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ADS-926GC中文资料

ADS-926

14-Bit, 500kHz, Low-Power

Sampling A/D Converters

Figure 1. ADS-926 Functional Block Diagram

FEATURES

?14-bit resolution

?500kHz sampling rate

?Functionally complete; No missing codes

?Small 24-pin DDIP or SMT package

?Operates from ±15V or ±12V supplies

?Low power, 1.75 Watts maximum

?Samples up to Nyquist frequencies

?Outstanding dynamic performance

?Bipolar ±5V input range

GENERAL DESCRIPTION

The ADS-926 is a high-performance, 14-bit, 500kHz sampling

A/D converter. This device accurately samples full-scale input

signals up to Nyquist frequencies with no missing codes and

exhibits outstanding dynamic performance that surpasses

most 16-bit, 500kHz sampling A/D's. THD and SNR, for

example, are typically –90dB and 80dB when converting full-

scale input signals up to 100kHz.

Housed in a small 24-pin DDIP or SMT (gull-wing) package,

the functionally complete ADS-926 contains a fast-settling

sample-hold amplifier, a subranging (two-pass) A/D converter,

a precise voltage reference, timing/control logic, and error-

correction circuitry. Digital input and output levels are TTL.

Requiring ±15V (or ±12V) and +5V supplies, the ADS-926

dissipates only 1.75W (1.6W for ±12V), maximum. The unit is

offered with a bipolar input (–5V to +5V). Models are available

for use in either commercial (0 to +70°C) or military (–55 to

+125°C) operating temperature ranges.

Applications include radar, sonar, spectrum analysis, and

graphic/medical imaging. Contact DATEL for information on

devices screened to MIL-STD-883.

INPUT/OUTPUT CONNECTIONS

PIN FUNCTION PIN FUNCTION

1BIT 14 (LSB)

24–12V/–15V SUPPL Y

2BIT 1323ANALOG GROUND

3BIT 1222+12V/+15V SUPPL Y

4BIT 1121+10V REFERENCE OUT

5BIT 1020ANALOG INPUT

6BIT 919ANALOG GROUND

7BIT 818BIT 1 (MSB)

8BIT 717BIT 2

9BIT 616ST ART CONVERT

10BIT 515EOC

11BIT 414DIGIT AL GROUND

12BIT 313+5V SUPPL Y

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

18 BIT 1 (MSB)

17 BIT 2

12 B IT 3

11 BIT 4

10 BIT 5

9 BIT 6

8 BIT 7

7 BIT 8

6 BIT 9

5 BIT 10

4 BIT 11

3 BIT 12

2 BIT 13

1 BIT 14 (LSB)

+5V SUPPLY

+12V/+15V SUPPLY

19, 23

ANALOG GROUND

DIGITAL GROUND

–12V/–15V SUPPLY

ADS-926

ABSOLUTE MAXIMUM RATINGS

PARAMETERS

LIMITS UNITS +12V/+15V Supply (Pin 22)0 to +16Volts –12V/–15V Supply (Pin 24)0 to –16Volts +5V Supply (Pin 13)0 to +6Volts Digital Input (Pin 16)–0.3 to +V DD +0.3

Volts Analog Input (Pin 20)

±15Volts Lead Temperature (10 seconds)

+300

°C

PHYSICAL/ENVIRONMENTAL

PARAMETERS

MIN.TYP .MAX.UNITS Operating Temp. Range, Case ADS-926MC, GC

0—+70°C ADS-926MM, GM, 883–55

—

+125

°C

Thermal Impedance θj c 6°C/Watt θca

24°C/Watt

Storage Temperature –65—+150°C Package Type 24-pin, metal-sealed, ceramic DDIP or SMT

Weight

0.42 ounces (12 grams)

+25°C

0 to +70°C –55 to +125°C

ANALOG INPUT MIN. TYP. MAX. MIN. TYP. MAX. MIN. TYP. MAX.UNITS Input Voltage Range —±5——±5——±5—Volts Input Resistance —1——1——1—k ?Input Capacitance —

