Rainbow Electronics MAX1421 User Manual

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-to-noise ratio (SNR) of 66dB at an input frequency
of 15MHz and a sampling frequency of 40Msps. 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 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 f

IN

= 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

Pin Configuration

19-1900; Rev 0; 5/01

Ordering Information

48 TQFP

PIN-PACKAGETEMP. RANGE

0°C to +70°CMAX1421CCM

PART

Functional Diagram appears at end of data sheet.

48 TQFP-40°C to +85°CMAX1421ECM

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.

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

MAX1421

CLK

AGND

48-TQFP

CLK

AGND

AV

DDDVDD

DGND

D11

D0

D10

37

24

D1

36

D9
D8

35

D7

34

D6

33

DV

32

DD

DV

31

DD

DGND

30

DGND

29

D5

28

D4

27

D3

26

D2

25

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= T

MIN

to T

MAX

, unless otherwise noted. 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 (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

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

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

Spurious-Free Dynamic Range SFDR

Total Harmonic Distortion THD

Signal-To-Noise Plus Distortion SINAD

Effective Number of Bits ENOB

Two-Tone Intermodulation
Distortion

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

TA = +25°C, no missing codes -1 1

= T

T

A

MSOTC 3

Internal reference (Note 1) -5 0.1 5

External reference applied to REFIN (Note 2) -5 ±3 5

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

GETC

= 40MHz, 4096-point FFT)

CLK

IMD

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

fIN = 5MHz 67

f

IN

fIN = 5MHz 73

f

IN

fIN = 5MHz -74

f

IN

fIN = 5MHz 66

f

IN

fIN = 5MHz 10.7

f

IN

f

IN1

TT

(Note 4)

to T

MIN

MAX

to T

MIN

MAX

= 15MHz, TA = +25°C6266

= 15MHz, TA = +25°C6470

= 15MHz, TA = +25°C -69 -62

= 15MHz, TA = +25°C 60 63.5

= 15MHz, TA = +25°C 60 10.3

= 11.569MHz, f

= 13.445MHz

IN2

±0.5

±2 LSB

-4

✕

10

-1.5 ±0.5 1.5

-6

✕

10

15

-80 dBc

LSB

%/°C

%FSR

%/°C

dB

dBc

dBc

dB

Bits

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= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at

T

A

= +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Differential Gain DG ±1%
Differential Phase DP ±0.25 degrees

ANALOG INPUTS (INP, INN, CML)

Input Resistance R

Input Capacitance C

Common-Mode Input Level,
(Note 5)

Common-Mode Input Voltage
Range, (Note 5)

V

V

CMVR

CML

Differential Input Range V

Small-Signal Bandwidth BW

Large-Signal Bandwidth FPBW

Over-Voltage Recovery OVR 1.5 ✕ FS input 1

Either input to ground 32.5 kΩ

IN

Either input to ground 4 pF

IN

V

AVDD

× 0.5

V

CML

±5%

V

- V

IN

-3dB

INP

(Note 7) 400 MHz

(Note 7) 150 MHz

-3dB

(Note 6) ±V

INN

DIFF

V

V

V

Clock
Cycle

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

Common-Mode Reference Input
Voltage

V

CML

At CML

V

AVDD

✕

0.5

V

Positive Reference Voltage
Range

Negative Reference Voltage
Range

Differential Reference Voltage
Range

Differential Reference
Temperature Coefficient

V

V

V

REFTC ±100 ppm/°C

EXTER N AL R EF ER EN C E

REFIN Input Resistance R

REFIN Input Capacitance C

REFIN Reference Input Voltage V

Differential Reference Voltage V

EXTERNAL REFERENCE (V

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

REFIN

REFP, REFN, CML Input Current I

REFP, REFN, CML Input
Capacitance

REFP

REFN

DIFF

IN

IN

REFIN

DIFF

IN

C

IN

V

At REFP

At REFN

V

= V

DIFF

REFP

- V

REFN

CML

+ 0.512

V

CML

- 0.512

1.024

±5%

(Note 8) 5 kΩ

10 pF

2.048
±10%

V

DIFF

= (V

REFP

- V

REFN

✕

)

0.95

V

REFIN/2

V

REFIN/2

1.05

V

REFIN/2

✕

-200 200 µA

15 pF

V

V

V

V

V

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= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at

T

A

= +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Differential Reference Voltage
Range

CML Input Voltage Range V

REFP Input Voltage Range V

REFN Input Voltage Range V

V

DIFF

CML

REFP

REFN

V

DIFF

= V

REFP

- V

REFN

1.024
±10%

1.65

±10%

V

CML

V

DIFF

V

CML

V

DIFF

V

V

+
/2

-

/2

V

V

DIGITAL INPUTS (CLK, CLK, OE, PD)

