Rainbow Electronics MAX1208 User Manual

Page 1

General Description

The MAX1208 is a 3.3V, 12-bit, 80Msps analog-to-digital converter (ADC) featuring a fully differential wideband track-and-hold (T/H) input amplifier, driving a low-noise internal quantizer. The analog input stage accepts singleended or differential signals. The MAX1208 is optimized for low power, small size, and high dynamic performance in baseband applications.

Powered from a single 3.0V to 3.6V supply, the MAX1208 consumes only 373mW while delivering a typical signal-to-noise (SNR) performance of 68.2dB at an input frequency of 32.5MHz. In addition to low operating power, the MAX1208 features a 3µW power-down mode to conserve power during idle periods.

A flexible reference structure allows the MAX1208 to use the internal 2.048V bandgap reference or accept an externally applied reference. The reference structure allows the full-scale analog input range to be adjusted from ±0.35V to ±1.15V. The MAX1208 provides a common-mode reference to simplify design and reduce external component count in differential analog input circuits.

The MAX1208 supports both a single-ended and differential input clock drive. Wide variations in the clock duty cycle are compensated with the ADC’s internal duty-cycle equalizer (DCE).

ADC conversion results are available through a 12-bit, parallel, CMOS-compatible output bus. The digital output format is pin selectable to be either two’s complement or Gray code. A data-valid indicator eliminates external components that are normally required for reliable digital interfacing. A separate digital power input accepts a wide 1.7V to 3.6V supply, allowing the MAX1208 to interface with various logic levels.

The MAX1208 is available in a 6mm x 6mm x 0.8mm, 40-pin thin QFN package with exposed paddle (EP), and is specified for the extended industrial (-40°C to +85°C) temperature range.

See the Pin-Compatible Versions table for a complete family of 14-bit and 12-bit high-speed ADCs.

Applications

Communication Receivers

Cellular, Point-to-Point Microwave, HFC, WLAN Ultrasound and Medical Imaging Portable Instrumentation Low-Power Data Acquisition

Features

♦ Excellent Dynamic Performance

68.2dB/68.0dB SNR at fIN= 3MHz/70MHz

89.3dBc/85.1dBc SFDR at fIN= 3MHz/70MHz

♦ 3.3V Low-Power Operation

373mW (Single-Ended Clock Mode) 399mW (Differential Clock Mode) 3µW (Power-Down Mode)

♦ Differential or Single-Ended Clock

♦ Fully Differential or Single-Ended Analog Input

♦ Adjustable Full-Scale Analog Input Range: ±0.35V

to ±1.15V

♦ Common-Mode Reference

♦ CMOS-Compatible Outputs in Two’s Complement

or Gray Code

♦ Data-Valid Indicator Simplifies Digital Design

♦ Data Out-of-Range Indicator

♦ Miniature, 40-Pin Thin QFN Package with Exposed

Paddle

♦ Evaluation Kit Available (Order MAX1211EVKIT)

MAX1208

12-Bit, 80Msps, 3.3V ADC

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-1002; Rev 0; 8/04

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.

EVALUATION KIT

AVAILABLE

PART

PINPACKAGE

PKG

CODE

MAX1208ETL

40 Thin QFN (6mm x 6mm x

0.8mm)

T4066-3

Pin-Compatible Versions

PART

SAMPLING

RESOLUTION

(BITS)

TARGET

APPLICATION

MAX12553

65 14

IF/Baseband

MAX1209

80 12 IF

MAX1211

65 12 IF

MAX1208

80 12 Baseband

MAX1207

65 12 Baseband

MAX1206

40 12 Baseband

Pin Configuration appears at end of data sheet.

TEMP RANGE

-40°C to +85°C

RATE (Msps)

Page 2

MAX1208

12-Bit, 80Msps, 3.3V ADC

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

T = low, f

CLK

= 80MHz (50% duty cycle), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)

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.

VDDto GND...........................................................-0.3V to +3.6V

to GND........-0.3V to the lower of (VDD+ 0.3V) and +3.6V

INP, INN to GND ...-0.3V to the lower of (V

+ 0.3V) and +3.6V

REFIN, REFOUT, REFP, REFN,

COM to GND......-0.3V to the lower of (V

+ 0.3V) and +3.6V

CLKP, CLKN, CLKTYP, G/T, DCE,

PD to GND ........-0.3V to the lower of (V

+ 0.3V) and +3.6V

D11 Through D0 I.C., DAV, DOR to GND ...-0.3V to (OV

+ 0.3V)

Continuous Power Dissipation (T

= +70°C) 40-Pin Thin QFN 6mm x 6mm x 0.8mm

(derated 26.3mW/°C above +70°C)........................2105.3mW

Operating Temperature Range ...........................-40°C to +85°C

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

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

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

PARAMETER

CONDITIONS

UNITS

DC ACCURACY (Note 2)

Resolution 12 Bits

Integral Nonlinearity INL fIN = 20MHz

LSB

Differential Nonlinearity DNL

= 20MHz, no missing codes over

temperature

LSB

Offset Error V

REFIN

= 2.048V

%FS

Gain Error V

REFIN

= 2.048V

%FS

ANALOG INPUT (INP, INN)

Differential Input Voltage Range V

DIFF

Differential or single-ended inputs

Common-Mode Input Voltage

PAR

Fixed capacitance to ground 2

Input Capacitance (Figure 3)

Switched capacitance 1.9

CONVERSION RATE

Maximum Clock Frequency f

CLK

MHz

Minimum Clock Frequency 5

MHz

Data Latency Figure 6 8.5

Clock

cycles

DYNAMIC CHARACTERISTICS (differential inputs, Note 2)

Small-Signal Noise Floor SSNF Input at less than -35dBFS

dBFS

fIN = 3MHz at -0.5dBFS 68.2

fIN = 32.5MHz at -0.5dBFS

68.2Signal-to-Noise Ratio SNR

= 70MHz at -0.5dBFS 68.0

fIN = 3MHz at -0.5dBFS 68.1

fIN = 32.5MHz at -0.5dBFS

68.1

Signal-to-Noise and Distortion SINAD

= 70MHz at -0.5dBFS 67.8

SYMBOL

MIN TYP MAX

±0.65

-0.83 ±0.35

±0.25 ±0.92

±1.0 ±5.6

±1.024

/ 2

SAMPLE

65.4

65.2

-68.8

Page 3

MAX1208

12-Bit, 80Msps, 3.3V ADC

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

fIN = 3MHz at -0.5dBFS 89.3

fIN = 32.5MHz at -0.5dBFS

88.2

Spurious-Free Dynamic Range SFDR

fIN = 70MHz at -0.5dBFS 85.1

dBc

fIN = 3MHz at -0.5dBFS

fIN = 32.5MHz at -0.5dBFS

Total Harmonic Distortion THD

fIN = 70MHz at -0.5dBFS

dBc

fIN = 3MHz at -0.5dBFS -93

fIN = 32.5MHz at -0.5dBFS -89Second Harmonic HD2

fIN = 70MHz at -0.5dBFS

dBc

fIN = 3MHz at -0.5dBFS

fIN = 32.5MHz at -0.5dBFS

Third Harmonic HD3

fIN = 70MHz at -0.5dBFS

dBc

Intermodulation Distortion IMD

fIN1 = 68.5MHz at -7dBFS fIN2 = 71.5MHz at -7dBFS

dBc

Third-Order Intermodulation IM3

fIN1 = 68.5MHz at -7dBFS fIN2 = 71.5MHz at -7dBFS

dBc

Two-Tone Spurious-Free Dynamic Range

fIN1 = 68.5MHz at -7dBFS fIN2 = 71.5MHz at -7dBFS

85.4 dBc

Aperture Delay tAD Figure 4 0.9 ns

Aperture Jitter tAJ Figure 4 <0.2

psRMS

Output Noise nOUT INP = INN = COM 0.52

LSBRM

Overdrive Recovery Time ±10% beyond full scale 1

Clock

cycles

INTERNAL REFERENCE (REFIN = REFOUT; VREFP, VREFN, and VCOM are generated internally)

REFOUT Output Voltage

COM Output Voltage VCOM VDD / 2 1.65 V

Differential Reference Output

VREF VREF = VREFP - VREFN

REFOUT Load Regulation 35

mV/mA

REFOUT Temperature Coefficient

TCREF +50

ppm/°C

Short to VDD—sinking 0.24

REFOUT Short-Circuit Current

Short to GND—sourcing 2.1

BUFFERED EXTERNAL REFERENCE (REFIN driven externally; VREFIN = 2.048V, VREFP, VREFN, and VCOM are generated internally)