—

DIGITAL INPUT

Logic Levels Logic "1"+2.0——+2.0——+2.0——Volts Logic "0"

——+0.8——+0.8——+0.8Volts Logic Loading "1"——+20——+20——+20μA Logic Loading "0"

——–20——–20——–20μA Start Convert Positive Pulse Width 175

200

225

175

200

225

175

200

225

STATIC PERFORMANCE Resolution

—14——14——14—Bits Integral Nonlinearity (f in = 10kHz)—±0.5——±0.75——±1.5—LSB Differential Nonlinearity (f in = 10kHz)—±0.5±0.95—±0.5±0.95—±0.75±0.99LSB Full Scale Absolute Accuracy —±0.08±0.15—±0.15±0.25—±0.3±0.5%FSR Bipolar Zero Error (Tech Note 2)—±0.05±0.1—±0.1±0.25—±0.15±0.3%FSR Bipolar Offset Error (Tech Note 2)—±0.05±0.1—±0.1±0.25—±0.25±0.4%FSR Gain Error (Tech Note 2)

—±0.1±0.15—±0.15±0.25—±0.25±0.4%No Missing Codes (f in = 10kHz)14

—

Bits

DYNAMIC PERFORMANCE Peak Harmonics (–0.5dB)dc to 100kHz —–92–88—–90–85—–88–81dB 100kHz to 250kHz

—–90–85—–90–85—–86–80dB Total Harmonic Distortion (–0.5dB)dc to 100kHz —–90–86—–89–82—–87–78dB 100kHz to 250kHz —–87–82—–87–82—–81–76dB Signal-to-Noise Ratio (w/o distortion, –0.5dB)dc to 100kHz 7880—7880—7478—dB 100kHz to 250kHz 7880—7880—7477—dB Signal-to-Noise Ratio (& distortion, –0.5dB)dc to 100kHz 7779—7779—7478—dB 100kHz to 250kHz

7779—7779—7377—dB Two-Tone Intermodulation Distortion (f in = 100kHz,240kHz, f s = 500kHz, –0.5dB)—–87——–86——–85—dB Noise

—300——300——350—μVrms Input Bandwidth (–3dB)Small Signal (–20dB input)—7——7——7—MHz Large Signal (–0.5dB input)

—3——3——3—MHz Feedthrough Rejection (f in = 250kHz)—84——84——84—dB Slew Rate

—±40——±40——±40—V/μs Aperture Delay Time —±20——±20——±20—ns Aperture Uncertainty —5——5——5—ps rms S/H Acquisition Time

(to ±0.003%FSR, 10V step)133513901445133513901445133513901445ns Overvoltage Recovery Time —14002000—14002000—14002000ns A/D Conversion Rate

500

—

500

—

500

—

kHz

FUNCTIONAL SPECIFICATIONS

(T A = +25°C, ±V CC = ±15V (or ±12V), +V DD = +5V, 500kHz sampling rate, and a minimum 1 minute warmup unless otherwise specified.)

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ADS-926

+25°C

0 to +70°C

–55 to +125°C

ANALOG OUTPUT MIN. TYP. MAX. MIN. TYP. MAX. MIN. TYP. MAX.UNITS Internal Reference Voltage +9.95+10.0+10.05+9.95+10.0+10.05+9.95+10.0+10.05Volts Drift

—±5——±5——±5—ppm/°C External Current —

—

1.5

—

1.5

—

1.5

DIGITAL OUTPUTS Logic Levels Logic "1"+2.4——+2.4——+2.4——Volts Logic "0"

——+0.4——+0.4——+0.4Volts Logic Loading "1"——–4——–4——–4mA Logic Loading "0"

——+4——+4——+4mA Delay, Falling Edge of EOC to Output Data Valid —

—

—35

—

Output Coding

Offset Binary

POWER REQUIREMENTS, ±15V Power Supply Ranges +15V Supply +14.5+15.0+15.5+14.5+15.0+15.5+14.5+15.0+15.5Volts –15V Supply –14.5–15.0–15.5–14.5–15.0–15.5–14.5–15.0–15.5Volts +5V Supply

