
Signal-to-Noise Plus Distortion (SINAD)
SINAD is the ratio of the fundamental input frequency’s
RMS amplitude to RMS equivalent of all other ADC out-
put signals:
SINAD (dB) = 20 log (SignalRMS / NoiseRMS)
Effective Number of Bits (ENOB)
ENOB indicates the global accuracy of an ADC at a
specific input frequency and sampling rate. An ideal
ADC’s error consists only of quantization noise. With an
input range equal to the ADC’s full-scale range, calcu-
late ENOB as follows:
ENOB = (SINAD - 1.76) / 6.02
Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of the input signal’s
first five harmonics to the fundamental itself. This is
expressed as:
where V1 is the fundamental amplitude, and V2 through
V5 are the amplitudes of the 2nd- through 5th-order
harmonics.
Spurious-Free Dynamic Range (SFDR)
SFDR is the ratio of the RMS amplitude of the funda-
mental (maximum signal component) to the RMS value
of the next-largest distortion component.
THD 20
log
V
VVV
V
2
3
2
4
2
4
2
5
2
1
=×
+
+++
MAX1080/MAX1081
300ksps/400ksps, Single-Supply, Low-Power,
8-Channel, Serial 10-Bit ADCs with Internal Reference
22
______________________________________________________________________________________
SCLK
DIN
DOUT
SSTRB
SEL2
START
SEL1
SEL0
PD1
PD0
CS
UNI/BIP SGI/DIF
B8
S1
MSB
S0
HIGH IMPEDANCE
Figure 19. MAX1080/MAX1081-to-TMS320 Serial Interface
PART
TEMP.
RANGE
PIN-
PACKAGE
MAX1080BEUP
MAX1081AEUP
MAX1081BEUP
-40°C to +85°C
20 TSSOP
±1
±1/2
INL
(LSB)
±1
MAX1081ACUP
MAX1081BCUP
0°C to +70°C
20 TSSOP
±1/2
±1
Ordering Information (continued)
Typical Operating Circuit
VDD
I/O
SCK (SK)
MOSI (SO)
MISO (SI)
VSS
SHDN
SSTRB
DOUT
DIN
SCLK
CS
COM
GND
VDD1
VDD2
CH7
4.7
F
0.1
F
CH0
0 TO
+2.5V
ANALOG
INPUTS
MAX1080
MAX1081
CPU
+5V OR
+3V
REF
0.01
F
REFADJ
VDD2
Chip Information
TRANSISTOR COUNT: 4286
PROCESS: BiCMOS