ADC12762
12-Bit, 1.4 MHz, 300 mW A/D Converter
with Input Multiplexer and Sample/Hold

General Description

Using an innovative multistep conversion technique, the
12-bit ADC12762 CMOS analog-to-digital converter digitizes
signals at a 1.4 MHz sampling rate while consuming a maxi-
mum of only 300 mW on a single +5V supply. The
ADC12762

performs

12-bit

conversion

three

lower-resolution "flash" conversions, yielding a fast A/D with-
out the cost and power dissipation associated with true flash
approaches.

The analog input voltage to the ADC12762 is tracked and
held by an internal sampling circuit, allowing high frequency
input signals to be accurately digitized without the need for
an external sample-and-hold circuit. The ADC12762 features
two sample-and-hold/flash comparator sections which allow
the converter to acquire one sample while converting the
previous. This pipelining technique increases conversion
speed without sacrificing performance. The multiplexer out-
put is available to the user in order to perform additional ex-
ternal signal processing before the signal is digitized.

When the converter is not digitizing signals, it can be placed
in the Standby mode; typical power consumption in this
mode is 250 µW.

Features

Built-in sample-and-hold

Single +5V supply

Single channel or 2 channel multiplexer operation

Key Specifications

Sampling rate

1.4 MHz (min)

Conversion time

593 ns (typ)

SNR, f

= 100 kHz

67.5 dB (min)

Power dissipation (f

= 1.4 MHz)

300 mW (max)

No missing codes over temperature

Guaranteed

Applications

CCD image scanners

Digital signal processor front ends

Instrumentation

Disk drives

Mobile telecommunications

Waveform digitizers

ADC12762 Block Diagram

Ordering Information

Commercial (0°C

+70°C)

Package

ADC12762CCV

V44 Plastic Leaded Chip Carrier

ADC12062EVAL

Evaluation Board

TRI-STATE

is a registered trademark of National Semiconductor Corporation.

DS012811-1

June 1999

ADC12762

12-Bit,

1.4

MHz,

300

A/D

Converter

with

Input

Multiplexer

and

Sample/Hold

DS012811

www.national.com

Absolute Maximum Ratings

(Notes 1, 2)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage (V

= DV

= AV

)

-0.3V to +6V

Voltage at Any Input or Output

-0.3V to V

+ 0.3V

Input Current at Any Pin (Note 3)

25 mA

Package Input Current (Note 3)

50 mA

Power Dissipation (Note 4)

ADC12762CCV

875 mW

ESD Susceptibility (Note 5)

2000V

Soldering Information (Note 6)

V Package, Infrared, 15 seconds

+300°C

Storage Temperature Range

-65°C to +150°C

Maximum Junction Temperature (T

JMAX

)

150°C

Operating Ratings

(Notes 1, 2)

Temperature Range

MIN

MAX

ADC12762CCV

-0°C

+70°C

Supply Voltage Range (DV

= AV

)

4.75V to 5.25V

Converter Characteristics

The following specifications apply for DV

= AV

= +5V, V

REF+(SENSE)

= +4.096V, V

REF-(SENSE)

= AGND, and f

1.4 MHz, unless otherwise specified. Boldface limits apply for T

= T

from T

MIN

to T

MAX

; all other limits T

= T

= +25°C.

Symbol

Parameter

Conditions

Typ

Limit

Units

(Note 7)

(Note 8)

(Limit)

Resolution

Bits

Differential Linearity Error

MIN

to T

MAX

0.4

0.95

LSB (max)

Integral Linearity Error

MIN

to T

MAX

0.4

2.0

LSB (max)

(Note 9)

Offset Error

MIN

to T

MAX

0.3

4.0

LSB (max)

Full-Scale Error

MIN

to T

MAX

0.3

4.0

LSB (max)

Power Supply Sensitivity

= AV

= 5V

0.75

LSB (max)

(Note 15)

REF

Reference Resistance

940

500

(min)

1300

(max)

REF(+)

REF+(SENSE)

Input Voltage

V (max)