✕

Input Logic High V

Input Logic Low V

IH

IL

0.7

V

DVDD

0.3

V

DVDD

V

✕

V

CLK, CLK ±330

Input Current

PD -20 20

µA

OE -20 20

Input Capacitance 10 pF

DIGITAL OUTPUTS (D0–D11)

Output Logic High V

Output Logic Low V

OH

OL

IOH = 200µA

DVDD

- 0.5

IOL = -200µA 0 0.5 V

V

DVDD

V

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

AVDD

DVDD

AVDD

REFIN = AGND 50 63 mA

Analog Shutdown Current PD = DV

Digital Supply Current I

DVDD

Digital Shutdown Current PD = DV

Power Dissipation P

DISS

Analog power 188 214 mW

DD

DD

3.135 3.3 3.465 V

2.7 3.3 3.6 V

52 65 mA

20 µA

5.5 mA

20 µA

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

TIMING CHARACTERISTICS

Clock Frequency f

Clock High t

Clock Low t

CLK

CH

CL

Figure 5 0.1 40 MHz

Figure 5, clock period 25ns 12.5 ns

Figure 5, clock period 25ns 12.5 ns

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= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at

T

A

= +25°C.)

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 = 7.5439934MHz
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 = 19.9047628MHz
A

IN

= -0.50dB FS

HD2

HD3

-120

-80

-100

-40

-60

-20

0

01051520

FFT PLOT, 4096-POINT RECORD,

DIFFERENTIAL INPUT

MAX1421 toc03

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

fIN = 38.5440183MHz
A

IN

= -0.49dB FS

HD3

HD2

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Pipeline Delay (Latency) Figure 5 7

Aperture Delay t

Aperture Jitter t

Data Output Delay t

Bus Enable Time t

Bus Disable Time t

AD

AJ

OD

BE

BD

Figure 9 2 ns

Figure 9 2 ps

Figure 5 5 10 14 ns

Figure 4 5 ns

Figure 4 5 ns

f

CLK

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 C

L

= 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 101214166 8 18 20

TWO-TONE IMD, 8192-POINT RECORD,

DIFFERENTIAL INPUT

MAX1421 toc04

ANALOG INPUT FREQUENCY (MHz)

AMPLITUDE (dB)

f

IN1

= 11.5104229MHz

f

IN2

= 13.5126603MHz

TWO-TONE ENVELOPE:

-0.49dB FS
A

IN1

= A

IN2

= -6.5dB FS

IMD2

IMD3

f

IN1

f

IN2

70

50

110100

SIGNAL-TO-NOISE PLUS DISTORTION

vs. ANALOG INPUT FREQUENCY

54

MAX1421 toc08

ANALOG INPUT FREQUENCY (MHz)

SINAD (dB)

58

62

66

20

40

30

60

50

70

80

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

SPURIOUS-FREE DYNAMIC RANGE

vs. INPUT POWER (f

IN

= 15MHz)

MAX1421 toc09

INPUT POWER (dB FS)

SFDR (dBc)

-80

-70

-50

-60

-40

-30

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

TOTAL HARMONIC DISTORTION

vs. INPUT POWER (f

IN

= 15MHz)

MAX1421 toc11

INPUT POWER (dB FS)

THD (dBc)

-20

0

40

20

60

80

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

SIGNAL-TO-NOISE PLUS DISTORTION

vs. INPUT POWER (f

IN

= 15MHz)

MAX1421 toc12

INPUT POWER (dB FS)

SINAD (dB)

-50

-80
110100

TOTAL HARMONIC DISTORTION vs.

ANALOG INPUT FREQUENCY

-74

MAX1421 toc07

ANALOG INPUT FREQUENCY (MHz)

THD (dBc)

-68

-62

-56

0

10

20

30

40

50

60

70

80

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

SIGNAL-TO-NOISE RATIO

vs. INPUT POWER (f

IN

= 15MHZ)

MAX1421 toc10

INPUT POWER (dB FS)

SNR (dB)

85

45

1 10 100

SPURIOUS-FREE DYNAMIC RANGE vs.

ANALOG INPUT FREQUENCY

53

MAX1421 toc05

ANALOG INPUT FREQUENCY (MHz)

SFDR (dBc)

61

69

77

70

50

1 10 100

SIGNAL-TO-NOISE RATIO vs.

ANALOG INPUT FREQUENCY

54

MAX1421 toc06

ANALOG INPUT FREQUENCY (MHz)

SNR (dB)

58

62

66