+4.75+5.0+5.25+4.75+5.0+5.25+4.75+5.0+5.25Volts Power Supply Currents +15V Supply —+41+60—+41+60—+41+60mA –15V Supply —–23–40—–23–40—–23–40mA +5V Supply —+71+85—+71+85—+71+85mA Power Dissipation

— 1.4 1.75— 1.4 1.75— 1.4 1.75Watts Power Supply Rejection

—

±0.02

—

±0.02

—

±0.02

%FSR/%V

POWER REQUIREMENTS, ±12V Power Supply Ranges +12V Supply +14.5+15.0+15.5+14.5+15.0+15.5+14.5+15.0+15.5Volts –12V Supply –14.5–15.0–15.5–14.5–15.0–15.5–14.5–15.0–15.5Volts +5V Supply

+4.75+5.0+5.25+4.75+5.0+5.25+4.75+5.0+5.25Volts Power Supply Currents +12V Supply —+41+60—+41+60—+41+60mA –12V Supply —–23–40—–23–40—–23–40mA +5V Supply —+71+85—+71+85—+71+85mA Power Dissipation

— 1.3 1.6— 1.3 1.6— 1.3 1.6Watts Power Supply Rejection

—

±0.02

—

±0.02

—

±0.02

%FSR/%V

TECHNICAL NOTES

1.Obtaining fully specified performance from the ADS-926requires careful attention to pc-card layout and power

supply decoupling. The device's analog and digital ground systems are connected to each other internally. For optimal performance, tie all ground pins (14, 19 and 23)directly to a large analog ground plane beneath the unit.Bypass all power supplies and the REFERENCE OUTPUT (pin 21) to ground with 4.7μF tantalum capacitors in parallel with 0.1μF ceramic capacitors. Locate the bypass capaci-tors as close to the unit as possible. If the user-installed offset and gain adjusting circuit shown in Figure 2 is used,also locate it as close to the ADS-926 as possible.2.The ADS-926 achieves its specified accuracies without the

need for external calibration. If required, the device's small initial offset and gain errors can be reduced to zero using the input circuit of Figure 2. When using this circuit, or any similar offset and gain-calibration hardware, make adjust-ments following warmup. To avoid interaction, always adjust offset before gain.

3.When operating the ADS-926 from ±12V supplies, do not drive external circuitry with the REFERENCE OUTPUT. The reference's accuracy and drift specifications may not be met, and loading the circuit may cause accuracy errors within the converter.

4.Applying a start convert pulse while a conversion is in progress (EOC = logic "1") initiates a new and inaccurate conversion cycle. Data for the interrupted and subsequent conversions will be invalid.

6.02

(SNR + Distortion) – 1.76 + 20 log

Full Scale Amplitude Actual Input Amplitude

Effective bits is equal to:

This is the time required before the A/D output data is valid after the analog input is back within the specified range.

Footnotes:

All power supplies must be on before applying a start convert pulse. All supplies and the clock (START CONVERT) must be present during warmup periods. The device must be continuously converting during this time. See Ordering Information for 0 to +10V input range. Contact DATEL for availability of other input voltage ranges. A 500kHz clock with a 200ns wide start convert pulse is used for all production testing. For applications requiring less than a 500kHz sampling rate, wider start convert pulses can be used. See Timing Diagram for more details.

ADS-926

987654321BIT 1 (MSB)

BIT 2BIT 3BIT 4BIT 5BIT 6BIT 7BIT 8BIT 9BIT 10BIT 11BIT 12BIT 13BIT 14 (LSB)CALIBRATION PROCEDURE

(Refer to Figures 2 and 3)

Any offset and/or gain calibration procedures should not be implemented until devices are fully warmed up. To avoid

interaction, offset must be adjusted before gain. The ranges of adjustment for the circuit of Figure 2 are guaranteed to

compensate for the ADS-926's initial accuracy errors and may not be able to compensate for additional system errors.All fixed resistors in Figure 2 should be metal-film types, and multiturn potentiometers should have TCR’s of 100ppm/°C or less to minimize drift with temperature.