REFIN Input Voltage

REFP Output Voltage VREFP (VDD/2) + (VREFIN / 4)

SFDRTT

VREFOUT 1.978 2.048 2.079

VREFIN 2.048

78.7

-87.1

-85.0 -77.2

-81.2

-86.5

-96.8

-95.1

-85.1

-81.1

-84.4

1.024

2.162

Page 4

MAX1208

12-Bit, 80Msps, 3.3V ADC

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

REFN Output Voltage V

REFN

/ 2) - (V

REFIN

/ 4)

COM Output Voltage V

COM

/ 2

Differential Reference Output Voltage

REF

= V

REFP

- V

REFN

Differential Reference Temperature Coefficient

ppm/°C

REFIN Input Resistance

MΩ

UNBUFFERED EXTERNAL REFERENCE (REFIN = GND; V

REFP

, V

REFN

, and V

COM

are applied externally)

COM Input Voltage V

COM

/ 2

REFP Input Voltage V

REFP

- V

COM

REFN Input Voltage V

REFN

- V

COM

Differential Reference Input Voltage

REF

= V

REFP

- V

REFN

REFP Sink Current I

REFP

= 2.162V 1.1 mA

REFN Source Current I

REFN

= 1.138V 1.1 mA

COM Sink Current I

COM

0.3 mA

REFP, REFN Capacitance 13 pF

COM Capacitance 6pF

CLOCK INPUTS (CLKP, CLKN)

Single-Ended Input High Threshold

CLKTYP = GND, CLKN = GND

0.8 x V

Single-Ended Input Low Threshold

CLKTYP = GND, CLKN = GND

0.2 x V

Differential Input Voltage Swing CLKTYP = high 1.4

P-P

Differential Input Common-Mode Voltage

CLKTYP = high

Input Resistance R

CLK

Figure 5 5 kΩ

Input Capacitance C

CLK

2pF

DIGITAL INPUTS (CLKTYP, G/T, PD)

Input High Threshold V

0.8 x V

1.138

1.60 1.65 1.70

0.969 1.024 1.069

±25

>50

1.65

0.512

-0.512

1.024

/ 2

Page 5

MAX1208

12-Bit, 80Msps, 3.3V ADC

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Input Low Threshold V

0.2 x V

VIH = OV

±5

Input Leakage Current

= 0 ±5

µA

Input Capacitance C

DIN

5pF

DIGITAL OUTPUTS (D11–D0, DAV, DOR)

D11–D0, DOR, I

SINK

= 200µA 0.2

Output Voltage Low V

DAV, I

SINK

= 600µA 0.2

D11–D0, DOR, I

SOURCE

= 200µA

0.2

Output Voltage High V

DAV, I

SOURCE

= 600µA

0.2

Tri-State Leakage Current I

LEAK

(Note 3) ±5 µA

D11–D0, DOR Tri-State Output Capacitance

OUT

(Note 3) 3 pF

DAV Tri-State Output Capacitance

DAV

(Note 3) 6 pF

POWER REQUIREMENTS

Analog Supply Voltage V

3.0 3.3 3.6 V

Digital Output Supply Voltage OV

1.7 2.0

Normal operating mode, f

= 32.5MHz at -0.5dBFS,

CLKTYP = GND, single-ended clock

Normal operating mode, f

= 32.5MHz at -0.5dBFS,

CLKTYP = OV

DD,

differential clock

Analog Supply Current I

VDD

Power-down mode clock idle, PD = OV

Normal operating mode, f

= 32.5MHz at -0.5dBFS,

CLKTYP = GND, single-ended clock

Normal operating mode, f

= 32.5MHz at -0.5dBFS,

CLKTYP = OV

, differential clock

Analog Power Dissipation P

DISS

Power-down mode clock idle, PD = OV

OVDD -

113

121 132.2

0.001

373

399 436.3

0.003

VDD +

0.3V

Page 6

MAX1208

12-Bit, 80Msps, 3.3V ADC

6 _______________________________________________________________________________________

Note 1: Specifications ≥+25°C guaranteed by production test, <+25°C guaranteed by design and characterization.

Note 2: See definitions in the Parameter Definitions section. Note 3: During power-down, D11–D0, DOR, and DAV are high impedance. Note 4: Guaranteed by design and characterization. Note 5: Digital outputs settle to V

or VIL.

ELECTRICAL CHARACTERISTICS (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Normal operating mode, f

= 32.5MHz at -0.5dBFS, OVDD = 2.0V,

≈ 5pF

9.9 mA

Digital Output Supply Current I

OVDD

Power-down mode clock idle, PD = OV

0.9 µA

TIMING CHARACTERISTICS (Figure 6)

Clock Pulse Width High t

Clock Pulse Width Low t

Data-Valid Delay t

DAV

CL = 5pF (Note 5) 6.4 ns

Data Setup Time Before Rising Edge of DAV

SETUP

CL = 5pF (Note 4, Note 5) 7.7 ns

Data Hold Time After Rising Edge of DAV

HOLD

CL = 5pF (Note 4, Note 5) 4.2 ns

Wake-Up Time from Power-Down

WAKE

REFIN

= 2.048V 10 ms

6.25

Page 7

MAX1208

12-Bit, 80Msps, 3.3V ADC

_______________________________________________________________________________________ 7

SINGLE-TONE FFT PLOT

(8192-POINT DATA RECORD)

MAX1208 toc01

FREQUENCY (MHz)

AMPLITUDE (dBFS)

363224 2881216204

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

-110 040

CLK

= 80.00353MHz

= 2.99817879MHz AIN = -0.527dBFS SNR = 68.100dB SINAD = 68.061dB THD = -88.539dBc SFDR = 90.612dBc

HD3

HD2

SINGLE-TONE FFT PLOT

(8192-POINT DATA RECORD)

MAX1208 toc02

FREQUENCY (MHz)

AMPLITUDE (dBFS)

363224 2881216204

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

-110 040

CLK

= 80.00353MHz

= 32.49166395MHz

= -0.495dBFS SNR = 68.236dB SINAD = 68.173dB THD = -86.624dBc SFDR = 89.446dBc

HD3

HD2

SINGLE-TONE FFT PLOT

(8192-POINT DATA RECORD)

MAX1208 toc03

FREQUENCY (MHz)

AMPLITUDE (dBFS)

363224 2881216204

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

-110 040

CLK

= 80.00353MHz

= 69.99331395MHz

= -0.510dBFS SNR = 68.011dB SINAD = 67.819dB THD = -81.470dBc SFDR = 85.617dBc

HD3

HD2

HD4

SINGLE-TONE FFT PLOT

(16,384-POINT DATA RECORD)

MAX1208 toc04

FREQUENCY (MHz)

AMPLITUDE (dBFS)

363224 2881216204

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

-110 040

CLK

= 80MHz

IN1

= 43.90137MHz

IN1

= -7.010dBFS

IN2

= 45.90332MHz

IN2

= -7.041dBFS

SFDR

= 87.239dBc IMD = -85.288dBc IM3 = -87.415dBc

IN1

IN2

2 x f

IN1

+ f

IN2

SINGLE-TONE FFT PLOT

(16,384-POINT DATA RECORD)

MAX1208 toc05

FREQUENCY (MHz)

AMPLITUDE (dBFS)

363224 2881216204

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

-110 040

CLK

= 80MHz

IN1

= 68.50098MHz

IN1

= -7.043dBFS

IN2

= 71.499MHz

IN2

= -7.041dBFS IMD = -80.988dBc IM3 = -84.424dBc

IN1

IN2

2 x f

IN1

+ f

IN2

IN1

+ 2 x f

IN2

IN1

+ f

IN2

INTEGRAL NONLINEARITY

MAX1208 toc06

DIGITAL OUTPUT CODE

INL (LSB)

358430722048 25601024 1536512

-0.8

-0.6

-0.4

-0.2

0.2

0.4

0.6

0.8

1.0

-1.0 04096

DIFFERENTIAL NONLINEARITY

MAX1208 toc07

DIGITAL OUTPUT CODE

DNL (LSB)

358430722048 25601024 1536512

-0.8

-0.6

-0.4

-0.2

0.2

0.4

0.6

0.8

1.0

-1.0 04096

Typical Operating Characteristics

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = +25°C, unless otherwise noted.)