REF(-)

REF-(SENSE)

Input Voltage

AGND

V (min)

Input Voltage Range

To V

IN1

, V

IN2

, or ADC IN

+0.05V

V (max)

AGND - 0.05V

V (min)

ADC IN Input Leakage

AGND to AV

- 0.3V

0.1

µA (max)

ADC

ADC IN Input Capacitance

MUX On-Channel Leakage

AGND to AV

- 0.3V

0.1

µA (max)

MUX Off-Channel Leakage

AGND to AV

- 0.3V

0.1

µA (max)

MUX

Multiplexer Input Cap

MUX Off Isolation

= 100 kHz

Dynamic Characteristics

(Note 10)

The following specifications apply for DV

= AV

= +5V, V

REF+(SENSE)

= +4.096V, V

REF-(SENSE)

= AGND, R

= 25

, f

100 kHz, 0 dB from fullscale, and f

= 1.4 MHz, unless otherwise specified. Boldface limits apply for T

= T

from T

MIN

MAX

; all other limits T

= T

= +25°C.

Symbol

Parameter

Conditions

Typ

Limit

Units

(Note 7)

(Note 8)

(Limit)

SINAD

Signal-to-Noise Plus

MIN

to T

MAX

67.0

dB (min)

Distortion Ratio

SNR

Signal-to-Noise Ratio

MIN

to T

MAX

67.5

dB (min)

(Note 11)

THD

Total Harmonic Distortion

MIN

to T

MAX

-80

-70

dBc (max)

(Note 12)

ENOB

Effective Number of Bits

MIN

to t

MAX

11.3

10.8

Bits (min)

(Note 13)

IMD

Intermodulation Distortion

= 88.7 kHz, 89.5 kHz

-80

dBc

www.national.com

DC Electrical Characteristics

The following specifications apply for DV

= AV

= +5V, V

REF+(SENSE)

= +4.096V, V

REF-(SENSE)

= AGND, and f

1.4 MHz, unless otherwise specified. Boldface limits apply for T

= T

from T

MIN

to T

MAX

; all other limits T

= T

= +25°C.

Symbol

Parameter

Conditions

Typ

Limit

Units

(Note 7)

(Note 8)

(Limit)

IN(1)

Logical "1" Input Voltage

= AV

= +5.5V

2.0

V (min)

IN(0)

Logical "0" Input Voltage

= AV

= +4.5V

0.8

V (max)

IN(1)

Logical "1" Input Current

0.1

1.0

µA (max)

IN(0)

Logical "0" Input Current

0.1

1.0

µA (max)

OUT(1)

Logical "1" Output Voltage

= AV

= +4.5V,

OUT

= -360 µA

2.4

V (min)

OUT

= -100 µA

4.25

V (min)

OUT(0)

Logical "0" Output Voltage

= AV

= +4.5V,

0.4

V (max)

OUT

= 1.6 mA

OUT

TRI-STATE

Output

Pins DB0DB11

0.1

µA (max)

Leakage Current

OUT

TRI-STATE Output Capacitance

Pins DB0DB11

Digital Input Capacitance

Supply Current

mA (max)

Supply Current

mA (max)

STANDBY

Standby Current (DI

+ AI

)

PD = 0V

µA

AC Electrical Characteristics

The following specifications apply for DV

= AV

= +5V, V

REF+(SENSE)

= +4.096V, V

REF-(SENSE)

= AGND, and f

1.4 MHz, unless otherwise specified. Boldface limits apply for T

= T

from T

MIN

to T

MAX

; all other limits T

= T

= +25°C.

