SFDR (dBc)

SNR (dB), SFDR (dBc)

Power Dissipation vs. Conversion Rate

200

150

100

Power (mW)

Sample Rate (MSPS)

Features

Very low/programmable power

0.07W @ 5MSPS
0.22W @ 20MSPS
0.40W @ 30MSPS

Single supply operation (+5V)

0.5 LSB differential linearity error

Wide dynamic range

72dBc spurious-free dynamic range
68dB signal-to-noise ratio

No missing codes

Applications

CCD imaging

IR imaging

FLIR processing

Medical imaging

High definition video

Instrumentation

Radar processing

Digital communications

General Description

The Comlinear CLC949 is a 12-bit analog-to-digital converter sub-
system including 12-bit quantizer, sample-and-hold amplifier, and
internal reference. The CLC949 has been optimized for low power
operation with high dynamic range. The CLC949 has a unique
feature which allows the user to adjust internal bias levels in the
converter which results in a trade-off between power dissipation
and maximum conversion rate. With bias set for 220mW power
dissipation the converter operates at 20MSPS. Under these
conditions, dynamic performance with a 9.9MHz analog input is
typically 68dB SNR and 72dBc SFDR. When bias is set for only
65mW power dissipation the converter maintains excellent perfor-
mance at 5MSPS. With a 2.4MHz analog input signal the SNR is
70dB and SFDR is 78dBc. This excellent dynamic performance in
the frequency domain without high power requirements make the
part a strong performer for communications and radar applications.
The low input noise of the CLC949, its 0.5LSB differential linearity
error specification, fast settling, and low power dissipation also
lead to excellent performance in imaging systems. All parts are
thoroughly tested to insure that guaranteed specifications are met.

The CLC949 incorporates an input sample-and-hold amplifier
followed by a quantizer which uses a pipelined architecture to min-
imize comparator count and the associated power dissipation
penalty. An on-board voltage reference is provided. Analog input
signals, conversion clock, and a single supply are all that are
required for CLC949 operation.

The CLC949 exhibits very stable performance over the commercial
and industrial temperature ranges. Most parameters shift very
little as the ambient temperature changes from -40°C to 85°C. An
exception to this rule is the dynamic performance of the converter.
As the temperature is increased, the distortion increases,
especially at higher input frequencies. This can be seen in the plot
on page 3. For input frequencies below 7MHz, there is relatively
little variation in distortion as the temperature is changed, but at
higher input frequencies, it is apparent that the performance
degrades as the temperature is increased.

Note that the reason for this degradation is the reduced ability of
the CLC949 to handle high slew rates at high temperatures. In
applications such as CCD imaging systems, where the slew rate at
the A/D sampling instant is very low, this degradation will not be
nearly so pronounced.

For applications requiring high temperature operation and very low
distortion with high frequency input signals, use of an external
sample-and-hold amplifier may enhance performance by reducing
the slew rates that the CLC949 sees during its sampling period (just
after the falling edge of CLK).

The CLC949 is fabricated in a 0.9

m CMOS technology. The

CLC949ACQ is specified over the commercial temperature range
of 0°C to +70°C and the CLC949AJQ is specified over the indus-
trial range of -40°C to +85°C. Both are packaged in a 44-pin
Plastic Leaded Chip Carrier (PLCC)

Comlinear CLC949
Very Low-Power, 12-Bit,
20MSPS Monolithic A/D Convertter

August 1996

Comlinear CLC949

ery Low-Power

, 12-Bit, 20MSPS Monolithic Converter

http://www.national.com

Printed in the U.S.A.

http://www.national.com

PARAMETERS

CONDITIONS

TYP

MIN/MAX RATINGS

UNITS SYMBOL

Case Temperature

+25°C

0 to 70°C -40 to 85°C

DYNAMIC CHARACTERISTICS

overvoltage recovery V

= 1.5FS

effective aperture delay

3.0

6.2

aperture jitter

7.0

ps(rms)

slew rate

400

settling time

NOISE and DISTORTION (20MSPS)

Signal-to-Noise Ratio (no harmonics)

4.985MHz;

SNR2

9.663MHz;

SNR3

Spurious-Free Dynamic Range

4.985MHz;

FS -1dB

dBc

SFDR2

9.663MHz;

FS -1dB

dBc

SFDR3

Intermodulation Distortion

= 5.58MHz @ FS -7dB; f

= 5.70MHz @ FS -7dB

-70

dBc

IMD

3dB bandwidth (full power)

