ADC-207MM - C&D Technologies, Inc.

INNOVATION and EX C ELL E N C E

® ®

INPUT/OUTPUT

CONNECTIONS

DIP LCC

PINS FUNCTION PINS

1CLOCK INPUT 1

2DIGITAL GROUND 4

3–REFERENCE 5

4ANALOG INPUT 6

5MIDPOINT 7

6+REFERENCE 8

7ANALOG GROUND 9

8CS1 11

9CS2 12

10 OVERFLOW13

11 BIT 1 (MSB) 14

12 BIT 2 16

13 BIT 3 17

14 BIT 4 19

15 BIT 5 20

16 BIT 6 21

17 BIT 7 (LSB) 23

18 +5V SUPPLY24

Figure 1. ADC-207 Functional Block Diagram (DIP Pinout)

FEATURES

•7-bit flash A/D converter

•20MHz sampling rate

•Low power (250mW)

•Single +5V supply

•1.2 micron CMOS technology

•7-bit latched 3-state output with overflow bit

•Surface-mount versions

•High-reliability version

•No missing codes

GENERAL DESCRIPTION

The ADC-207 is the industry’s first 7-bit flash converter using an

advanced high-speed VLSI 1.2 micron CMOS process. This

process offers some very distinctive advantages over other

processes, making the ADC-207 unique. The smaller

geometrics of the process achieve high speed, better linearity

and superior temperature performance.

Since the ADC-207 is a CMOS device, it also has very low

power consumption (250mW). The device draws power from

a single +5V supply and is conservatively rated for 20MHz

operation. The ADC-207 allows using sampling apertures as

small as 12ns, making it more closely approach an ideal

sampler. The small sampling apertures also let the device

operate at greater than 20MHz.

The ADC-207 has 128 comparators which are auto-balanced

on every conversion to cancel out any offsets due to

temperature and/or dynamic effects. The resistor ladder has a

midpoint tap for use with an external voltage source to improve

integral linearity beyond 7 bits. The ADC-207 also provides the

user with 3-state outputs for easy interfacing to other

components.

There are six models of the ADC-207 covering two operating

temperature ranges, 0 to +70°C and –55 to +125°C. Two high-

reliability "QL" models are also available.

G Q

ANALOG INPUT 4

+REFERENCE 6

DIGITAL GROUND 2

ANALOG GROUND 7

RANGE MIDPOINT 5

R/2

–REFERENCE 3

CS1 8

+5V SUPPLY 18 +VDD

1 CLOCK INPUT

CLOCK

GENERATOR

10 OVERFLOW

11 BIT 1 (MSB)

12 BIT 2

13 BIT 3

14 BIT 4

15 BIT 5

16 BIT 6

17 BIT 7 (LSB)

128-TO-7

ENCODER

CS2

G Q

∅1

∅2∅2

∅1

ADC-207

7-Bit, 20MHz, CMOS

Flash A/D Converters

DATEL, Inc., 11 Cabot Boulevard, Mansfield, MA 02048-1151 (U.S.A.) • Tel: (508) 339-3000 Fax: (508) 339-6356 • For immediate assistance (800) 233-2765

ADC-207 ® ®

PHYSICAL/ENVIRONMENTAL

PARAMETERS MIN. TYP.MAX. UNITS

Operating Temp. Range, Case:

LC/MC Versions 0—+70 °C

MM/LM/QL Versions –55 —+125 °C

Storage Temp. Range –65 —+150 °C

Package Type

DIP 18-pin ceramic DIP

LCC 24-pin ceramic LCC

TECHNICAL NOTES

1. Input Buffer Amplifier – Since the ADC-207 has a switched

capacitor type input, the input impedance of the 207 is

dependent on the clock frequency. At relatively slow

conversion rates, a general purpose type input buffer can be

used; at high conversion rates DATEL recommends either

the HA-5033 or Elantec 2003. See Figure 2 for typical

connections.

2. Reference Ladder – Adjusting the voltage at +REFERENCE

adjusts the gain of the ADC-207. Adjusting the voltage at –

REFERENCE adjusts the offset or zero of the ADC-207.

The midpoint pin is usually bypassed to ground through a

0.1µF capacitor, although it can be tied to a precision

voltage halfway between +REFERENCE and

–REFERENCE. This would improve integral linearity

beyond 7 bits.

3. Clock Pulse Width – To improve performance at Nyquist

bandwidths, the clock duty cycle can be adjusted so that the

low portion of the clock pulse is 12ns wide. The smaller

aperture allows the ADC-207 to closely resemble an ideal

sampler. See Figure 4.

4. At sampling rates less than 100kHz, there may be some

degradation in offset and differential nonlinearity.

Performance may be improved by increasing the clock duty

cycle (decreasing the time spent in the sample mode).

