AD7988-1 Analog Devices, AD7988-1 Datasheet - Page 19

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AD7988-1

Manufacturer Part Number
AD7988-1
Description
16-Bit, 100ksps, Ultra Low Power 16-Bit SAR ADC
Manufacturer
Analog Devices
Datasheet

Specifications of AD7988-1

Resolution (bits)
16bit
# Chan
1
Sample Rate
100kSPS
Interface
Ser,SPI
Analog Input Type
Diff-Uni
Ain Range
(Vref) p-p,5V p-p,Uni (Vref),Uni 5.0V
Pkg Type
SOP

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Data Sheet
CS MODE 4-WIRE
This mode is typically used when multiple
are connected to an SPI-compatible digital host.
A connection diagram example using two
shown in Figure 36, and the corresponding timing is given in
Figure 37.
With SDI high, a rising edge on CNV initiates a conversion,
selects the CS mode, and forces SDO to high impedance. In this
mode, CNV must be held high during the conversion phase and
the subsequent data readback (if SDI and CNV are low, SDO is
driven low). Prior to the minimum conversion time, SDI can be
used to select other SPI devices, such as analog multiplexers,
but SDI must be returned high before the minimum conversion
time elapses and then held high for the maximum conversion time.
ACQUISITION
SDI (CS1)
SDI (CS2)
CNV
t
SCK
SDO
SSDICNV
t
HSDICNV
CONVERSION
t
CONV
SDI
t
EN
AD7988-1/
AD7988-5
CNV
SCK
D15
1
t
AD7988-x
HSDO
AD7988-x
SDO
D14
2
Figure 37. 4-Wire CS Mode Serial Interface Timing
Figure 36. 4-Wire CS Mode Connection Diagram
D13
devices is
devices
3
t
DSDO
t
SCKL
t
14
Rev. A | Page 19 of 24
SCKH
SDI
t
SCK
15
D1
AD7988-1/
AD7988-5
t
CYC
CNV
SCK
When the conversion is complete, the
acquisition phase and powers down. Each ADC result can
be read by bringing its SDI input low, which consequently
outputs the MSB 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 to capture
the data, a digital host using the SCK falling edge allows a faster
reading rate, provided that it has an acceptable hold time. After
the 16th SCK falling edge or when SDI goes high, whichever is
earlier, SDO returns to high impedance and another
can be read.
ACQUISITION
16
D0
t
ACQ
SDO
D15
17
D14
18
CS2
CS1
CONVERT
DATA IN
CLK
DIGITAL HOST
30
AD7988-1/AD7988-5
31
D1
AD7988-x
32
D0
enters the
t
DIS
AD7988-x

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