MAX1031BEEG+ - Maxim Integrated - Datasheet.Directory

General Description

The MAX1027/MAX1029/MAX1031 are serial 10-bit ana-

log-to-digital converters (ADCs) with an internal reference

and an internal temperature sensor. These devices fea-

ture on-chip FIFO, scan mode, internal clock mode, inter-

nal averaging, and AutoShutdown™. The maximum

sampling rate is 300ksps using an external clock. The

MAX1031 has 16 input channels, the MAX1029 has 12

input channels, and the MAX1027 has 8 input channels.

All input channels are configurable for single-ended or

differential inputs in unipolar or bipolar mode. All three

devices operate from a +3V supply and contain a 10MHz

SPI™/QSPI™/MICROWIRE™-compatible serial port.

The MAX1031 is available in 28-pin, 5mm x 5mm, TQFN

with exposed pad and 24-pin QSOP packages. The

MAX1027/MAX1029 are only available in QSOP pack-

ages. All three devices are specified over the extended

-40°C to +85°C temperature range.

________________________Applications

System Supervision

Data-Acquisition Systems

Industrial Control Systems

Patient Monitoring

Data Logging

Instrumentation

Features

oInternal Temperature Sensor (±0.7°C Accuracy)

o16-Entry First-In/First-Out (FIFO)

oAnalog Multiplexer with True Differential

Track/Hold

16-, 12-, 8-Channel Single Ended

8-, 6-, 4-Channel True Differential

(Unipolar or Bipolar)

oAccuracy: ±1 LSB INL, ±1 LSB DNL, No Missing

Codes Over Temperature

oScan Mode, Internal Averaging, and Internal Clock

oLow-Power Single +3V Operation

1mA at 300ksps

oInternal 2.5V Reference or External Differential

Reference

o10MHz 3-Wire SPI/QSPI/MICROWIRE-Compatible

Interface

oSpace-Saving 28-Pin 5mm x 5mm TQFN Package

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

________________________________________________________________

Maxim Integrated Products

Pin Configurations

19-2854; Rev 5; 8/11

EVALUATION KIT

AVAILABLE

Ordering Information

Ordering Information continued at end of data sheet.

AIN0 EOC

DOUT

DIN

SCLK

VDD

GND

REF+

MAX1027

QSOP

AIN1

AIN2

AIN5

AIN3

AIN4

REF-/AIN6

CNVST/AIN7

+20

EOC

DOUT

DIN

CSAIN3

AIN2

AIN1

AIN0

SCLK

VDD

GND

REF+AIN7

AIN6

AIN5

AIN4

CNVST/AIN11

REF-/AIN10AIN9

AIN8

MAX1029

QSOP

TOP VIEW

PART TEMP RANGE PIN-PACKAGE

MAX1027BCEE+T 0°C to +70°C 16 QSOP

MAX1027BEEE+T -40°C to +85°C 16 QSOP

MAX1029BCEP+T 0°C to +70°C 20 QSOP

MAX1029BEEP+T -40°C to +85°C 20 QSOP

Pin Configurations continued at end of data sheet.

AutoShutdown is a trademark of Maxim Integrated Products, Inc.

SPI/QSPI are trademarks of Motorola, Inc.

MICROWIRE is a trademark of National Semiconductor Corp.

Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VDD = +2.7V to +3.6V, fSAMPLE = 300kHz, fSCLK = 4.8MHz (50% duty cycle), VREF = 2.5V, TA= TMIN to TMAX, unless otherwise

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

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.

VDD to GND..............................................................-0.3V to +6V

CS, SCLK, DIN, EOC, DOUT to GND.........-0.3V to (VDD + 0.3V)

AIN0–AIN13, REF-/AIN_, CNVST/AIN_,

REF+ to GND.........................................-0.3V to (VDD + 0.3V)

Maximum Current into Any Pin............................................50mA

Continuous Power Dissipation (TA= +70°C)

16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW

20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW

24-Pin QSOP (derate 9.5mW/°C above +70°C)...........762mW

28-Pin TQFN (derate 20.8mW/°C above +70°C) .......1667mW

Operating Temperature Ranges

MAX10__C__.......................................................0°C to +70°C

MAX10__E__....................................................-40°C to +85°C

Storage Temperature Range .............................-60°C to +150°C

Junction Temperature......................................................+150°C

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

Soldering Temperature (reflow) .......................................+260°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DC ACCURACY (Note 1)

Resolution RES 10 Bits

Integral Nonlinearity INL ±1.0 LSB

Differential Nonlinearity DNL No missing codes over temperature ±1.0 LSB

Offset Error ±0.5 ±2.0 LSB

Gain Error (Note 2) ±0.5 ±2.0 LSB

Offset Error Temperature

Coefficient ±2 ppm/°C

FSR

Gain Temperature Coefficient ±0.8 ppm/°C

Channel-to-Channel Offset

Matching ±0.1 LSB

DYNAMIC SPECIFICATIONS (30kHz sine wave input, 2.5VP-P, 300ksps, fSCLK = 4.8MHz)

Signal-to-Noise Plus Distortion SINAD 62 dB

Total Harmonic Distortion THD Up to the 5th harmonic -79 dBc

Spurious-Free Dynamic Range SFDR -81 dBc

Intermodulation Distortion IMD fin1 = 29.9kHz, fin2 = 30.1kHz -74 dBc

Full-Power Bandwidth -3dB point 1 MHz

Full-Linear Bandwidth S/(N + D) > 68dB 100 kHz

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VDD = +2.7V to +3.6V, fSAMPLE = 300kHz, fSCLK = 4.8MHz (50% duty cycle), VREF = 2.5V, TA= TMIN to TMAX, unless otherwise

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

CONVERSION RATE

External reference 0.8

Power-Up Time tPU Internal reference (Note 3) 65 μs

Acquisition Time tACQ 0.6 μs

Internally clocked 3.5

Conversion Time tCONV Externally clocked (Note 4) 2.7 μs

Externally clocked conversion 0.1 4.8

External Clock Frequency fSCLK Data I/O 10 MHz

Aperture Delay 30 ns

Aperture Jitter <50 ps

ANALOG INPUT

Unipolar 0 VREF

Input Voltage Range Bipolar (Note 5) - V

RE F

/2 V

RE F

/2 V

Input Leakage Current VIN = VDD ±0.01 ±1 μA

Input Capacitance During acquisition time (Note 6) 24 pF

INTERNAL TEMPERATURE SENSOR

TA = +25°C ±0.7

Measurement Error (Note 7) TA = TMIN to TMAX ±1.2 ±2.5 °C

Temperature Measurement Noise 0.1 °CRMS

Temperature Resolution 1/8 °C

Power-Supply Rejection 0.3 °C/V

INTERNAL REFERENCE

REF Output Voltage 2.48 2.50 2.52 V

REF Temperature Coefficient TCREF ±30 ppm/°C

Output Resistance 6.5 kΩ

REF Output Noise 200 μVRMS

REF Power-Supply Rejection PSRR -70 dB

EXTERNAL REFERENCE INPUT

REF- Input Voltage Range VREF- 0 500 mV

REF+ Input Voltage Range VREF+ 1.0 VDD + 50mV V

VREF+ = 2.5V, fSAMPLE = 300ksps 40 100

REF+ Input Current IREF+ VREF+ = 2.5V, fSAMPLE = 0 ±0.1 ±5 μA

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

4 _______________________________________________________________________________________

Note 1: Tested at VDD = +2.7V, unipolar input mode.