CAUTION

Since the ADC-207 is a CMOS device, normal precautions

against static electricity should be taken. Use ground straps,

grounded mats, etc. The Absolute Maximum Ratings of the

device MUST NOT BE EXCEEDED as irrevocable damage to

the ADC-207 will occur.

ABSOLUTE MAXIMUM RATINGS

PARAMETERS LIMITS UNITS

Power Supply Voltage (+VDD)–0.5 to +7 Volts

Digital Inputs –0.5 to +5.5 Volts

Analog Input –0.5 to (+VDD +0.5) Volts

Reference Inputs –0.5 to +VDD Volts

Digital Outputs –0.5 to +5.5 Volts

(short circuit protected to ground)

Lead Temperature (10 sec. max.) +300 °C

Figure 2. Typical Connections for Using the ADC-207

FUNCTIONAL SPECIFICATIONS

(Typical at +5V power, +25°C, 20MHz clock, +REFERENCE = +5V,

–REFERENCE = ground, unless noted)

ANALOG INPUT MIN. TYP.MAX. UNITS

Input Type Single-ended, non-isolated

Input Range (dc-20MHz) 0—+5 Volts

Input Impedance —1000 —Ohms

Input Capacitance

(Full Range) —10 —pF

DIGITAL INPUTS

Logic Levels

Logic "1" +3.2 — — Volts

Logic "0" — — +0.8 Volts

Logic Loading "1" —±1 ±5 microamps

Logic Loading "0" —±1 ±5 microamps

Sample Pulse Width

(During Sampling Portion of Clock) 12 — — ns

Reference Ladder Resistance 225 330 —Ohms

PERFORMANCE

Conversion Rate ➀20 25 —MHz

Harmonic Distortion ➁

(8MHz 2nd Order Harmonic) —–40 —dB

Differential Gain ➂—3—%

Differential Phase ➂—1.5 —degrees

Aperture Delay —8—ns

Aperture Jitter —50 —ps

No Missing Codes

LC/MC grade 0—+70 °C

LM/MM grade –55 —+125 °C

Integral Linearity ➃—±0.8 ±1 LSB

Over Temperature Range ±0.8 ±1 LSB

Differential Nonlinearity —±0.3 ±0.6LSB

Over Temperature Range —±0.4 ±0.6 LSB

Power Supply Rejection —±0.02 —

%FSR/%Vs

DIGITAL OUTPUTS

Data Coding Straight binary

Data Output Resolution 7——Bits

Logic Levels

Logic "1" +2.4 +4.5 —Volts

Logic "0" (at 1.6mA) — — +0.4 Volts

Logic Loading "1" –4 — — mA

Logic Loading "0" +4 — — mA

Output Data Valid Delay

(From Rising Edge) —15 25 ns

POWER REQUIREMENTS

Power Supply Range (+VDD)+3.0 +5.0 +5.5 Volts

Power Supply Current —+50 +70 mA

Power Dissipation —250 385 mW

Footnotes:

➀At full power input and chip selects enabled.

➁At 4MHz input and 20MHz clock.

➂For 10-step, 40 IRE NTSC ramp test.

➃Adjustable using reference ladder midpoint tap. See ADC-207 Operation.

(MSB)

0.1µF

4.7µF

0.01µF

+5V

+15

–15

47µF

5HA-5033 10 Ω

+5V

20MHz

CLOCK

(LSB)B7

+VDD

CS2

CS1

+REFERENCE

MID

VIN

–REFERENCE

DIGITAL GND

ANALOG GND

CLOCK 181

0.1µF +

47µF

ADC-207

® ®

OUTPUT CODING

(+REFERENCE = +5.12V, –REFERENCE = ground, MIDPOINT = no connection)

NOTE: The reference should be held to ±0.1% accuracy or

better. Do not use the +5V power supply as a

reference input without precision regulation and high

frequency decoupling.

Values shown here are for a +5.12V reference. Scale other

references proportionally. Calibration equipment should test for

code changes at the midpoints between these center values

shown in Table 1. For example, at the half-scale major carry,

set the input to 2.54V and adjust the reference until the code

flickers equally between 63 and 64. Note also that the

weighting for the comparator resistor network leaves the first

and last thresholds within 1/2LSB of the end points to adjust

the code transition to the proper midpoint values.

Continuous conversion requires one cycle/sample (one positive

pulse and one negative pulse). The 3-state buffer has two

enable lines, CS1 and CS2. Table 2 shows the truth table for

chip select signals. CS1 has the function of enabling/disabling

bits 1 through 7. CS2 has the function of enabling/disabling

bits 1 through 7 and the overflow bit. Also, a full-scale input

produces all ones, including the overflow bit at the output. The

ADC-207 has an adjustable resistor ladder string. The top end,

idle point, and bottom end are brought out for use with

applications circuits.

