AD7661 Analog Devices, AD7661 Datasheet - Page 23

• Manufacturer Part Number: AD7661
• Manufacturer: Analog Devices

Specifications of AD7661

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 100kSPS
• Interface: Par,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p,2.5V p-p,Uni (Vref),Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

MASTER SERIAL INTERFACE
Internal Clock
The AD7661 is configured to generate and provide the serial
data clock SCLK when the EXT/ INT pin is held LOW. The
AD7661 also generates a SYNC signal to indicate to the host
when the serial data is valid. The serial clock SCLK and the
SYNC signal can be inverted if desired. Depending on the
RDC/SDIN input, the data can be read after each conversion or
during the following conversion. Figure 39 and Figure 40 show
detailed timing diagrams of these two modes.
CS, RD
CS, RD
CNVST
SDOUT
CNVST
SDOUT
BUSY
SYNC
SCLK
BUSY
SYNC
SCLK
t
16
t
3
Figure 40. Master Serial Data Timing for Reading (Read Previous Conversion during Convert)
t
t
t
14
15
16
t
t
t
14
15
29
t
17
X
t
t
18
22
Figure 39. Master Serial Data Timing for Reading (Read after Convert)
EXT/INT = 0
t
EXT/INT = 0
1
t
D15
3
t
X
t
1
20
22
t
19
t
21
t
20
D14
t
D15
2
23
1
t
19
t
18
Rev. 0 | Page 23 of 28
RDC/SDIN = 0
RDC/SDIN = 1
D14
t
21
2
t
3
23
t
28
3
Usually, because the AD7661 has a longer acquisition phase
than the conversion phase, the data is read immediately after
conversion. This makes the Master Read After Conversion the
most recommended serial mode when it can be used. In this
mode, it should be noted that unlike in other modes, the BUSY
signal returns LOW after the 16 data bits are pulsed out and not
at the end of the conversion phase, which results in a longer
BUSY width.
In the Read During Conversion mode, the serial clock and data
toggle at appropriate instants, which minimizes potential feed-
through between digital activity and critical conversion
decisions
INVSCLK = INVSYNC = 0
14
D2
INVSCLK = INVSYNC = 0
14
D2
15
D1
15
D1
16
t
24
16
t
30
D0
t
D0
24
t
t
t
t
t
t
25
26
27
25
26
27
AD7661