Datasheet AD7708, AD7718 (Analog Devices) - 36

AD7708/AD7718 AD7708/AD7718-to-ADSP-2103/ADSP-2105 Interface BASIC CONFIGURATION
Figure 21 shows an interface between the AD7708/AD7718 and The basic connection diagram for the AD7708/AD7718 in 10- the ADSP-2103/ADSP-2105 DSP processor. In the interface channel mode is shown in Figure 22. This shows both the AVDD shown, the RDY bit of the Status Register is again monitored to and DVDD pins of the converters being driven from the analog determine when the Data Register is updated. The alternative 5 V supply. Some applications will have AVDD and DVDD driven scheme is to use an interrupt-driven system, in which case the from separate supplies. AVDD and DVDD can be operated inde- RDY output is connected to the IRQ2 input of the ADSP-2103/ pendently of each other, allowing the device to be operated with ADSP-2105. The serial interface of the ADSP-2103/ADSP-2105 5 V analog supply and 3 V digital supply or vice versa. The parts is set up for alternate framing mode. The RFS and TFS pins of can be operated in 8- or 10-channel configurations. In 8-channel the ADSP-2103/ADSP-2105 are configured as active low outputs mode the user has two reference input options. This allows the and the ADSP-2103/ADSP-2105 serial clock line, SCLK, is also user to operate some channels in ratiometric mode and others configured as an output. The CS for the AD7708/AD7718 is in absolute measurement mode. In 10-channel mode only one active when either the RFS or TFS outputs from the ADSP-2103/ reference option is available. An AD780/REF195, precision 2.5 V ADSP-2105 are active. The serial clock rate on the ADSP- reference, provides the reference source for the part. A quartz 2103/ADSP-2105 should be limited to 3 MHz to ensure correct crystal or ceramic resonator provides the 32.768 kHz master operation with the AD7708/AD7718. clock source for the part. In some cases, it will be necessary to connect capacitors on the crystal or resonator to ensure that it does not oscillate at overtones of its fundamental operating fre-
DVDD
quency. The values of capacitors will vary, depending on the
AD7708/ ADSP-2103 /
manufacturer’s specifications.
ADSP-2105 AD7718 RESET ANALOG 5V SUPPLY 10
␮
F 0.1
␮
F 0.1
␮
F RFS CS TFS 5V AV DV DD DD AIN1 RESET DR DOUT AIN2 CHIP AIN3 CS SELECT AD7708/ DT DIN AIN4 RECEIVE AD7718 DOUT (READ) AIN5 SCLK SCLK AIN6 SERIAL DIN DATA (WRITE) AIN7
Figure 21. AD7708/AD7718-to-ADSP-2103/ADSP-2105
SERIAL AIN8 SCLK
Interface
CLOCK AIN9 AIN10 P1 AINCOM P2 ANALOG 5V SUPPLY 10
␮
F REF1IN(+) MCLKIN 0.1
␮
F 32kHz CRYSTAL MCLKOUT REF1IN(–) VIN VOUT AD780 / REF195 AGND DGND GND
Figure 22. Basic Configuration for 10-Channel Mode –36– REV. 0