MAXIM MAX1421 Technical data

General Description

The MAX1421 is a 3.3V, 12-bit analog-to-digital con­verter (ADC), featuring a fully-differential input,
pipelined, 12-stage ADC architecture with wideband
track-and-hold (T/H) and digital error correction incor­porating a fully-differential signal path. The MAX1421 is
optimized for low-power, high-dynamic performance
applications in imaging and digital communications.
The converter operates from a single 3.3V supply, con­suming only 188mW while delivering a typical signal-to­noise ratio (SNR) of 66dB at an input frequency of
15MHz and a sampling frequency of 40Msps. The fully­differential 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 full-scale range of the ADC. A flexible reference
structure accommodates an internal 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 MAX1421 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 typical 2mA supply current reduction. For idle peri­ods, a full shutdown mode is available to maximize
power savings.

The MAX1421 provides parallel, offset binary, CMOS­compatible three-state outputs.

The MAX1421 is available in a 7mm x 7mm, 48-pin
TQFP package, and is specified over the commercial
(0°C to +70°C) and the extended industrial (-40°C to
+85°C) temperature ranges.

Pin-compatible higher- and lower-speed versions of the
MAX1421 are also available. Please refer to the
MAX1420 data sheet for a frequency of 60Msps and
the MAX1422 data sheet for a frequency of 20Msps.

________________________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

♦ 66dB SNR at fIN= 15MHz

♦ Internal, 2.048V Precision Bandgap Reference

♦ Differential, Wideband Input T/H Amplifier

♦ Power-Down Modes

180mW (Reference Shutdown Mode)
10µW (Shutdown Mode)

♦ Space-Saving 48-Pin TQFP Package

MAX1421

12-Bit, 40Msps, 3.3V, Low-Power ADC

with Internal Reference

________________________________________________________________ Maxim Integrated Products 1

D9
D8
D7
D6
DV

DD

DV

DD

DGND
DGND
D5
D4
D3
D2

AGND

AV

DD

AV

DD

AGND
AGND

INP

INN
AGND
AGND

AV

DD

AV

DD

AGND

1

2

3

4

5

6

7

8

9

10

11

12

36

35

34

33

32

31

30

29

28

27

26

25

48-TQFP

MAX1421

AGND

AV

DDAVDD

AGND

CLK

CLK

AGND

AV

DDDVDD

DGND

D0

D1

1314151617181920212223

24

4847464544434241403938

37

AGND

AVDDCML

REFN

REFP

REFIN

AVDDAGNDPDOE

D11

D10

Pin Configuration

19-1900; Rev 1; 5/06

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.

+Denotes lead-free package.

PART* TEMP RANGE

PIN-

PKG

CODE

M AX1421CCM

0°C to +70°C 48 TQFP

C48-2

M AX1421ECM

-40°C to +85°C 48 TQFP

C48-2

M AX1421ECM+

-40°C to +85°C 48 TQFP

C48-2

PACKAGE

MAX1421

12-Bit, 40Msps, 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

= 40MHz (50% duty cycle), digital output load CL≈ 10pF, TA≥ +25°C guaranteed by production test, TA< +25°C guarnateed

by design and characterization. Typical values are at T

A

= +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 (AVDD+ 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

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

Operating Temperature Ranges

MAX1421CCM ...................................................0°C to +70°C

MAX1421ECM ................................................-40°C to +85°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

A

= T

MIN

to T

MAX

LSB

Integral Nonlinearity INL TA = T

MIN

to T

MAX

±2

LSB

Midscale Offset MSO -3

+3

%FSR

Midscale Offset Temperature
Coefficient

%/°C

Internal reference (Note 1) -5

+5

-5 ±3 +5

Gain Error GE

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

%FSR

Gain-Error Temperature
Coefficient

GETC

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

15

✕

10

-6

%/°C

DYNAMIC PERFORMANCE (f

CLK

= 40MHz, 4096-point FFT)

fIN = 5MHz 67

Signal-to-Noise Ratio SNR

f

IN

= 15MHz, TA = +25°C6266

dB

fIN = 5MHz 73

Spurious-Free Dynamic Range SFDR

f

IN

= 15MHz, TA = +25°C6470

dBc

fIN = 5MHz -74

Total Harmonic Distortion THD

f

IN

= 15MHz, TA = +25°C -69 -62

dBc

fIN = 5MHz 66

Signal-To-Noise Plus Distortion

fIN = 15MHz, TA = +25°C60

dB

fIN = 5MHz

Effective Number of Bits

fIN = 15MHz, TA = +25°C60

Bits

Two-Tone Intermodulation
Distortion

f

IN1

= 11.569MHz, f

IN2

= 13.445MHz

(Note 4)

-80

dBc

SYMBOL

MIN TYP MAX

MSOTC 3 ✕ 10

SINAD

ENOB

IMD

TT

External reference applied to REFIN (Note 2)

±0.5

±.75

+0.1

-1.5 ±0.5 +1.5

63.5

10.7

10.3

-4

MAX1421

12-Bit, 40Msps, 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, internal reference,

f

CLK

= 40MHz (50% duty cycle), digital output load CL≈ 10pF, TA≥ +25°C guaranteed by production test, TA< +25°C guarnateed

by design and characterization. Typical values are at T

A

= +25°C.)

