MAXIM MAX1422 Technical data

General Description

The MAX1422 3.3V, 12-bit analog-to-digital converter (ADC) features a fully differential input, pipelined, 12stage ADC architecture with wideband track-and-hold (T/H) and digital error correction incorporating a fully-differential signal path. The MAX1422 is optimized for lowpower, high dynamic performance applications in imaging and digital communications. The converter operates from a single 3.3V supply, consuming only 137mW while delivering a 67dB (typ) signal-to-noise ratio (SNR) at a 5MHz input frequency and a 20Msps sampling frequency. The fully-differential input stage has a small signal -3dB bandwidth of 400MHz and may be operated with single-ended inputs.

An internal 2.048V precision bandgap reference sets the ADCs full-scale range. A flexible reference structure accommodates an internally or externally applied buffered or unbuffered reference for applications requiring increased accuracy or a different input voltage range.

In addition to low operating power, the MAX1422 features two power-down modes, a reference power-down, and a shutdown mode. In reference power-down, the internal bandgap reference is deactivated, resulting in a 2mA (typ) supply current reduction. For idle periods, a full shutdown mode is available to maximize power savings.

The MAX1422 provides parallel, offset binary, CMOScompatible three-state outputs.

The MAX1422 is available in a 7mm ✕ 7mm ✕ 1.4mm, 48-pin TQFP package and is specified over the commercial (0°C to +70°C) and extended industrial (-40°C to +85°C) temperature ranges.

Pin-compatible higher-speed versions of the MAX1422 are also available. Please refer to the MAX1421 data sheet for 40Msps and the MAX1420 data sheet for 60Msps.

________________________Applications

Medical Ultrasound Imaging

CCD Pixel Processing

Data Acquisition

Radar

IF and Baseband Digitization

Features

♦ Single 3.3V Power Supply

♦ 67dB SNR at f

= 5MHz

♦ Internal 2.048V Precision Bandgap Reference

♦ Differential Wideband Input T/H Amplifier

♦ Power-Down Modes

130mW (Reference Shutdown Mode) 10µW (Shutdown Mode)

♦ Space-Saving 48-Pin TQFP Package

MAX1422

12-Bit, 20Msps, 3.3V, Low-Power ADC with

Internal Reference

________________________________________________________________ Maxim Integrated Products 1

D9 D8 D7 D6 DV

DGND DGND D5 D4 D3 D2

AGND

AGND AGND

INP

INN AGND AGND

AGND

TQFP

MAX1422

AGND

DDAVDD

AGND

CLK

AGND

DDDVDD

DGND

1314151617181920212223

4847464544434241403938

AGND

AVDDCML

REFN

REFP

REFIN

AVDDAGNDPDOE

D11

D10

Pin Configuration

19-1899; Rev 1; 5/04

Ordering Information

PART TEMP RANGE PIN-PACKAGE

MAX1422CCM

0°C to +70°C 48 TQFP

MAX1422ECM

48 TQFP

Functional Diagram appears at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

-40°C to +85°C

MAX1422

12-Bit, 20Msps, 3.3V, Low-Power ADC with Internal Reference

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

AVDD

= V

DVDD

= 3.3V, AGND = DGND = 0, VIN= ±1.024V, differential input voltage at -0.5dBFS, internal reference, f

CLK

= 20MHz (50%

duty cycle); digital output load C

= 10pF, ≥+25°C guaranteed by production test, <+25°C guaranteed by design and characterization.

Typical values are at T

= +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.

AVDD, DVDDto AGND..............................................-0.3V to +4V

, AVDDto DGND..............................................-0.3V to +4V

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

INP, INN, REFP, REFN, REFIN,

CML,CLK,

CLK, ....................(AGND - 0.3V) to (AVDD+ 0.3V)

D0–D11, OE, PD .......................(DGND - 0.3V) to (DV

+ 0.3V)

Continuous Power Dissipation (T

= +70°C)

48-Pin TQFP (derate 21.7mW/°C above +70°C)........1739mW

Operating Temperature Ranges

MAX1422CCM ....................................................0°C to +70°C

MAX1422ECM .................................................-40°C to +85°C

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

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

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

PARAMETER

CONDITIONS

UNITS

DC ACCURACY

Resolution RES 12 Bits

TA = +25°C, no missing codes -1 1

Differential Nonlinearity DNL

= T

MIN

to T

MAX

LSB

Integral Nonlinearity INL TA = T

MIN

to T

MAX

±2 LSB

Mid-scale Offset MSO -3

%FSR

Mid-scale Offset Temperature Coefficient

%/°C

Internal reference (Note 1) -5

-5

Gain Error GE

External reference applied to REFP, CML, and REFN (Note 3)

1.5

%FSR

Gain Error Temperature Coefficient

GETC

External reference applied to REFP, CML, and REFN (Note 3)

