ADS-325A Datel, Inc., ADS-325A Datasheet - Page 6

• Manufacturer Part Number: ADS-325A
• Description: 10-Bit,20MHz, Sampling A/D Converter
• Manufacturer: Datel, Inc.

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
(+2V to +4V)
ANALOG IN
EXT. CAL.
PULSE IN
(+4V)
(+2V)
V
V
RT
RB
ANALOG INPUT
ANALOG INPUT
A/D CLOCK
A/D CLOCK
RESET
RESET
JP1
JP2
CAL
CAL
0.1µF
BIT 10
37
38
39
40
41
42
43
44
45
46
47
48
(LSB)
36
1
V
CAL
AGND
+DV
DGND
IN
35
S
2
V
RB
34
0.1µF
3
33
Figure 7. Typical ADS-325A Connection Diagram
4
Figure 6a. Applying CAL Pulse Every H Sync.
Figure 6b. Applying CAL Pulse Every V Sync.
32
ADS-325A
5
0.1µF
31
6
V
0.1µF
RT
30
7
29
8
28
9
AGND
27
10
0.1µF
RESET
MODE 19
DGND
26
11
MINV
+AV
LINV
CLK
SEL 17
OE
CE
(MSB)
BIT 1
S
12
25
6
24
23
22
21
20
18
16
15
13
0.1µF
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.
10µF
0.1µF
+AV
+
0.1µF
S
+
10µF
JP3
JP4
JP5
JP6
CLOCK IN
A/D
RESET
+AV
IN
S
NOTES:
1. For using Start-up calibration and
2. For using Start-up calibration and
3. For using Start-up calibration Mode
4. RESET pin (Pin 15) should normally
External CAL Pulse Mode, close
JP1 and JP4, and open JP2 and
JP3.
Internal Auto-calibration Mode, close
JP2 and JP3, and open JP1 and
JP3.
only, close JP2 and JP4, and open
JP1 and JP3.
be connected to +AV
To re-initiate the start-up calibration
after power-up, close JP6 to apply
external RESET pulse.
®
S
(close JP5).
®