Page 8

MAX1208

12-Bit, 80Msps, 3.3V ADC

8 _______________________________________________________________________________________

SNR, SINAD

vs. SAMPLING RATE

MAX1208 toc08

CLK

(MHz)

SNR, SINAD (dB)

806020 40

0100

fIN ≈ 32.5MHz

SNR SINAD

SFDR, -THD

vs. SAMPLING RATE

MAX1208 toc09

CLK

(MHz)

SFDR, -THD (dBc)

806020 40

100

0 100

fIN ≈ 32.5MHz

SFDR

-THD

POWER DISSIPATION

vs. SAMPLING RATE

MAX1208 toc10

CLK

(MHz)

POWEER DISSIPATION (mW)

806020 40

250

300

350

400

450

500

200

0100

DIFFERENTIAL CLOCK f

≈ 32.5MHz

≈ 5pF

ANALOG + DIGITAL POWER ANALOG POWER

SNR, SINAD

vs. SAMPLING RATE

MAX1208 toc11

CLK

(MHz)

SNR, SINAD (dB)

806020 40

0100

fIN ≈ 70MHz

SNR SINAD

SFDR, -THD

vs. SAMPLING RATE

MAX1208 toc12

CLK

(MHz)

SFDR, -THD (dBc)

806020 40

100

0 100

fIN ≈ 70MHz

SFDR

-THD

POWER DISSIPATION

vs. SAMPLING RATE

MAX1208 toc13

CLK

(MHz)

POWEER DISSIPATION (mW)

806020 40

250

300

350

400

450

200

0120100

DIFFERENTIAL CLOCK f

≈ 70MHz

≈ 5pF

ANALOG + DIGITAL POWER ANALOG POWER

SNR, SINAD

vs. ANALOG INPUT FREQUENCY

MAX1208 toc14

ANALOG INPUT FREQUENCY (MHz)

SNR, SINAD (dB)

100755025

0125

CLK

≈ 80MHz

SNR SINAD

SFDR, -THD

vs. ANALOG INPUT FREQUENCY

MAX1208 toc15

ANALOG INPUT FREQUENCY (MHz)

SFDR, -THD (dBc)

100755025

0125

CLK

≈ 80MHz

SFDR

-THD

POWER DISSIPATION

vs. ANALOG INPUT FREQUENCY

MAX1208 toc16

ANALOG INPUT FREQUENCY (MHz)

POWER DISSIPATION (mW)

100755025

350

400

450

500

300

0125

ANALOG + DIGITAL POWER ANALOG POWER

DIFFERENTIAL CLOCK f

CLK

≈ 80MHz

= 5pF

Typical Operating Characteristics (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = +25°C, unless otherwise noted.)

Page 9

MAX1208

12-Bit, 80Msps, 3.3V ADC

_______________________________________________________________________________________ 9

SNR, SINAD

vs. ANALOG INPUT AMPLITUDE

MAX1208 toc17

ANALOG INPUT AMPLITUDE (dBFS)

SNR, SINAD (dB)

-5-10-20 -15-30 -25-35

-40 0

CLK

= 80.003702MHz

= 32.125257MHz

SNR SINAD

SFDR, -THD

vs. ANALOG INPUT AMPLITUDE

MAX1208 toc18

ANALOG INPUT AMPLITUDE (dBFS)

SFDR, -THD (dBc)

-5-10-20 -15-30 -25-35

-40 0

CLK

= 80.003702MHz

= 32.125257MHz

SFDR

-THD

POWER DISSIPATION

vs. ANALOG INPUT AMPLITUDE

MAX1208 toc19

ANALOG INPUT AMPLITUDE (dBFS)

POWER DISSIPATION (mW)

-5-10-20 -15-30 -25-35

350

400

450

500

300

-40 0

DIFFERENTIAL CLOCK f

CLK

= 80.003702MHz

= 32.125257MHz

≈ 5pF

ANALOG + DIGITAL POWER ANALOG POWER

SNR, SINAD

vs. ANALOG POWER-INPUT VOLTAGE

MAX1208 toc20

VDD (V)

SNR, SINAD (dB)

3.43.23.02.8

2.6 3.6

CLK

= 80.03584MHz

= 32.11399MHz

SNR SINAD

SFDR, -THD

vs. ANALOG POWER-INPUT VOLTAGE

MAX1208 toc21

VDD (V)

SFDR, -THD (dBc)

3.43.23.02.8

100

2.6 3.6

CLK

= 80.03584MHz

= 32.11399MHz

SFDR

-THD

POWER DISSIPATION

vs. ANALOG POWER-INPUT VOLTAGE

MAX1208 toc22

VDD (V)

POWER DISSIPATION (mW)

3.43.23.02.8

250

300

350

400

450

500

550

200

2.6 3.6

DIFFERENTIAL CLOCK f

CLK

= 80.03584MHz

= 32.11399MHz

≈

5pF

ANALOG + DIGITAL POWER ANALOG POWER

SNR, SINAD

vs. OUTPUT-DRIVER POWER-INPUT VOLTAGE

MAX1208 toc23

OVDD (V)

SNR, SINAD (dB)

3.43.02.62.21.8

1.4 3.8

CLK

= 80.03584MHz

= 32.11399MHz

SNR SINAD

SFDR, -THD

vs. OUTPUT-DRIVER POWER-INPUT VOLTAGE

MAX1208 toc24

OVDD (V)

SFDR, -THD (dBc)

3.43.02.62.21.8

100

1.4 3.8

CLK

= 80.03584MHz

= 32.11399MHz

SFDR

-THD

POWER DISSIPATION

vs. OUTPUT-DRIVER POWER-INPUT VOLTAGE

MAX1208 toc25

OVDD (V)

SFDR, -THD (dBc)

3.43.02.62.21.8

250

225

300

350

400

450

500

550

200

1.4 3.8

DIFFERENTIAL CLOCK f

CLK

= 80.03584MHz

= 32.11399MHz

≈ 5pF

ANALOG + DIGITAL POWER ANALOG POWER

Typical Operating Characteristics (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = +25°C, unless otherwise noted.)

Page 10

MAX1208

12-Bit, 80Msps, 3.3V ADC

10 ______________________________________________________________________________________

SNR, SINAD

vs. TEMPERATURE

MAX1208 toc26

TEMPERATURE (°C)

SNR, SINAD (dB)

603510-15

-40 85

CLK

= 80.003072MHz

= 32.481716MHz

SNR SINAD

SFDR, -THD

vs. TEMPERATURE

MAX1208 toc27

TEMPERATURE (°C)

SFDR, -THD (dBc)

603510-15

-40 85

CLK

= 80.003072MHz

= 32.481716MHz

SFDR

-THD

ANALOG POWER DISSIPATION

vs. TEMPERATURE

MAX1208 toc28

TEMPERATURE (°C)

ANALOG POWER DISSIPATION (mW)

603510-15

250

300

350

400

450

500

550

200

-40 85

DIFFERENTIAL CLOCK f

CLK

= 80.003072MHz

= 32.481716MHz

OFFSET ERROR vs. TEMPERATURE

MAX1208 toc29

TEMPERATURE (°C)

OFFSET ERROR (%FS)

603510-15

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5

-0.5

-40 85

REFIN

= 2.048V

GAIN ERROR vs. TEMPERATURE

MAX1208 toc30

TEMPERATURE (°C)

GAIN ERROR (%FS)

603510-15

-2

-1

-3

-40 85

REFIN

= 2.048V

Typical Operating Characteristics (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = +25°C, unless otherwise noted.)

Page 11

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 11

REFERENCE OUTPUT VOLTAGE

LOAD REGULATION

MAX1208 toc31

REFOUT

SINK CURRENT (mA)

REFOUT

(V)

0-0.5-1.0-1.5

1.96

1.97

1.98

1.99

2.00

2.01

2.02

2.03

2.04

2.05

1.95

-2.0 0.5

+85°C

+25°C

-40°C

REFERENCE OUTPUT VOLTAGE

SHORT-CIRCUIT PERFORMANCE

MAX1208 toc32

REFOUT

SINK CURRENT (mA)

REFOUT

(V)

0-1.0-2.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-3.0 1.0

+85°C

+25°C

-40°C

REFERENCE OUTPUT VOLTAGE

vs. TEMPERATURE

MAX1208 toc33

TEMPERATURE (°C)

REFOUT

(V)

603510-15

2.031

2.033

2.035

2.037

2.039

2.029

-40 85

REFP, COM, REFN

LOAD REGULATION

MAX1208 toc34

SINK CURRENT (mA)

VOLTAGE (V)

10-1

0.5

1.0

1.5

2.0

2.5

3.0

-2 2

REFP

COM

REFN

INTERNAL REFERENCE MODE AND BUFFERED EXTERNAL REFERENCE MODE

REFP, COM, REFN

SHORT-CIRCUIT PERFORMANCE

MAX1208 toc35

SINK CURRENT (mA)

VOLTAGE (V)

40-4

0.5

1.0

1.5

2.0

2.5

3.5

3.0

-8 8

REFP

COM

REFN

INTERNAL REFERENCE MODE AND BUFFERED EXTERNAL REFERENCE MODE

Typical Operating Characteristics (continued)

= 3.3V, OV

= 2.0V, GND = 0, REFIN = REFOUT (internal reference), V

= -0.5dBFS, CLKTYP = high, DCE = high, PD = low,

G/T = low, f

CLK

= 80MHz (50% duty cycle), TA = +25°C, unless otherwise noted.)