PARAMETER

CONDITIONS

UNITS

Differential Gain DG ±1%

Differential Phase DP

degrees

ANALOG INPUTS (INP, INN, CML)

Input Resistance R

IN

Either input to ground

kΩ

Input Capacitance C

IN

Either input to ground 4 pF

Common-Mode Input Level
(Note 5)

V

CML

V

Common-Mode Input Voltage
Range (Note 5)

V

Differential Input Range V

IN

V

INP

- V

INN

(Note 6)

V

Small-Signal Bandwidth

(Note 7) 400

MHz

Large-Signal Bandwidth

(Note 7) 150

MHz

Overvoltage Recovery OVR 1.5 ✕ FS input 1

Clock

Cycle

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

Common-Mode Reference Input
Voltage

V

CML

At CML

V

Positive Reference Voltage
Range

V

REFP

At REFP

V

Negative Reference Voltage
Range

At REFN

V

Differential Reference Voltage
Range

V

DIFF

(Note 6)

V

Differential Reference
Temperature Coefficient

ppm/°C

EXTER N AL R EF ER EN C E (V

REFIN

= 2.048V)

REFIN Input Resistance R

IN

(Note 8) 5 kΩ

REFIN Input Capacitance C

IN

10 pF

REFIN Reference Input Voltage

V

Differential Reference Voltage V

DIFF

(Note 6)

0.92

✕

V

REFIN /

2

V

REFIN /

2

1.08

✕

V

REFIN /

2

V

EXTERNAL REFERENCE (V

REFIN

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

I

IN

µA

REFP, REFN, CML Input
Capacitance

C

IN

15 pF

SYMBOL

MIN TYP MAX

±0.25

32.5

V

AVDD

× 0.5

V

CML

±5%

±V

DIFF

V

AVDD

✕

0.5

V

CML

+ 0.512

V

CML

- 0.512

V

CMVR

BW

-3dB

FPBW

-3dB

V

REFN

1.024

±5%

REFTC ±100

REFP, REFN, CML Input Current

V

REFIN

2.048
±10%

-200 +200

MAX1421

12-Bit, 40Msps, 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, internal reference,

f

CLK

= 40MHz (50% duty cycle), digital output load CL≈ 10pF, TA≥ +25°C guaranteed by production test, TA< +25°C guarnateed

by design and characterization. Typical values are at T

A

= +25°C.)

PARAMETER

CONDITIONS

UNITS

Differential Reference Voltage
Range

V

DIFF

(Note 6)

V

CML Input Voltage Range V

CML

V

REFP Input Voltage Range V

REFP

V

CML

+

V

REFN Input Voltage Range

V

CML

­V

DIGITAL INPUTS (CLK, CLK, OE, PD)

Input Logic-High V

IH

0.7

✕

V

Input Logic-Low V

IL

0.3

✕

V

CLK, CLK

PD -20

Input Current

OE -20

µA

Input Capacitance 10 pF

DIGITAL OUTPUTS (D0–D11)

Output Logic-High V

OH

IOH = 200µA

V

Output Logic-Low V

OL

IOL = -200µA 0 0.5 V

Three-State Leakage -10

µA

Three-State Capacitance 2pF

POWER REQUIREMENTS

Analog Supply Voltage

3.3

V

Digital Supply Voltage

2.7 3.3 3.6 V

Analog Supply Current I

AVDD

52 65

mA

Analog Supply Current with
Internal Reference in Shutdown

REFIN = AGND 50 63

mA

Analog Shutdown Current PD = DV

DD

20 µA

Digital Supply Current I

DVDD

5.5

mA

Digital Shutdown Current PD = DV

DD

20 µA

Power Dissipation P

DISS

Analog power 188 214

mW

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

mV/V

TIMING CHARACTERISTICS

Clock Frequency f

CLK

Figure 5 0.1

MHz

Clock High t

CH

Figure 5, clock period 25ns

ns

Clock Low t

CL

Figure 5, clock period 25ns

ns

SYMBOL

MIN TYP MAX

1.024

±10%

1.65

±10%

V

/ 2

V

REFN

V

DIFF

DIFF

/ 2

V

DVDD

±330

V

DVDD

+20

V

DVDD

- 0.5

+20

V

DVDD

+10

V

AVDD

V

DVDD

3.135

3.465

12.5

12.5

40.0

MAX1421

12-Bit, 40Msps, 3.3V, Low-Power ADC

with Internal Reference

_______________________________________________________________________________________ 5

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 MAX1421.
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.