100

MHz

NOISE and DISTORTION (5MSPS, low bias)

Signal-to-Noise Ratio (no harmonics)

2.4MHz;

SNR1

Spurious-Free Dynamic Range

2.4MHz;

FS -1dB

dBc

SFDR1

NOISE and DISTORTION (25.6MSPS, high bias)

Signal-to-Noise Ratio (no harmonics)

9.894MHz;

SNR4

Spurious-Free Dynamic Range

9.894MHz;

FS-1dB

dBc

SFDR4

DC ACCURACY and PERFORMANCE

differential non-linearity

dc; FS

0.5

1.0

LSB

DNL

integral non-linearity

dc; FS

1.2

3.5

LSB

INL

common mode rejection ratio

CMRR

missing codes

codes

mid-scale offset

5.0

VIO

temperature coefficient

V/°C

DVIO

gain error

1.0

5.0

%FS

power supply rejection

dda

PSRA

ddd

PSRD

VOLTAGE REFERENCE CHARACTERISTICS

positive reference voltage (internal)

3.25

3.24-3.26

VREFP

negative reference voltage (internal)

1.25

1.24-1.26

VREFN

differential reference voltage (Vrefp - Vrefn)

2.0

1.98-2.02

VDIFF

ANALOG INPUT PERFORMANCE

common mode range

2 - 3

VCM

differential range

± 2

VDM

analog input bias current

±0.1

±1.0

IBN

analog input capacitance

5.0

CIN

DIGITAL INPUTS

CMOS input voltage

logic LOW

VIL

logic HIGH

4.0

VIH

CMOS input current

logic LOW

±0.1

±1.0

IIL

logic HIGH

±0.1

±1.0

IIH

DIGITAL OUTPUTS

CMOS output voltage

logic LOW

0.25

0.5

VOL

logic HIGH

4.8

4.5

VOH

TIMING

maximum conversion rate

MSPS

minimum conversion rate

KSPS

CRM

data hold time

7.0

4.5

THLD

pipeline delay

6.5

clocks

POWER REQUIREMENTS

supply current (+V

)

IDD

power dissipation

20MSPS

220

300

PDM

power dissipation (low bias)

5MSPS

PDL

power dissipation (high bias)

30MSPS

400

PDH

Min/max ratings are based on product characterization and simulation. Individual parameters are tested as noted. Outgoing quality levels
are determined from tested parameters.

CLC949 Electrical Characteristics

(+V

= + 5V, Medium Bias (200

A): unless specified)

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CLC949 Typical Performance Characteristics

(+V

= + 5V, Med Bias, F

= 20MSPS: unless specified)

Output Spectrum 1MHz

Output Level (dBFS)

Frequency (MHz)

-40

-120

-80

-20

-60

-100

Output Spectrum 9MHz

Output Level (dBFS)

Frequency (MHz)

-40

-120

-80

-20

-60

-100

Output Spectrum 15MHz

Output Level (dBFS)

Frequency (MHz)

-40

-120

-80

-20

-60

-100

SNR & SFDR vs. Input Amplitude 1MHz

SNR (dB) & SFDR (dBc)

Input Amplitude (dBFS)

-50

-30

-10

SNR

SFDR

-40

-20

SNR & SFDR vs. Input Amplitude 5MHz

SNR (dB) & SFDR (dBc)

Input Amplitude (dBFS)

-50

-30

-10

SNR

SFDR

-40

-20

SNR & SFDR vs. Input Amplitude 9MHz

SNR (dB) & SFDR (dBc)

Input Amplitude (dBFS)

-50

-30

-10

SNR

SFDR

-40

-20

SNR & SFDR vs. Input Frequency

SNR (dB), SFDR (dBc)

Input Frequency (MHz)

100k

10M

100M

= 20MHz

SFDR (dBc)

SNR (dB)

SNR vs. Sample Rate vs. Bias

SNR (dB)

Sample Rate (MSPS)

0.1

1.0

100

Low Bias

High Bias

Medium Bias

= 5MHz

SFDR vs. Sample Rate vs. Bias

SFDR (dBc)

Sample Rate (MSPS)

0.1

1.0

100

Low Bias

Medium Bias

High Bias

= 5MHz

Two Tone Intermodulation Distortion

Output Level (dBFS)

Frequency (MHz)

-40

-120

-80

-20

-60

-100

Integral Non-Linearity

INL (LSBs)

