AD7476AYRM Analog Devices Inc, AD7476AYRM Datasheet - Page 24

• Manufacturer Part Number: AD7476AYRM
• Description: IC ADC 12BIT 2.35V 1MSPS 8-MSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7476AYRM

• Rohs Status: RoHS non-compliant
• Design Resources: Output Channel Monitoring Using AD5380 (CN0008) AD5382 Channel Monitor Function (CN0012) AD5381 Channel Monitor Function (CN0013) AD5383 Channel Monitor Function (CN0015) AD5390/91/92 Channel Monitor Function (CN0030) Power off protected data acquisition signal chain using ADG4612 , AD711, and AD7476 (CN0165)
• Number Of Bits: 12
• Sampling Rate (per Second): 1M
• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 17.5mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• For Use With: EVAL-AD7476ACBZ - BOARD EVALUATION FOR AD7476AAD7476-DBRD - BOARD EVAL FOR AD7476AD7476A-DBRD - BOARD EVAL FOR AD7476A

AD7476A/AD7477A/AD7478A
To implement the power-down mode, set SLEN to 0111 to issue
an 8-bit SCLK burst. The connection diagram is shown in
Figure 29. The ADSP-218x has the TFS and RFS of the SPORT
tied together, with TFS set as an output and RFS set as an input.
The DSP operates in alternate framing mode, and the SPORT
control register is set up as described. The frame synchronization
signal generated on the TFS is tied to CS , and, as with all signal
processing applications, equidistant sampling is necessary.
However, in this example, the timer interrupt is used to control
the sampling rate of the ADC and, under certain conditions,
equidistant sampling may not be achieved.
The timer registers, for example, are loaded with a value that
provides an interrupt at the required sample interval. When an
interrupt is received, a value is transmitted with TFS/DT (ADC
control word). The TFS controls the RFS and, thus, the reading
of data. The frequency of the serial clock is set in the SCLKDIV
register. When the instruction to transmit with TFS is given,
that is, TX0 = AX0, the state of the SCLK is checked. The DSP
waits until the SCLK has gone high, low, and high before
transmission starts. If the timer and SCLK values are chosen
such that the instruction to transmit occurs on or near the
rising edge of SCLK, the data can be transmitted or it can wait
until the next clock edge. For example, the ADSP-2111 has a
master clock frequency of 16 MHz. If the SCLKDIV register is
loaded with the Value 3, an SCLK of 2 MHz is obtained and
eight master clock periods will elapse for every one SCLK
period. If the timer registers are loaded with the Value 803,
100.5 SCLKs occur between interrupts and, subsequently,
between transmit instructions. This situation results in
nonequidistant sampling as the transmit instruction is
occurring on an SCLK edge. If the number of SCLKs between
interrupts is a whole integer figure of N, equidistant sampling is
implemented by the DSP.
AD7476A/
AD7477A/
AD7478A
1
1
ADDITIONAL PINS OMITTED FOR CLARITY.
Figure 29. Interfacing to the ADSP-218x
SDATA
SCLK
CS
SCLK
DR
RFS
TFS
ADSP-218x
1
Rev. F | Page 24 of 28
AD7476A/AD7477A/AD7478A TO DSP563xx
INTERFACE
The connection diagram in Figure 30 shows how the
AD7476A/AD7477A/AD7478A 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 Control Register B, CRB) with
internally generated word length frame sync for both Tx and Rx
(Bit FSL1 = 0 and Bit FSL0 = 0 in CRB). Set the word length in
Control Register A (CRA) to 16 by setting Bit WL2 = 0, Bit
WL1 = 1, and Bit WL0 = 0 for the AD7476A. The word length
for the AD7478A can be set to 12 bits (WL2 = 0, WL1 = 0, and
WL0 = 1). This DSP does not offer the option for a 14-bit word
length, so the AD7477A word length is set up to 16 bits, the
same as the AD7476A. For the AD7477A, 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 AD7476A/AD7477A/
AD7478A, the word length can be changed to eight bits by setting
Bit WL2 = 0, Bit WL1 = 0, and Bit WL0 = 0 in CRA. The FSP
bit in the CRB register can be set to 1, meaning the frame goes
low and a conversion starts. Likewise, by means of the Bit SCD2,
Bit SCKD, and Bit SHFD in the CRB register, it establishes that
Pin SC2 (the frame sync signal) and Pin SCK in the serial port
are configured as outputs and the MSB is shifted first.
In summary:
MOD = 0
SYN = 1
WL2, WL1, and WL0 depend on the word length
FSL1 = 0 and FSL0 = 0
FSP = 1, negative frame sync
SCD2 = 1
SCKD = 1
SHFD = 0
Note that for signal processing applications, it is imperative that
the frame synchronization signal from the DSP563xx provide
equidistant sampling.
AD7476A/
AD7477A
AD7478A
1
1
SDATA
ADDITIONAL PINS OMITTED FOR CLARITY.
Figure 30. Interfacing to the DSP563xx
SCLK
CS
SCK
SRD
SC2
DSP563xx
1