ADS-325A Ver la hoja de datos (PDF) - DATEL Data Acquisition products
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ADS-325A Datasheet PDF : 8 Pages
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ADS-325A
®
®
As stated before, the five lower bits of the output data will
remain constant for 4 clock cycles with every generation of the
calibration pulse. Since the auto calibration pulses are
generated asynchronously, this may create problems in certain
applications.
External Calibration Function
To avoid the asynchronous data fixation due to the calibration
process, you can disable the internal auto calibration function
and use an external calibration pulse which is synchronized
with the analog input. Input the external calibration pulse to the
CAL pin (pin 14) and tie the SEL pin (pin 17) to AGND. When
digitizing a video signal, for example, you can synchronize the
external calibration pulses with the V-sync or H-sync cycles of
the video signal to avoid losing any data during the video signal
cycles. See figure 6a. and 6b.
ANALOG INPUT
A/D CLOCK
RESET
CAL
Figure 6a. Applying CAL Pulse Every H Sync.
ANALOG INPUT
A/D CLOCK
RESET
CAL
Figure 6b. Applying CAL Pulse Every V Sync.
VRT
(+4V)
VRB
(+2V)
ANALOG IN
(+2V to +4V)
EXT. CAL.
PULSE IN
+AVS
10µF
+
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
NOTES:
1. For using Start-up calibration and
External CAL Pulse Mode, close
JP1 and JP4, and open JP2 and
JP3.
36 35 34 33 32 31 30 29 28 27 26 25
37
VRB
VRT
AGND CE 24
2. For using Start-up calibration and
Internal Auto-calibration Mode, close
38
OE 23
JP2 and JP3, and open JP1 and
39 VIN
JP1
CLK 22
A/D
CLOCK IN
JP3.
40
MINV 21
3. For using Start-up calibration Mode
41 CAL
LINV 20
JP2
42
MODE 19
ADS-325A
JP3
only, close JP2 and JP4, and open
JP1 and JP3.
43
+AVS 18
+AVS
0.1µF
AGND
44
SEL 17
JP4
4. RESET pin (Pin 15) should normally
be connected to +AVS (close JP5).
45 +DVS
DGND 16
JP5
To re-initiate the start-up calibration
46
47
RESET 15
10µF+
RESET
JP6
IN
after power-up, close JP6 to apply
external RESET pulse.
48 DGND
13
1 2 3 4 5 6 7 8 9 10 11 12
0.1µF
BIT 10
(LSB)
0.1µF
BIT 1
(MSB)
Figure 7. Typical ADS-325A Connection Diagram
6
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