AD6620S/PCB Analog Devices Inc, AD6620S/PCB Datasheet - Page 19

• Manufacturer Part Number: AD6620S/PCB
• Description: BOARD EVAL DUAL RCVR W/AD6620AS
• Manufacturer: Analog Devices Inc

Specifications of AD6620S/PCB

• Rohs Status: RoHS non-compliant
• Module/board Type: Evaluation Board
• For Use With/related Products: AD6620

Figure 31 shows two AD6620s illustrating the cascade capability
for the chip. The first is connected as a serial master and the
second is configured in serial cascade mode. The SDFE signal
of the master is connected to the SDFS of the slave. This allows
the master AD6620 data to be obtained first by the DSP, fol-
lowed by the cascaded AD6620 data.
The AD6620 also supports a serial slave mode, where the serial
clock and interface is provided by a DSP or ASIC that is set to
operate in the master mode. Note that the AD6620 cannot be
booted through the serial port. The microport must be used to
initialize the device, then serial operation is supported.
In the serial slave mode, DV
ence of a new word in the output buffers of the shift register.
This pin may thus be used by the DSP to generate an interrupt
to service the serial port. The DSP then generates an SFDS
pulse to drive the AD6620. The first serial clock rising edge
CASCADE
2
2
2
WL
WL
WL
AD6620
AD6620
AD6620
AD
AD
AD
+3.3V
+3.3V
SBM
SBM
SBM
4
4
4
SDIV
SDIV
SDIV
SCLK
SDFS
SDFE
SCLK
SCLK
SDFS
SDFE
SDFS
SDFE
SDO
SDO
SDO
SDI
SDI
SDI
10k
OUT
is valid and indicates the pres-
10k
SCLK
DT
DR
RFS
SCLK
DT
DR
RFS
10k
DSP
DSP
10k
after SDFS makes the first bit available at SDO. The falling
edge of serial clock can be used to sample the data. The total
number of bits are then read from the AD6620 (determined by
the serial port word length). If the DSP has the ability to count
bits, the DSP will know when the complete frame is read. If not,
the DSP can monitor the SDFE pin to determine that the com-
plete frame is read. The serial clock provided by the DSP can be
asynchronous with the AD6620 clock and input data.
In either the serial master or slave mode, there are two con-
straints that must be observed. The first is that the clock must
be fast enough to read the serial frame prior to the next frame
becoming available. Since the AD6620 output is synchronous
with its input sample rate, the output update rate can be deter-
mined by the user-programmed decimation rate. The timing
diagram in Figure 33 details how serial slave mode is imple-
mented. The second constraint is that the time between serial
frames may be either zero SCLK periods (the end of one frame
adjoins the beginning of the next) or two or more SCLK peri-
ods. One SCLK period between frames is not allowed.
FREQUENCY TRANSLATOR
The first signal processing stage is a frequency translator con-
sisting of two multipliers and a 32-bit complex numerically
controlled oscillator (NCO). The NCO serves as a quadrature
local oscillator capable of producing any analytic frequency
between –f
the Single Channel Real input mode, f
plied by the fraction of CLK cycles that A/B is high. In the
Diversity Channel Real and Single Channel Complex input
DV
SCLK
SDFS
SDO
OUT
DSP USES FALLING EDGE OF
DV
2
WL
OUT
AD6620
SBM
SAMP
TO GENERATE SDFS
AD
FIRST DATA IS AVAILABLE THE FIRST
RISING SCLK AFTER SDFS GOES HIGH
/2 and +f
DV
4
SDIV
OUT
SCLK
SDFS
SDFE
SDO
SDI
SAMP
10k
/2 with a resolution of f
t
10k
DSO
DV
SINGLE CHANNEL AND 4 CLKIN
DUAL CHANNEL
SAMP
OUT
SCLK
DT
DR
RFS
PULSEWIDTH IS 2 CLKIN
is equal to f
IRQ
AD6620
DSP
I
MSB
SAMP
CLK
I
MSB – 1
/2
multi-
32
. In