Page 12

MAX1208

12-Bit, 80Msps, 3.3V ADC

12 ______________________________________________________________________________________

PIN NAME FUNCTION

1 REFP

Positive Reference I/O. The full-scale analog input range is ±(V

REFP

- V

REFN

). Bypass REFP to GND with

a 0.1µF capacitor. Connect a 1µF capacitor in parallel with a 10µF capacitor between REFP and REFN.

Place the 1µF REFP to REFN capacitor as close to the device as possible on the same side of the printed circuit (PC) board.

2 REFN

Negative Reference I/O. The full-scale analog input range is ±(V

REFP

- V

REFN

). Bypass REFN to GND with a 0.1µF capacitor. Connect a 1µF capacitor in parallel with a 10µF capacitor between REFP and REFN. Place the 1µF REFP to REFN capacitor as close to the device as possible on the same side

of the PC board.

3 COM

Common-Mode Voltage I/O. Bypass COM to GND with a 2.2µF capacitor. Place the 2.2µF COM to GND capacitor as close to the device as possible. This 2.2µF capacitor can be placed on the opposite side of the PC board and connected to the MAX1208 through a via.

4, 7, 16,

GND Ground. Connect all ground pins and EP together.

5 INP Positive Analog Input

6INN Negative Analog Input

8 DCE

Duty-Cycle Equalizer Input. Connect DCE low (GND) to disable the internal duty-cycle equalizer. Connect DCE high (OV

or VDD) to enable the internal duty-cycle equalizer.

9 CLKN

Negative Clock Input. In differential clock input mode (CLKTYP = OV

or VDD), connect the differential clock signal between CLKP and CLKN. In single-ended clock mode (CLKTYP = GND), apply the singleended clock signal to CLKP and connect CLKN to GND.

10 CLKP

Positive Clock Input. In differential clock input mode (CLKTYP = OV

or VDD), connect the differential clock signal between CLKP and CLKN. In single-ended clock mode (CLKTYP = GND), apply the singleended clock signal to CLKP and connect CLKN to GND.

11 CLKTYP

Clock Type Definition Input. Connect CLKTYP to GND to define the single-ended clock input. Connect CLKTYP to OV

or VDD to define the differential clock input.

12–15, 36

Analog Power Input. Connect VDD to a 3.0V to 3.6V power supply. Bypass VDD to GND with a parallel capacitor combination of ≥2.2µF and 0.1µF. Connect all V

pins to the same potential.

17, 34 OV

Output-Driver Power Input. Connect OVDD to a 1.7V to VDD power supply. Bypass OVDD to GND with a parallel capacitor combination of ≥2.2µF and 0.1µF.

18 DOR

Data Out-of-Range Indicator. The DOR digital output indicates when the analog input voltage is out of range. When DOR is high, the analog input is beyond its full-scale range. When DOR is low, the analog input is within its full-scale range (Figure 6).

19 D11 CMOS Digital Output, Bit 11 (MSB)

20 D10 CMOS Digital Output, Bit 10

21 D9 CMOS Digital Output, Bit 9

22 D8 CMOS Digital Output, Bit 8

23 D7 CMOS Digital Output, Bit 7

24 D6 CMOS Digital Output, Bit 6

25 D5 CMOS Digital Output, Bit 5

26 D4 CMOS Digital Output, Bit 4

27 D3 CMOS Digital Output, Bit 3

Pin Description

Page 13

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 13

PIN NAME FUNCTION

28 D2 CMOS Digital Output, Bit 2

29 D1 CMOS Digital Output, Bit 1

30 D0 CMOS Digital Output, Bit 0 ( LSB)

31, 32 I.C.

Internally Connected. Leave I.C. unconnected.

33 DAV

Data-Valid Output. DAV is a single-ended version of the input clock that is compensated to correct for any input clock duty-cycle variations. DAV is typically used to latch the MAX1208 output data into an external back-end digital circuit.

37 PD Power-Down Input. Force PD high for power-down mode. Force PD low for normal operation.

38 REFOUT

Internal Reference Voltage Output. For internal reference operation, connect REFOUT directly to REFIN or use a resistive divider from REFOUT to set the voltage at REFIN. Bypass REFOUT to GND with a ≥0.1µF capacitor.

39 REFIN

Reference Input. In internal reference mode and buffered external reference mode, bypass REFIN to GND with a ≥0.1µF capacitor. In these modes, V

REFP

- V

REFN

= V

REFIN

/ 2. For unbuffered external

reference-mode operation, connect REFIN to GND.

40 G/T

Output Format Select Input. Connect G/T to GND for the two’s complement digital output format. Connect G/T to OV

or VDD for the Gray code digital output format.

—EP

Exposed Paddle. The MAX1208 relies on the exposed paddle connection for a low-inductance ground connection. Connect EP to GND to achieve specified performance. Use multiple vias to connect the top-side PC board ground plane to the bottom-side PC board ground plane.

Pin Description (continued)

MAX1208

−

DIGITAL ERROR CORRECTION

FLASH

ADC

T/H

DAC

STAGE 2

D11–D0

INP

INN

STAGE 1

T/H

STAGE 9

STAGE 10

END OF PIPE

OUTPUT DRIVERS

D11–D0

Figure 1. Pipeline Architecture—Stage Blocks

Page 14

MAX1208

Detailed Description

The MAX1208 uses a 10-stage, fully differential, pipelined architecture (Figure 1) that allows for highspeed conversion while minimizing power consumption. Samples taken at the inputs move progressively through the pipeline stages every half-clock cycle. From input to output, the total clock-cycle latency is 8.5 clock cycles.

Each pipeline converter stage converts its input voltage into a digital output code. At every stage, except the last, the error between the input voltage and the digital output code is multiplied and passed along to the next pipeline stage. Digital error correction compensates for ADC comparator offsets in each pipeline stage and ensures no missing codes. Figure 2 shows the MAX1208 functional diagram.

Input Track-and-Hold (T/H) Circuit

Figure 3 displays a simplified functional diagram of the input T/H circuit. This input T/H circuit allows for high analog input frequencies up to 70MHz and supports a common-mode input voltage of V

/ 2 ±0.5V.

The MAX1208 sampling clock controls the ADC’s switched-capacitor T/H architecture (Figure 3), allowing the analog input signal to be stored as charge on the sampling capacitors. These switches are closed (track) when the sampling clock is high and open (hold) when the sampling clock is low (Figure 4). The analog input signal source must be capable of providing the dynamic current necessary to charge and discharge the sampling capacitors. To avoid signal degradation, these

capacitors must be charged to one-half LSB accuracy within one-half of a clock cycle.

The analog input of the MAX1208 supports differential or single-ended input drive. For optimum performance with differential inputs, balance the input impedance of INP and INN and set the common-mode voltage to midsupply (V

/ 2). The MAX1208 provides the optimum

common-mode voltage of V

/ 2 through the COM output when operating in internal reference mode and buffered external reference mode. This COM output voltage can be used to bias the input network as shown in Figures 10, 11, and 12.

Reference Output (REFOUT)

An internal bandgap reference is the basis for all the internal voltages and bias currents used in the MAX1208. The power-down logic input (PD) enables and disables the reference circuit. The reference circuit requires 10ms to power up and settle when power is applied to the MAX1208 or when PD transitions from high to low. REFOUT has approximately 17kΩ to GND when the MAX1208 is in power-down.

The internal bandgap reference and its buffer generate V

REFOUT

to be 2.048V. The reference temperature coeffi-

cient is typically +50ppm/°C. Connect an external ≥0.1µF bypass capacitor from REFOUT to GND for stability.

