TEXAS INSTRUMENTS ADS7818 Technical data

For most current data sheet and other product

information, visit www.burr-brown.com

12-Bit High Speed Low Power Sampling

ANALOG-TO-DIGITAL CONVERTER

ADS7818

FEATURES

● 500kHz THROUGHPUT RATE

● 2.5V INTERNAL REFERENCE

● LOW POWER: 11mW

● SINGLE SUPPLY +5V OPERATION

● DIFFERENTIAL INPUT

● SERIAL INTERFACE

● GUARANTEED NO MISSING CODES

● MINI-DIP-8 AND MSOP-8

● UNIPOLAR INPUT RANGE

APPLICATIONS

● BATTERY OPERATED SYSTEMS

● DIGITAL SIGNAL PROCESSING

● HIGH SPEED DATA ACQUISITION

● WIRELESS COMMUNICATION SYSTEMS

DESCRIPTION

The ADS7818 is a 12-bit sampling analog-to-digital converter (A/D) complete with sample/hold, internal

2.5V reference, and synchronous serial interface. Typical power dissipation is 11mW at a 500kHz throughput rate. The device can be placed into a power down mode which reduces dissipation to just 2.5mW. The input range is zero to two times the reference voltage, and the internal reference can be overdriven by an external voltage.

Low power, small size, and high-speed make the ADS7818 ideal for battery operated systems such as wireless communication devices, portable multi-channel data loggers, and spectrum analyzers. The serial interface also provides low-cost isolation for remote data acquisition. The ADS7818 is available in a plastic mini-DIP-8 or an MSOP-8 package and is guaranteed over the –40°C to +85°C temperature range.

CLK

SAR

CONV

SBAS078

+In

–In

S/H Amp

REF

International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111

Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132

1998 Burr-Brown Corporation PDS-1408B Printed in U.S.A. May, 2000

CDAC

Buffer

Comparator

Internal

+2.5V Ref

10kΩ ±30%

Serial

Interface

DATA

ADS7818

SPECIFICATIONS

At TA = –40°C to +85°C, +VCC = +5V, f

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS ANALOG INPUT

Full-Scale Input Span

(1)

Absolute Input Range +In –0.2 V

Capacitance 15 ✻ pF Leakage Current 1 ✻ µA

SYSTEM PERFORMANCE

Resolution 12 ✻ Bits No Missing Codes 12 ✻ Bits Integral Linearity Error ±1 ±2 ±0.5 ±1 LSB Differential Linearity Error ±0.8 ±0.5 ±1 LSB Offset Error ±2 ±5 ±1 ✻ LSB Gain Error

(3)

Common-Mode Rejection DC, 0.2Vp-p 70 ✻ dB

Noise 150 ✻ µVrms Power Supply Rejection Worst Case ∆, +V

SAMPLING DYNAMICS

Conversion Time 1.625 ✻ µs Acquisition Time 0.350 ✻ µs Throughput Rate 500 ✻ kHz Aperture Delay 5 ✻ ns Aperture Jitter 30 ✻ ps Step Response 350 ✻ ns

DYNAMIC CHARACTERISTICS

Signal-to-Noise Ratio V Total Harmonic Distortion

(4)

Signal-to-(Noise+Distortion) V Spurious Free Dynamic Range V Usable Bandwidth SINAD > 68dB 350 ✻ kHz

REFERENCE OUTPUT

Voltage I Source Current

(5)

Drift I Line Regulation 4.75V ≤ V

REFERENCE INPUT

Range 2.0 2.55 ✻✻V Resistance

(6)

DIGITAL INPUT/OUTPUT

Logic Family CMOS ✻ Logic Levels:

Data Format Straight Binary ✻

POWER SUPPLY REQUIREMENT

Quiescent Current f

Power Dissipation f

TEMPERATURE RANGE

Specified Performance –40 +85 ✻✻°C

✻ Specifications same as ADS7818P,E.

NOTES: (1) Ideal input span, does not include gain or offset error. (2) LSB means Least Significant Bit, with V relative to an ideal, full-scale input (+In – (–In)) of 4.999V. Thus, gain error includes the error of the internal voltage reference. (4) Calculated on the first nine harmonics of the input frequency. (5) If the internal reference is required to source current to an external load, the reference voltage will change due to the internal 10kΩ resistor. (6) Can vary ±30%.

SAMPLE

= 500kHz, f

CLK

= 16 • f

, internal reference, unless otherwise specified.

