AD7923 Analog Devices, AD7923 Datasheet - Page 21

• Manufacturer Part Number: AD7923
• Description: 4-Channel 200 kSPS, 12-Bit A/D Converter with Sequencer in 16-Lead TSSOP
• Manufacturer: Analog Devices

Specifications of AD7923

• Resolution (bits): 12bit
• # Chan: 4
• Sample Rate: 200kSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni (Vref) x 2
• Adc Architecture: SAR
• Pkg Type: SOP

MICROPROCESSOR INTERFACING
The serial interface on the AD7923 allows the part to be directly
connected to a range of many different microprocessors. This
section explains how to interface the AD7923 with some of the
more common microcontroller and DSP serial interface protocols.
AD7923-to-TMS320C541
The serial interface on the TMS320C541 uses a continuous
serial clock and frame synchronization signals to synchronize
the data transfer operations with peripheral devices like the
AD7923. The CS input allows easy interfacing between the
TMS320C541 and the AD7923 without any glue logic required.
The serial port of the TMS320C541 is set up to operate in burst
mode with internal CLKX0 (Tx serial clock on Serial Port 0)
and FSX0 (Tx frame sync from Serial Port 0). The serial port
control register (SPC) must have the following setup: FO = 0,
FSM = 1, MCM = 1, and TXM = 1. The connection diagram is
shown in Figure 29. It should be noted that for signal processing
applications, it is imperative that the frame synchronization
signal from the TMS320C541 provides equidistant sampling.
The V
the TMS320C541. This allows the ADC to operate at a higher
voltage than the serial interface, that is, the TMS320C541, if
necessary.
DRIVE
DOUT
SCLK
DIN
CS
pin of the AD7923 takes the same supply voltage as
THREE-
STATE
t
t
2
3
ZERO
WRITE
1
ZERO
SEQ1
t
9
DOUT
SCLK
2
2 IDENTIFICATION
ADD1
DIN
CS
DONTC
BITS
3
ADD0
t
4
1
DONTC
VALID DATA
4
DB11
16
ADD1
t
Figure 27. Serial Interface Timing Diagram
6
Figure 28. General Timing Diagram
5
t
DB10
7
t
CONVERT
t
ADD0
CYCLE
t
Rev. C | Page 21 of 24
10
6
5s MIN
11
1
POWER-UP
DB4
CODING
AD7923-to-ADSP-21xx
The ADSP-21xx family of DSPs is interfaced directly to the
AD7923 without any glue logic required. The V
AD7923 takes the same supply voltage as the ADSP-218x,
which allows the ADC to operate at a higher voltage than the
serial interface, that is, ADSP-218x, if necessary.
The SPORT0 control register should be set up as follows:
TFSW = RFSW = 1, alternate framing
INVRFS = INVTFS = 1, active low frame signal
DTYPE = 00, right justify data
SLEN = 1111, 16-bit data-words
ISCLK = 1, internal serial clock
TFSR = RFSR = 1, frame every word
IRFS = 0
ITFS = 1
1
ADDITIONAL PINS REMOVED FOR CLARITY.
12
AD7923
16
DB3
DONTC
DOUT
SCLK
V
13
DRIVE
1
DIN
CS
DB2
Figure 29. Interfacing to the TMS320C541
DONTC
1
VALID DATA
t
QUIET
B
14
t
5
MIN
DB1
DONTC
16
15
t
DB0
8
DONTC
16
t
11
THREE-
STATE
t
QUIET
CLKX
CLKR
DR
DT
FSX
FSR
TMS320C541
DRIVE
V
DD
pin of the
AD7923
1