12-Bit, 80Msps, 3.3V ADC

14 ______________________________________________________________________________________

MAX1208

INP

INN

12-BIT

PIPELINE

ADC

DEC

REFERENCE

SYSTEM

COM

REFOUT

REFN

REFP

DAV

OUTPUT DRIVERS

D11–D0

DOR

REFIN

T/H

POWER CONTROL

AND

BIAS CIRCUITS

CLKP

CLOCK

GENERATOR

AND

DUTY-CYCLE

EQUALIZER

CLKN

CLKTYP

GND

DCE

G/T

Figure 2. Simplified Functional Diagram

MAX1208

PAR

2pF

BOND WIRE

INDUCTANCE

1.5nH

INP

SAMPLING

CLOCK

*THE EFFECTIVE RESISTANCE OF THE SWITCHED SAMPLING CAPACITORS IS:

SAMPLE

1.9pF

PAR

2pF

BOND WIRE

INDUCTANCE

1.5nH

INN

SAMPLE

1.9pF

SAMPLE

CLK

x C

SAMPLE

Figure 3. Simplified Input Track-and-Hold Circuit

Page 15

REFOUT sources up to 1.0mA and sinks up to 0.1mA for external circuits with a load regulation of 35mV/mA. Short-circuit protection limits I

REFOUT

to a 2.1mA source current when shorted to GND and a 0.24mA sink current when shorted to VDD.

Analog Inputs and Reference

Configurations

The MAX1208 full-scale analog input range is adjustable from ±0.35V to ±1.15V with a commonmode input range of V

/ 2 ±0.5V. The MAX1208 provides three modes of reference operation. The voltage at REFIN (V

REFIN

) sets the reference operation mode

(Table 1).

To operate the MAX1208 with the internal reference, connect REFOUT to REFIN either with a direct short or through a resistive divider. In this mode, COM, REFP, and REFN are low-impedance outputs with V

COM

/ 2, V

REFP

= V

/ 2 + V

REFIN / 4, VREFN

= V

/ 2

- V

REFIN

/ 4. The REFIN input impedance is very large

(>50MΩ). When driving REFIN through a resistive

divider, use resistances ≥10kΩ to avoid loading REFOUT.

Buffered external reference mode is virtually identical to internal reference mode except that the reference source is derived from an external reference and not the MAX1208 REFOUT. In buffered external reference mode, apply a stable 0.7V to 2.3V source at REFIN. In this mode, COM, REFP, and REFN are low-impedance outputs with V

COM

= V

/ 2, V

REFP

= V

/ 2 + V

REFIN

4, and V

REFN

= V

/ 2 - V

REFIN

/ 4.

To operate the MAX1208 in unbuffered external reference mode, connect REFIN to GND. Connecting REFIN to GND deactivates the on-chip reference buffers for COM, REFP, and REFN. With the respective buffers deactivated, COM, REFP, and REFN become highimpedance inputs and must be driven through separate, external reference sources. Drive V

COM

to V

/ 2

±5%, and drive REFP and REFN such that V

COM

REFP

+ V

REFN

/ 2. The full-scale analog input range is

±(V

REFP

- V

REFN

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 15

T/H

CLKN

CLKP

TRACK HOLDTRACK HOLDTRACK HOLDTRACKHOLD

ANALOG

INPUT

SAMPLED

DATA

Figure 4. T/H Aperture Timing

REFIN

REFERENCE MODE

35% V

REFOUT

100% V

REFOUT

Internal Reference Mode. Drive REFIN with REFOUT either through a direct short or a resistive divider. The full-scale analog input range is ±V

REFIN

/ 2:

COM

= V

/ 2

REFP

= V

/ 2 + V

REFIN

/ 4

REFN

= V

/ 2 - V

REFIN

/ 4

0.7V to 2.3V

Buffered External Reference Mode. Apply an external 0.7V to 2.3V reference voltage to REFIN. The full-scale analog input range is ±V

REFIN

/ 2:

COM

= V

/ 2

REFP

= V

/ 2 + V

REFIN

/ 4

REFN

= V

/ 2 - V

REFIN

/ 4

<0.4V

Unbuffered External Reference Mode. Drive REFP, REFN, and COM with external reference sources. The full-scale analog input range is ±(V

REFP

- V

REFN

Table 1. Reference Modes

Page 16

MAX1208

All three modes of reference operation require the same bypass capacitor combinations. Bypass COM with a 2.2µF capacitor to GND. Bypass REFP and REFN each with a 0.1µF capacitor to GND. Bypass REFP to REFN with a 1µF capacitor in parallel with a 10µF capacitor. Place the 1µF capacitor as close to

the device as possible on the same side of the PC board. Bypass REFIN and REFOUT to GND with a

0.1µF capacitor.

For detailed circuit suggestions, see Figures 13 and 14.

Clock Input and Clock Control Lines

(CLKP, CLKN, CLKTYP)

The MAX1208 accepts both differential and singleended clock inputs. For single-ended clock-input operation, connect CLKTYP to GND, CLKN to GND, and drive CLKP with the external single-ended clock signal. For differential clock-input operation, connect CLKTYP to OVDDor VDD, and drive CLKP and CLKN with the external differential clock signal. To reduce clock jitter, the external single-ended clock must have sharp falling edges. Consider the clock input as an analog input and route it away from any other analog inputs and digital signal lines.

CLKP and CLKN are high impedance when the MAX1208 is powered down (Figure 5).

Low clock jitter is required for the specified SNR performance of the MAX1208. Analog input sampling occurs on the falling edge of the clock signal, requiring this edge to have the lowest possible jitter. Jitter limits the maximum SNR performance of any ADC according to the following relationship:

where f

represents the analog input frequency and t

is the total system clock jitter. Clock jitter is especially critical for undersampling applications. For example, assuming that clock jitter is the only noise source, to obtain the specified 68.2dB of SNR with an input frequency of 32.5MHz, the system must have less than

1.9ps of clock jitter.

Clock Duty-Cycle Equalizer (DCE)

Enable the MAX1208 clock duty-cycle equalizer by connecting DCE to OVDDor VDD. Disable the MAX1208 clock duty-cycle equalizer by connecting DCE to GND.

The clock duty-cycle equalizer uses a delay-locked loop (DLL) to create internal timing signals that are duty-cycle independent. Due to this DLL, the MAX1208 requires approximately 100 clock cycles to acquire and lock to new clock frequencies.

Disabling the clock duty-cycle equalizer reduces the analog supply current by 1.5mA.

System Timing Requirements

Figure 6 shows the relationship between the clock, analog inputs, DAV indicator, DOR indicator, and the resulting output data. The analog input is sampled on the falling edge of the clock signal and the resulting data appears at the digital outputs 8.5 clock cycles later.

The DAV indicator is synchronized with the digital output and optimized for use in latching data into digital back-end circuitry. Alternatively, digital back-end circuitry can be latched with the rising edge of the conversion clock (CLKP-CLKN).

SNR

IN J

log

=×

×π ×













12-Bit, 80Msps, 3.3V ADC

16 ______________________________________________________________________________________

MAX1208

CLKP

CLKN

GND

10kΩ

DUTY-CYCLE

EQUALIZER

SWITCHES S

AND S2_ ARE OPEN DURING POWER-DOWN, MAKING CLKP AND CLKN HIGH IMPEDANCE. SWITCHES S

ARE OPEN IN

SINGLE-ENDED CLOCK MODE.

Figure 5. Simplified Clock Input Circuit

Page 17

Data-Valid Output (DAV)

DAV is a single-ended version of the input clock (CLKP). Output data changes on the falling edge of DAV, and DAV rises once output data is valid (Figure 6).

The state of the duty-cycle equalizer input (DCE) changes the waveform at DAV. With the duty-cycle equalizer disabled (DCE = low), the DAV signal is the inverse of the signal at CLKP delayed by 6.8ns. With the duty-cycle equalizer enabled (DCE = high), the DAV signal has a fixed pulse width that is independent of CLKP. In either case, with DCE high or low, output data at D11–D0 and DOR are valid from 7.7ns before the rising edge of DAV to 4.2ns after the rising edge of DAV, and the rising edge of DAV is synchronized to have a

6.4ns (t

DAV

) delay from the falling edge of CLKP.

DAV is high impedance when the MAX1208 is in power-down (PD = high). DAV is capable of sinking and sourcing 600µA and has three times the drive strength of D11–D0 and DOR. DAV is typically used to latch the MAX1208 output data into an external backend digital circuit.

Keep the capacitive load on DAV as low as possible (<25pF) to avoid large digital currents feeding back into the analog portion of the MAX1208 and degrading its dynamic performance. An external buffer on DAV isolates it from heavy capacitive loads. Refer to the MAX1211 evaluation kit schematic for an example of DAV driving back-end digital circuitry through an external buffer.