ELECTRICAL CHARACTERISTICS (continued)

(V

AVDD

= V

DVDD

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

f

CLK

= 40MHz (50% duty cycle), digital output load CL≈ 10pF, TA≥ +25°C guaranteed by production test, TA< +25°C guarnateed

by design and characterization. Typical values are at T

A

= +25°C.)

PARAMETER

CONDITIONS

Pipeline Delay (Latency) Figure 5 7

f

CLK

Aperture Delay t

AD

Figure 9 2 ns

Aperture Jitter t

AJ

Figure 9 2 ps

Data Output Delay t

OD

Figure 5 5 10 14 ns

Bus Enable Time t

BE

Figure 4 5 ns

Bus Disable Time t

BD

Figure 4 5 ns

Typical Operating Characteristics

(V

AVDD

= V

DVDD

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

CLK

= 40MHz (50% duty cycle), digital output

load CL= 10pF, TA= T

MIN

to T

MAX,

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

-120

-80

-100

-40

-60

-20

0

01051520

FFT PLOT, 4096-POINT RECORD,

DIFFERENTIAL INPUT

MAX1421 toc01

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

fIN = 7.54MHz
A

IN

= -0.45dB FS

HD3

HD2

-120

-80

-100

-40

-60

-20

0

01051520

FFT PLOT, 4096-POINT RECORD,

DIFFERENTIAL INPUT

MAX1421 toc02

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

fIN = 19.90MHz
A

IN

= -0.50dB FS

HD2

HD3

f

IN

-120

-80

-100

-40

-60

-20

0

01051520

FFT PLOT, 4096-POINT RECORD,

DIFFERENTIAL INPUT

MAX1421 toc03

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

fIN = 38.54MHz
A

IN

= -0.49dB FS

HD3

HD2

MIN TYP MAX UNITS

SYMBOL

cycles

MAX1421

12-Bit, 40Msps, 3.3V, Low-Power ADC
with Internal Reference

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

AVDD

= V

DVDD

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

CLK

= 40MHz (50% duty cycle), digital output

load CL= 10pF, TA= T

MIN

to T

MAX,

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

-120

-80

-100

-40

-60

-20

0

024 1012141668 1820

TWO-TONE IMD, 8192-POINT RECORD,

DIFFERENTIAL INPUT

MAX1421 toc04

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

f

IN1

= 11.51MHz

f

IN2

= 13.51MHz

A

IN1

= A

IN2

= -6.5dB FS

IM2

IM3

f

IN1

f

IN2

SIGNAL-TO-NOISE PLUS DISTORTION

vs. ANALOG INPUT FREQUENCY

ANALOG INPUT FREQUENCY (MHz)

SINAD (dB)

MAX1421 toc08

05101520 25 30 35 40 45 50 55

50

54

58

62

66

70

SPURIOUS-FREE DYNAMIC RANGE

vs. ANALOG INPUT POWER (f

IN

= 15MHz)

ANALOG INPUT POWER (dBFS)

SFDR (dBc)

MAX1421 toc09

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

20

30

40

50

60

70

80

TOTAL HARMONIC DISTORTION

vs. ANALOG INPUT POWER (f

IN

= 15MHz)

ANALOG INPUT POWER (dBFS)

THD (dBc)

MAX1421 toc11

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

-80

-70

-60

-50

-40

-30

SIGNAL-TO-NOISE PLUS DISTORTION

vs. ANALOG INPUT POWER (f

IN

= 15MHz)

ANALOG INPUT POWER (dBFS)

SINAD (dB)

MAX1421 toc12

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

0

10

20

30

40

50

60

70

80

TOTAL HARMONIC DISTORTION

vs. ANALOG INPUT FREQUENCY

ANALOG INPUT FREQUENCY (MHz)

THD (dBc)

MAX1421 toc07

051015 20 25 30 35 40 45 50 55

-80

-74

-68

-62

-56

-50

SIGNAL-TO-NOISE RATIO

vs. ANALOG INPUT POWER (f

IN

= 15MHz)

ANALOG INPUT POWER (dBFS)

SNR (dB)

MAX1421 toc10

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

0

10

20

30

40

50

60

70

80

SPURIOUS-FREE DYNAMIC RANGE

vs. ANALOG INPUT FREQUENCY

ANALOG INPUT FREQUENCY (MHz)

SFDR (dBc)

MAX1421 toc05

05101520 25 30 35 40 45 50 55

45

53

61

69

77

85

SIGNAL-TO-NOISE RATIO

vs. ANALOG INPUT FREQUENCY

ANALOG INPUT FREQUENCY (MHz)

SNR (dB)

MAX1421 toc06

05101520 25 30 35 40 45 50 55

50

54

58

62

66

70