Symbol

Parameter

Conditions

Typ

Limit

Units

(Note 7)

(Note 8)

(Limits)

Maximum Sampling Rate

1.5

MHz (min)

(1/t

THROUGHPUT

)

CONV

Conversion Time

593

560

ns (min)

(S/H Low to EOC High)

710

ns (max)

Aperture Delay

(S/H Low to Input Voltage Held)

S/H

S/H Pulse Width

ns (min)

400

ns (max)

EOC

S/H Low to EOC Low

ns (min)

126

ns (max)

ACC

Access Time

= 100 pF

ns (max)

(RD Low or OE High to Data Valid)

, t

TRI-STATE Control

= 1k, C

= 10 pF

ns (max)

(RD High or OE Low to Databus TRI-STATE)

INTH

Delay from RD Low to INT High

= 100 pF

ns (max)

INTL

Delay from EOC High to INT Low

= 100 pF

-25

-35

ns (min)

-10

ns (max)

UPDATE

EOC High to New Data Valid

ns (max)

Multiplexer Address Setup Time

ns (min)

(MUX Address Valid to EOC Low)

Multiplexer Address Hold Time

ns (min)

(EOC Low to MUX Address Invalid)

CSS

CS Setup Time

ns (min)

(CS Low to RD Low, S/H Low, or OE High)

www.national.com

AC Electrical Characteristics

(Continued)

The following specifications apply for DV

= AV

= +5V, V

REF+(SENSE)

= +4.096V, V

REF-(SENSE)

= AGND, and f

1.4 MHz, unless otherwise specified. Boldface limits apply for T

= T

from T

MIN

to T

MAX

; all other limits T

= T

= +25°C.

Symbol

Parameter

Conditions

Typ

Limit

Units

(Note 7)

(Note 8)

(Limits)

CSH

CS Hold Time

ns (min)

(CS High after RD High, S/H High, or OE Low)

Wake-Up Time

µs

(PD High to First S/H Low)

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is func-
tional. These ratings do not guarantee specific performance limits, however. For guaranteed specifications and test conditions, see the Electrical Characteristics. The
guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed
test conditions.

Note 2: All voltages are measured with respect to GND (GND = AGND = DGND), unless otherwise specified.

Note 3: When the input voltage (V

) at any pin exceeds the power supply rails (V

GND or V

) the absolute value of current at that pin should be limited

to 25 mA or less. The 50 mA package input current limits the number of pins that can safely exceed the power supplies with an input current of 25 mA to two.

Note 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by T

JMAX

and the ambient temperature T

. The maximum

allowable power dissipation at any temperature is P

= (T

JMAX

- T

or the number given in the Absolute Maximum Ratings, whichever is lower.

for the V

(PLCC) package is 55°C/W. In most cases the maximum derated power dissipation will be reached only during fault conditions.

Note 5: Human body model, 100 pF discharged through a 1.5 k

resistor. Machine model ESD rating is 200V.

Note 6: See AN-450 "Surface Mounting Methods and Their Effect on Product Reliability" or the section titled "Surface Mount" found in a current National Semicon-
ductor Linear Data Book for other methods of soldering surface mount devices.

Note 7: Typicals are at +25°C and represent most likely parametric norm.

Note 8: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).

Note 9: Integral Linearity Error is the maximum deviation from a straight line between the measured offset and full scale endpoints.

Note 10: Dynamic testing of the ADC12762 is done using the ADC IN input. The input multiplexer adds harmonic distortion at high frequencies. See the graph in the
Typical Performance Characteristics section for a typical graph of THD performance vs input frequency with and without the input multiplexer.

Note 11: The signal-to-noise ratio is the ratio of the signal amplitude to the background noise level. Harmonics of the input signal are not included in its calculation.

Note 12: The contributions from the first nine harmonics are used in the calculation of the THD.

Note 13: Effective Number of Bits (ENOB) is calculated from the measured signal-to-noise plus distortion ratio (SINAD) using the equation ENOB = (SINAD - 1.76)/
6.02.

Note 14: The digital power supply current takes up to 10 seconds to decay to its final value after PD is pulled low. This prohibits production testing of the standby
current. Some parts may exhibit significantly higher standby currents than the 50 µA typical.

Note 15: Power Supply Sensitivity is defined as the change in the Offset Error or the Full Scale Error due to a change in the supply voltage.

TRI-STATE Test Circuit and Waveforms

DS012811-2

DS012811-3

Part Number ADC12062EVAL