AD7607_16 Datasheet, PDF (26/33 Pages) Analog Devices – 8-Channel DAS with 14-Bit, Bipolar Input, Simultaneous Sampling ADC

Data Sheet
Figure 42 shows a read of eight simultaneous conversion results
using two DOUT lines on the AD7607. In this case, a 56 SCLK
transfer is used to access data from the AD7607, and CS is held
low to frame the entire 56 SCLK cycles. Data can also be clocked
out using just one DOUT line; in which case, it is recommended
that DOUTA be used to access all conversion data because the
channel data is output in ascending order. For the AD7607 to
access all eight conversion results on one DOUT line, a total of
112 SCLK cycles are required. These 112 SCLK cycles can be
framed by one CS signal, or each group of 14 SCLK cycles can be
individually framed by the CS signal. The disadvantage of using
just one DOUT line is that the throughput rate is reduced if reading
occurs after conversion. The unused DOUT line should be left
unconnected in serial mode. If DOUTB is to be used as a single
DOUT line, the channel results are output in the following order:
V5, V6, V7, V8, V1, V2, V3, and V4; however, the FRSTDATA
indicator returns low after V5 is read on DOUTB.
Figure 6 shows the timing diagram for reading one channel of
data, framed by the CS signal, from the AD7607 in serial mode.
The SCLK input signal provides the clock source for the serial
read operation. The CS goes low to access the data from the
AD7607. The falling edge of CS takes the bus out of three-state
and clocks out the MSB of the 14-bit conversion result. This
MSB is valid on the first falling edge of the SCLK after the CS
falling edge.
AD7607
The subsequent 13 data bits are clocked out of the AD7607 on the
SCLK rising edge. Data is valid on the SCLK falling edge. To access
each conversion result, 14 clock cycles must be provided.
The FRSTDATA output signal indicates when the first channel,
V1, is being read back. When the CS input is high, the FRSTDATA
output pin is in three-state. In serial mode, the falling edge of CS
takes FRSTDATA out of three-state and sets the FRSTDATA pin
high, indicating that the result from V1 is available on the DOUTA
output data line. The FRSTDATA output returns to a logic low
following the 14^th SCLK falling edge. If all channels are read on
DOUTB, the FRSTDATA output does not go high when V1 is output
on this serial data output pin. It goes high only when V1 is available
on DOUTA (and this is when V5 is available on DOUTB).
READING DURING CONVERSION
Data can be read from the AD7607 while BUSY is high and the
conversions are in progress. This has little effect the performance
of the converter, and it allows a faster throughput rate to be
achieved. A parallel, parallel byte, or serial read can be performed
during conversions and when oversampling is or is not enabled.
Figure 3 shows the timing diagram for reading while BUSY is
high in parallel or serial mode. Reading during conversions
allows the full throughput rate to be achieved when using the
serial interface with VDRIVE above 3.3 V.
Data can be read from the AD7607 at any time other than on
the falling edge of BUSY because this is when the output data
registers get updated with the new conversion data. Time t6, as
outlined in Table 3, should be observed in this condition.
CS
SCLK
D_OUTA
D_OUTB
56
V1
V2
V3
V4
V5
V6
V7
V8
Figure 42. Serial Interface with Two DOUT Lines
Rev. C | Page 25 of 32