AD7920BRMZ Analog Devices Inc, AD7920BRMZ Datasheet - Page 21

• Manufacturer Part Number: AD7920BRMZ
• Description: IC ADC 12BIT 250KSPS 8-MSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7920BRMZ

• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Bits: 12
• Sampling Rate (per Second): 250k
• Number Of Converters: 1
• Power Dissipation (max): 15mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Resolution (bits): 12bit
• Sampling Rate: 250kSPS
• Input Channel Type: Differential
• Supply Current: 3mA
• Digital Ic Case Style: SOP
• No. Of Pins: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7920CBZ - BOARD EVALUATION FOR AD7920
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

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
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.
AD7910/AD7920 TO DSP563xx INTERFACE
The diagram in Figure 27 shows how the AD7910/AD7920 can
be connected to the synchronous serial interface (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 frame sync for both Tx and Rx (Bit
FSL1 = 0 and Bit 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 AD7920. This DSP does not
offer the option for a 14-bit word length, so the AD7910 word
length is set to 16 bits like the AD7920. For the AD7910, 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 AD7910/AD7920,
the word length can be changed to eight 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 the frame goes low
and a conversion starts. Likewise, by means of Bits SCD2,
SCKD, and SHFD in the CRB register, it is established that Pin
SC2 (the frame sync signal) and SCK in the serial port is
configured as outputs and the MSB is shifted first.
Rev. C | Page 21 of 24
To summarize:
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
It should be noted that for signal processing applications, it is
imperative that the frame synchronization signal from the
DSP563xx provides equidistant sampling.
AD7910/AD7920*
*ADDITIONAL PINS OMITTED FOR CLARITY
SDATA
Figure 27. Interfacing to the DSP563xx
SCLK
CS
AD7910/AD7920
SCK
SRD
SC2
DSP563xx*