MAXIM MAX125, MAX126 User Manual

General Description

The MAX125/MAX126 are high-speed, multichannel, 14-bit data-acquisition systems (DAS) with simultaneous track/holds (T/Hs). These devices contain a 14-bit, 3µs, successive-approximation analog-to-digital converter (ADC), a +2.5V reference, a buffered reference input, and a bank of four simultaneous-sampling T/H amplifiers that preserve the relative phase information of the sampled inputs. The MAX125/MAX126 have two multiplexed inputs for each T/H, allowing a total of eight inputs. In addition, the converter is overvoltage tolerant to ±17V; a fault condition on any channel will not harm the IC. Available input ranges are ±5V (MAX125) and ±2.5V (MAX126).

An on-board sequencer converts one to four channels per CONVST pulse. In the default mode, one T/H output (CH1A) is converted. An interrupt signal (INT) is provided after the last conversion is complete. Convert two, three, or four channels by reprogramming the MAX125/MAX126 through the bidirectional parallel interface. Once programmed, the MAX125/MAX126 continue to convert the specified number of channels per CONVST pulse until they are reprogrammed. The channels are converted sequentially, beginning with CH1. The INT signal always follows the end of the last conversion in a conversion sequence. The ADC converts each assigned channel in 3µs and stores the result in an internal 14x4 RAM. Upon completion of the conversions, data can be accessed by applying successive pulses to the RD pin. Four successive reads access four data words sequentially.

The parallel interface’s data-access and bus-release timing specifications are compatible with most popular digital signal processors and 16-bit/32-bit microprocessors, so the MAX125/MAX126 conversion results can be accessed without resorting to wait states.

Applications

Multiphase Motor Control

Power-Grid Synchronization

Power-Factor Monitoring

Digital Signal Processing

Vibration and Waveform Analysis

Features

o Four Simultaneous-Sampling T/H Amplifiers with

Two Multiplexed Inputs (eight single-ended inputs total)

o 3µs Conversion Time per Channel

o Throughput: 250ksps (1 channel)

142ksps (2 channels) 100ksps (3 channels) 76ksps (4 channels)

o Input Range: ±5V (MAX125)

±2.5V (MAX126)

o Fault-Protected Input Multiplexer (±17V)

o ±5V Supplies

o Internal +2.5V or External Reference Operation

o Programmable On-Board Sequencer

o High-Speed Parallel DSP Interface

MAX125/MAX126

2x4-Channel, Simultaneous-Sampling

14-Bit DAS

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-1319; Rev 2; 6/07

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.

Typical Operating Circuit appears at end of data sheet.

Pin Configuration appears at end of data sheet.

EVALUATION KIT

AVAILABLE

PART

TEMP RANGE

PIN-

INL

PKG

CODE

MAX125CCAX

A36-4

MAX125CEAX

A36-4

MAX126CCAX

A36-4

MAX126CEAX

A36-4

PACKAGE

0°C to +70°C 36 SSOP ±4

-40°C to +85°C 36 SSOP ±4

0°C to +70°C 36 SSOP ±4

-40°C to +85°C 36 SSOP ±4

(LSB)

MAX125/MAX126

2x4-Channel, Simultaneous-Sampling 14-Bit DAS

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(AVDD= +5V ±5%, AVSS= -5V ±5%, DVDD= +5V ±5%, V

REFIN

= 2.5V, AGND = DGND = 0V, 4.7µF capacitor from REFOUT to

AGND, 0.1µF capacitor from REFIN to AGND, f

CLK

= 16MHz, external clock, 50% duty cycle, TA= T

MIN

to T

MAX

, unless otherwise

noted.)

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.

AVDDto AGND ...........................................................-0.3V to 6V

to AGND ............................................................0.3V to -6V

DVDDto DGND ...........................................................-0.3V to 6V

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

CH_ _ to AGND....................................................................±17V

REFIN, REFOUT to AGND ..........................................-0.3V to 6V

Digital Inputs/Outputs to DGND ..............-0.3V to (DV

+ 0.3V)

Continuous Power Dissipation (T

= +70°C)

SSOP (derate 11.8mW/°C above +70°C) ....................941mW

Operating Temperature Ranges

MAX125CCAX/MAX126CCAX ............................0°C to +70°C

MAX125CEAX/MAX126CEAX..........................-40°C to +85°C

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

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

DC ACCURACY (Note 1)

