Rainbow Electronics MAX1422 User Manual

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, 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

IN

= 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

Pin Configuration

19-1899; Rev 0; 5/01

Ordering Information

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.

PART TEMP. RANGE PIN-PACKAGE

MAX1422CCM 0°C to +70°C 48 TQFP
MAX1422ECM -40°C to +85°C 48 TQFP

AGND

AVDDCML

REFN

REFP

REFIN

AGND

AV

AV
AGND
AGND

INP

INN
AGND
AGND

AV
AV

AGND

AVDDAGNDPDOE

4847464544434241403938

1

2

DD

3

DD

4

5

6

7

8

9

10

DD

11

DD

12

1314151617181920212223

DDAVDD

AV

AGND

AGND

MAX1422

CLK

CLK

AGND

DD

AV

48-TQFP

D11

D10

37

36

35

34

33

32

31

30

29

28

27

26

25

24

DD

D0

DV

D1

DGND

D9
D8
D7
D6
DV

DD

DV

DD

DGND
DGND
D5
D4
D3
D2

MAX1422

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

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

AVDD

= V

DVDD

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

CLK

= 20MHz

(50% duty cycle), digital output load C

L

≈ 10pF, TA= T

MIN

to T

MAX

, 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.

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

DV

DD

, 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 (AV

DD

+ 0.3V)

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

DD

+ 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

48-Pin TQFP (derate 12.5mW/°C above +70°C)........1000mW

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

DC ACCURACY

Resolution RES 12 bits

Differential Nonlinearity DNL

Integral Nonlinearity INL TA = T
Mid-scale Offset MSO -3 ±.75 3 %FSR

Mid-scale Offset Temperature
Coefficient

Gain Error GE

Gain Error Temperature
Coefficient

DYNAMIC PERFORMANCE (f

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 SINAD fIN = 5MHz, TA = +25°C6065dB
Effective Number of Bits ENOB

Two-Tone Intermodulation
Distortion

Differential Gain DG ±1%
Differential Phase DP ±0.25

ANALOG INPUTS (INP, INN, CML)

Input Resistance R

Input Capacitance C

Common-Mode Input Level
(Note 5)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MSOTC 3

GETC

= 20MHz, 4096-point FFT)

CLK

IMD f

IN

IN

V

CML

TA = +25°C, no missing codes -1 1

= T

T

A

Internal reference (Note 1) -5 ±0.1 5
External reference applied to REFIN, (Note 2) -5 ±0.2 5

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

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

f

IN

IN1

Either input to ground 61 kΩ

Either input to ground 4 pF

to T

MIN

to T

MIN

= 5MHz

= 7.028MHz, f

MAX

MAX

-1.5 1.5

= 8.093MHz (Note 4) -77 dBc

IN2

±0.5

±2 LSB

- 4

✕

10

- 6

✕

10

15

10.5 Bits

✕

V

AV DD

0.5

LSB

%/°C

%FSR

%/°C

degrees

V

MAX1422

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

Internal Reference

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

AVDD

= V

DVDD

= +3.3V, AGND = DGND = 0, VIN= ±1.024V, differential input voltage at -0.5dB FS, +2.048V internal reference, f

CLK

=

20MHz (50% duty cycle), digital output load C

L

≈ 10pF, TA= T

MIN

to T

MAX

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

Common-Mode Input Voltage
Range (Note 5)

Differential Input Range V

Small-Signal Bandwidth BW

Large-Signal Bandwidth FPBW

Overvoltage Recovery OVR 1.5 ✕ FS input 1

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

Common-Mode Reference
Voltage

Positive Reference Voltage V

Negative Reference Voltage V

Differential Reference Voltage V

Differential Reference
Temperature Coefficient

EXTERNAL REFERENCE (V

REFIN Input Resistance R

REFIN Input Capacitance C

REFIN Reference Input Voltage
Range

Differential Reference Voltage
Range

EXTERNAL REFERENCE (V

REFP, REFN, CML Input Current I

REFP, REFN, CML Input
Capacitance

Differential Reference Voltage
Range

CML Input Voltage Range V

REFP Input Voltage Range V

REFN Input Voltage Range V

DIGITAL INPUTS (CLK, CLK, PD, OE)

Input Logic High V

Input Logic Low V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

CMVR

V

- V

(Note 6) ±V

INN

= V

REFP

- V

REFN

AVDD

V

CML

REFP

REFN

DIFF

IN

-3dB

-3dB

INP

(Note 7) 400 MHz

(Note 7) 150 MHz

At CML V

At REFP

At REFN

V

DIFF

REFTC ±100 ppm/°C

= +2.048V)

REFIN

IN

IN

V

REFIN

V

DIFF

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

REFIN

IN

C

IN

V

DIFF

CML

REFP

REFN

IH

(Note 8) 5 kΩ

✕

V

DIFF

= (V

REFP

- V

REFN

)

0.95

V

REFIN

/2

-200 200 µA

V

= V

DIFF

IL

REFP

- V

REFN

0.7
V

DVDD

✕

V

CML

±5%

DIFF

✕ 0.5 V

V

CML

+ 0.512

V

CML

- 0.512

1.024

±5%

10 pF

2.048
±10%

✕

V

REFIN

1.05

/2

V

/2

REFIN

15 pF

1.024
±10%

1.65

±10%

V

+

CML

V

/2

DIFF

V

-

CML

/2

V

DIFF

✕

0.3
V

DVD

V

V

Clock
Cycle

V

V

V

V

V

V

V

V

V

V

V

MAX1422

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

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(V

AVDD

= V

DVDD

= +3.3V, AGND = DGND = 0, VIN= ±1.024V, differential input voltage at -0.5dB FS, +2.048V internal reference, f

CLK

=

20MHz (50% duty cycle), digital output load C

L

≈ 10pF, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +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.

