Agilent Technologies 93000 SOC Series Training Manual page 296

Lesson 1 – The Training ADC
FS = Full analog scale
n
DeviceLSB = FS / 2
+Vref
2 -1
R
Analog
input
R
R
R
–Vref
Flash ADC Block Diagram
ADC Input-Output Chart
Linear ADCs have a transfer characteristic as shown below:
Binary Output Code
111
110
code
101
center
100
011
010
001
000
1/8
1/4 3/8
Analog Input
Input-Output Chart of an Ideal 3-bit ADC
In case of a 3-bit ADC, as shown above, the analog equivalent to
1 LSB is 1/8 of the full analog scale (FS).
In general, the analog equivalent to 1 LSB is FS divided by 2
where n = number of bits. The analog equivalent to 1 LSB is also
called DeviceLSB.
296
n
comparators
n
Sampling clock
code
width
code transition
1 LSB
1/2 5/8 3/4 7/8 FS
n lines
n
,