Note 2: Offset nulled.

Note 3: Time for reference to power up and settle to within 1 LSB.

Note 4: Conversion time is defined as the number of clock cycles multiplied by the clock period; clock has 50% duty cycle.

Note 5: The operational input voltage range for each individual input of a differentially configured pair is from GND to VDD. The

operational input voltage difference is from -VREF/2 to +VREF/2.

Note 6: See Figure 3 (Input Equivalent Circuit) and the

Sampling Error vs. Source Impedance

curve in the

Typical Operating

Characteristics

section.

Note 7: Fast automated test, excludes self-heating effects.

Note 8: When CNVST is configured as a digital input, do not apply a voltage between VIL and VIH.

Note 9: Supply current is specified depending on whether an internal or external reference is used for voltage conversions.

Temperature measurements always use the internal reference.

ELECTRICAL CHARACTERISTICS (continued)

(VDD = +2.7V to +3.6V, fSAMPLE = 300kHz, fSCLK = 4.8MHz (50% duty cycle), VREF = 2.5V, TA= TMIN to TMAX, unless otherwise

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DIGITAL INPUTS (SCLK, DIN, CS, CNVST) (Note 8)

Input Voltage Low VIL VDD x 0.3 V

Input Voltage High VIH VDD x 0.7 V

Input Hysteresis VHYST 200 mV

Input Leakage Current IIN VIN = 0 or VDD ±0.01 ±1.0 μA

Input Capacitance CIN 15 pF

DIGITAL OUTPUTS (DOUT, EOC)

ISINK = 2mA 0.4

Output Voltage Low VOL ISINK = 4mA 0.8 V

Output Voltage High VOH ISOURCE = 1.5mA VDD - 0.5 V

Tri-State Leakage Current ILCS = VDD ±0.05 ±1 μA

Tri-State Output Capacitance COUT CS = VDD 15 pF

POWER REQUIREMENTS

Supply Voltage VDD 2.7 3.6 V

During temp sense 2400 2700

fSAMPLE = 300ksps 1750 2000

fSAMPLE = 0, REF on 1000 1200

Internal

reference

Shutdown 0.2 5

During temp sense 1550 2000

fSAMPLE = 300ksps 1050 1200

Supply Current (Note 9) IDD

External

reference

Shutdown 0.2 5

μA

Power-Supply Rejection PSR VDD = 2.7V to 3.6V; full-scale input ±0.2 ±1.4 mV

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

_______________________________________________________________________________________ 5

Note 10: This time is defined as the number of clock cycles needed for conversion multiplied by the clock period. If the internal refer-

ence needs to be powered up, the total time is additive. The internal reference is always used for temperature measure-

ments..

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Externally clocked conversion 208

SCLK Clock Period tCP Data I/O 100 ns

SCLK Duty Cycle tCH 40 60 %

SCLK Fall to DOUT Transition tDOT CLOAD = 30pF 40 ns

CS Rise to DOUT Disable tDOD CLOAD = 30pF 40 ns

CS Fall to DOUT Enable tDOE CLOAD = 30pF 40 ns

DIN to SCLK Rise Setup tDS 40 ns

SCLK Rise to DIN Hold tDH 0ns

CS Fall to SCLK Rise Setup Time tCSS0 40 ns

CS Fall to SCLK Rise Hold Time tCSH0 0ns

CS Rise to SCLK Rise Hold Time tCSH1 0ns

CS Rise to SCLK Rise Setup Time tCSS1 40 ns

CKSEL = 00, CKSEL = 01 (temp sense) 40 ns

CNVST Pulse Width tCSW CKSEL = 01 (voltage conversion) 1.4 μs

T S Temp sense 56

Voltage conversion 7

CS or CNVST Rise to EOC

Low (Note 10)

R P Reference power-up 65

μs

TIMING CHARACTERISTICS (Figure 1)

INTEGRAL NONLINEARITY

vs. OUTPUT CODE

MAX1027/29/31 toc01

OUTPUT CODE (DECIMAL)

INL (LSB)

768512256

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5

-0.5

01024

fSAMPLE = 300ksps

DIFFERENTIAL NONLINEARITY

vs. OUTPUT CODE

MAX1027/29/31 toc02

OUTPUT CODE (DECIMAL)

DNL (LSB)

768512256

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5

-0.5

0 1024

fSAMPLE = 300ksps

SINAD vs. FREQUENCY

MAX1027/29/31 toc03

FREQUENCY (kHz)

SINAD (dB)

1001011k

Typical Operating Characteristics

(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA= +25°C, unless otherwise noted.)

SHUTDOWN SUPPLY CURRENT

vs. TEMPERATURE

MAX1027/29/31 toc10

TEMPERATURE (°C)

3510-15

0.2

0.4

0.6

0.8

1.0

-40 85

IDD (µA)

VDD = 3V

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

6 _______________________________________________________________________________________

2.7 3.6

VREF (V)

2.498

2.499

2.500

2.501

2.502

2.497

INTERNAL REFERENCE VOLTAGE

vs. SUPPLY VOLTAGE

MAX1027/29/31 toc11

VDD (V)

3.0 3.3

VDD = 3V

INTERNAL REFERENCE VOLTAGE

vs. TEMPERATURE

MAX1027/29/31 toc12

TEMPERATURE (°C)

3510-15

2.480

2.490

2.500

2.510

2.520

2.470

-40 85

VREF (V)

VDD = 3V

SFDR vs. FREQUENCY

MAX1027/29/31 toc04

SFDR (dB)

100

FREQUENCY (kHz)

1001011k

THD vs. FREQUENCY

MAX1027/29/31 toc05

THD (dB)

-90

-80

-70

-60

-50

-100

FREQUENCY (kHz)

1001011k

SUPPLY CURRENT vs. SAMPLING RATE

MAX1027/29/31 toc06

IVDD (µA)

200

400

600

800

1000

1200

1400

1600

1800

SAMPLING RATE (ksps)

1001011k

VDD = 3V

INTERNAL REFERENCE

EXTERNAL REFERENCE

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX1027/29/31 toc07

3.53.43.2 3.32.9 3.0 3.12.8

200

400

600

800

1000

1200

1400

1600

1800

2000

2.7 3.6

IDD (µA)

VDD (V)

fSAMPLE = 300ksps

EXTERNAL REFERENCE

INTERNAL REFERENCE

SHUTDOWN SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX1027/29/31 toc08

3.53.43.33.23.13.02.92.8

0.1

0.2

0.3

0.4

0.5

2.7 3.6

IDD (µA)

VDD (V)

VDD = 3V

SUPPLY CURRENT vs. TEMPERATURE

MAX1027/29/31 toc09

800

1000

1200

1400

1600

1800

600

TEMPERATURE (°C)

3510-15-40 85

IDD (µA)

VDD = 3V

fSAMPLE = 300ksps

INTERNAL REFERENCE

EXTERNAL REFERENCE

Typical Operating Characteristics (continued)

(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA= +25°C, unless otherwise noted.)

