AD7922ARMZ Analog Devices Inc, AD7922ARMZ Datasheet - Page 27

• Manufacturer Part Number: AD7922ARMZ
• Description: IC ADC 12BIT 1MSPS DUAL 8-MSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7922ARMZ

• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Operating Temperature: -40°C ~ 85°C
• Number Of Bits: 12
• Sampling Rate (per Second): 1M
• Number Of Converters: 1
• Power Dissipation (max): 20mW
• Voltage Supply Source: Single Supply
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Resolution (bits): 12bit
• Input Channel Type: Single Ended
• Supply Voltage Range - Analogue: 2.35V To 5.25V
• Supply Current: 4mA
• No. Of Pins: 8
• Sampling Rate: 1MSPS
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7922CBZ - BOARD EVAL FOR AD7922
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

For example, the ADSP-2189 has a master clock frequency of
40 MHz. If the SCLKDIV register is loaded with the value of 3,
then an SCLK of 5 MHz is obtained, and eight master clock
periods elapse for every one SCLK period. Depending on the
throughput rate selected, if the timer register is loaded with the
value 803 (803 + 1 = 804), then 100.5 SCLK occur between
interrupts and subsequently between transmit instructions. This
situation results in nonequidistant sampling, because the
transmit instruction occurs on a SCLK edge. If the number of
SCLKs between interrupts is a whole integer figure of N, then
equidistant sampling is implemented by the DSP.
AD7912/AD7922 to DSP563xx Interface
The connection diagram in Figure 41 shows how the AD7912/
AD7922 can be connected to the SSI (synchronous serial
interface) of the DSP563xx family of DSPs from Motorola. The
SSI is operated in synchronous and normal mode (SYN = 1 and
MOD = 0 in the Control Register B, CRB) with internally
generated word frame sync for both Tx and Rx (Bits FSL1 = 0
and FSL0 = 0 in the CRB). Set the word length in the Control
Register A (CRA) to 16 by setting bits WL2 = 0, WL1 = 1, and
WL0 = 0 for the AD7922. This DSP does not offer the option for
a 14-bit word length, so the AD7912 word length is set up to
16 bits like the AD7922. For the AD7912, the conversion process
uses 16 SCLK cycles, with the last two clock periods clocking
out two trailing zeros to fill the 16-bit word.
To implement the power-down mode on the AD7912/AD7922,
the word length can be changed to 8 bits by setting Bits
WL2 = 0, WL1 = 0, and WL0 = 0 in CRA. The FSP bit in the
CRB register can be set to 1, which means that the frame goes
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low and a conversion starts. Likewise, by means of the Bits
SCD2, SCKD, and SHFD in the CRB register, the Pin SC2 (the
frame sync signal) and SCK in the serial port are configured as
outputs, and the MSB is shifted first.
The values are as follows:
MOD = 0
SYN = 1
WL2, WL1, WL0 depend on the word length
FSL1 = 0, FSL0 = 0
FSP = 1, negative frame sync
SCD2 = 1
SCKD = 1
SHFD = 0
Note that, for signal processing applications, the frame
synchronization signal from the DSP563xx must provide
equidistant sampling.
*ADDITIONAL PINS REMOVED FOR CLARITY
AD7922*
AD7912/
DOUT
SCLK
DIN
CS
Figure 41. Interfacing to the DSP563xx
AD7912/AD7922
SCK
SRD
STD
SC2
DSP563xx*