%/°C

DYNAMIC PERFORMANCE (f

CLK

= 20MHz, 4096-point FFT)

Signal-to-Noise Ratio SNR fIN = 5MHz, TA = +25°C6367dB

Spurious-Free Dynamic Range SFDR fIN = 5MHz, TA = +25°C 64 74 dBc

Total Harmonic Distortion THD fIN = 5MHz, TA = +25°C -72 -63 dBc

Signal-to-Noise and Distortion

fIN = 5MHz, TA = +25°C6065dB

Effective Number of Bits ENOB

= 5MHz

Bits

Two-Tone Intermodulation Distortion

IMD f

IN1

= 7.028MHz, f

IN2

= 8.093MHz (Note 4) -77 dBc

Differential Gain DG ±1%

Differential Phase DP

Degrees

ANALOG INPUTS (INP, INN, CML)

Input Resistance R

Either input to ground 61 kΩ

Input Capacitance C

Either input to ground 4 pF

Common-Mode Input Level (Note 5)

CML

AV DD

0.5

SYMBOL

MIN TYP MAX

±0.5

15 ✕ 10

±.75

±0.1

±0.2

10.5

±0.25

- 4

- 6

MSOTC 3 ✕ 10

SINAD

External reference applied to REFIN, (Note 2)

-1.5

MAX1422

12-Bit, 20Msps, 3.3V, Low-Power ADC with

Internal Reference

_______________________________________________________________________________________ 3

PARAMETER

CONDITIONS

UNITS

Common-Mode Input Voltage Range (Note 5)

CML

Differential Input Range V

INP

- V

INN

(Note 6)

Small-Signal Bandwidth

(Note 7)

MHz

Large-Signal Bandwidth

(Note 7)

MHz

Overvoltage Recovery OVR 1.5 ✕ FS input 1

Clock

cycles

INTERNAL REFERENCE (REFIN bypassed with 0.22µF in parallel with 1nF)

Common-Mode Reference Voltage

CML

At CML V

AVDD

✕ 0.5 V

Positive Reference Voltage V

REFP

At REFP

CML

Negative Reference Voltage V

REFN

At REFN

CML

Differential Reference Voltage V

DIFF

(Note 6)

Differential Reference Temperature Coefficient

ppm/°C

EXTERNAL REFERENCE (V

REFIN

= 2.048V)

REFIN Input Resistance R

(Note 8) 5 kΩ

REFIN Input Capacitance C

10 pF

REFIN Reference Input Voltage Range

2.048 V

Differential Reference Voltage Range

DIFF

(Note 6)

0.92

1.08

EXTERNAL REFERENCE (V

REFIN

= 0, reference voltage applied to REFP, REFN, and CML)

REFP, REFN, CML Input Current

200 µA

REFP, REFN, CML Input Capacitance

15 pF

Differential Reference Voltage Range

DIFF

(Note 6)

1.024 V

CML Input Voltage Range V

CML

1.65 V

REFP Input Voltage Range V

REFP

CML

DIFF

REFN Input Voltage Range V

REFN

CML

DIFF

DIGITAL INPUTS (CLK, CLK, PD, OE)

Input Logic High V

0.7

DVDD

Input Logic Low V

DVD

ELECTRICAL CHARACTERISTICS (continued)

AVDD

= V

DVDD

= 3.3V, AGND = DGND = 0, VIN= ±1.024V, differential input voltage at -0.5dBFS, internal reference, f

CLK

= 20MHz (50%

duty cycle); digital output load C

= 10pF, ≥+25°C guaranteed by production test, <+25°C guaranteed by design and characterization.

Typical values are at T

= +25°C.)

SYMBOL

CMVR

-3dB

FPBW

-3dB

REFTC ±100

MIN TYP MAX

±5%

±V

DIFF

400

150

+ 0.512

- 0.512

1.024

±5%

REFIN

-200

±10%

REFIN

±10%

REFIN

0.3

MAX1422

12-Bit, 20Msps, 3.3V, Low-Power ADC with Internal Reference

4 _______________________________________________________________________________________

PARAMETER

CONDITIONS

UNITS

CLK, CLK

PD -20 20

Input Current

OE -20 20

µA

Input Capacitance 10 pF

DIGITAL OUTPUTS (D0–D11)

