MAXIM MAX127, MAX128 User Manual

General Description

The MAX127/MAX128 are multirange, 12-bit data
acquisition systems (DAS) that require only a single
+5V supply for operation, yet accept signals at their
analog inputs that may span above the power-supply
rail and below ground. These systems provide eight
analog input channels that are independently software
programmable for a variety of ranges: ±10V, ±5V, 0 to
+10V, 0 to +5V for the MAX127; and ±V

REF

, ±V

REF

/2, 0

to +V

REF

, 0 to +V

REF

/2 for the MAX128. This range
switching increases the effective dynamic range to 14
bits and provides the flexibility to interface 4–20mA,
±12V, and ±15V-powered sensors directly to a single
+5V system. In addition, these converters are fault pro­tected to ±16.5V; a fault condition on any channel will
not affect the conversion result of the selected channel.
Other features include a 5MHz bandwidth track/hold,
an 8ksps throughput rate, and the option of an internal

4.096V or external reference.
The MAX127/MAX128 feature a 2-wire, I2C-compatible

serial interface that allows communication among multi­ple devices using SDA and SCL lines.

A hardware shutdown input (SHDN) and two software­programmable power-down modes (standby and full
power-down) are provided for low-current shutdown
between conversions. In standby mode, the reference­buffer remains active, eliminating start-up delays.

The MAX127/MAX128 are available in 24-pin DIP or
space-saving 28-pin SSOP packages.

Applications

Industrial Control Systems
Data-Acquisition Systems
Robotics
Automatic Testing
Battery-Powered Instruments
Medical Instruments

Features

♦ 12-Bit Resolution, 1/2 LSB Linearity
♦ +5V Single-Supply Operation
♦ I

2

C-Compatible, 2-Wire Serial Interface

♦ Four Software-Selectable Input Ranges

MAX127: 0 to +10V, 0 to +5V, ±10V, ±5V
MAX128: 0 to +V

REF

, 0 to +V

REF

/2, ±V

REF

,

±V

REF

/2

♦ 8 Analog Input Channels
♦ 8ksps Sampling Rate
♦ ±16.5V Overvoltage-Tolerant Input Multiplexer
♦ Internal 4.096V or External Reference
♦ Two Power-Down Modes
♦ 24-Pin Narrow DIP or 28-Pin SSOP Packages

EVALUATION KIT

AVAILABLE

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone] ext. 3468.

MAX127/MAX128

Multirange, +5V, 12-Bit DAS with

2-Wire Serial Interface

________________________________________________________________

Maxim Integrated Products

1

V

DD

CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7

DGND

0.01µF

µC

4.7µF

0.1µF

1k

SHDN

MAX127
MAX128

+5V

ANALOG

INPUTS

SCL

SDA

A0
A1
A2

REF
REFADJ

AGND

SCL SDA

Typical Operating Circuit

19-4773; Rev 0; 7/98

Ordering Information continued at end of data sheet.

PART

MAX127ACNG

MAX127ACNG 0°C to +70°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

24 Narrow Plastic DIP
24 Narrow Plastic DIP ±1

±1/2

INL

(LSB)

Pin Configurations appear at end of data sheet.

Ordering Information

MAX127/MAX128

Multirange, +5V, 12-Bit DAS with
2-Wire Serial Interface

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

VDDto AGND............................................................-0.3V to +6V

AGND to DGND.....................................................-0.3V to +0.3V

CH0–CH7 to AGND ......................................................... ±16.5V

REF to AGND..............................................-0.3V to (V

DD

+ 0.3V)

REFADJ to AGND.......................................-0.3V to (V

DD

+ 0.3V)

A0, A1, A2 to DGND...................................-0.3V to (V

DD

+ 0.3V)

SHDN, SCL, SDA to DGND......................................-0.3V to +6V

Max Current into Any Pin ....................................................50mA