Output Code

2.5

1.5

1000

2000

-2.5

0.5

3000

4000

-0.5

-1

-1.5

-2

Differential Non-Linearity

DNL (LSBs)

Output Code

1.5

0.5

1000

2000

-1.5

-0.5

3000

4000

-1

Pulse Settling Response

ADC Output Code

Time (ns)

4000

100

150

1000

2000

200

3000

SFDR vs. Input Frequency

-20

SFDR (dBc)

Input Frequency (MHz)

100

I/O Timing (Convert CLK & Bit Skew)

)

Time (ns)

400

300

100

200

Output Data

Convert

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Recommended Operating Conditions

Absolute Maximum Ratings*

upply voltage (V

)

+5V ± 5%

differential voltage between any two GND's

<10mV

analog input voltage range (full scale)

1.25 3.25V

digital input voltage range

0 to V

operating temperature range

0°C to 70°C

clock pulse-width high (C

pwh

)

> 25ns

supply voltage (V

)

-0.5V to +7V

differential voltage between any two GND's

200mV

analog input voltage range

-0.5V to +V

digital input voltage range

-0.5V to +V

output short circuit duration (one pin to gnd)

infinite

junction temperature

+175°C

storage temperature range

-65°C to +150°C

lead solder duration (+300°C)

10 sec

*NOTE: Absolute maximum ratings are limiting values, to be applied individually, and beyond which the serviceability of the circuit may be impaired.
Functional operability under any of these conditions is not necessarily implied. Exposure to maximum ratings for extended periods may affect device
reliability.

Pinout & Pin Description and Usage

References (V

REFN

, V

REFP

, V

REFNO

, V

REFPO

, V

REFNC

REFPC

, V

REFMO

)

To use the internal references, connect V

REFPO

to V

REFP

and V

REFNO

to V

REFN

. The nominal value for V

REFPO

3.25V and for V

REFNO

is 1.25V. V

REFPC

and V

REFNC

are

internal reference points which should be bypassed to
GND with a 0.1

F capacitor. V

REFMO

is an output

voltage that is equal to the mid point of the reference
range and can be used to apply the appropriate offset to
the analog inputs. For a more detailed discussion on
references, see the paragraph on references in the
applications section of this datasheet.

Analog Input (V

INP

, V

INN

)

The analog input to the CLC949 is a differential signal
applied to V

INP

and V

INN

. For more detail on driving the

inputs, see the paragraphs in the applications section of
this datasheet.

Power Supplies and Grounds (V

DDA

, V

DDD

, GND

)

The power and ground pins of the CLC949 are split into
those that supply the analog portions of the integrated
circuit (V

DDA

, GND

) and the digital portions of the chip

DDD

, GND

). If your system uses separate power and

ground planes, then performance can be improved by
making use of the appropriate pins. In many systems,
the power pins will all be tied together and the GND pins

will all be tied together. For more detailed discussion,
please refer to the paragraph on power and grounds in
the applications section of the databook.

Clock (CLK)
The CLK accepts a CMOS clock input. Samples are
taken on the falling edges of the CLK and data emerges
6 1/2 clock cycles later, on to the rising edge of the CLK.

Output Data (D1-D12, MSBINV, OE\)
The data emerges from the CLC949 as CMOS level
digital data on D1(MSB) through D12(LSB). The
outputs can be put into a high impedance state by
bringing OE\ high. There is an internal pulldown

resistor so that if this input is left open, the output data is

enabled. MSBINV will invert the MSB of the output data.
With MSBINV in the high state, the output data is two's
complement, when low, the output data format is offset
binary. An internal pulldown resistor makes the output
default to offset binary if MSBINV is left open.

Bias Control (BCO, BC1, BIASC)
The DC bias current of the CLC949 is controlled by three
pins: BCO, BC1, and BIASC. BC0 and BC1 are digital
CMOS inputs and set the bias current in accordance with
the truth table below:

BC0

BC1

Bias Current

PD@10MSPS

Default: Med Bias (200

200mW

Analog Mode

Variable

High Bias (400

350mW

Low Bias (50

75mW

In the analog mode, the user provides a bias current
through the BIASC pin of the CLC949. As the bias
current is increased, the power dissipation of the CLC949
is increased and the part becomes capable of increased
conversion rates.

NC
No connection - leave these pins open.

