AD7621 Analog Devices, AD7621 Datasheet - Page 26

• Manufacturer Part Number: AD7621
• Description: 16-Bit, 2 LSB INL, 3 MSPS PulSAR® ADC
• Manufacturer: Analog Devices

Specifications of AD7621

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 3MSPS
• Interface: Byte,Par,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

AD7621
MICROPROCESSOR INTERFACING
The AD7621 is ideally suited for traditional dc measurement
applications supporting a microprocessor, and ac signal
processing applications interfacing to a digital signal processor.
The AD7621 is designed to interface 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 AD7621 to prevent digital noise from coupling
into the ADC. The following section illustrates the use of the
AD7621 with an
SPI Interface (ADSP-219x)
Figure 42 shows an interface diagram between the AD7621 and
an SPI-equipped DSP, ADSP-219x. To accommodate the slower
speed of the DSP, the AD7621 acts as a slave device and data
must be read after conversion. This mode also allows the daisy-
chain feature. The convert command could be initiated in
response to an internal timer interrupt. The reading process can
be initiated in response to the end-of-conversion signal (BUSY
ADSP-219x
SPI-equipped DSP.
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going low) using an interrupt line of the DSP. The serial
peripheral interface (SPI) on the
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). It should be
noted that to meet all timing requirements, the SPI clock should
be limited to 17 Mb/s allowing it to read an ADC result in less
than 1 μs. When a higher sampling rate is desired, use one of
the parallel interface modes.
DVDD
Figure 42. Interfacing the AD7621 to SPI Interface
*ADDITIONAL PINS OMITTED FOR CLARITY
SER/PAR
EXT/INT
RD
INVSCLK
AD7621*
SDOUT
CNVST
BUSY
SCLK
CS
ADSP-219x
PFx
SPIxSEL (PFx)
MISOx
SCKx
PFx OR TFSx
ADSP-219x*
is configured for