Data Out-of-Range Indicator (DOR)

The DOR digital output indicates when the analog input voltage is out of range. When DOR is high, the analog input is out of range. When DOR is low, the analog input is within range. The valid differential input range is from (V

REFP

- V

REFN

) to (V

REFN

- V

REFP

). Signals out-

side this valid differential range cause DOR to assert high as shown in Table 2 and Figure 6.

DOR is synchronized with DAV and transitions along with the output data D11–D0. There is an 8.5 clockcycle latency in the DOR function as with the output data (Figure 6).

DOR is high impedance when the MAX1208 is in power-down (PD = high). DOR enters a high-impedance state within 10ns after the rising edge of PD and becomes active 10ns after PD’s falling edge.

Digital Output Data (D11–D0), Output Format (G/T)

The MAX1208 provides a 12-bit, parallel, tri-state output bus. D11–D0 and DOR update on the falling edge of DAV and are valid on the rising edge of DAV.

The MAX1208 output data format is either Gray code or two’s complement, depending on the logic input G/T. With G/T high, the output data format is Gray code. With G/T low, the output data format is two’s complement. See Figure 8 for a binary-to-Gray and Gray-tobinary code-conversion example.

The following equations, Table 2, Figure 7, and Figure 8 define the relationship between the digital output and the analog input:

for Gray code (G/T = 1)

VV V V

CODE

INP INN REFP REFN

( )

−= − ××

−22048

4096

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 17

DAV

D11–D0

N+1

N+2

N+3

N+4

N+5

N+6

N+7

N+8

N+9

DAV

SETUP

N-1

N-2

N-3

HOLD

DOR

8.5 CLOCK-CYCLE DATA LATENCY

DIFFERENTIAL ANALOG INPUT (INP–INN)

SETUP

HOLD

NN+1N+2N+3 N+5N+6N+7N-1N-2N-3 N+9N+4 N+8

CLKN

CLKP

REFP

- V

REFN

)

REFN

- V

REFP

)

Figure 6. System Timing Diagram

Page 18

MAX1208

for two’s complement (G/T = 0)

where CODE

is the decimal equivalent of the digital

output code as shown in Table 2.

Digital outputs D11–D0 are high impedance when the MAX1208 is in power-down (PD = high). D11–D0 transition high 10ns after the rising edge of PD and become active 10ns after PD’s falling edge.

Keep the capacitive load on the MAX1208 digital outputs D11–D0 as low as possible (<15pF) to avoid large digital currents feeding back into the analog portion of the MAX1208 and degrading its dynamic performance. The addition of external digital buffers on the digital outputs isolates the MAX1208 from heavy capacitive loading. To improve the dynamic performance of the MAX1208, add 220Ω resistors in series with the digital outputs close to the MAX1208. Refer to the MAX1211 evaluation kit schematic for an example of the digital outputs driving a digital buffer through 220Ω series resistors.

Power-Down Input (PD)

The MAX1208 has two power modes that are controlled with the power-down digital input (PD). With PD low, the

VV V V

CODE

INP INN REFP REFN

( ) −= − ××2

4096

12-Bit, 80Msps, 3.3V ADC

18 ______________________________________________________________________________________

GRAY CODE OUTPUT CODE (G/T = 1) TWO’S-COMPLEMENT OUTPUT CODE (G/T = 0)

BINARY

D11➝D0

EQUIVALENT

D11➝D0

DECIMAL

EQUIVALENT

D11➝D0

BINARY D11➝D0

EQUIVALENT

D11➝D0

DECIMAL

D11➝D0

INP

- V

INN

REFP

= 2.162V

REFN

= 1.138V

1000 0000 0000

0x800 +4095

0x7FF +2047

>+1.0235V

(DATA OUT OF

RANGE)

1000 0000 0000

0x800 +4095

0x7FF +2047 +1.0235V

1000 0000 0001

0x801 +4094

0x7FE +2046 +1.0230V

1100 0000 0011

0xC03 +2050

0x002 +2 +0.0010V

1100 0000 0001

0xC01 +2049

0x001 +1 +0.0005V

1100 0000 0000

0xC00 +2048

0x000 0 +0.0000V

0100 0000 0000

0x400 +2047

0xFFF -1 -0.0005V

0100 0000 0001

0x401 +2046

0xFFE -2 -0.0010V

0000 0000 0001

0x001 +1

0x801 -2047 -1.0235V

0000 0000 0000

0x000 0

0x800 -2048 -1.0240V

0000 0000 0000

0x000 0

0x800 -2048

<-1.0240V

(DATA OUT OF

RANGE)

Table 2. Output Codes vs. Input Voltage

(

)

HEXADECIMAL

DOR

(CODE10)

0111 1111 1111 1

0111 1111 1111 0

0111 1111 1110 0

0000 0000 0010 0

0000 0000 0001 0

0000 0000 0000 0

1111 1111 1111 0

1111 1111 1110 0

1000 0000 0001 0

1000 0000 0000 0

1000 0000 0000 1

HEXADECIMAL

DOR

EQUIVALENT

(CODE10)

Page 19

MAX1208 is in normal operating mode. With PD high, the MAX1208 is in power-down mode.

The power-down mode allows the MAX1208 to efficiently use power by transitioning to a low-power state when conversions are not required. Additionally, the MAX1208 parallel output bus is high impedance in power-down mode, allowing other devices on the bus to be accessed.

In power-down mode, all internal circuits are off, the analog supply current reduces to 1µA, and the digital supply current reduces to 0.9µA. The following list shows the state of the analog inputs and digital outputs in power-down mode:

• INP, INN analog inputs are disconnected from the internal input amplifier (Figure 3).

• REFOUT has approximately 17kΩ to GND.

• REFP, COM, and REFN go high impedance with respect to V

and GND, but there is an internal 4kΩ

resistor between REFP and COM, as well as an internal 4kΩ resistor between REFN and COM.

• D11–D0, DOR, and DAV go high impedance.

• CLKP and CLKN go high impedance (Figure 5).

The wake-up time from power-down mode is dominated by the time required to charge the capacitors at REFP, REFN, and COM. In internal reference mode and buffered external reference mode, the wake-up time is typically 10ms with the recommended capacitor array (Figure 13). When operating in unbuffered external reference mode, the wake-up time is dependent on the external reference drivers.

Applications Information

Using Transformer Coupling

In general, the MAX1208 provides better SFDR and THD performance with fully differential input signals as opposed to single-ended input drive. In differential input mode, even-order harmonics are lower as both inputs are balanced, and each of the ADC inputs only requires half the signal swing compared to single-ended input mode.

An RF transformer (Figure 10) provides an excellent solution to convert a single-ended input source signal to a fully differential signal, required by the MAX1208 for optimum performance. Connecting the center tap of the transformer to COM provides a V

/ 2 DC level

shift to the input. Although a 1:1 transformer is shown, a

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 19

DIFFERENTIAL INPUT VOLTAGE (LSB)

-1-2045

4096

2 x V

REF

1 LSB =

REF

= V

REFP

- V

REFN

REF

0+1-2047 +2047+2045

TWO'S COMPLEMENT OUTPUT CODE (LSB)

0x800

0x801

0x802

0x803

0x7FF 0x7FE

0x7FD

0xFFF

0x000

0x001

Figure 7. Two’s Complement Transfer Function (G/T= 0)

DIFFERENTIAL INPUT VOLTAGE (LSB)

-1-2045

4096

2 x V

REF

1 LSB =

REF

= V

REFP

- V

REFN

REF

0+1-2047 +2047+2045

GRAY OUTPUT CODE (LSB)

0x000

0x001

0x003

0x002

0x800 0x801 0x803

0x400

0xC00

0xC01

Figure 8. Gray Code Transfer Function (G/T= 1)

Page 20

MAX1208

12-Bit, 80Msps, 3.3V ADC

20 ______________________________________________________________________________________

BINARY-TO-GRAY CODE CONVERSION

1) THE MOST SIGNIFICANT GRAY-CODE BIT IS THE SAME AS THE MOST SIGNIFICANT BINARY BIT.

0111 0100 1100 BINARY

GRAY CODE0

2) SUBSEQUENT GRAY-CODE BITS ARE FOUND ACCORDING TO THE FOLLOWING EQUATION:

D11 D7 D3 D0

GRAYX = BINARYX +BINARY

X + 1

BIT POSITION

0111 0100 1100 BINARY

GRAY CODE0

D11 D7 D3 D0

BIT POSITION

GRAY

= BINARY10BINARY

GRAY10 = 1 0

GRAY

= 1

3) REPEAT STEP 2 UNTIL COMPLETE:

01 11 0100 1100 BINARY

GRAY CODE0

D11 D7 D3 D0

BIT POSITION

GRAY

= BINARY9BINARY

GRAY9 = 1 1

GRAY

= 0

4) THE FINAL GRAY CODE CONVERSION IS:

0111 0100 1100 BINARY

GRAY CODE0

D11 D7 D3 D0

BIT POSITION

100 1101 1010

GRAY-TO-BINARY CODE CONVERSION

1) THE MOST SIGNIFICANT BINARY BIT IS THE SAME AS THE MOST SIGNIFICANT GRAY-CODE BIT.