A/D converters are calibrated by positioning their digital outputs exactly on the transition point between two adjacent digital output codes. This can be accomplished by connecting LED's to the digital outputs and adjusting until certain LED's "flicker"equally between on and off. Other approaches employ digital comparators or microcontrollers to detect when the outputs change from one code to the next.

For the ADS-926, offset adjusting is normally accomplished at the point where the MSB is a 1 and all other output bits are 0's

and the LSB just changes from a 0 to a 1. This digital output transition ideally occurs when the applied analog input is +? LSB (+305μV).

Gain adjusting is accomplished when all bits are 1's and the LSB just changes from a 1 to a 0. This transition ideally occurs when the analog input is at +full scale minus 1? LSB's (+4.999085V).

Zero/Offset Adjust Procedure

1.Apply a train of pulses to the START CONVERT input

(pin 16) so the converter is continuously converting. If using LED's on the outputs, a 200kHz conversion rate will reduce flicker.2.Apply +305μV to the ANALOG INPUT (pin 20).3.Adjust the offset potentiometer until the output bits are a 1 and all 0's and the LSB flickers between 0 and 1.Gain Adjust Procedure

1.Apply +4.999085V to the ANALOG INPUT (pin 20).

2.Adjust the gain potentiometer until the output bits are all 1's and the LSB flickers between 1 and 0.

INPUT VOLTAGE

ZERO ADJUST

GAIN ADJUST RANGE

+? LSB

+FS –1? LSB ±5V

+305μV

+4.999085V

Table 1. Zero and Gain Adjust

OUTPUT CODING INPUT RANGE

BIPOLAR MSB LSB ±5V SCALE 11 1111 1111 1111+4.99939+FS –1 LSB 11 1000 0000 0000+3.75000+3/4 FS 11 0000 0000 0000+2.50000+1/2FS 10 0000 0000 00000.000000

01 0000 0000 0000–2.50000–1/2FS 00 1000 0000 0000–3.75000–3/4FS

00 0000 0000 0001–4.99939–FS +1 LSB 00 0000 0000 0000

–5.00000

–FS

Table 2. Output Coding

Figure 3. Typical ADS-926 Connection Diagram

Figure 2. ADS-926 Calibration Circuit

Coding is offset binary; 1LSB = 610μV .

To Pin 20of ADS-926

ZERO/OFFSET ADJUST

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ADS-926

THERMAL REQUIREMENTS

All DATEL sampling A/D converters are fully characterized and specified over operating temperature (case) ranges of 0 to +70°C and –55 to +125°C. All room-temperature

(T A = +25°C) production testing is performed without the use of heat sinks or forced-air cooling. Thermal impedance figures for each device are listed in their respective specification tables.These devices do not normally require heat sinks, however,standard precautionary design and layout procedures should be used to ensure devices do not overheat. The ground and power planes beneath the package, as well as all pcb signal runs to and from the device, should be as heavy as possible to help conduct heat away from the package.

Electrically-insulating, thermally-conductive "pads" may be installed underneath the package. Devices should be soldered to boards rather than "socketed", and of course, minimal air flow over the surface can greatly help reduce the package temperature.

In more severe ambient conditions, the package/junction temperature of a given device can be reduced dramatically (typically 35%) by using one of DATEL's HS Series heat sinks.See Ordering Information for the assigned part number. See page 1-183 of the DATEL Data Acquisition Components Catalog for more information on the HS Series. Request DATEL Application Note AN-8, "Heat Sinks for DIP Data Converters", or contact DATEL directly, for additional information.

Figure 4. ADS-926 Timing Diagram

Notes: 1.f s = 500kHz.