MAX1027/MAX1029/MAX1031

OFFSET ERROR vs. SUPPLY VOLTAGE

MAX1027/29/31 toc13

VDD (V)

OFFSET ERROR (LSB)

0.55

0.60

0.65

0.70

0.50

2.7 3.6

3.0 3.3

fSAMPLE = 300ksps

OFFSET ERROR vs. TEMPERATURE

MAX1027/29/31 toc14

OFFSET ERROR (LSB)

0.5

0.6

0.7

0.8

0.4

TEMPERATURE (°C)

603510-15-40 85

fSAMPLE = 300ksps

GAIN ERROR vs. SUPPLY VOLTAGE

MAX1027/29/31 toc15

VDD (V)

GAIN ERROR (LSB)

3.33.0

-0.1

3.62.7

-0.2

fSAMPLE = 300ksps

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA= +25°C, unless otherwise noted.)

-1.00

-0.50

-0.75

0.50

0.75

1.00

-40 10-15 356085

TEMPERATURE SENSOR ERROR

vs. TEMPERATURE

MAX1027/29/31 toc17

TEMPERATURE (°C)

TEMPERATURE SENSOR ERROR (LSB)

0.25

-0.25

-1.0

-0.5

0.5

1.0

0426810

SAMPLING ERROR

vs. SOURCE IMPEDANCE

MAX1027/29/31 toc18

SOURCE IMPEDANCE (kΩ)

SAMPLING ERROR (LSB)

GAIN ERROR vs. TEMPERATURE

MAX1027/29/31 toc16

GAIN ERROR (LSB)

-0.1

0.1

0.3

0.5

-0.3

TEMPERATURE (°C)

603510-15-40 85

fSAMPLE = 300ksps

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

8 _______________________________________________________________________________________

Pin Description

MAX1031

TQFN

MAX1031

QSOP MAX1029 MAX1027 NAME FUNCTION

2–12, 26,

27, 28 1–14 — — AIN0–13 Analog Inputs

— — 1–10 — AIN0–9 Analog Inputs

— — — 1–6 AIN0–5 Analog Inputs

13 15 — — REF-/AIN14 Negative Input for External Differential Reference/Analog Input 14.

See Table 3 for details on programming the setup register.

— — 11 — REF-/AIN10 Negative Input for External Differential Reference/Analog Input 10.

See Table 3 for details on programming the setup register.

— — — 7 REF-/AIN6 Negative Input for External Differential Reference/Analog Input 6.

See Table 3 for details on programming the setup register.

14 16 — — CNVST/

AIN15

Active-Low Conversion Start Input/Analog Input 15. See Table 3

for details on programming the setup register.

— — 12 — CNVST/

AIN11

Active-Low Conversion Start Input/Analog Input 11. See Table 3

for details on programming the setup register.

——— 8

CNVST/

AIN7

Active-Low Conversion Start Input/Analog Input 7. See Table 3 for

details on programming the setup register.

15 17 13 9 REF+ Positive Reference Input. Bypass to GND with a 0.1μF capacitor.

16 18 14 10 GND Ground

18 19 15 11 VDD Power Input. Bypass to GND with a 0.1μF capacitor.

20 20 16 12 SCLK

Serial Clock Input. Clocks data in and out of the serial interface

(duty cycle must be 40% to 60%). See Table 3 for details on

programming the clock mode.

21 21 17 13 CS Active-Low Chip Select Input. When CS is low, the serial interface

is enabled. When CS is high, DOUT is high impedance.

22 22 18 14 DIN Serial Data Input. DIN data is latched into the serial interface on

the rising edge of SCLK.

23 23 19 15 DOUT Serial Data Output. Data is clocked out on the falling edge of

SCLK. High impedance when CS is connected to VDD.

24 24 20 16 EOC End of Conversion Output. Data is valid after EOC pulls low.

1, 17, 19,

25 — — — N.C. No Connection. Not internally connected.

— — — — EP Exposed Pad (TQFN Only). Connect EP to GND.

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

_______________________________________________________________________________________ 9

SCLK

DIN

DOUT

tDH

tDOE

tDS

tCH

tCL

tCSS0 tCP tCSH1 tCSH0

tCSS1

tDOD

tDOT

Figure 1. Detailed Serial-Interface Timing Diagram

12-BIT

SAR

ADC

CONTROL

SERIAL INTERFACE

OSCILLATOR

FIFO AND

ACCUMULATOR

T/H

TEMP

SENSE

REF-

CNVST

SCLK

DIN

EOC

DOUT

AIN15

AIN1

AIN2

INTERNAL

REFERENCE

REF+

MAX1027

MAX1029

MAX1031

Figure 2. Functional Diagram

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

10 ______________________________________________________________________________________

Detailed Description

The MAX1027/MAX1029/MAX1031 are low-power, seri-

al-output, multichannel ADCs with temperature-sensing

capability for temperature-control, process-control, and

monitoring applications. These 10-bit ADCs have inter-

nal track and hold (T/H) circuitry that supports single-

ended and fully differential inputs. Data is converted

from an internal temperature sensor or analog voltage

sources in a variety of channel and data-acquisition

configurations. Microprocessor (μP) control is made

easy through a 3-wire SPI/QSPI/MICROWIRE-compati-

ble serial interface.

Figure 2 shows a simplified functional diagram of the

MAX1027/MAX1029/MAX1031 internal architecture.

The MAX1027 has eight single-ended analog input

channels or four differential channels. The MAX1029

has 12 single-ended analog input channels or six differ-

ential channels. The MAX1031 has 16 single-ended

analog input channels or eight differential channels.

Converter Operation

The MAX1027/MAX1029/MAX1031 ADCs use a fully dif-

ferential, successive-approximation register (SAR) con-

version technique and an on-chip T/H block to convert

temperature and voltage signals into a 10-bit digital

result. Both single-ended and differential configurations

are supported, with a unipolar signal range for single-

ended mode and bipolar or unipolar ranges for differ-

ential mode.

Input Bandwidth

The ADC’s input-tracking circuitry has a 1MHz small-

signal bandwidth, so it is possible to digitize high-

speed transient events and measure periodic signals

with bandwidths exceeding the ADC’s sampling rate by

using undersampling techniques. Anti-alias prefiltering

of the input signals is necessary to avoid high-frequen-

cy signals aliasing into the frequency band of interest.

Analog Input Protection

Internal ESD protection diodes clamp all pins to VDD

and GND, allowing the inputs to swing from (GND -

0.3V) to (VDD + 0.3V) without damage. However, for

accurate conversions near full scale, the inputs must

not exceed VDD by more than 50mV or be lower than

GND by 50mV. If an off-channel analog input voltage

exceeds the supplies, limit the input current to 2mA.

