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參數(shù)資料
| 型號： | ADS-945 |
| 廠商： | MURATA POWER SOLUTIONS INC |
| 元件分類： | ADC |
| 中文描述： | 1-CH 14-BIT FLASH METHOD ADC, PARALLEL ACCESS, MDIP75 |
| 封裝： | ROHS COMPLIANT, PACKAGE-75 |
| 文件頁數(shù)： | 4/8頁 |
| 文件大?。?/td> | 285K |
| 代理商： | ADS-945 |
CALIBRATION PROCEDURE (Refer to Figure 2 and Table 1)
Note: Connect pin 18 to ANALOG GROUND (pin 19) for operation without
zero/offset adjustment. Connect pin 9 to ANALOG GROUND (pin 8) for
operation without gain adjustment.
Any offset and/or gain calibration procedures should not be implemented
until devices are fully warmed up. To avoid interaction, offset must be
adjusted before gain. The ranges of adjustment for the circuit in Figure 2
are guaranteed to compensate for the ADS-945's initial accuracy errors and
may not be able to compensate for additional system errors.
A/D converters are calibrated by positioning their digital outputs exactly
on the transition point between two adjacent digital output codes. This can
be accomplished by connecting LED's to the digital outputs and adjusting
until certain LED's "flicker" equally between on and off. Other approaches
employ digital comparators or microcontrollers to detect when the outputs
change from one code to the next.
For the ADS-945, offset adjusting is normally accomplished at the point
where the MSB is a 1 and all other output bits are 0's and the LSB just
changes from a 0 to a 1. This digital output transition ideally occurs when
the applied analog input is + LSB (+76.3μV).
Gain adjusting is accomplished when all bits are 0's and the LSB just
changes from a 0 to a 1. This transition ideally occurs when the analog
input is at +full scale minus 1 LSB's (+1.249771V).
Note: Due to inherent system noise, the averaging of several conversions
may be needed to accurately adjust both offset and gain to 1LSB of
accuracy.
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input (pin 32) so the con-
verter is continuously converting.
2. Apply +76.3μV to the ANALOG INPUT (pin 4).
3. Adjust the offset potentiometer until the output bits are 10 0000 0000 0000
and the LSB flickers between 0 and 1.
Gain Adjust Procedure
1. Apply +1.249771V to the ANALOG INPUT (pin 4).
2. Adjust the gain potentiometer until all output bits are 0's and the LSB flick-
ers between 0 and 1.
3. To confirm proper operation of the device, vary the applied input voltage to
obtain the output coding listed in Table 1.
Note: A single +5V supply can be used for both the +5V ANALOG and the
+5V DIGITAL. If separate supplies are used, the difference between the two
can not exceed 100mV. This also applies to the –5.2V supply requirements.
Datel recommends using ferrite beads to separate the analog and digital sup-
plies (FAIR-RITE # 2643000301).
ADS-945
20k
7
53
52
51
50
49
48
47
46
45
44
43
42
41
40
34
33
30
29
4
BIT 1 (MSB)
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
BIT 13
BIT 14 (LSB)
OUTPUT ENABLE
OVERFLOW
T/H STATUS
T/H STATUS
ANALOG INPUT
ANALOG
SUPPLY
DIGITAL
SUPPLY
55
54
58-60
OFFSET
ADJUST
18
0.1μF
10μF
64-68
63
0.1μF
10μF
69
+
+
–5.2V
+5V
32
START CONVERT
7
+10 REF. OUT
0.1μF
10μF
0.1μF
10μF
+
+
–5.2V
+5V
57
0.1μF
10μF
13
15-17
13
0.1μF
10μF
12
+
+
–15V
+15V
DIGITAL
SUPPLY
ANALOG
SUPPLY
0.1μF
9
GAIN
ADJUST
20k
7
DIGITAL
GROUND
ANALOG
GROUND
ANALOG
GROUND
–15V
+15V
+15V
–15V
Figure 2. ADS-945 Connection Diagram
Table 1. Output Coding
OUTPUT CODING
MSB
00 0000 0000 0000
00 0111 1111 1111
00 1111 1111 1111
01 1111 1111 1111
10 1111 1111 1111
11 0111 1111 1111
11 1111 1111 1110
11 1111 1111 1111
INPUT RANGE
±1.25V
+1.249847
+0.937500
+0.625000
0.000000
–0.625000
–0.937500
–1.249847
–1.250000
BIPOLAR
SCALE
+FS –1 LSB
+3/4 FS
+1/2FS
0
–1/2FS
–3/4FS
–FS +1 LSB
–FS
LSB
ADS-945
14-Bit, 10MHz Sampling A/D Converters
DATEL
11 Cabot Boulevard, Mansfield, MA 02048-1151 USA Tel: (508) 339-3000 www.datel.com e-mail: help@datel.com
01 Apr 2011 MDA_ADS-945.B02
Page 4 of 8
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