2.The ADS-926 is a pulse-triggered device. Its internal operations are triggered by both the rising and falling edges of the start

convert pulse. When sampling at 500kHz, the start pulse must be between 175 and 225nsec wide. For lower sampling rates, wider start pulses may be used, however, a 50nsec minimum pulse width low must be maintained.

Data

ADS-926

F i g u r e 5. A D S -926 E v a l u a t i o n B o a r d S c h e m a t i c

A D S -926/927

1D 2D

C L K

4Q 5Q

O C

+5V

-15V -15V

-15V

+15V

+15V +15V

+5V +5V +5V

-15V

A G N D

+15V

+10V R E F

I N P U T

A G N D

B 1

B 2

S T R T C O N V

D G N D +5V

B 12

B 11

B 10

B 9

B 8B 7

B 6

B 5

B 4

B 3B 13B 14E O

C '

N /C

U 5S G 1

U 2U 4U 4

R 1

R 2P 1

C 14

C 11C 8C 9C 4C 6C 13C 12C 10C 2C 15C 1C 16C 3C 5C 7U 4U 4

P 4

P 3U 1

R 5R 4R 3

P 276

3211916151296522010

111817

3147

2421

2017

1815

1411

129

107

465

1312

109

2322

1312

11109

765432

3032A D 84574A L S 534

74L S 86

5020K

2.2M F

2.2M F 2.2M F

2.2M F

0.1M F

0.1M F 0.1M F 15p F 0.1M F

0.1M F

0.1M F 0.1M F

0.1M F 74L S 8674L S 86

0.1%

1.98K

.1%1.2M 5%A N A L O G I N P U T S T A R T C O N V E R T

O F F S E T A D J

G A I N A D J

C O G +-B 1B 2B 3B 4B 5B 6B 7B 8

B 9

B 10

B 11

B 12

B 13

B 14

C L K

+5V

C 1720

74A L S 534

0.1M F

O C

119

U 3

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ADS-926

Figure 6. ADS-926 FFT Analysis

Figure 7. ADS-926 Histogram and Differential Nonlinearity

0–10–20–30–40–50–60–70–80–90–100–110–120–130–140–150

Frequency (kHz)

(fs = 500kHz, fin = 240kHz, Vin = –0.5dB, 16,384-point FFT)

A m p l i t u d e R e l a t i v e t o F u l l S c a l e (d

B )

0 25 50 75 100 125 150 175 200 225 250

N u m b e r o f O c c u r r e n c e s

Digital Output Code

16,384

+0.59

–0.57

16,384

DNL (LSB's)

Digital Output Code

ADS-926

MECHANICAL DIMENSIONS INCHES (mm)

ORDERING INFORMATION

MODEL OPERATING ANALOG NUMBER TEMP. RANGE INPUT ADS-926MC 0 to +70°C Bipolar (±5V)ADS-926MM –55 to +125°C Bipolar (±5V)ADS-926/883–55 to +125°C Bipolar (±5V)ADS-926GC 0 to +70°C Bipolar (±5V)ADS-926GM –55 to +125°C Bipolar (±5V)ADS-916MC 0 to +70°C Unipolar (0 to +10V)*ADS-916MM –55 to +125°C Unipolar (0 to +10V)*ADS-916GC 0 to +70°C Unipolar (0 to +10V)*ADS-916GM

–55 to +125°C

Unipolar (0 to +10V)*

ACCESSORIES ADS-B926/927Evaluation Board (without ADS-926)

HS-24

Heat Sinks for all ADS-916/926 DDIP models.

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.

ISO 9001

I S

DS-0265C 11/96

Receptacles for PC board mounting can be ordered through

AMP Inc. Part #3-331272-8 (Component Lead Socket), 24 required.For MIL-STD-883 product specifications, contact DATEL.* For information, see ADS-916 data sheet.

DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356Internet: https://www.wendangku.net/doc/081714738.html, E-mail:sales@https://www.wendangku.net/doc/081714738.html, 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: 1-34-60-01-01DATEL GmbH München, Germany Tel: 89-544334-0

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

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