Effective Number of Bits

Effective number of bits (ENOB) indicates the global

accuracy of an ADC at a specific input frequency and

sampling rate. An ideal ADC’s error consists of quanti-

zation noise only. With an input range equal to the

ADC’s full-scale range, calculate the ENOB as follows:

ENOB = (SINAD - 1.76) / 6.02

Total Harmonic Distortion

Total harmonic distortion (THD) is the ratio of the RMS

sum of the input signal’s first five harmonics to the fun-

damental itself. This is expressed as:

harmonics.

Spurious-Free Dynamic Range

Spurious-free dynamic range (SFDR) is the ratio of the

RMS amplitude of the fundamental (maximum signal

component) to the RMS value of the next largest distor-

tion component.

THD

VVV

V

V

log

=×

++

+





























20

2

2

3

2

4

2

5

2

1

2.7V to 3.6V and 4.5V to 5.5V, Low-Power,

4-/12-Channel, 2-Wire Serial, 12-Bit ADCs

20

______________________________________________________________________________________

*OPTIONAL

**AIN11/REF (MAX1238/MAX1239)

ANALOG

INPUTS

µC

SDA

SCL

GND

SDA

SCL

AIN0

AIN1

AIN3**/REF

3.3V or 5V

5V

5V

MAX1236

MAX1237

MAX1238

MAX1239

0.1

µF

0.1

µF

Typical Operating Circuit

SDA

SCL

AIN3/REF

1

2

8

7

GND

AIN1

AIN2

AIN0

µMAX

TOP VIEW

3

4

6

5

MAX1236

MAX1237

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

AIN0

AIN8

AIN9

AIN10

AIN11/REF

GND

SDA

SCL

MAX1238

MAX1239

QSOP

AIN1

AIN2

AIN5

AIN3

AIN4

AIN6

AIN7

Pin Configurations

Ordering Information (continued)

PART

TEMP

RANGE

PIN-

PACKAGE

I

ADDRESS

INL

(LSB)

MAX1238EEE

-40

°C to +85°C 16 QSOP

0110101

±1

MAX1238KEEE* -40

°C to +85°C 16 QSOP

0110001

±1

MAX1238LEEE* -40

°C to +85°C 16 QSOP

0110011

±1

MAX1238MEEE* -40

°C to +85°C 16 QSOP

0110111

±1

MAX1239EEE

-40

°C to +85°C 16 QSOP

0110101

±1

MAX1239KEEE

-40

°C to +85°C 16 QSOP

0110001

±1

MAX1239LEEE

-40

°C to +85°C 16 QSOP

0110011

±1

MAX1239MEEE -40

°C to +85°C 16 QSOP

0110111

±1

Chip Information

MAX1236/MAX1237 TRANSISTORS COUNT: 11,362

MAX1238/MAX1239 TRANSISTORS COUNT: 12,956

PROCESS: BiCMOS

*Future product—contact factory for availability.