SAMPLE

ADS7818P, E ADS7818PB, EB

+In – (–In) 0 5 ✻✻V

+0.2 ✻✻V

–In –0.2 +0.2 ✻✻V

25°C ±12 ±30 ±7 ±15 LSB

–40°C to +85°C ±50 ±35 LSB

1MHz, 0.2Vp-p 50 ✻ dB

= 5V ±5% 1.2 ✻ LSB

= 5Vp-p at 100kHz 72 ✻ dB

VIN = 5Vp-p at 100kHz –78 –72 –82 –75 dB

= 5Vp-p at 100kHz 68 70 70 72 dB

= 5Vp-p at 100kHz 72 78 75 82 dB

= 0 2.475 2.50 2.525 2.48 ✻ 2.52 V

OUT

Static Load 50 ✻ µA

= 0 20 ✻ ppm/°C

OUT

≤ 5.25V 0.6 ✻ mV

to Internal Reference Voltage 10 ✻✻✻ kΩ

|IIH| ≤ +5µA 3.0 V |IIL| ≤ +5µA –0.3 0.8 ✻✻V

+0.3 ✻✻V

IOH = –500µA 3.5 ✻✻V

IOL = 500µA 0.4 ✻✻V

Specified Performance 4.75 5.25 ✻✻V

= 500kHz 2.2 ✻ mA

SAMPLE

Power Down 0.5 ✻ mA

= 500kHz 11 20 ✻✻ mW

SAMPLE

Power Down 2.5 ✻ mW

equal to +2.5V, one LSB is 1.22mV. (3) Measured

REF

(2)

The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems.

ADS7818

ABSOLUTE MAXIMUM RATINGS

+VCC to GND............................................................................ –0.3V to 6V

Analog Inputs to GND .............................................. –0.3V to (V

Digital Inputs to GND ............................................... –0.3V to (V

Power Dissipation .......................................................................... 325mW

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

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

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

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

NOTE: (1) Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. Exposure to absolute maximum conditions for extended periods may affect device reliability.

(1)

+ 0.3V)

PIN CONFIGURATION

Top View

ELECTROSTATIC DISCHARGE SENSITIVITY

Electrostatic discharge can cause damage ranging from performance degradation to complete device failure. BurrBrown Corporation recommends that all integrated circuits be handled and stored using appropriate ESD protection methods.

ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet published specifications.

REF

+In –In

GND

1 2

ADS7818

3 4

Plastic Mini-DIP-8

CLK

DATA

CONV

REF

+In –In

GND

1 2

ADS7818

3 4

MSOP-8

CLK

DATA

CONV

PIN ASSIGNMENTS

PIN NAME DESCRIPTION

1V 2 +In Non-Inverting Input. 3 –In Inverting Input. Connect to ground or to remote ground sense point. 4 GND Ground. 5 CONV Convert Input. Controls the sample/hold mode, start of conversion, start of serial data transfer, type of serial transfer, and power

6 DATA Serial Data Output. The 12-bit conversion result is serially transmitted most significant bit first with each bit valid on the rising edge

7 CLK Clock Input. Synchronizes the serial data transfer and determines conversion speed. 8+V

REF

Reference Output. Decouple to ground with a 0.1µF ceramic capacitor and a 2.2µF tantalum capacitor.

down mode. See the Digital Interface section for more information.

of CLK. By properly controlling the CONV input, it is possibly to have the data transmitted least significant bit first. See the Digital Interface section for more information.

Power Supply. Decouple to ground with a 0.1µF ceramic capacitor and a 10µF tantalum capacitor.

PACKAGE/ORDERING INFORMATION

MAXIMUM MAXIMUM

INTEGRAL DIFFERENTIAL

LINEARITY LINEARITY PACKAGE SPECIFICATION

PRODUCT (LSB) (LSB) PACKAGE NUMBER

ADS7818E ±2 N/S

ERROR ERROR DRAWING TEMPERATURE PACKAGE ORDERING TRANSPORT

(4)

MSOP-8 337 –40°C to +85°C A18 ADS7818E/250 Tape and Reel

"" " " " " "ADS7818E/2K5 Tape and Reel

ADS7818EB ±1 ±1 MSOP-8 337 –40°C to +85°C A18 ADS7818EB/250 Tape and Reel

"" " " " " "ADS7818EB/2K5 Tape and Reel

ADS7818P ±2 N/S ADS7818PB ±1 ±1

NOTE: (1) For detail drawing and dimension table, please see end of data sheet or Package Drawing File on Web. (2) Performance Grade information is marked on the reel. (3) Models with a slash(/) are available only in Tape and reel in quantities indicated (e.g. /250 indicates 250 units per reel, /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of ”ADS7818E/2K5“ will get a single 2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to the www.burr-brown.com web site under Applications and Tape and Reel Orientation and Dimensions. (4) N/S = Not Specified, typical only. However, 12-Bits no missing codes is guaranteed over temperature.