These pins are called +REFERENCE, MIDPOINT and

–REFERENCE, respectively. In typical operation

+REFERENCE is tied to +5V, –REFERENCE is tied to ground,

and MIDPOINT is bypassed to ground. Such a configuration

results in a 0 to +5V input voltage range. The MIDPOINT pin

can also be tied to a +2.5V source to further improve integral

linearity. This is usually not necessary unless better than 7-bit

linearity is needed.

Table 2. Chip Select Truth Table

CS1 CS2 Bits 1-7 Overflow Bit

0 0 3-State Mode 3-State Mode

1 0 3-State Mode 3-State Mode

0 1 Data Outputed Data Outputed

1 1 3-State Mode Data Outputed

NOTE: Reduce the sample time (sample pulse)

ADC-207 OPERATION

The ADC-207 uses a switched capacitor scheme in which

there is an auto-zero phase and a sampling phase. See

Figure 1 and Timing Diagram. The ADC-207 uses a single

clock input. When the clock is at a high state (logic 1), the

ADC-207 is in the auto-zero phase (Ø1). When the clock is at

a low state (logic 0), the ADC-207 is in the sampling phase

(Ø2). During phase 1, the 128 comparator outputs are shorted

to their inputs through CMOS switches. This serves the

purpose of bringing the inputs and outputs to the transition

levels of the respective comparators. The inputs to the

comparators are also connected to 128 sampling capacitors.

The other end of the 128 capacitors are also shorted to 128

taps of a resistor ladder, via CMOS switches. Therefore, during

phase 1 the sampling capacitors are charged to the differential

voltage between a resistor tap and its respective comparator

transition voltage.

This eliminates offset differences between comparators and

yields better temperature performance. During phase 2 (Ø2) the

input voltage is applied to the 128 capacitors, via CMOS

switches. This forces the comparators to trip either high or low.

Since the comparators during phase 1 were sitting at their

transition point, they can trip very quickly to the correct state.

Also during phase 2, the outputs of the comparators are loaded

into internal latches which in turn feed a128-to-7 encoder. When

going back into phase 1, the output of the encoder is loaded into

an output latch. This latch then feeds the 3-state output buffer.

This means that the ADC-207 is of pipeline design. To do a

single conversion, the ADC-207 requires a positive pulse

followed by a negative pulse followed by a positive pulse.

Table 1. ADC-207 Output Coding

Analog Input 1234567 Hexadecimal

(Center Value) Code Overflow MSB LSB Decimal (Incl. 0V)

0.00V Zero 0 0000000 0 00

+0.04V +1LSB 0 0000001 1 01

+1.28V +1/4FS 0 0100000 32 20

+2.52V +1/2FS – 1LSB 0 0111111 63 3F

+2.56V +1/2FS 0 1000000 64 40

+2.60V +1/2FS + 1LSB 0 1000001 65 41

+3.84V +3/4FS 0 1100000 96 60

+5.08V +FS 0 1111111 127 7F

+5.12V Overflow 1 1111111 255* FF

*Note that the overflow code does not clear the data bits.

CLOCK

OUTPUT

DATA

AUTO

ZERO

N DATA

N+1 DATA

SAMPLE

NSAMPLE

N + 1 SAMPLE

N + 2

AUTO

ZERO AUTO

ZERO

25ns max.25ns max.

∅1∅2∅1∅1∅2∅2

TIMING DIAGRAM

ADC-207 ® ®

USING TWO ADC-207’S FOR 8-BIT RESOLUTION

Two ADC-207’s (A and B) are cascadable for applications

requiring 8-bit resolution. The device A provides a typical 7-bit

output. The OVERFLOW signal of device A turns off device A

and turns on the device B. The OVERFLOW signal of device A

is also used as MSB for 8-bit operation. The device B provides

the other seven bits from the input signal. Figure 4 shows the

circuit connections for the application.

BEAT FREQUENCY AND ENVELOPE TESTS

Figure 5 shows an actual ADC-207 plot of the Beat Frequency

Test. This test uses a 20MHz clock input to the ADC-207 with

a 20.002MHz full-scale sine wave input. Although the

converter would not normally be used in this mode because

the input frequency violates Nyquist criteria for full recovery of

signal information, the test is an excellent demonstration of the

ADC-207’s high-frequency performance.

The effect of the 2kHz frequency difference between the input

and the clock is that the output will be a 2kHz sinusoidal digital

data array which "walks" along the actual input at the 2kHz

beat note frequency. Any inability to follow the 20.002MHz

input will be immediately obvious by plotting the digital data

array. Further arithmetic analysis may be done on the data

array to determine spectral purity, harmonic distortion, etc.

This test is an excellent indication of:

1. Full power input bandwidth of all 128 comparators.

(Any gain loss would show as signal distortion.)

2. Phase response linearity vs. instantaneous signal

magnitude. (Phase problems would show as

improper codes.)