Input Current

Input Capacitance 10 pF

DIGITAL OUTPUTS (D0–D11)

Output Logic High V

Output Logic Low V
Three-State Leakage -10 10 µA

Three-State Capacitance 2pF

POWER REQUIREMENTS

Analog Supply Voltage V

Digital Supply Voltage V

Analog Supply Current I

Analog Supply Current with
Internal Reference in Shutdown

Analog Shutdown Current PD = DV

Digital Supply Current I

Digital Shutdown Current PD = DV

Power Dissipation P
Power-Supply Rejection Ratio PSRR (Note 9) ±1 mV/V

TIMING CHARACTERISTICS

Clock Frequency f

Clock High t

Clock Low t

Pipeline Delay (Latency) Figure 5 7

Aperture Delay t

Aperture Jitter t

Data Output Delay t

Bus Enable Time t

Bus Disable Time t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

OH

OL

AVDD

DVDD

AVDD

DVDD

DISS

CLK

CH

CL

AD

AJ

OD

BE

BD

CLK, CLK ±330

PD -20 20
OE -20 20

IOH = 200µA

IOL = -200µA00.5V

REFIN

Analog power dissipation 137 152 mW

Figure 5 0.1 20 MHz

Figure 5, clock period 50ns 25 ns

Figure 5, clock period 50ns 25 ns

Figure 9 2 ns

Figure 9 2 ps

Figure 5 5 10 14 ns

Figure 4 5 ns

Figure 4 5 ns

= AGND 37 44 mA

DD

DD

V

D V DD

- 0.5

3.138 3.3 3.465 V

2.7 3.3 3.63 V

V

DVDD

39 46 mA

20 µA

3mA

20 µA

µA

V

f

CLK

Cycles

MAX1422

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

Internal Reference

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(V

AVDD

= V

DVDD

= +3.3V, AGND = DGND = 0, VIN= ±1.024V, differential input voltage, f

CLK

= 20MHz (50% duty cycle) digital out-

put load C

L

= 10pF, TA= T

MIN

to T

MAX

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

FFT PLOT, 4096-POINT RECORD

DIFFERENTIAL INPUT

0

fIN = 5.2234999MHz

= -0.53dB FS

A

IN

-20

-40

-60

AMPLITUDE (dB)

-80

-100

-120

HD3

04312 5678910

ANALOG INPUT FREQUENCY (MHz)

TWO-TONE IMD PLOT, 4096-POINT RECORD

DIFFERENTIAL INPUT

0

f

= 7.0283622MHz

IN1

= 8.0931176MHz

f

IN2

-20

= 20.0056789MHz

f

CLK

TWO-TONE-ENVELOPE = -0.53dBFS

= A

= -6.5dB FS

A

IN1

IMD2

IN2

f

IMD3

-40

-60

AMPLITUDE (dB)

-80

-100

FFT PLOT, 4096-POINT RECORD

DIFFERENTIAL INPUT

0

fIN = 8.1636865MHz

= -0.54dB FS

A

IN

-20

MAX1422 toc01

-40

HD2

-60

AMPLITUDE (dB)

-80

-100

-120
04312 5678910

HD2

ANALOG INPUT FREQUENCY (MHz)

HD3

SPURIOUS-FREE DYNAMIC RANGE vs.

ANALOG INPUT FREQUENCY

85

MAX1422 toc04

f

IN2

IN1

77

69

SFDR (dBc)

61

53

MAX1422 toc02

MAX1422 toc05

FFT PLOT, 4096-POINT RECORD

DIFFERENTIAL INPUT

0

fIN = 19.8051329MHz

= -0.52dB FS

A

IN

-20

-40
HD2

-60

HD3

AMPLITUDE (dB)

-80

-100

-120
04312 5678910

ANALOG INPUT FREQUENCY (MHz)

SIGNAL-TO-NOISE RATIO vs.

ANALOG INPUT FREQUENCY

70

66

62

SNR (dB)

58

54

MAX1422 toc03

MAX1422 toc06

-120
04312 5678910

ANALOG INPUT FREQUENCY (MHz)

TOTAL HARMONIC DISTORTION vs.

ANALOG INPUT FREQUENCY

-50

-56

-62

THD (dBc)

-68

-74

-80
110100

ANALOG INPUT FREQUENCY (MHz)

MAX1422 toc07

45

110100

ANALOG INPUT FREQUENCY (MHz)

SIGNAL-TO-NOISE PLUS DISTORTION

vs. ANALOG INPUT FREQUENCY

70

66

62

SINAD (dB)

58

54

50

110100

ANALOG INPUT FREQUENCY (MHz)

MAX1422 toc08

50

1 10 100

ANALOG INPUT FREQUENCY (MHz)

SPURIOUS-FREE DYNAMIC RANGE

vs. INPUT POWER (f

80

70

60

50

40

SFDR (dBc)

30

20

10

0

-60 -40 -30-50 -20 -10 0
INPUT POWER (dB FS)

= 5MHz)

IN

MAX1422 toc09