(4)

Plastic DIP-8 006 –40°C to +85°C ADS7818P ADS7818P Rails

"" "ADS7818PB ADS7818PB Rails

(1)

RANGE MARKING

(2)

NUMBER

(3)

MEDIA

ADS7818

TYPICAL PERFORMANCE CURVES

At TA = +25°C, VCC = +5V, f

= 500kHz, f

SAMPLE

CHANGE IN FULL-SCALE ERROR

vs TEMPERATURE

CLK

= 16 • f

SAMPLE

, and internal +2.5V reference, unless otherwise specified.

2.0

CHANGE IN OFFSET vs TEMPERATURE

–2

–4

–6

Delta from 25°C (LSB)

–8

–10

Temperature (°C)

POWER-DOWN SUPPLY CURRENT

470 460 450 440 430 420 410 400

Power-down Supply Current (µA)

390

vs TEMPERATURE

Temperature (°C)

20–40 100–20 0 40

60 80

1.6

1.2

0.8

0.4

Delta from 25°C (LSB)

0.0

–0.4

2.3

2.2

2.1

2.0

1.9

1.8

Supply Current (mA)

1.7

1.6

20–40 100–20 0 40

Temperature (°C)

SUPPLY CURRENT vs TEMPERATURE

= 500kHz

SAMPLE

= 125kHz

SAMPLE

20–40 100–20 0 40

Temperature (°C)

60 80

2.4

2.3

2.2

2.1

2.0

1.9

Supply Current (mA)

1.8

1.7

SUPPLY CURRENT vs SAMPLE RATE

ADS7818

400100 600200 300 500

Sample Rate (kHz)

0.4

0.3

0.2

0.1

= 500kHz (LSB)

0.0

SAMPLE

–0.1

–0.2

Delta from f

–0.3

CHANGE IN INTEGRAL LINEARITY and

DIFFERENTIAL LINEARITY vs SAMPLE RATE

Change in Integral

Linearity (LSB)

Change in Differential

Linearity (LSB)

400100 600200 300 500

Sample Rate (kHz)

TYPICAL PERFORMANCE CURVES (Cont.)

At TA = +25°C, VCC = +5V, f

SAMPLE

= 500kHz, f

CLK

= 16 • f

, and internal +2.5V reference, unless otherwise specified.

SAMPLE

0.2

0.0

–0.2

–0.4

= 2.5V (mV)

REF

–0.6

–0.8

Delta from V

–1.0

–1.2

0.70

0.65

0.60

CHANGE IN FULL-SCALE ERROR

vs EXTERNAL REFERENCE VOLTAGE

2.32.0 2.52.1 2.2 2.4

External Reference Voltage (V)

PEAK-TO-PEAK NOISE

vs EXTERNAL REFERENCE VOLTAGE

0.5

0.4

0.3

0.2

0.1

= 2.5V (mV)

REF

0.0 –0.1 –0.2

Delta from V

–0.3 –0.4

CHANGE IN OFFSET

vs EXTERNAL REFERENCE VOLTAGE

2.51.9 3.12.1 2.3 2.7 2.9

External Reference Voltage (V)

POWER SUPPLY REJECTION

vs POWER SUPPLY RIPPLE FREQUENCY

0.55

0.50

Peak-to-Peak Noise (LSB)

0.45

0.40

–20

–40

–60

–80

Amplitude (dB)

–100

–120

0 25062.5 187.5125

(4096 Point FFT; f

2.32.0 2.52.1 2.2 2.4

External Reference Voltage (LSB)

FREQUENCY SPECTRUM

= 10.9kHz, –0.2dB)

Frequency (kHz)

Power Supply Rejection (mV/V)

1 10 100 1k 10k 100k 1M

Power Supply Ripple Frequency (Hz)

FREQUENCY SPECTRUM

–20

–40

–60

–80

Amplitude (dB)

–100

–120

0 25062.5 187.5125

(4096 Point FFT; f

= 102kHz, –0.2dB)

Frequency (kHz)

ADS7818

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