The digital output LED display can be decoded by dividing

the 8 bits into the 4 most significant bits and 4 least signifi-

cant bits Table I shows the fractional binary equivalent of

these two 8-bit groups By adding the decoded voltages

which are obtained from the column ‘‘Input Voltage Value

value of the digital display can be determined For example

for an output LED display of ‘‘1011 0110’’ or ‘‘B6’’ (in hex)

ues of a perfect AD converter The input voltage has to

ty’’ of an AD to obtain an output digital code change The

effects of this quantization error have to be accounted for in

the interpretation of the test results A plot of this natural

error source is shown in

Figure 5 where for clarity both the

analog input voltage and the error voltage are normalized to

LSBs

TABLE I DECODING THE DIGITAL OUTPUT LEDs

INPUT VOLTAGE

FRACTIONAL BINARY VALUE FOR

VALUE WITH

HEX

BINARY

MS GROUP

LS GROUP

MS GROUP

LS GROUP

F

1

1

1

1

1516

15256

9600

0600

E

1

1

1

0

78

7128

8960

0560

D

1

1

0

1

1316

13256

8320

0520

C

1

1

0

0

34

364

7680

0480

B

1

0

1

1

1116

11256

7040

0440

A

1

0

1

0

58

5128

6400

0400

9

1

0

0

1

916

9256

5760

0360

8

1

0

0

0

12

132

5120

0320

7

0

1

1

1

716

7256

4480

0280

6

0

1

1

0

38

3128

3840

0240

5

0

1

0

1

516

5256

3200

0200

4

0

1

0

0

14

164

2560

0160

3

0

0

1

1

316

3256

1920

0120

2

0

0

1

0

18

1128

1280

0080

1

0

0

0

1

116

1256

0640

0040

00

0

0

0

00

TLH5670 – 8

FIGURE 5 Error Plot of a Perfect AD Showing Effects of Quantization Error

8