Resolution N All channels 14 Bits

Integral Nonlinearity INL (Note 2) ±2 ±4 LSB

Differential Nonlinearity DNL Guaranteed monotonic to 13 bits ±2 LSB

Bipolar Zero Error

Bipolar Zero-Error Match Between all channels 1.2 5 mV

Zero-Code Tempco ±5 ppm/°C

Gain Error

Gain-Error Match Between all channels 1.2 5 mV

Gain-Error Tempco ±5 ppm/°C

DYNAMIC PERFORMANCE (f

Signal-to-Noise Plus Distortion SINAD

Total Harmonic Distortion THD

Spurious-Free Dynamic Range SFDR

Channel-to-Channel Isolation

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

= 16MHz, fIN = 10.06kHz (Notes 1, 3)

CLK

TA = +25°C ±5 ±15

A = TMIN

TA = +25°C ±5 ±10

A = TMIN

Single-channel mode, channel 1A, 250ksps (Note 4)

Single-channel mode, channel 1A, 250ksps (Notes 4, 5)

Single-channel mode, channel 1A, 250ksps (Note 4)

Single-channel mode, channel 1A, 250ksps (Note 6)

to T

MAX

to T

MAX

MAX125 72 75

MAX126 70 72

80 90 dB

-89 -80 dB

80 dB

±25

±15

µA

MAX125/MAX126

2x4-Channel, Simultaneous-Sampling

14-Bit DAS

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(AVDD= +5V ±5%, AVSS= -5V ±5%, DVDD= +5V ±5%, V

REFIN

= 2.5V, AGND = DGND = 0V, 4.7µF capacitor from REFOUT to

AGND, 0.1µF capacitor from REFIN to AGND, f

CLK

= 16MHz, external clock, 50% duty cycle, TA= T

MIN

to T

MAX

, unless otherwise

noted.)

CONDITIONS UNITSMIN TYP MAXSYMBOLPARAMETER

MAX125

±5

Input Voltage Range

MAX125, VIN= ±5V

µA±667I

Input Current

(Note 7) pF16C

Input Capacitance

µs1t

ACQ

Acquisition Time

MHz8Small-Signal Bandwidth

MHz0.5Full-Power Bandwidth

mV/ms2Droop Rate

ns5Aperture Delay

RMS

30Aperture Jitter

ps500Aperture-Delay Matching

TA= +25°C V2.475 2.500 2.525V

REFOUT

Output Voltage

0mA < I

LOAD

< 1mA %±1External Load Regulation

(Note 9) ppm/°C30REFOUT Tempco

µF0.1

External Capacitive Bypass at REFIN

V2.50 ±10%Input Voltage Range

µF4.7 22

External Capacitive Bypass at REFOUT

REFIN = 2.5V µA±10Input Current

(Note 10) kΩ10Input Resistance

(Note 7) pF10Input Capacitance

MHz0.1 16External Clock Frequency

V2.4V

Input High Voltage

V0.8V

Input Low Voltage

CONVST, RD, WR, CS, CLK

±1

(Note 7) pF15C

Input Capacitance

A0–A3

µA

±10

Input Current

MAX126 ±2.5

MAX126, VIN= ±2.5V

ANALOG INPUT

TRACK/HOLD

REFERENCE OUTPUT (Note 8)

REFERENCE INPUT

EXTERNAL CLOCK

DIGITAL INPUTS (CONVST, RD, WR, CS, CLK, A0–A3) (Note 1)

MAX125/MAX126

2x4-Channel, Simultaneous-Sampling 14-Bit DAS

4 _______________________________________________________________________________________

CONDITIONS UNITSMIN TYP MAXSYMBOLPARAMETER

OUT

= 1mA V4V

Output High Voltage

OUT

= -1.6mA V0.4V

Output Low Voltage

D0–D13 µA±10Three-State Leakage Current

(Note 7) pF10

Three-State Output Capacitance

V4.75 5 5.25AV

Positive Supply Voltage

V-5.25 -5 -4.75AV

Negative Supply Voltage

V4.75 5 5.25DV

Digital Supply Voltage

mA17 25I(AVDD)Positive Supply Current

mA-17 -13I(AVSS)Negative Supply Current

mA3 5I(DVDD)Digital Supply Current

mA3Shutdown Positive Current

mA-1Shutdown Negative Current

mA3Shutdown Digital Current

(Note 11) LSB±1 ±2PSRR+Positive Supply Rejection

(Note 11) LSB±2PSRR-Negative Supply Rejection

(Note 12) mW165 250Power Dissipation

DIGITAL OUTPUTS (D0–D13, INT) (Note 1)

