AD7729ARU Analog Devices Inc, AD7729ARU Datasheet - Page 14

• Manufacturer Part Number: AD7729ARU
• Description: IC ADC 15BIT DUAL W/DAC 28-TSSOP
• Manufacturer: Analog Devices Inc
• Type: ADC, DACr

Specifications of AD7729ARU

• Rohs Status: RoHS non-compliant
• Resolution (bits): 15 b
• Sampling Rate (per Second): 270.8k
• Data Interface: Serial
• Voltage Supply Source: Analog and Digital
• Voltage - Supply: 3V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 28-TSSOP

AD7729
Bit
BCRB0
BCRB1
BCRB2
BCRB3
BCRB4
BCRB5
BCRB6
BCRB7
BCRB8
BCRB9
Bit
ACRA0
ACRA1
ACRA2
ACRA3
ACRA4
ACRA5
ACRA6
ACRA7
ACRA8
ACRA9
Bit
ACRB0
ACRB1
ACRB2
ACRB3
ACRB4
ACRB5
ACRB6
ACRB7
ACRB8
ACRB9
Writing Over the Baseband (or Auxiliary) SPORT
Writing to and reading from registers via the SPORT involves
the transfer of 16 bit words, 10 bits of data and 6 bits of address
(with the exception of the Rx data). The frame format is as
shown in Figure 19, Bit 15 being the first input bit of the frame.
The destination of the 10-bit data is determined by the 6-bit
destination address as indicated in Figure 19. Note that some
registers are read only and, hence, cannot be written to.
Table VIII. Baseband Control Register B (BCRB)
Table IX. Auxiliary Control Register A (ACRA)
Table X. Auxiliary Control Register B (ACRB)
Name
Reserved
Reserved
RU
LP
RxSPORTSEL
Reserved
Reserved
Reserved
Reserved
Reserved
Name
Reserved
Reserved
AUXDACON
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Name
ARESET
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Function
Power On for Auxiliary DAC
Function
Resets the Auxiliary Converter
Function
REFOUT Use.
Reference Low Power.
Selects the SPORT
that will provide
RxDATA when RxON is
asserted. When set to 0,
the BSPORT is selected
and, when set to 1, the
ASPORT is selected.
–14–
Reading Over the Baseband (or Auxiliary) SPORT
To read the contents of a register, the address of the appropriate
register is written to the read address register, ARDADDR or
BRDADDR. The time interval between writing to the read
address register and the frame synchronization signal becoming
active equals 4 MCLK cycles. The read address register is
6 bits wide and Bits D11 to D6 of the input frame are used to
write to this register, Bits D12 to D15 being don’t cares, as
shown in Figure 20. The frame format for reading is identical to
that for writing i.e., 10 bits of data followed by 6 address bits
corresponding to the source address of the data (with the excep-
tion of the Rx data).
Receiving RxDATA
The Rx ADC is activated by taking either the RxON bit or the
RxON pin high. In this mode, Rx data is automatically output
on the SDO pin of the SPORT at a word rate of 270 kHz for
each of I and Q, after a delay of T1 + T2 + T3 (see Figure 16).
The data format is I followed by Q. The AD7729 will output
16 bits of data, the 15-bit I or Q word, which is in twos comple-
ment format, and a flag bit. This flag bit (LSB) distinguishes
between the I and Q words, the bit being at 0 when the word
being output is an I word while this bit is at 1 when the output
is a Q word.
When RxON is taken high, the serial clock will have a frequency
of 13 MHz, irrespective of the value in the clock rate register.
When the AD7729 is ready to output Rx data, an output frame
synchronization signal is generated and the Rx data is automati-
cally output on the SDO pin, an I and Q word being output
every 48 MCLK cycles (see Figure 17). Data can be output on
the ASPORT or the BSPORT, bit RxSPORTSEL in control
register BCRB being used to select the SPORT. Rx data can be
received on one SPORT only, the user cannot interchange from
one SPORT to the other.
MICROPROCESSOR INTERFACING
The AD7729 has a standard serial interface which allows the
user to interface the part to several DSPs. In all cases, the
AD7729 operates as the master with the DSP acting as the
slave. The AD7729 provides its own serial clock to clock the
serial data/control information to/from the DSP.
AD7721-to-ADSP-21xx Interface
Figure 21 shows the AD7729 interface to the ADSP-21xx. For
the ADSP-21xx, the bits in the serial port control register
should be set up as TFSR = RFSR = 1 (a frame sync is needed
for each transfer), SLEN = 15 (16-bit word length), TFSW =
RFSW = 0 (normal framing), INVTFS = INVRFS = 0 (active
high frame sync signals), IRFS = 0 (external RFS), ITFS = 1
(internal TFS) and ISCLK = 0 (external serial clock).
DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 A5
15
15
X
14
14
Figure 20. Writing to the Read Address Register
(BRDADDR Shown Here)
X
Figure 19. Write Operation Frame Format
13
13
X
12
12
X
RA5 RA4 RA3 RA2 RA1 RA0
11
11
10
10
9
9
8
8
7
7
6
6
5
5
0
A4
4
4
0
A3
3
3
1
A2
2
2
0
A1
1
REV. 0
1
1
A0
0
0
0