44-Pin PLCC

TOP VIEW

44 43 42 41 40

DDD

CLK

BC1

DDA

REFNO

REFPO

24 25 26 27 28

GND

MSBINV

OE\

D1(MSB)

GND

BIASC

GND

INP

INN

GND

REFNC

REFPC

REFN

REFP

REFMO

D10

D11

D12(LSB)

BCO

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CLC949 OPERATION

Application
In a high speed data acquisition system, the overall
performance is often determined by the A/D converter
and its surrounding circuitry. You should pay special
attention to the data converter and its support circuitry if
you want to obtain the best possible performance. The
information on these pages is intended to help you
design the circuitry surrounding the CLC949 in such
a way as to achieve superior results. Additional
information is available in the form of Comlinear
applications notes. Especially useful are AD-01 and
AD-02.

Circuit Description
The CLC949 ADC consists of an input Sample-and-Hold
Amplifier (SHA) followed by a pipelined quantizer.
Internal reference sources and output data latches
complete the major functions required of an A/D
converter. Digital error correction in the quantizer helps
to provide accurate conversions of high speed dynamic
signals. The speed of the analog circuitry is determined
in part by the internal bias currents applied. The CLC949
allows you to make this important tradeoff between
power and performance through settings on two digital
control pins and for fine adjustments through the use of
an external resistor.

Timing and CLK Generation
The falling edge of the CLK pulse causes the input sam-
ple-and-hold amplifier to transition into the hold mode.
The sample is taken approximately 3ns after this falling
edge. The digitized data is presented to the output latch-
es 6 1/2 clock cycles later and is held until after the next
rising edge of CLK. This timing is shown in the timing
diagram, Figure 1.

Figure 1: Timing Diagram

The CLC949 is designed to operate with a CMOS clock
signal. To obtain the lowest possible noise when
digitizing a high frequency input, more care must be
taken in the generation of this clock than is usually
accorded to CMOS Clocks. To minimize aperture jitter
induced errors, the CLK needs to have as low a
jitter as possible and as fast an edge rate as possible. To
obtain a very low jitter clock from a sinusoidal source, the
circuit shown in Figure 2 is recommended.

Figure 2: Clock Generation

Here the CLC006 cable driver is used as a comparator to
generate a high speed clock. The CLC006 has less than
2ps of jitter and has rise and fall times less than 1ns. The
CLC006 output is then buffered by a 74AC04 which
maintains fast edge rates and provides CMOS levels for
the CLC949. If there is excessive jitter in the CLK, then
the digitized signal will exhibit an excessive amount of
noise, especially for high frequency inputs. For a more
detailed description of this phenomenon, please read the
Comlinear Application Note AD-03.

In addition to the circuitry generating the clock, the
layout of the clock distribution network can affect the
overall performance of the converter. To obtain the best
possible performance, a clock driver with very low output
impedance and fast edge rates such as the 74AC04,
should be placed as close as possible to the CLC949
clock input pin. Additional length in the circuit trace for
the clock will cause an increase in the jitter seen by the
converter.

On the CLC949 evaluation board, the

E949PCASM, there is less than 1/16th of an inch
between the 74AC04 that is driving the clock input and
the input to the CLC949. If the system has several
CLC949s, and jitter is liable to generate problems, then
use a separate clock driver for each CLC949. Each
driver should be placed as close to the converter that it is
driving as is practicable.

Driving the Differential Input
The CLC949 has a differential input with a common
mode voltage of 2.25V. Since not all applications have a
signal preconditioned in this manner there is often a need
to do a single-ended-to-differential conversion and to add
offset. In systems which do not need to be DC coupled,
the best method for doing this is with an RF transformer
such as the Minicircuits TMO1-1T. This is an RF
transformer with a center tapped secondary which will
operate over a frequency range of 50kHz to 200MHz.
You can offset the input and split the phases simply by
connecting the center tap to the mid scale reference
output (V

REFMO

) as shown in Figure 3.

This set up can be realized on the CLC949 evaluation
board by enabling option 1. See E949PCASM data
sheet for details. A transformer coupled input will allow
the CLC949 to exhibit the best possible distortion
performance for high frequency input signals.

Analog

Input

CLK

Output

Data

Effective Aperture Delay

Output Hold Time

Sample 0

Sample 1

Sample 2

Sample

Sample 4

Sample

Sample 6

Sample 7

Sample

-3 Valid

Sample

-2 Valid

Sample

-1 Valid

Sample

0 Valid

Sinusoisal

Clock Input

+5V

CLC006

0.1

10k

0.1

2.2k

10k

+5V

0.1

74AC04

To CLC949
Clock

+5V

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: CLC949A

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