2) SUBSEQUENT BINARY BITS ARE FOUND ACCORDING TO THE FOLLOWING EQUATION:

D11 D7 D3 D0

BINARYX = BINARY

X+1

BIT POSITION

BINARY

= BINARY11GRAY

BINARY10 = 0 1

BINARY

= 1

3) REPEAT STEP 2 UNTIL COMPLETE:

4) THE FINAL BINARY CONVERSION IS:

0100 1110 1010

BINARY

GRAY CODE

D11 D7 D3 D0

BIT POSITION

0 BINARY

GRAY CODE0100 11 011010

BINARY

= BINARY10GRAY

BINARY9 = 1 0

BINARY

= 1

GRAY

01001110 1010

BINARY

GRAY CODE

D11 D7 D3 D0

BIT POSITION

01 00 1110 1010

BINARY

GRAY CODE

D11 D7 D3 D0

BIT POSITION

0111 0100 1100

AB Y=AB

00 01 10 11

0 1 1 0

EXCLUSIVE OR TRUTH TABLE

WHERE IS THE EXCLUSIVE OR FUNCTION (SEE TRUTH TABLE BELOW) AND X IS THE BIT POSITION:

Figure 9. Binary-to-Gray and Gray-to-Binary Code Conversion

Page 21

step-up transformer can be selected to reduce the drive requirements. A reduced signal swing from the input driver, such as an op amp, can also improve the overall distortion. The configuration of Figure 10 is good for frequencies up to Nyquist (f

CLK

/ 2).

The circuit of Figure 11 converts a single-ended input signal to fully differential just as Figure 10. However, Figure 11 utilizes an additional transformer to improve the common-mode rejection, allowing high-frequency signals beyond the Nyquist frequency. The two sets of termination resistors provide an equivalent 75Ω termi- nation to the signal source. The second set of termina-

tion resistors connects to COM, providing the correct input common-mode voltage. Two 0Ω resistors in series with the analog inputs allow high IF input frequencies. These 0Ω resistors can be replaced with low-value resistors to limit the input bandwidth.

Single-Ended AC-Coupled Input Signal

Figure 12 shows an AC-coupled, single-ended input application. The MAX4108 provides high speed, high bandwidth, low noise, and low distortion to maintain the input signal integrity.

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 21

MAX1208

N.C. N.C.

MINICIRCUITS

ADT1-1WT

N.C.

0.1µF

MINICIRCUITS

ADT1-1WT

0Ω*

5.6pF

2.2µF

INP

COM

INN

110

Ω

0.1%

110

Ω

0.1%

Ω

0.5%

Ω

0.5%

*0Ω RESISTORS CAN BE REPLACED WITH LOW-VALUE RESISTORS TO LIMIT THE INPUT BANDWIDTH.

Figure 11. Transformer-Coupled Input Drive for Input Frequencies Beyond Nyquist

MAX1208

N.C.

0.1µF

MINICIRCUITS

TT1-6 OR T1-1T

24.9Ω

12pF

2.2µF

INP

COM

INN

Figure 10. Transformer-Coupled Input Drive for Input Frequencies Up to Nyquist

MAX1208

5.6pF

2.2µF

INP

COM

INN

24.9Ω

100Ω

0.1µF

MAX4108

Figure 12. Single-Ended, AC-Coupled Input Drive

Page 22

MAX1208

Buffered External Reference

Drives Multiple ADCs

The buffered external reference mode allows for more control over the MAX1208 reference voltage and allows multiple converters to use a common reference. The REFIN input impedance is >50MΩ.

Figure 13 uses the MAX6029EUK21 precision 2.048V reference as a common reference for multiple converters. The 2.048V output of the MAX6029 passes through a one-pole, 10Hz lowpass filter to the MAX4230. The MAX4230 buffers the 2.048V reference and provides additional 10Hz lowpass filtering before its output is applied to the REFIN input of the MAX1208.

12-Bit, 80Msps, 3.3V ADC

22 ______________________________________________________________________________________

MAX1208

NOTE: ONE FRONT-END REFERENCE CIRCUIT IS CAPABLE OF SOURCING 15mA AND SINKING 30mA OF OUTPUT CURRENT.

*PLACE THE 1µF REFP-to-REFN BYPASS CAPACITOR AS CLOSE TO THE DEVICE AS POSSIBLE.

16.2kΩ

0.1µF

1µF

2.048V

+3.3V

47Ω

1.47kΩ

+3.3V

10µF 6V

330µF 6V

+3.3V

2.2µF

0.1µF

1µF* 10µF

0.1µF

REFP

REFN

COM

GND

REFIN

REFOUT

MAX1208

+3.3V

2.2µF

0.1µF

1µF* 10µF

0.1µF

REFP

REFN

COM

GND

REFIN

REFOUT

MAX6029EUK21

MAX4230

Figure 13. External Buffered Reference Driving Multiple ADCs

Page 23

Unbuffered External

Reference Drives Multiple ADCs

The unbuffered external reference mode allows for precise control over the MAX1208 reference and allows multiple converters to use a common reference. Connecting REFIN to GND disables the internal reference, and allows REFP, REFN, and COM to be driven directly by a set of external reference sources.

Figure 14 uses the MAX6029EUK30 precision 3.000V reference as a common reference for multiple converters. A five-component resistive divider chain follows the MAX6029 voltage reference. The 0.47µF capacitor along this chain creates a 10Hz lowpass filter. Three MAX4230 operational amplifiers buffer taps along this resistor chain providing 2.157V, 1.649V, and 1.141V to the MAX1208’s REFP, COM, and REFN reference inputs,

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 23

MAX1208

*PLACE THE 1µF REFP-TO-REFN BYPASS CAPACITOR AS CLOSE TO THE DEVICE AS POSSIBLE.

0.1µF

2.157V

+3.3V

Ω

1.47k

Ω

+3.3V

10µF 6V

330µF 6V

+3.3V

2.2µF

0.1µF

1µF*

10µF

0.1µF

REFOUT

REFN

REFIN

GND

COM

REFP

MAX6029EUK30

MAX4230

0.1µF

0.47µF

1.649V

Ω

1.47k

Ω

+3.3V

10µF 6V

330µF 6V

MAX4230

0.1µF

1.141V

Ω

1.47k

Ω

+3.3V

10µF 6V

330µF 6V

MAX4230

MAX1208

+3.3V

2.2µF

0.1µF

1µF*

10µF

0.1µF

REFOUT

REFN

REFIN

GND

COM

REFP

3.000V

24.3k

Ω

20k

Ω

26.7k

Ω

26.7k

Ω

20k

Ω

20k

Ω

20k

Ω

0.1µF

2.2µF

Figure 14. External Unbuffered Reference Driving Multiple ADCs

Page 24

MAX1208

respectively. The feedback around the MAX4230 op amps provides additional 10Hz lowpass filtering. The

2.157V and 1.141V reference voltages set the full-scale analog input range to ±1.016V.

A common power source for all active components removes any concern regarding power-supply sequencing when powering up or down.

Grounding, Bypassing, and

Board Layout

The MAX1208 requires high-speed board layout design techniques. Refer to the MAX1211 evaluation kit data sheet for a board layout reference. Locate all bypass capacitors as close to the device as possible, preferably on the same side of the board as the ADC, using surface-mount devices for minimum inductance. Bypass VDDto GND with a 0.1µF ceramic capacitor in parallel with a 2.2µF ceramic capacitor. Bypass OV

to GND with a 0.1µF ceramic capacitor in parallel with a

2.2µF ceramic capacitor.

Multilayer boards with ample ground and power planes produce the highest level of signal integrity. All MAX1208 GNDs and the exposed backside paddle must be connected to the same ground plane. The MAX1208 relies on the exposed backside paddle connection for a low-inductance ground connection. Use multiple vias to connect the top-side ground to the bottom-side ground. Isolate the ground plane from any noisy digital system ground planes such as a DSP or output buffer ground.

Route high-speed digital signal traces away from the sensitive analog traces. Keep all signal lines short and free of 90° turns.