Output Logic High V

IOH = 200µA

D V DD

- 0.5

Output Logic Low V

IOL = -200µA 0 0.5 V

Three-State Leakage -10 10 µA

Three-State Capacitance 2pF

POWER REQUIREMENTS

Analog Supply Voltage

3.3

Digital Supply Voltage

2.7 3.3

Analog Supply Current I

AVDD

39 46 mA

Analog Supply Current with Internal Reference in Shutdown

REFIN

= 0 37 44 mA

Analog Shutdown Current PD = DV

20 µA

Digital Supply Current I

DVDD

3mA

Digital Shutdown Current PD = DV

20 µA

Power Dissipation P

DISS

Analog power dissipation

152 mW

Power-Supply Rejection Ratio PSRR (Note 9) ±1

mV/V

TIMING CHARACTERISTICS

Maximum Clock Frequency f

CLK

Figure 6 20

MHz

Clock High t

Figure 6, clock period 50ns 25 ns

Clock Low t

Figure 6, clock period 50ns 25 ns

Pipeline Delay (Latency) Figure 6 7

Clock

cycles

Aperture Delay t

Figure 10 2 ns

Aperture Jitter t

Figure 10 2 ps

Data Output Delay t

Figure 6 5 10 14 ns

Bus Enable Time t

Figure 5 5 ns

Bus Disable Time t

Figure 5 5 ns

ELECTRICAL CHARACTERISTICS (continued)

AVDD

= V

DVDD

= 3.3V, AGND = DGND = 0, VIN= ±1.024V, differential input voltage at -0.5dBFS, internal reference, f

CLK

= 20MHz (50%

duty cycle); digital output load C

= 10pF, ≥+25°C guaranteed by production test, <+25°C guaranteed by design and characterization.

Typical values are at T

= +25°C.)

Note 1: Internal reference, REFIN bypassed to AGND with a combination of 0.22µF in parallel with 1nF capacitor. Note 2: External 2.048V reference applied to REFIN. Note 3: Internal reference disabled. V

REFIN

= 0, V

REFP

= 2.162V, V

CML

= 1.65V, and V

REFN

= 1.138V.

Note 4: IMD is measured with respect to either of the fundamental tones. Note 5: Specifies the common-mode range of the differential input signal supplied to the MAX1422. Note 6: V

DIFF

= V

REFP

- V

REFN.

Note 7: Input bandwidth is measured at a 3dB level. Note 8: V

REFIN

is internally biased to 2.048V through a 10kΩ resistor.

Note 9: Measured as the ratio of the change in mid-scale offset voltage for a ±5% change in V

AVDD

, using the internal reference.

SYMBOL

MIN TYP MAX

±330

DVDD

AVDD

DVDD

3.138

137

3.465

3.63

MAX1422

12-Bit, 20Msps, 3.3V, Low-Power ADC with

Internal Reference

_______________________________________________________________________________________ 5

-120

-60

-80

-100

-40

-20

04312 5678910

FFT PLOT (4096-POINT DATA RECORD)

MAX1422 toc01

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

HD2

HD3

fIN = 5.2235MHz

-120

-60

-80

-100

-40

-20

04312 5678910

FFT PLOT (4096-POINT DATA RECORD)

MAX1422 toc02

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

fIN = 8.1637MHz

HD2

HD3

-120

-60

-80

-100

-40

-20

04312 5678910

FFT PLOT (4096-POINT DATA RECORD)

MAX1422 toc03

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

fIN = 19.8051MHz

HD2

HD3

-120

-60

-80

-100

-40

-20

04312 5678910

TWO-TONE IMD PLOT

(4096-POINT DATA RECORD)

MAX1422 toc04

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

IMD2

IMD3

IN2

IN1

= 7.0283MHz

IN2

= 8.0931MHz

CLK

= 20.0056MHz

IN1

= A

IN2

= -6.5dB FS

110100

SPURIOUS-FREE DYNAMIC RANGE vs.

ANALOG INPUT FREQUENCY

MAX1422 toc05

ANALOG INPUT FREQUENCY (MHz)

SFDR (dBc)

110100

SIGNAL-TO-NOISE RATIO vs.

ANALOG INPUT FREQUENCY

MAX1422 toc06

ANALOG INPUT FREQUENCY (MHz)

SNR (dB)

-50

-80 1 10 100

TOTAL HARMONIC DISTORTION vs.

ANALOG INPUT FREQUENCY

-74

MAX1422 toc07

ANALOG INPUT FREQUENCY (MHz)

THD (dBc)

-68

-62

-56

110100

SIGNAL-TO-NOISE PLUS DISTORTION

vs. ANALOG INPUT FREQUENCY

MAX1422 toc08

ANALOG INPUT FREQUENCY (MHz)

SINAD (dB)

-60 -40 -30-50 -20 -10 0

SPURIOUS-FREE DYNAMIC RANGE

vs. ANALOG INPUT POWER (f

= 5MHz)

MAX1422 toc09

ANALOG INPUT POWER (dB FS)

SFDR (dBc)

Typical Operating Characteristics

AVDD

= V

DVDD

= 3.3V, AGND = DGND = 0, VIN= ±1.024V, differential input drive, AIN= -0.5dBFS, f

CLK

= 20MHz (50% duty

cycle) digital output load CL= 10pF, TA= T

MIN

to T

MAX

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

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