ADC-208A
8-Bit, 20MSPS CMOS Flash A/D (ADC-208 Compatible)
7. Connect the converter appropriately; a typical connection circuit is shown in Figure 2.
Then apply an appropriate clock input.The reference input should be held to ±0.1% accuracy
or better. Do not use the +5V power supply as a reference without precision regulation and
high-frequency decoupling capacitors.
8. Zero Adjustment - Adjusting the voltage at –REFERENCE (pin 3) adjusts the offset or
zero of the device. Pin 3 can be tied to GROUND for operation without adjustments
9. Full Scale Adjustment - Adjusting the voltage at +REFERENCE (pin 9) adjusts the gain of
the device. Pin 9 can be tied directly to a +5V reference for operation without adjustment.
10. Integral Nonlinearity Adjustments - Provision is made for optional adjustment of Integral
Nonlinearity through access of the reference's ¼, ½, and ¾ full scale points. For example, the
REF. MIDPOINT (pin 6) can be tied to a precision voltage halfway between +REFERENCE
and –REFERENCE. Pins 6, 18 and 20 should be bypassed to GROUND through 0.1µF
capacitors for operation without INL adjustments
ANALOG
INPUT
0.00V
+0.02V
+1.28V
+2.54V
+2.56V
+2.58V
+3.84V
+5.10V
Table 1. ADC-208A Output Code
CODE
DATA DATA 5678 DECIMAL HEX
1234
Zero 0000
0000
0000
0
00
+1 LSB
0000
0001
1
01
+¼ FS
0100
0000
64
40
+½ FS-ILSB
0111
1111
127
7F
+½ FS
1000
0000
128
80
+½ FS+ILSB 1000
0001
129
81
+¾ FS
1100
0000
192
C0
+FS
1111
1111
255
FF
Note: Values shown here are for a +5.12Vdc reference. Scale other refereces proportion-
ally. (+REF=+5.12V, –REF=GND, ¼, ½, and ¾ References FS=No Connection)
+15
+5V
0.1μF
+
4.7μF
12
5
11 10Ω
HA-5033
10
4.7μF
–15
0.1μF
+
HP2811
+15V
2
6
REF. D2
5
4
+5V
4.7μF
+
0.01μF
20MHz CLOCK
CLOCK 2
VIN 5,7
10kΩ
+15V
2 1-N
1
LM324
3
1+N
2kΩ
+
4.7μF
0.1μF
1kΩ
1.5kΩ
0.1μF
1kΩ
1.5kΩ
1kΩ
2kΩ
0.1μF
0.1μF
B8 24 (LSB)
B7 23
B6 22
B5 21
B4 17
B3 16
B2 15
B1 14 (MSB)
20
R¼
R¾
18
9 1-N
8
LM324
10
1+N
+ 0.1μF
4.7μF
6 1-N
7
LM324
5
1+N
+
4.7μF
0.1μF
12 1-N
14
LM324
13
1+N
+ 0.1μF
4.7μF
Figure 2. ADC-208A Typical Connection Diagram
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MDA_ADC-208A.B01 Page 3 of 4