3-Wire Serial Interface

The MAX1027/MAX1029/MAX1031 feature a serial

interface compatible with SPI/QSPI and MICROWIRE

devices. For SPI/QSPI, ensure the CPU serial interface

runs in master mode so it generates the serial clock

signal. Select the SCLK frequency of 10MHz or less,

and set clock polarity (CPOL) and phase (CPHA) in the

μP control registers to the same value. The MAX1027/

MAX1029/MAX1031 operate with SCLK idling high or

low, and thus operate with CPOL = CPHA = 0 or CPOL

= CPHA = 1. Set CS low to latch input data at DIN on

the rising edge of SCLK. Output data at DOUT is

updated on the falling edge of SCLK. Bipolar true-dif-

ferential results and temperature sensor results are

available in two’s complement format, while all others

are in binary.

Serial communication always begins with an 8-bit input

data byte (MSB first) loaded from DIN. Send a second

byte, immediately following the setup byte, to write to

the unipolar mode or bipolar mode registers (see

Tables 1, 3, 4, and 5). A high-to-low transition on CS ini-

tiates the data input operation. The input data byte and

the subsequent data bytes are clocked from DIN into

the serial interface on the rising edge of SCLK.

Tables 1–7 detail the register descriptions. Bits 5 and 4,

CKSEL1 and CKSEL0, respectively, control the clock

modes in the setup register (see Table 3). Choose

between four different clock modes for various ways to

start a conversion and determine whether the acquisi-

tions are internally or externally timed. Select clock

mode 00 to configure CNVST/AIN_ to act as a conver-

sion start and use it to request the programmed inter-

nally timed conversions without tying up the serial bus.

In clock mode 01, use CNVST to request conversions

one channel at a time, controlling the sampling speed

without tying up the serial bus. Request and start inter-

nally timed conversions through the serial interface by

writing to the conversion register in the default clock

mode, 10. Use clock mode 11 with SCLK up to 4.8MHz

for externally timed acquisitions to achieve sampling

rates up to 300ksps. Clock mode 11 disables scanning

and averaging. See Figures 4–7 for timing specifica-

tions and how to begin a conversion.

These devices feature an active-low, end-of-conversion

output. EOC goes low when the ADC completes the

last-requested operation and is waiting for the next input

data byte (for clock modes 00 and 10). For clock mode

01, EOC goes low after the ADC completes each

requested operation. EOC goes high when CS or

CNVST goes low. EOC is always high in clock mode 11.

Single-Ended/Differential Input

The MAX1027/MAX1029/MAX1031 use a fully differen-

tial ADC for all conversions. The analog inputs can be

configured for either differential or single-ended con-

versions by writing to the setup register (see Table 3).

Single-ended conversions are internally referenced to

GND (Figure 3).

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

______________________________________________________________________________________ 11

In differential mode, the T/H samples the difference

between two analog inputs, eliminating common-mode

DC offsets and noise. IN+ and IN- are selected from

the following pairs: AIN0/AIN1, AIN2/AIN3, AIN4/AIN5,

AIN6/AIN7, AIN8/AIN9, AIN10/AIN11, AIN12/AIN13,

and AIN14/AIN15. AIN0–AIN7 are available on the

MAX1027, MAX1029, and MAX1031. AIN8–AIN11 are

only available on the MAX1029 and MAX1031.

AIN12–AIN15 are only available on the MAX1031. See

Tables 2–5 for more details on configuring the inputs.

For the inputs that can be configured as CNVST or an

analog input, only one can be used at a time. For the

inputs that can be configured as REF- or an analog

input, the REF- configuration excludes the analog input.

Unipolar/Bipolar

Address the unipolar and bipolar registers through the

setup register (bits 1 and 0). Program a pair of analog

channels for differential operation by writing a 1 to the

appropriate bit of the bipolar or unipolar register.

Unipolar mode sets the differential input range from 0

to VREF. A negative differential analog input in unipolar

mode causes the digital output code to be zero.

Selecting bipolar mode sets the differential input range

to ±VREF / 2. The digital output code is binary in unipo-

lar mode and two’s complement in bipolar mode (see

the transfer function graphs, Figures 8 and 9).

In single-ended mode, the MAX1027/MAX1029/

MAX1031 always operate in unipolar mode. The analog

inputs are internally referenced to GND with a full-scale

input range from 0 to VREF.

True Differential Analog Input T/H

The equivalent circuit of Figure 3 shows the

MAX1027/MAX1029/MAX1031s’ input architecture. In

track mode, a positive input capacitor is connected to

AIN0–AIN15 in single-ended mode (and AIN0, AIN2,

AIN4…AIN14 in differential mode). A negative input

capacitor is connected to GND in single-ended mode

(or AIN1, AIN3, AIN5…AIN15 in differential mode). For

external track-and-hold timing, use clock mode 01.

After the T/H enters hold mode, the difference between

the sampled positive and negative input voltages is

converted. The time required for the T/H to acquire an

input signal is determined by how quickly its input

capacitance is charged. If the input signal’s source

impedance is high, the required acquisition time

lengthens. The acquisition time, tACQ, is the maximum

time needed for a signal to be acquired, plus the power-

up time. It is calculated by the following equation:

where RIN = 1.5kΩ, RSis the source impedance of the

input signal, and tPWR = 1μs, the power-up time of the

device. The varying power-up times are detailed in the

explanation of the clock mode conversions.

tACQ is never less than 1.4μs, and any source imped-

ance below 300Ωdoes not significantly affect the

ADC’s AC performance. A high-impedance source can

be accommodated either by lengthening tACQ or by

placing a 1μF capacitor between the positive and neg-

ative analog inputs.

Internal FIFO

The MAX1027/MAX1029/MAX1031 contain a FIFO

buffer that can hold up to 16 ADC results plus one tem-

perature result. This allows the ADC to handle multiple

internally clocked conversions and a temperature mea-

surement, without tying up the serial bus.

If the FIFO is filled and further conversions are request-

ed without reading from the FIFO, the oldest ADC

results are overwritten by the new ADC results. Each

result contains 2 bytes, with the MSB preceded by four

leading zeros and the LSB followed by two sub-bits.

After each falling edge of CS, the oldest available byte

of data is available at DOUT, MSB first. When the FIFO

is empty, DOUT is zero.

The first 2 bytes of data read out after a temperature

measurement always contain the temperature result

preceded by four leading zeros, MSB first. If another

txRRxpFt

ACQ S IN PWR

()

+924

HOLD

CIN+

REF

GND DAC

CIN-

VDD/2

COMPARATOR

AIN0-AIN15

(SINGLE ENDED);

AIN0, AIN2,

AIN4…AIN14

(DIFFERENTIAL)

GND

(SINGLE ENDED);

AIN1, AIN3,

AIN5…AIN15

(DIFFERENTIAL) HOLD

HOLD

Figure 3. Equivalent Input Circuit

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

12 ______________________________________________________________________________________

temperature measurement is performed before the first

temperature result is read out, the old measurement is

overwritten by the new result. Temperature results are

in degrees Celsius (two’s complement) at a resolution

of 1/8 of a degree. See the

Temperature Measurements

section for details on converting the digital code to a

temperature.