Continuous Power Dissipation (T

A

= +70°C)
24-Pin Narrow DIP (derate 13.33mW/°C above +70°C)..1067mW

28-Pin SSOP (derate 9.52mW/°C above +70°C)...............762mW

Operating Temperature Ranges

MAX127_ C_ _/MAX128_ C_ _.............................0°C to +70°C

MAX127_ E_ _/MAX128_ E_ _ ..........................-40°C to +85°C

Storage Temperature Range ............................-65°C to +150°C

Lead Temperature (soldering, 10sec) ............................+300°C

MAX127A/MAX128A

4kHz, VIN= ±5V (Note 3)

Up to the 5th harmonic

Bipolar

MAX127B/MAX128B

Unipolar

CONDITIONS

10Aperture Jitter

ns200Aperture Delay

dB

-86

Channel-to-Channel Crosstalk

dB81SFDRSpurious-Free Dynamic Range

dB-87 -80THDTotal Harmonic Distortion

dB70

LSB

±1/2

INLIntegral Nonlinearity

Bits12Resolution

±0.3

LSB

±0.1

Channel-to-Channel Offset
Error Matching

±10

±5

±1

LSB±1DNLDifferential Nonlinearity

LSB

±3

Offset Error

±5

UNITSMIN TYP MAXSYMBOLPARAMETER

Bipolar

Unipolar

5

ppm/°C

3

Gain Tempco (Note 2)

±10

±7

LSB

±7

Gain Error (Note 2)

±10

SINAD

Signal-to-Noise plus Distortion
Ratio

ns

Bipolar

Unipolar

Bipolar

MAX127B/MAX128B

MAX127B/MAX128B

Unipolar

MAX127B/MAX128B

MAX127B/MAX128B

MAX127A/MAX128A

MAX127A/MAX128A

MAX127A/MAX128A

MAX127A/MAX128A

ELECTRICAL CHARACTERISTICS

(VDD= +5V ±5%; unipolar/bipolar range; external reference mode, V

REF

= 4.096V; 4.7µF at REF; external clock, f

CLK

= 400kHz;

T

A

= T

MIN

to T

MAX

; unless otherwise noted. Typical values are at TA= +25°C.)

DYNAMIC SPECIFICATIONS (800Hz sine-wave input, ±10Vp-p (MAX127) or ±4.096Vp-p (MAX128), f

SAMPLE

= 8ksps)

DC, VIN= ±16.5V -96

ACCURACY (Note 1)

MAX127/MAX128

Multirange, +5V, 12-Bit DAS with

2-Wire Serial Interface

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VDD= +5V ±5%; unipolar/bipolar range; external reference mode, V

REF

= 4.096V; 4.7µF at REF pin; external clock, f

CLK

= 400kHz;

T

A

= T

MIN

to T

MAX

; unless otherwise noted. Typical values are at TA= +25°C.)

MAX128

MAX127

MAX127

-600 360

I

IN

-1200 720

µA

±V

REF

/2 range

±V

REF

range

±5V range

-1200 10

±10V range

-600 10

Bipolar

Input Voltage Range V

IN

-10 10

TC V

REF

-5 5

MAX127

-V

REF

V

REF

-V

REF

/2 V

REF

/2

MAX128

Bipolar,
Table 3

MAX127

MAX128

0 to 5V or 0 to V

REF

/2 range

0 to 10V or 0 to V

REF

range

±5V or ±V

REF

/2 range

±10V or ±V

REF

range

Buffer Voltage Gain 1.638 V/V

REFADJ Adjustment Range ±1.5 %Figure 12

Capacitive Bypass at REF 4.7 µF
REFADJ Output Voltage 2.465 2.500 2.535 V

Load Regulation (Note 5) 10 mV0 to 0.5mA output current

0 V

REF

0 V

REF

/2

Unipolar,
Table 3

Input Resistance

∆V

IN

∆I

IN

21

kΩ

16

-10 360

Unipolar

Input Current

-10 720

Bipolar

MAX128

0 to 5V range

-10 0.1 10

0 to 10V range

Unipolar

2.5

Small-Signal Bandwidth

5

MHz

PARAMETER SYMBOL MIN TYP MAX UNITS

2.5

-3dB
rolloff

1.25

0 10

V

0 5

Track/Hold Acquisition Time 3 µs

Input Capacitance 40 pF

REFOUT Voltage V

REF

4.076 4.096 4.116 V

REFOUT Tempco

±15

ppm/°C

Output Short-Circuit Current 30 mA

CONDITIONS

(Note 4)

