AD7609BSTZ Analog Devices Inc, AD7609BSTZ Datasheet - Page 22

• Manufacturer Part Number: AD7609BSTZ
• Description: 58T8900
• Manufacturer: Analog Devices Inc

Specifications of AD7609BSTZ

• Resolution (bits): 18bit
• Sampling Rate: 250kSPS
• Input Channel Type: Differential
• Data Interface: Serial, SPI
• Supply Voltage Range - Analog: 4.75V To 5.25V
• Rohs Compliant: Yes

AD7609
Analog Input Antialiasing Filter
An analog antialiasing filter is also provided on the AD7609.
The filter is a second-order Butterworth. Figure 35 and
Figure 36 show the frequency and phase response respectively
of the analog antialiasing filter. In the ±5 V range, the −3 dB
frequency is typically 23 kHz. In the ±10 V range, the −3 dB
frequency is typically 32 kHz.
Track-and-Hold Amplifiers
The track-and-hold amplifiers on the
accurately acquire an input sine wave of full-scale amplitude
to 18-bit resolution. The track-and-hold amplifiers sample
their respective inputs simultaneously on the rising edge of
CONVST x. The aperture time for track-and-hold (that is, the
delay time between the external CONVST x signal and the
track-and-hold actually going into hold) is well matched, by design,
across all eight track-and-holds on one device and from device
to device. This matching allows more than one
to be sampled simultaneously in a system.
The end of the conversion process across all eight channels is
indicated by the falling edge of BUSY; and it is at this point that the
track-and-holds return to track mode and the acquisition time
for the next set of conversions begins.
–10
–15
–20
–25
–30
–35
–40
–5
14
13
12
11
10
0
9
8
7
6
5
4
3
2
1
0
100
Figure 35. Analog Antialiasing Filter Frequency Response
10
Figure 36. Analog Antialiasing Filter Phase Response
AV
f
T
±10V RANGE
SAMPLE
±5V RANGE
A
10V
5V
CC
= 25°C
, V
TEMP
–40°C 13,354Hz 33,520Hz
–40°C 10,303Hz 24,365Hz
25°C 12,769Hz 32,397Hz
85°C 12,427Hz 31,177Hz
25°C
85°C
DRIVE
= 200kSPS
9619Hz 23,389Hz
9326Hz 22,607Hz
= 5V
0.1dB
INPUT FREQUENCY (Hz)
1k
1k
FREQUENCY (Hz)
3dB
AD7609
10k
10k
5V DIFF
allow the ADC to
AD7609
10V DIFF
100k
100k
device
Rev. 0 | Page 22 of 36
The conversion clock for the part is internally generated, and
the conversion time for all channels is 4 μs on the AD7609. The
BUSY signal returns low after all eight conversions to indicate the
end of the conversion process. On the falling edge of BUSY, the
track-and-hold amplifiers return to track mode. New data can
be read from the output register via the parallel, or serial
interface after BUSY goes low; or, alternatively, data from the
previous conversion can be read while BUSY is high. Reading data
from the
effect on performance and allows a faster throughput to be
achieved. With a V
when reading during a conversion.
ADC TRANSFER FUNCTION
The output coding of the
designed code transitions occur midway between successive
integer LSB values, that is, 1/2 LSB, 3/2 LSB. The LSB size is
FSR/262,144 for the AD7609. The FSR for the
for the ±10 V range and 20 V for the ±5 V range. The ideal
transfer characteristic for the
The LSB size is dependent on the analog input range selected
(see Table 7).
Table 7. Output Codes and Ideal Input Values
Description
FSR − 0.5 LSB
Midscale + 1 LSB
Midscale
Midscale – 1 LSB
−FSR + 1 LSB
−FSR
AD7609
011...111
011...110
000...001
000...000
111...111
100...010
100...001
100...000
Figure 37.
–FS + 1/2LSB
while a conversion is in progress has little
DRIVE
±10V CODE =
Analog Input
(V+ − (V−)
10 V Range
+19.99992 V
+152.58 μV
0 V
−152.58 μV
−19.99984 V
−20 V
±5V CODE =
AD7609
> 3.3 V, the SNR is reduced by ~1.5 dB
0V – 1LSB +FS – 3/2LSB
AD7609
ANALOG INPUT
AD7609
V+ ± (V–)
V+ ± (V–)
Transfer Characteristic
10V
5V
is twos complement. The
Analog
Input
V+ − (V−)
5 V Range
9.999961 V
0 V
−76 μV
−9.99992 V
−10 V
76 μV
× 131,072 ×
× 131,072 ×
is shown in Figure 37.
LSB =
+FSR – (–FSR)
2.5V
2.5V
AD7609
REF
REF
2
18
Digital
Output
Code (Hex)
0x1FFFF
0x00001
0x00000
0x3FFFF
0x20001
0x20000
is 40 V