Internal Clock

The MAX1027/MAX1029/MAX1031 operate from an inter-

nal oscillator, which is accurate within 10% of the 4.4MHz

nominal clock rate. The internal oscillator is active in

clock modes 00, 01, and 10. Read out the data at clock

speeds up to 10MHz. See Figures 4–7 for details on tim-

ing specifications and starting a conversion.

Applications Information

The MAX1027/MAX1029/MAX1031 communicate

between the internal registers and the external circuitry

through the SPI/QSPI-compatible serial interface. Table

1 details the registers and the bit names. Tables 2–7

show the various functions within the conversion regis-

ter, setup register, averaging register, reset register,

unipolar register, and bipolar register.

Conversion Time Calculations

The conversion time for each scan is based on a num-

ber of different factors: conversion time per sample,

samples per result, results per scan, if a temperature

measurement is requested, and if the external refer-

ence is in use.

Use the following formula to calculate the total conver-

sion time for an internally timed conversion in clock

modes 00 and 10 (see the

Electrical Characteristics

section as applicable):

total conversion time = tCONV x navg x nresult + tTS + tRP

where:

tCONV = tACQ(max) + tCONV(max)

navg = samples per result (amount of averaging)

nresult = number of FIFO results requested; determined

by number of channels being scanned or by NSCAN1,

NSCAN0

tTS = time required for temperature measurement; set

to zero if temp measurement is not requested

tRP = internal reference wake-up; set to zero if the inter-

nal reference is already powered up or if the external

reference is being used

In clock mode 01, the total conversion time depends on

how long CNVST is held low or high, including any time

required to turn on the internal reference. Conversion

time in externally clocked mode (CKSEL1, CKSEL0 = 11)

depends on the SCLK period and how long CS is held

high between each set of eight SCLK cycles.

Conversion Register

Select active analog input channels, scan modes, and

a single temperature measurement per scan by writing

to the conversion register. Table 2 details channel

selection, the four scan modes, and how to request a

temperature measurement. Request a scan by writing

to the conversion register when in clock mode 10 or 11,

or by applying a low pulse to the CNVST pin when in

clock mode 00 or 01.

A conversion is not performed if it is requested on a

channel that has been configured as CNVST or REF-.

Do not request conversions on channels 8–15 on the

MAX1027 and channels 12–15 on the MAX1029. Set

CHSEL3:CHSEL0 to the lower channel’s binary value. If

the last two channels are configured as a differential

Conversion 1 CHSEL3 CHSEL2 CHSEL1 CHSEL0 SCAN1 SCAN0 TEMP

Setup 0 1 CKSEL1 CKSEL0 REFSEL1 REFSEL0 DIFFSEL1 DIFFSEL0

Averaging 0 0 1 AVGON NAVG1 NAVG0 NSCAN1 NSCAN0

Reset 0001RESET XXX

Unipolar Mode (Setup) UCH0/1 UCH2/3 UCH4/5 UCH6/7 UCH8/9*UCH10/11*UCH12/13** UCH14/15**

Bipolar Mode (Setup) BCH0/1 BCH1/2 BCH4/5 BCH6/7 BCH8/9*BCH10/11*BCH12/13** BCH14/15**

Table 1. Input Data Byte (MSB First)

Unipolar/bipolar channels 8–15 are only valid on the MAX1029 and MAX1031.

Unipolar/bipolar channels 12–15 are only valid on the MAX1031.

X = Don’t care.

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

______________________________________________________________________________________ 13

pair and one of them has been reconfigured as CNVST

or REF-, the pair is ignored.

Select scan mode 00 or 01 to return one result per sin-

gle-ended channel and one result per differential pair

within the requested range, plus one temperature result

if selected. Select scan mode 10 to scan a single input

channel numerous times, depending on NSCAN1 and

NSCAN0 in the averaging register (see Table 6). Select

scan mode 11 to return only one result from a single

channel.

Setup Register

Write a byte to the setup register to configure the clock,

reference, and power-down modes. Table 3 details the

bits in the setup register. Bits 5 and 4 (CKSEL1 and

CKSEL0) control the clock mode, acquisition and sam-

pling, and the conversion start. Bits 3 and 2 (REFSEL1

and REFSEL0) control internal or external reference use.

Bits 1 and 0 (DIFFSEL1 and DIFFSEL0) address the

unipolar mode and bipolar mode registers and configure

the analog input channels for differential operation.

Unipolar/Bipolar Registers

The final 2 bits (LSBs) of the setup register control the

unipolar/bipolar mode address registers. Set bits 1 and

0 (DIFFSEL1 and DIFFSEL0) to 10 to write to the unipo-

lar mode register. Set bits 1 and 0 to 11 to write to the

bipolar mode register. In both cases, the setup byte

must be followed immediately by 1 byte of data written

to the unipolar register or bipolar register. Hold CS low

and run 16 SCLK cycles before pulling CS high. If the

last 2 bits of the setup register are 00 or 01, neither the

unipolar mode register nor the bipolar mode register is

written. Any subsequent byte is recognized as a new

input data byte. See Tables 4 and 5 to program the

unipolar and bipolar mode registers.

If a channel is configured as both unipolar and bipolar,

the unipolar setting takes precedence. In unipolar

mode, AIN+ can exceed AIN- by up to VREF. The out-

put format in unipolar mode is binary. In bipolar mode,

either input can exceed the other by up to VREF / 2. The

output format in bipolar mode is two's complement.

Averaging Register

Write to the averaging register to configure the ADC to

average up to 32 samples for each requested result,

and to independently control the number of results

requested for single-channel scans.

Table 2 details the four scan modes available in the con-

version register. All four scan modes allow averaging as

long as the AVGON bit, bit 4 in the averaging register, is

BIT

NAME BIT FUNCTION

— 7 (MSB) Set to 1 to select conversion register.

CHSEL3 6 Analog input channel select.

CHSEL2 5 Analog input channel select.

CHSEL1 4 Analog input channel select.

CHSEL0 3 Analog input channel select.

SCAN1 2 Scan mode select.

SCAN0 1 Scan mode select.

TEMP 0 (LSB)

Set to 1 to take a single temperature

measurement. The first conversion result

of a scan contains temperature information.

Table 2. Conversion Register*

See below for bit details.

CHSEL3 CHSEL2 CHSEL1 CHSEL0 SELECTED

CHANNEL (N)

0 0 0 0 AIN0

0 0 0 1 AIN1

0 0 1 0 AIN2

0 0 1 1 AIN3

0 1 0 0 AIN4

0 1 0 1 AIN5

0 1 1 0 AIN6

0 1 1 1 AIN7

1 0 0 0 AIN8

1 0 0 1 AIN9

1 0 1 0 AIN10

1 0 1 1 AIN11

1 1 0 0 AIN12

1 1 0 1 AIN13

1 1 1 0 AIN14

1 1 1 1 AIN15

SCAN1 SCAN0 SCAN MODE (CHANNEL N IS

SELECTED BY BITS CHSEL3–CHSEL0)

0 0 Scans channels 0 through N.