3. Comparator slew rate limiting.

Figure 6 shows an actual ADC-207 plot of the Envelope Test.

This test is a variation of the previous test but uses a

10.002MHz sinewave input to give two overlapping cycles

when the data is reconstructed by a D/A converter output to an

oscilloscope. The scope is triggered by the 20MHz clock used

by the A/D. Any asymmetry between positive and negative

portions of the signal will be very obvious. This test is an

excellent indication of slew rate capability. At the peaks of the

envelope, consecutive samples swing completely through the

input voltage range.

to 12ns to improve performance above

20MHz. Such a configuration will closely

resemble an ideal sampler.

Figure 3. Optional Pulse Shaping Circuit

Figure 4. Using Two ADC-207’s for 8-Bit Operation

NOTE: The output data bit numbering is offset

by a bit to the device B’s output.

CLOCK IN

GROUND

+5 VOLTS

12 11 CLOCK OUT

20k

0.01µF

10pF

TURN

+5V

REFERENCE

GROUND

OVERFLOW

ANALOG IN

CLOCK IN

OPTIONAL

MIDSCALE

ADJUST

+5.12

REFERENCE

BIT 1 (MSB)

BIT2

BIT3

BIT4

BIT5

BIT6

BIT7

BIT8 (LSB)

+REFERENCE

+VDD OF

DIG GND

CS1

ANALOG INPUT

CLOCK

CS2

–REFERENCE

ANALOG GROUND

+REFERENCE OF

CS1

CLOCK

ANALOG INPUT

+VDD

CS2

–REFERENCE

ANALOG GROUND

DIG GND

ADC-207

® ®

0 1 2 3 4 5 6 7 8 9 10

FREQUENCY (MHz)

–5

–10

AMPLITUDE (dB)

69.2

27.3

SAMPLE PULSE WIDTH = 25ns 4MHz FUNDAMENTAL

Figure 5. Beat Frequency Test at 20MHz Figure 6. 10MHz Envelope Test

FFT TEST

This test actually produces an amplitude versus frequency graph (Figure 7) which indicates harmonic distortion and signal-to-noise

ratio. The theoretical rms signal-to-noise ration for a 7-bit converter is +43.8dB.

Figure 7. FFT Test Using the ADC-207

0 1 2 3 4 5 6 7 8 9 10

–5

–10

SAMPLE PULSE = 25ns

69.2

27.3

4MHz FUNDAMENTAL

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

NUMBER OF SAMPLES(X10 )

OUTPUT

CODES

120

110

100

OUTPUT

CODES

120

110

100

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

NUMBER OF SAMPLES(X10 )

MECHANICAL DIMENSIONS INCHES (MM)

ORDERING INFORMATION

MODEL TEMP. RANGE PACKAGE

ADC-207MC 0 to +70°C 18-pin DIP

ADC-207MM –55 to +125°C 18-pin DIP

ADC-207MM-QL –55 to +125°C 18-pin DIP

ADC-207LC 0 to +70°C 24-pin CLCC

ADC-207LM –55 to +125°C 24-pin CLCC

ADC-207LM-QL –55 to +125°C 24-pin CLCC

ACCESSORIES

ADC-B207/208 Evaluation Board for DIP Version

(without ADC-207)

0.400

(10.16 )

0.250 ±0.005

(6.35 ±0.13)

0.050

(1.270)

TYP.

0.020 ±0.005

(0.51 ±0.13)

124

0.090 MAX.

(2.29 MAX.)

+0.010

–0.005

+0.25

–0.13

0.400

(10.16 )

+0.010

–0.005

+0.25

–0.13

0.250 ±0.005

(6.35 ±0.13)

PIN 1

INDEX

TOP VIEW

24-Pin Ceramic LCC

18-Pin Ceramic DIP

0.960 MAX.

(24.38 MAX.)

0.220 / 0.310

(5.59 / 7.87)

DATEL

ADC-207MC

PIN 1

IDENTIFIER

18 10

0.200 MAX.

(5.1 MAX.)

0.100 TYP.

(2.540)

0.014 / 0.023

(0.35 / 0.58)

0.015 / 0.060

(0.38 /1.52)

0.290 / 0.320

(7.36 / 8.13)

SEATING

PLANE

0.035

(0.889)

0.008 / 0.015

(0.20 / 0.38)

INNOVATION and EX C ELL E N C E

® ®

DATEL makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein

do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.

DS-0038C 12/04

ISO 9001

REGISTERED

ADC-207 ® ®

DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151

Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356

Internet: www.datel.com E-mail:sales@datel.com

Data Sheet Fax Back: (508) 261-2857

DATEL (UK) LTD. Tadley, England Tel: (01256)-880444

DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 1-34-60-01-01

DATEL GmbH München, Germany Tel: 89-544334-0

DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-354-2025