Ensure that the differential analog input network layout is symmetric and that all parasitics are balanced equally. Refer to the MAX1211 evaluation kit data sheet for an example of symmetric input layout.

Parameter Definitions

Integral Nonlinearity (INL)

Integral nonlinearity is the deviation of the values on an actual transfer function from a straight line. For the MAX1208, this straight line is between the end points of the transfer function, once offset and gain errors have been nullified. INL deviations are measured at every step of the transfer function and the worst-case deviation is reported in the Electrical Characteristics table.

Differential Nonlinearity (DNL)

Differential nonlinearity is the difference between an actual step width and the ideal value of 1 LSB. A DNL error specification of less than 1 LSB guarantees no missing codes and a monotonic transfer function. For the MAX1208, DNL deviations are measured at every step of the transfer function and the worst-case deviation is reported in the Electrical Characteristics table.

Offset Error

Offset error is a figure of merit that indicates how well the actual transfer function matches the ideal transfer function at a single point. Ideally the midscale MAX1208 transition occurs at 0.5 LSB above midscale. The offset error is the amount of deviation between the measured midscale transition point and the ideal midscale transition point.

Gain Error

Gain error is a figure of merit that indicates how well the slope of the actual transfer function matches the slope of the ideal transfer function. The slope of the actual transfer function is measured between two data points: positive full scale and negative full scale. Ideally, the positive full-scale MAX1208 transition occurs at 1.5 LSBs below positive full scale, and the negative full-scale transition occurs at 0.5 LSB above negative full scale. The gain error is the difference of the measured transition points minus the difference of the ideal transition points.

Small-Signal Noise Floor (SSNF)

Small-signal noise floor is the integrated noise and distortion power in the Nyquist band for small-signal inputs. The DC offset is excluded from this noise calculation. For this converter, a small signal is defined as a single tone with an amplitude less than -35dBFS. This parameter captures the thermal and quantization noise characteristics of the converter and can be used to help calculate the overall noise figure of a receive channel. Go to www.maxim-ic.com for application notes on thermal + quantization noise floor.

Signal-to-Noise Ratio (SNR)

For a waveform perfectly reconstructed from digital samples, the theoretical maximum SNR is the ratio of the fullscale analog input (RMS value) to the RMS quantization error (residual error). The ideal, theoretical minimum analog-to-digital noise is caused by quantization error only and results directly from the ADC’s resolution (N bits):

SNR

[max]

= 6.02 × N + 1.76

12-Bit, 80Msps, 3.3V ADC

24 ______________________________________________________________________________________

Page 25

In reality, there are other noise sources besides quantization noise: thermal noise, reference noise, clock jitter, etc. SNR is computed by taking the ratio of the RMS signal to the RMS noise. RMS noise includes all spectral components to the Nyquist frequency excluding the fundamental, the first six harmonics (HD2–HD7), and the DC offset.

Signal-to-Noise Plus Distortion (SINAD)

SINAD is computed by taking the ratio of the RMS signal to the RMS noise plus distortion. RMS noise plus distortion includes all spectral components to the Nyquist frequency excluding the fundamental and the DC offset.

Effective Number of Bits (ENOB)

ENOB specifies the dynamic performance of an ADC at a specific input frequency and sampling rate. An ideal ADC’s error consists of quantization noise only. ENOB for a full-scale sinusoidal input waveform is computed from:

Single-Tone Spurious-Free Dynamic Range

(SFDR)

SFDR is the ratio expressed in decibels of the RMS amplitude of the fundamental (maximum signal component) to the RMS amplitude of the next-largest spurious component, excluding DC offset.

Total Harmonic Distortion (THD)

THD is the ratio of the RMS sum of the first six harmonics of the input signal to the fundamental itself. This is expressed as:

where V1is the fundamental amplitude, and V2through V7are the amplitudes of the 2nd- through 7th-order harmonics (HD2–HD7).

Intermodulation Distortion (IMD)

IMD is the ratio of the RMS sum of the intermodulation products to the RMS sum of the two fundamental input tones. This is expressed as:

The fundamental input tone amplitudes (V1and V2) are at -7dBFS. Fourteen intermodulation products (VIM_) are used in the MAX1208 IMD calculation. The intermodulation products are the amplitudes of the output spectrum at the following frequencies, where f

IN1

and

IN2

are the fundamental input tone frequencies:

• Second-order intermodulation products: f

IN1

+ f

IN2

, f

IN2

- f

IN1

• Third-order intermodulation products: 2 x f

IN1

- f

IN2

, 2 x f

IN2

- f

IN1

, 2 x f

IN1

+ f

IN2

, 2 x f

IN2

+ f

IN1

• Fourth-order intermodulation products: 3 x f

IN1

- f

IN2

, 3 x f

IN2

- f

IN1

, 3 x f

IN1

+ f

IN2

, 3 x f

IN2

+ f

IN1

• Fifth-order intermodulation products: 3 x f

IN1

- 2 x f

IN2

, 3 x f

IN2

- 2 x f

IN1

, 3 x f

IN1

+ 2 x f

IN2

3 x f

IN2

+ 2 x f

IN1

Third-Order Intermodulation (IM3)

IM3 is the total power of the third-order intermodulation products to the Nyquist frequency relative to the total input power of the two input tones f

IN1

and f

IN2

. The individual input tone levels are at -7dBFS. The thirdorder intermodulation products are 2 x f

IN1

- f

IN2

, 2 x

IN2

- f

IN1

, 2 x f

IN1

+ f

IN2

, 2 x f

IN2

+ f

IN1

Two-Tone Spurious-Free Dynamic Range

(SFDR

)

SFDRTTrepresents the ratio, expressed in decibels, of the RMS amplitude of either input tone to the RMS amplitude of the next-largest spurious component in the spectrum, excluding DC offset. This spurious component can occur anywhere in the spectrum up to Nyquist and is usually an intermodulation product or a harmonic.

Aperture Delay

The MAX1208 samples data on the falling edge of its sampling clock. In actuality, there is a small delay between the falling edge of the sampling clock and the actual sampling instant. Aperture delay (tAD) is the time defined between the falling edge of the sampling clock and the instant when an actual sample is taken (Figure 4).

Aperture Jitter

Figure 4 depicts the aperture jitter (tAJ), which is the sample-to-sample variation in the aperture delay.

IMD

VV V V

IM IM IM IM

log

.......

=×

+++ +





  







  



THD

VVVVVV

log

=×

+++++





  







  



ENOB

SINAD

−













176

602

MAX1208

12-Bit, 80Msps, 3.3V ADC

______________________________________________________________________________________ 25

Page 26

MAX1208

Output Noise (n

OUT

)

The output noise (n

OUT

) parameter is similar to the thermal + quantization noise parameter and is an indication of the ADC’s overall noise performance.

No fundamental input tone is used to test for n

OUT

; INP, INN, and COM are connected together and 1024k data points collected. n

OUT

is computed by taking the RMS

value of the collected data points.

Overdrive Recovery Time

Overdrive recovery time is the time required for the ADC to recover from an input transient that exceeds the full-scale limits. The MAX1208 specifies overdrive recovery time using an input transient that exceeds the full-scale limits by ±10%.

12-Bit, 80Msps, 3.3V ADC

26 ______________________________________________________________________________________

REFP 1

REFN 2

COM 3

GND 4

INP 5

INN 6

GND 7

DCE 8

CLKN 9

CLKP 10

D030

D129

D228

D327

D426

D525

D624

D723

D822

D921

REFIN39REFOUT38PD37V

GND35OV

DAV33I.C.32I.C.

CLKTYP

GND

DOR

D1119D10

G/T

TOP VIEW

MAX1208

EXPOSED PADDLE (GND)

THIN QFN

6mm x 6mm x 0.8mm

Pin Configuration

Page 27

MAX1208

12-Bit, 80Msps, 3.3V ADC

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 27

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages

QFN THIN 6x6x0.8.EPS

e e

A1 A2

E/2

D/2

E2/2

(NE-1) X e

(ND-1) X e

D2/2

21-0141

PACKAGE OUTLINE 36, 40, 48L THIN QFN, 6x6x0.8mm

8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.

6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.

5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP.

4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.

9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT FOR 0.4mm LEAD PITCH PACKAGE T4866-1.

7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.

3. N IS THE TOTAL NUMBER OF TERMINALS.

2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.

1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.

NOTES:

10. WARPAGE SHALL NOT EXCEED 0.10 mm.

21-0141

PACKAGE OUTLINE 36, 40, 48L THIN QFN, 6x6x0.8mm