Scans channels N through the highest

numbered channel.

S cans channel N r ep eated l y. The aver ag i ng

r eg i ster sets the num b er of r esul ts.

1 1 No scan. Converts channel N once only.

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

14 ______________________________________________________________________________________

Table 3. Setup Register*

BIT NAME BIT FUNCTION

— 7 (MSB) Set to zero to select setup register.

— 6 Set to 1 to select setup register.

CKSEL1 5 Clock mode and CNVST configuration. Resets to 1 at power-up.

CKSEL0 4 Clock mode and CNVST configuration.

REFSEL1 3 Reference mode configuration.

REFSEL0 2 Reference mode configuration.

DIFFSEL1 1 Unipolar/bipolar mode register configuration for differential mode.

DIFFSEL0 0 (LSB) Unipolar/bipolar mode register configuration for differential mode.

CKSEL1 CKSEL0 CONVERSION CLOCK ACQUISITION/SAMPLING CNVST CONFIGURATION

0 0 Internal Internally timed CNVST

0 1 Internal Externally timed through CNVST CNVST

1 0 Internal Internally timed AIN15/11/7

1 1 External (4.8MHz max) Externally timed through SCLK AIN15/11/7

REFSEL1 REFSEL0 VOLTAGE REFERENCE AutoShutdown REF- CONFIGURATION

0 0 Internal Reference off after scan; need

wake-up delay. AIN14/10/6

0 1 External single ended Reference off; no wake-up delay. AIN14/10/6

1 0 Internal Reference always on; no wake-up

delay. AIN14/10/6

1 1 External differential Reference off; no wake-up delay. REF-

DIFFSEL1 DIFFSEL0 FUNCTION

0 0 No data follows the setup byte. Unipolar mode and bipolar mode registers remain unchanged.

0 1 No data follows the setup byte. Unipolar mode and bipolar mode registers remain unchanged.

1 0 One byte of data follows the setup byte and is written to the unipolar mode register.

1 1 One byte of data follows the setup byte and is written to the bipolar mode register.

See below for bit details.

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

______________________________________________________________________________________ 15

set to 1. Select scan mode 10 to scan the same channel

multiple times. Clock mode 11 disables averaging.

Reset Register

Write to the reset register (as shown in Table 7) to clear

the FIFO or to reset all registers to their default states.

Set the RESET bit to 1 to reset the FIFO. Set the reset

bit to zero to return the MAX1027/MAX1029/MAX1031

to its default power-up state.

Power-Up Default State

The MAX1027/MAX1029/MAX1031 power up with all

blocks in shutdown, including the reference. All registers

power up in state 00000000, except for the setup regis-

ter, which powers up in clock mode 10 (CKSEL1 = 1).

Temperature Measurements

The MAX1027/MAX1029/MAX1031 perform tempera-

ture measurements with an internal diode-connected

transistor. The diode bias current changes from 68μA

to 4μA to produce a temperature-dependent bias volt-

age difference. The second conversion result at 4μA is

subtracted from the first at 68μA to calculate a digital

value that is proportional to absolute temperature. The

output data appearing at DOUT is the above digital

code minus an offset to adjust from Kelvin to Celsius.

The reference voltage used for the temperature mea-

surements is derived from the internal reference source

to ensure a resolution of 1/8 of a degree.

Output Data Format

Figures 4–7 illustrate the conversion timing for the

MAX1027/MAX1029/MAX1031. The 10-bit conversion

result is output in MSB-first format with four leading

zeroes and two trailing sub-bits. The 12-bit temperature

measurement is output with four leading zeros. DIN

data is latched into the serial interface on the rising

edge of SCLK. Data on DOUT transitions on the falling

edge of SCLK. Conversions in clock modes 00 and 01

are initiated by CNVST. Conversions in clock modes 10

and 11 are initiated by writing an input data byte to the

conversion register. Data is binary for unipolar mode and

two’s complement for bipolar mode.

BIT NAME BIT FUNCTION

UCH0/1 7 (MSB) Set to 1 to configure AIN0 and AIN1 for unipolar differential conversion.

UCH2/3 6 Set to 1 to configure AIN2 and AIN3 for unipolar differential conversion.

UCH4/5 5 Set to 1 to configure AIN4 and AIN5 for unipolar differential conversion.

UCH6/7 4 Set to 1 to configure AIN6 and AIN7 for unipolar differential conversion.

UCH8/9 3 Set to 1 to configure AIN8 and AIN9 for unipolar differential conversion (MAX1029/MAX1031 only).

UCH10/11 2 Set to 1 to configure AIN10 and AIN11 for unipolar differential conversion (MAX1029/MAX1031 only).

UCH12/13 1 Set to 1 to configure AIN12 and AIN13 for unipolar differential conversion (MAX1031 only).

UCH14/15 0 (LSB) Set to 1 to configure AIN14 and AIN15 for unipolar differential conversion (MAX1031 only).

Table 4. Unipolar Mode Register (Addressed Through Setup Register)

BIT NAME BIT FUNCTION

BCH0/1 7 (MSB) Set to 1 to configure AIN0 and AIN1 for bipolar differential conversion.

BCH2/3 6 Set to 1 to configure AIN2 and AIN3 for bipolar differential conversion.

BCH4/5 5 Set to 1 to configure AIN4 and AIN5 for bipolar differential conversion.

BCH6/7 4 Set to 1 to configure AIN6 and AIN7 for bipolar differential conversion.

BCH8/9 3 Set to 1 to configure AIN8 and AIN9 for bipolar differential conversion (MAX1029/MAX1031 only).

BCH10/11 2 Set to 1 to configure AIN10 and AIN11 for bipolar differential conversion (MAX1029/MAX1031 only).

BCH12/13 1 Set to 1 to configure AIN12 and AIN13 for bipolar differential conversion (MAX1031 only).

BCH14/15 0 (LSB) Set to 1 to configure AIN14 and AIN15 for bipolar differential conversion (MAX1031 only).

Table 5. Bipolar Mode Register (Addressed Through Setup Register)

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

16 ______________________________________________________________________________________

BIT NAME BIT FUNCTION

— 7 (MSB) Set to zero to select averaging register.

— 6 Set to zero to select averaging register.

— 5 Set to 1 to select averaging register.

AVGON 4 Set to 1 to turn averaging on. Set to zero to turn averaging off.

NAVG1 3 Configures the number of conversions for single channel scans.

NAVG0 2 Configures the number of conversions for single channel scans.

NSCAN1 1 Single channel scan count. (Scan mode 10 only.)

NSCAN0 0 (LSB) Single channel scan count. (Scan mode 10 only.)

Table 6. Averaging Register*

AVGON NAVG1 NAVG0 FUNCTION

0 x x Performs 1 conversion for each requested result.

1 0 0 Performs 4 conversions and returns the average for each requested result.

1 0 1 Performs 8 conversions and returns the average for each requested result.

