ad7688brm Analog Devices, Inc., ad7688brm Datasheet - Page 17

• Manufacturer Part Number: ad7688brm
• Description: 16-bit, 1.5 Lsb Inl, 500 Ksps Pulsar? Differential Adc In Msop/qfn
• Manufacturer: Analog Devices, Inc.

CS MODE 3-WIRE, NO BUSY INDICATOR
This mode is usually used when a single AD7688 is connected
to an SPI-compatible digital host. The connection diagram is
shown in Figure 34 and the corresponding timing is given in
Figure 35.
With SDI tied to VIO, a rising edge on CNV initiates a
conversion, selects the CS mode, and forces SDO to high
impedance. Once a conversion is initiated, it continues to
completion irrespective of the state of CNV. For instance, it
could be useful to bring CNV low to select other SPI devices,
such as analog multiplexers, but CNV must be returned high
before the minimum conversion time and held high until the
maximum conversion time to avoid the generation of the BUSY
signal indicator. When the conversion is complete, the AD7688
enters the acquisition phase and powers down. When CNV
goes low, the MSB is output onto SDO. The remaining data bits
are then clocked by subsequent SCK falling edges. The data is
valid on both SCK edges. Although the rising edge can be used
ACQUISITION
SDI = 1
CNV
SCK
SDO
t
CNVH
CONVERSION
t
CONV
Figure 35. CS Mode 3-Wire, No BUSY Indicator Serial Interface Timing (SDI High)
t
EN
D15
1
t
HSDO
Rev 0 | Page 17 of 28
D14
2
t
CYC
ACQUISITION
to capture the data, a digital host using the SCK falling edge
allows a faster reading rate provided it has an acceptable hold
time. After the 16th SCK falling edge or when CNV goes high,
whichever is earlier, SDO returns to high impedance.
D13
t
3
ACQ
VIO
t
DSDO
SDI
t
SCKL
t
AD7688
SCKH
Figure 34. CS Mode 3-Wire, No BUSY Indicator
14
CNV
SCK
Connection Diagram (SDI High)
t
SCK
15
SDO
D1
16
D0
CONVERT
DATA IN
CLK
t
DIGITAL HOST
DIS
AD7688