POWER REQUIREMENTS

ELECTRICAL CHARACTERISTICS (continued)

(AVDD= +5V ±5%, AVSS= -5V ±5%, DVDD= +5V ±5%, V

REFIN

= 2.5V, AGND = DGND = 0V, 4.7µF capacitor from REFOUT to

AGND, 0.1µF capacitor from REFIN to AGND, f

CLK

= 16MHz, external clock, 50% duty cycle, TA= T

MIN

to T

MAX

, unless otherwise

noted.)

MAX125/MAX126

2x4-Channel, Simultaneous-Sampling

14-Bit DAS

_______________________________________________________________________________________ 5

CONDITIONS

ns30t

CONVST Pulse Width

UNITSMIN TYP MAXSYMBOLPARAMETER

TIMING CHARACTERISTICS (Figure 4)

(AVDD= +5V, AVSS= -5V, DVDD= +5V, AGND = DGND = 0V, TA= T

MIN

to T

MAX

, unless otherwise noted.)

ns0t

CWS

CS to WR Setup Time

ns0t

CWH

CS to WR Hold Time

ns30t

WR Low Pulse Width

ns125t

CSD

CS to CONVST Delay

ns30t

Address Setup Time

ns0t

Address Hold Time

25pF load ns30t

RD to INT Delay

ns40t

Delay Time Between Reads

ns0t

CRS

CS to RD Setup Time

ns0t

CRH

CS to RD Hold Time

ns30t

RD Low Pulse Width

25pF load (Note 13) ns30t

Data-Access Time

25pF load (Note 14) ns5 45t

Bus-Relinquish Time

Mode 1, 1 channel

µs

Mode 2, 2 channel 6

Mode 3, 3 channel 9

Mode 4, 4 channel 12

CONV

Exiting shutdown µs5Start-Up Time

Note 1: AV

= +5V, AVSS= -5V, DVDD= +5V, V

REFIN

= 2.500V (external), VIN= ±5V (MAX125) or ±2.5V (MAX126).

Note 2: Relative accuracy is the analog value’s deviation at any code from its theoretical value after the full-scale range has been

calibrated.

Note 3: CLK synchronized with CONVST. Note 4: f

= 10.06kHz, VIN= ±5V (MAX125) or ±2.5V (MAX126).

Note 5: First five harmonics. Note 6: All inputs except CH1A driven with ±5V (MAX125) or ±2.5V (MAX126) 10kHz signal; CH1A connected to AGND and digitized. Note 7: Guaranteed by design. Not production tested. Note 8: AV

= +5V, AVSS= -5V, DVDD= +5V, VIN= 0V (all channels).

Note 9: Temperature drift is defined as the change in output voltage from +25°C to T

MIN

or T

MAX

. It is calculated as

TC = [∆REFOUT/REFOUT] / ∆T.

Note 10: See Figure 2. Note 11: Defined as the change in positive full scale caused by a ±5% variation in the nominal supply voltage. Tested with one input

at full scale and all others at AGND. V

REFIN

= 2.5V (internal).

Note 12: Tested with V

= AGND on all channels, V

REFIN

= 2.5V (internal).

Note 13: The data-access time is defined as the time required for an output to cross 0.8V or 2.0V. It is measured using the circuit of

Figure 1. The measured number is then extrapolated back to determine the value with a 25pF load.

Note 14: The bus-relinquish time is derived from the measured time taken for the data outputs to change 0.5V when loaded with the

circuit of Figure 1. The measured number is then extrapolated back to remove the effects of charging/discharging the 120pF capacitor. Thus, the time given is the part’s true bus-relinquish time, independent of the external bus loading capacitance.

Conversion Time

Mode 1, 1 channel

ksps

250

Conversion Rate/Channel

Mode 2, 2 channel 142

Mode 3, 3 channel 100

Mode 4, 4 channel 76

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