1 1 0 Performs 16 conversions and returns the average for each requested result.

1 1 1 Performs 32 conversions and returns the average for each requested result.

NSCAN1 NSCAN0 FUNCTION (APPLIES ONLY IF SCAN MODE 10 IS SELECTED)

0 0 Scans channel N and returns 4 results.

0 1 Scans channel N and returns 8 results.

1 0 Scans channel N and returns 12 results.

1 1 Scans channel N and returns 16 results.

BIT NAME BIT FUNCTION

— 7 (MSB) Set to zero to select reset register.

— 6 Set to zero to select reset register.

— 5 Set to zero to select reset register.

— 4 Set to 1 to select reset register.

RESET 3 Set to zero to reset all registers. Set to 1 to clear the FIFO only.

x 2 Reserved. Don’t care.

x 1 Reserved. Don’t care.

x 0 (LSB) Reserved. Don’t care.

Table 7. Reset Register

See below for bit details.

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

______________________________________________________________________________________ 17

Internally Timed Acquisitions and

Conversions Using

CNVST

Performing Conversions in Clock Mode 00

In clock mode 00, the wake up, acquisition, conversion,

and shutdown sequences are initiated through CNVST

and performed automatically using the internal oscilla-

tor. Results are added to the internal FIFO to be read

out later. See Figure 4 for clock mode 00 timing.

Initiate a scan by setting CNVST low for at least 40ns

before pulling it high again. The MAX1027/MAX1029/

MAX1031 then wake up, scan all requested channels,

store the results in the FIFO, and shut down. After the

scan is complete, EOC is pulled low and the results are

available in the FIFO. Wait until EOC goes low before

pulling CS low to communicate with the serial interface.

EOC stays low until CS or CNVST is pulled low again. A

temperature measurement result, if requested, pre-

cedes all other FIFO results.

Do not initiate a second CNVST before EOC goes low;

otherwise, the FIFO can become corrupted.

Externally Timed Acquisitions and

Internally Timed Conversions with

CNVST

Performing Conversions in Clock Mode 01

In clock mode 01, conversions are requested one at a

time using CNVST and performed automatically using the

internal oscillator. See Figure 5 for clock mode 01 timing.

Setting CNVST low begins an acquisition, wakes up the

ADC, and places it in track mode. Hold CNVST low for

at least 1.4μs to complete the acquisition. If the internal

reference needs to wake up, an additional 65μs is

required for the internal reference to power up. If a tem-

perature measurement is being requested, reference

power-up and temperature measurement are internally

timed. In this case, hold CNVST low for at least 40ns.

Set CNVST high to begin a conversion. After the con-

version is complete, the ADC shuts down and pulls

EOC low. EOC stays low until CS or CNVST is pulled

low again. Wait until EOC goes low before pulling CS or

CNVST low.

If averaging is turned on, multiple CNVST pulses need

to be performed before a result is written to the FIFO.

Once the proper number of conversions has been per-

formed to generate an averaged FIFO result, as speci-

fied by the averaging register, the scan logic

automatically switches the analog input multiplexer to

the next-requested channel. If a temperature measure-

ment is programmed, it is performed after the first rising

edge of CNVST following the input data byte written to

the conversion register. The result is available on DOUT

once EOC has been pulled low.

(UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)

DOUT

MSB1 MSB2

SCLK

CNVST

EOC

SET CNVST LOW FOR AT LEAST 40ns TO BEGIN A CONVERSION. X = DON'T CARE.

LSB1

Figure 4. Clock Mode 00

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

18 ______________________________________________________________________________________

Internally Timed Acquisitions and

Conversions Using the Serial Interface

Performing Conversions in Clock Mode 10

In clock mode 10, the wake up, acquisition, conversion,

and shutdown sequences are initiated by writing an

input data byte to the conversion register, and are per-

formed automatically using the internal oscillator. This

is the default clock mode upon power-up. See Figure 6

for clock mode 10 timing.

Initiate a scan by writing a byte to the conversion regis-

ter. The MAX1027/MAX1029/MAX1031 then power up,

scan all requested channels, store the results in the

FIFO, and shut down. After the scan is complete, EOC

is pulled low and the results are available in the FIFO. If

a temperature measurement is requested, the tempera-

ture result precedes all other FIFO results. EOC stays

low until CS is pulled low again.

Externally Clocked Acquisitions and

Conversions Using the Serial Interface

Performing Conversions in Clock Mode 11

In clock mode 11, acquisitions and conversions are ini-

tiated by writing to the conversion register and are per-

formed one at a time using the SCLK as the conversion

DOUT

SCLK

CNVST

EOC

(CONVERSION2)

MSB1 LSB1 MSB2

(ACQUISITION1) (ACQUISITION2)

(CONVERSION1)

REQUEST MULTIPLE CONVERSIONS BY SETTING CNVST LOW FOR EACH CONVERSION. X = DON'T CARE.

Figure 5. Clock Mode 01

(UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)

MSB2

(CONVERSION BYTE)

DOUT

SCLK

DIN

EOC

THE CONVERSION BYTE BEGINS THE ACQUISITION. CNVST IS NOT REQUIRED. X = DON'T CARE.

MSB1 LSB1

Figure 6. Clock Mode 10

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

______________________________________________________________________________________ 19

clock. Scanning and averaging are disabled, and the

conversion result is available at DOUT during the con-

version. See Figure 7 for clock mode 11 timing.

Initiate a conversion by writing a byte to the conversion

high between the eighth and ninth cycles, the pulse

width must be less than 100μs. To continuously convert

at 16 cycles per conversion, alternate 1 byte of zeros

between each conversion byte.

If reference mode 00 is requested, or if an external ref-

erence is selected but a temperature measurement is

being requested, wait 65μs with CS high after writing

the conversion byte to extend the acquisition and allow

the internal reference to power up. To perform a tem-

perature measurement, write 24 bytes (192 cycles) of

zeros after the conversion byte. The temperature result

appears on DOUT during the last 2 bytes of the 192

cycles.

Partial Reads and Partial Writes

If the first byte of an entry in the FIFO is partially read

(CS is pulled high after fewer than 8 SCLK cycles), the

second byte of data that is read out contains the next 8

bits (not b7–b0). The remaining bits are lost for that

entry. If the first byte of an entry in the FIFO is read out

fully, but the second byte is read out partially, the rest

of the entry is lost. The remaining data in the FIFO is

uncorrupted and can be read out normally after taking

CS low again, as long as the 4 leading bits (normally

zeros) are ignored. Internal registers that are written

partially through the SPI contain new values, starting at

the MSB up to the point that the partial write is stopped.

The part of the register that is not written contains previ-

ously written values. If CS is pulled low before EOC

goes low, a conversion cannot be completed and the

FIFO is corrupted.

Transfer Function

Figure 8 shows the unipolar transfer function for single-

ended or differential inputs. Figure 9 shows the bipolar

transfer function for differential inputs. Code transitions

occur halfway between successive-integer LSB values.

