AD7661 Analog Devices, AD7661 Datasheet - Page 26

• Manufacturer Part Number: AD7661
• Manufacturer: Analog Devices

Specifications of AD7661

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 100kSPS
• Interface: Par,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p,2.5V p-p,Uni (Vref),Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

AD7661
MICROPROCESSOR INTERFACING
The AD7661 is ideally suited for traditional dc measurement
applications supporting a microprocessor, and for ac signal
processing applications interfacing to a digital signal processor.
The AD7661 is designed to interface either with a parallel 8-bit
or 16-bit wide interface, or with a general-purpose serial port or
I/O ports on a microcontroller. A variety of external buffers can
be used with the AD7661 to prevent digital noise from coupling
into the ADC. The following section discusses the use of an
AD7661 with an ADSP-219x SPI equipped DSP.
SPI Interface (ADSP-219x)
Figure 44 shows an interface diagram between the AD7661 and
the SPI equipped ADSP-219x. To accommodate the slower
speed of the DSP, the AD7661 acts as a slave device and data
must be read after conversion. This mode also allows the daisy-
chain feature. The convert command can be initiated in
response to an internal timer interrupt. The reading process can
be initiated in response to the end-of-conversion signal (BUSY
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going LOW) using an interrupt line of the DSP. The serial inter-
face (SPI) on the ADSP-219x is configured for master mode—
(MSTR) = 1, Clock Polarity bit (CPOL) = 0, Clock Phase bit
(CPHA) = 1, and SPI Interrupt Enable (TIMOD) = 00—by
writing to the SPI control register (SPICLTx). To meet all timing
requirements, the SPI clock should be limited to 17 Mbps,
which allows it to read an ADC result in less than 1 µs. When a
higher sampling rate is desired, use of one of the parallel
interface modes is recommended.
DVDD
SER/PAR
EXT/INT
RD
INVSCLK
Figure 44. Interfacing the AD7661 to an SPI Interface
AD7661*
* ADDITIONAL PINS OMITTED FOR CLARITY
SDOUT
CNVST
BUSY
SCLK
CS
SPIxSEL (PFx)
PFx
MISOx
SCKx
PFx or TFSx
ADSP-219x*