 MHz clock. Notes 1. This document refers to the MicroConverter ADuC7020 External Reference (ADR291) Evaluation Board Rev. A. The external 2.5 V reference chip (U2) has two functions. It is provided on the evaluation board to demonstrate the 2. All references in this document to physical orientation external reference option of the ADuC7020, but its main of components on the board are made with respect to a purpose is to generate the V voltage of the differen- OCM component side view of the board, with the prototype tial amplifier, if required. area appearing in the bottom of the board. Reset/Download/IRQ0 Push-Buttons 3. The board is laid out to minimize coupling between A RESET push-button is provided to allow the user to the analog and digital sections of the board. The ground manually reset the part. When inserted, the RESET pin of plane is split with the analog section on the left-hand the ADuC7020 is pulled to DGND. Because the RESET pin side and a digital plane on the right-hand side of the on the ADuC7020 is Schmitt-triggered internally, there is board. The regulated 3.3 V power supply is routed no need to use an external Schmitt trigger on this pin. directly to the digital section, and is filtered before being routed into the analog section of the board. When inserted, the IRQ0 push-button switch drives REV. 0AN-718 AN-718 P0.4/IRQ0 high. This can be used to initiate an external DIP SWITCH LINK OPTIONS interrupt 0. S1-1 V REF Function: Connects the output of the 2.5 V external To enter serial download mode, the user must pull the reference (ADR291) to the V pin (Pin 35) REF P0.0/BM pin low while reset is toggled. On the evalua- of the ADuC7020. tion board, serial download mode can be easily initiated by holding down the serial download push-button (S2) Use: Slide S1-1 to the ON position to connect the while inserting and releasing the reset button (S3), as external reference to the ADuC7020. illustrated in Figure 1. Slide S1-1 to the OFF position to use the in- Power Indicator/General-Purpose LEDs ternal 2.5 V reference or a different external A red power LED (D3) is used to indicate that a sufficient reference on the V pin of the J3 header. REF supply is available on the board. A general-purpose LED S1-2 V OCM (D2) is directly connected to P4.2 of the ADuC7020. When Function: Connects 1.67 V to the V pin of the OCM P4.2 is cleared, the LED is turned on when P4.2 is set, AD8132. No extra dc voltage is required the LED is turned off. on the board to use the ADC in differential Analog I/O Connections mode. All analog I/O connections are brought out on header J3. Use: Slide S1-2 to the ON position to connect ADC0 and ADC1 are buffered using an AD8606 to V of the differential amplifier to 1.67 V, OCM evaluate single-ended and pseudo differential mode. divided output of the ADR291 reference. A potentiometer can be connected to ADC0 buffered. Slide S1-2 to the OFF position to use a dif- ADC3 and ADC4 can be buffered with a single-ended- ferent voltage for V by connecting a dc OCM to-differential op amp on board, with the AD8132 used voltage to the V pin of the J3 header. OCM to evaluate the ADC in fully differential mode. Note that V value is dependent on refer- OCM ADC2 is not buffered. Be sure to follow the data sheet ence value, as shown in Table I. recommendations when connecting signals to this input. Table I. V Range OCM DAC1 can be used to control the brightness of the green V V min V max LED, D1, when connected via the S1 switch. REF OCM OCM 2.5 V 1.25 V 2.05 V General-Purpose Prototype Area 2.048 V 1.024 V 2.276 V A general-purpose prototype area is provided at the 1.25 V 0.75 V 2.55 V bottom of the evaluation board for adding external components as required in the users application. As can be seen from the layout, AV , AGND, V , and DGND DD DDIO tracks are provided in this prototype area. Figure 1. Entering Serial Download Mode on the Evaluation Board 2 REV. 0 REV. 0 3