Output coding is binary, with 1 LSB = VREF / 1024V for

unipolar and bipolar operation, and 1 LSB = 0.125°C

for temperature measurements.

Layout, Grounding, and Bypassing

For best performance, use PC boards. Do not use wire-

wrap boards. For the TQFN package, connect its

exposed pad to GND. Board layout should ensure that

digital and analog signal lines are separated from each

other. Do not run analog and digital (especially clock)

signals parallel to one another or run digital lines under-

neath the MAX1027/MAX1029/MAX1031 package. High-

frequency noise in the VDD power supply can affect

performance. Bypass the VDD supply with a 0.1μF

capacitor to GND, close to the VDD pin. Minimize capac-

itor lead lengths for best supply-noise rejection. If the

power supply is very noisy, connect a 10Ωresistor in

series with the supply to improve power-supply filtering.

DOUT

SCLK

DIN

EOC

MSB1 LSB1 MSB2

(ACQUISITION1) (ACQUISITION2)(CONVERSION1)

(CONVERSION BYTE)

EXTERNALLY TIMED ACQUISITION, SAMPLING AND CONVERSION WITHOUT CNVST. X = DON'T CARE.

Figure 7. Clock Mode 11

MAX1027/MAX1029/MAX1031

Definitions

Integral Nonlinearity

Integral nonlinearity (INL) is the deviation of the values

on an actual transfer function from a straight line. This

straight line can be either a best-straight-line fit or a line

drawn between the end points of the transfer function,

once offset and gain errors have been nullified. INL for

the MAX1027/MAX1029/MAX1031 is measured using

the end-point method.

Differential Nonlinearity

Differential nonlinearity (DNL) is the difference between

an actual step width and the ideal value of 1 LSB. A

DNL error specification of less than 1 LSB guarantees

no missing codes and a monotonic transfer function.

Aperture Jitter

Aperture jitter (tAJ) is the sample-to-sample variation in

the time between the samples.

Aperture Delay

Aperture delay (tAD) is the time between the rising

edge of the sampling clock and the instant when an

actual sample is taken.

Signal-to-Noise Ratio

For a waveform perfectly reconstructed from digital

samples, signal-to-noise ratio (SNR) is the ratio of the

full-scale analog input (RMS value) to the RMS quanti-

zation error (residual error). The ideal, theoretical mini-

mum analog-to-digital noise is caused by quantization

error only and results directly from the ADC’s resolution

(N bits):

SNR = (6.02 x N + 1.76)dB

In reality, there are other noise sources besides quanti-

zation noise, including thermal noise, reference noise,

clock jitter, etc. Therefore, SNR is calculated by taking

the ratio of the RMS signal to the RMS noise, which

includes all spectral components minus the fundamen-

tal, the first five harmonics, and the DC offset.

Signal-to-Noise Plus Distortion

Signal-to-noise plus distortion (SINAD) is the ratio of the

fundamental input frequency’s RMS amplitude to the

RMS equivalent of all other ADC output signals:

SINAD (dB) = 20 x log (SignalRMS/NoiseRMS)

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

20 ______________________________________________________________________________________

OUTPUT CODE

FULL-SCALE

TRANSITION

11 . . . 111

11 . . . 110

11 . . . 101

00 . . . 011

00 . . . 010

00 . . . 001

00 . . . 000

123

(COM)

FS - 3/2 LSB

FS = VREF + VCOM

ZS = VCOM

INPUT VOLTAGE (LSB)

1 LSB = VREF

1024

Figure 9. Bipolar Transfer Function, Full Scale (±FS) = ±VREF/2

011 . . . 111

011 . . . 110

000 . . . 010

000 . . . 001

000 . . . 000

111 . . . 111

111 . . . 110

111 . . . 101

100 . . . 001

100 . . . 000

- FS COM*

INPUT VOLTAGE (LSB)

OUTPUT CODE

ZS = COM

+FS - 1 LSB

*VCOM ≥ VREF/2

+ VCOM

FS = VREF

-FS = -VREF

1 LSB = VREF

1024

Figure 8. Unipolar Transfer Function, Full Scale (FS) = VREF

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 error consists of quantiza-

tion noise only. With an input range equal to the full-

scale range of the ADC, calculate the effective number

of bits as follows:

ENOB = (SINAD - 1.76)/6.02

Total Harmonic Distortion

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

sum of the first five harmonics of the input signal to the

fundamental itself. This is expressed as:

where V1 is the fundamental amplitude, and V2–V5 are

the amplitudes of the first five 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 20 x log V V V V / V 2

= +++

()

⎛

⎝

⎜⎞

⎠

⎟

MAX1027/MAX1029/MAX1031

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

______________________________________________________________________________________ 21

Ordering Information (continued)

Pin Configurations (continued)

EOC

DOUT

DIN

CSAIN3

AIN2

AIN1

AIN0

SCLK

VDD

GND

REF+AIN7

AIN6

AIN5

AIN4

CNVST/AIN15

REF-/AIN14

AIN13

AIN12AIN11

AIN10

AIN9

AIN8

QSOP

MAX1031

AIN3

AIN5

AIN6

AIN7

AIN8

N.C.

SCLK

VDD

N.C.

GND

REF+

N.C.

4567

2021 19 17 16 15

AIN0

AIN1

AIN13

AIN12

AIN11

AIN10

MAX1031

AIN4 N.C.

28 8

AIN2 AIN9

EOC

23 13 REF-/AIN14

DOUT

22 14 CNVST/AIN15

DIN

TQFN

TOP VIEW

EP = Exposed pad (connect to GND).

Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

Chip Information

PROCESS: BiCMOS

Package Information

For the latest package outline information and land patterns

(footprints), go to www.maxim-ic.com/packages. Note that a

“+”, “#”, or “-” in the package code indicates RoHS status only.

Package drawings may show a different suffix character, but

the drawing pertains to the package regardless of RoHS status.

PART TEMP RANGE PIN-PACKAGE

MAX1031BCEG+T 0°C to +70°C 24 QSOP

MAX1031BEEG+T -40°C to +85°C 24 QSOP

MAX1031BCTI+T 0°C to +70°C 28

TQF

N-EP*

MAX1031BETI+T -40°C to +85°C 28 TQFN-EP*

PACKAGE

TYPE

PACKAG

E CODE

D O C U M EN T

N O .

LA ND

PA TTERN NO.

16 QSOP E16+5 90-0167

20 QSOP E20+3 90-0168

24 QSOP E24+3

21-0055

90-0172

28 TQFN-EP T2855+8 21-0140 90-0026

MAX1026/MAX1028/MAX1030

10-Bit 300ksps ADCs with FIFO,

Temp Sensor, Internal Reference

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

3 3/09 In the General Description section, corrected the text stating that all three devices

operate from a +5V supply to a +3V supply. 1

4 11/09 Removed the Grade A devices from the Ordering Information table and Electrical

Characteristics table. 1, 3, 21

5 8/11 Updated Ordering Information, General Description, Electrical Characteristics, Typical

Operating Characteristics, Pin Description, and Figure 1. 1–9, 11, 21

Revision History