ADA4841-X AD [Analog Devices], ADA4841-X Datasheet - Page 18

• Manufacturer Part Number: ADA4841-X
• Manufacturer: AD [Analog Devices]

AD7689
WITH BUSY INDICATOR
This mode is usually used when the AD7689 is connected to an
SPI-compatible digital host using an interrupt input. The
connection diagram is shown in Figure 19,, and the
corresponding timing is given in Figure 20.
A rising edge on CNV initiates a conversion and forces SDO to
high impedance. SDO is maintained in high impedance until
the completion of the conversion irrespective of the state of
CNV. Prior to the minimum conversion time, CNV can be
used to select other SPI devices, such as analog multiplexers,
but CNV must be returned low before the minimum conversion
time elapses and then held low for the maximum possible
conversion time to guarantee the generation of the busy signal
indicator.
Configuring the AD7689 for the (n + 1) conversion is initiated
when SCK is high and a rising edge on CNV. After this mode is
initiated, CNV is a don’t care as the CFG word is written in
MSB first with 14 SCK rising edges. As shown in Figure 20,
CFG is written to during the current (n) conversion before the
end of conversion, or t
conversion, the register is updated. In this mode, the new
configuration settings are used for the following (n + 1)
ACQUISITION
(n)
CNV
SDO
SCK
DIN
C13
CONV
1
t
t
CSCK
SDIN
minimum time. At the end of
C12
t
HDIN
2
t
(MIN)
CONV
C11
3
CONVERSION
t
(MAX)
C1
CONV
(n)
13
Figure 20. Wwith Busy Indicator Serial Interface Timing
Figure 19. With Busy Indicator Connection Diagram
C0
AD7689
14
CNV
SCK
SDO
DIN
Rev. PrC | Page 18 of 20
VIO
t
CONVERT
DATA IN
CFG DATA
CLK
1
IRQ
CYC
DIGITAL HOST
acquisition and conversion. Note that SCK must be high when
CNV goes high for this configuration mode. The AD7689 can
also be configured on the first 14 SCK of the data reading (not
shown), thus reducing the number of SCK bursts. However, this
new CFG setting is for the (n + 2) conversion.
When the conversion is complete, SDO goes from high
impedance to low impedance. With a pull-up on the SDO line,
this transition can be used as an interrupt signal to initiate the
data reading controlled by the digital host. The AD7689 then
enters the acquisition phase and powers down. The data bits are
clocked out, MSB first, by subsequent SCK falling edges. The
data is valid on both SCK edges. Although the rising edge can
be used to capture the data, a digital host using the SCK falling
edge will allow a faster reading rate, provided it has an
acceptable hold time. After the optional 17
when CNV goes high (whichever occurs first), SDO returns to
high impedance.
If multiple AD7689s are selected at the same time, the SDO
output pin handles this contention without damage or induced
latch-up. Meanwhile, it is recommended to keep this contention
as short as possible to limit extra power dissipation.
D15
2
t
t
HSDO
DSDO
D14
3
D13
4
Preliminary Technical Data
ACQUISITION
t
SCKH
14
(n + 1)
D3
t
ACQ
t
SCKL
15
D2
t
SCK
16
D1
t
DIS
th
17
SCK falling edge or
D0
CONVERSION
(n + 1)