TA= +25°C
MAX127_C/MAX128_C

±30MAX127_E/MAX128_E

ANALOG INPUT

INTERNAL REFERENCE

MAX127/MAX128

Multirange, +5V, 12-Bit DAS with
2-Wire Serial Interface

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VDD= +5V ±5%; unipolar/bipolar range; external reference mode, V

REF

= 4.096V; 4.7µF at REF pin; external clock, f

CLK

= 400kHz;

T

A

= T

MIN

to T

MAX

; unless otherwise noted. Typical values are at TA= +25°C.)

V2.4 4.18Input Voltage Range

VVDD- 0.5

REFADJ Threshold for
Buffer Disable

Normal or STANDBY power-down mode kΩ10

Input Resistance

FULL power-down mode 5 MΩ

External reference = 4.096V

CONDITIONS

FULL power-down mode

LSB

±0.1 ±0.5

PSRR

Power-Supply Rejection Ratio
(Note 7)

µs

V4.75 5.25V

DD

Supply Voltage

6.0 7.7 10.0t

CONV

Conversion Time

120 220

Normal mode, bipolar ranges

700 850

Normal mode, unipolar ranges

UNITSMIN TYP MAXSYMBOLPARAMETER

STANDBY power-down mode (Note 6)

mA

18

I

DD

Supply Current

6 10

µA

Internal reference ±0.5

0.4f

CLK

External Clock Frequency Range MHz

Power-up (Note 8) µs200

Bandgap Reference
Start-Up Time

ksps8Throughput Rate

C

IN

15 pF(Note 4)

Input Leakage Current I

IN

±0.1 ±10 µAVIN= 0 or V

DD

Input Low Threshold Voltage V

IL

0.8 V

Input High Threshold Voltage V

IH

2.4 V

Input Capacitance

V

HYS

0.2 VInput Hysteresis

400

V

REF

=

4.18V

µA

1

Input Current

FULL power-down mode

Normal, or STANDBY
power-down mode

To 0.1mV, REF bypass
capacitor fully discharged

ms

8

Reference Buffer Settling Time

POWER REQUIREMENTS

TIMING

REFERENCE INPUT (buffer disabled, reference input applied to REF)

DIGITAL INPUTS (SHDN, A2, A1, A0)

C

REF

= 4.7µF

C

REF

= 33µF 60

MAX127/MAX128

Multirange, +5V, 12-Bit DAS with

2-Wire Serial Interface

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(VDD= +5V ±5%; unipolar/bipolar range; external reference mode, V

REF

= 4.096V; 4.7µF at REF pin; external clock, f

CLK

= 400kHz;

T

A

= T

MIN

to T

MAX

; unless otherwise noted. Typical values are at TA= +25°C.)

Input Hysteresis V

HYS

0.05 x V

DD

V

Input Low Threshold Voltage V

IL

0.3 x V

DD

V

Input High Threshold Voltage V

IH

0.7 x V

DD

V

PARAMETER SYMBOL MIN TYP MAX UNITSCONDITIONS

TIMING CHARACTERISTICS

(VDD= +4.75V to +5.25V; unipolar/bipolar range; external reference mode, V

REF

= 4.096V; 4.7µF at REF pin; TA= T

MIN

to T

MAX

;

unless otherwise noted. Typical values are at T

A

= +25°C.)

Input Capacitance C

IN

15 pF