BURR-BROWN ADS8345 User Manual

ADS8345

A

®

D

S

8

3

4

5

ADS8345

®

SBAS177C – FEBRUARY 2001 – REVISED APRIL 2003

16-Bit, 8-Channel Serial Output Sampling

ANALOG-TO-DIGITAL CONVERTER

FEATURES

● BIPOLAR INPUT RANGE

● PIN-FOR-PIN COMPATIBLE WITH THE

ADS7844 AND ADS8344

● SINGLE SUPPLY: 2.7V to 5V

● 8-CHANNEL SINGLE-ENDED OR

4-CHANNEL DIFFERENTIAL INPUT

● UP TO 100kHz CONVERSION RATE

● 85dB SINAD

● SERIAL INTERFACE

● QSOP-20 AND SSOP-20 PACKAGES

APPLICATIONS

● DATA ACQUISITION

● TEST AND MEASUREMENT EQUIPMENT

● INDUSTRIAL PROCESS CONTROL

● PERSONAL DIGITAL ASSISTANTS

● BATTERY-POWERED SYSTEMS

DESCRIPTION

The ADS8345 is an 8-channel, 16-bit, sampling
Analog-to-Digital (A/D) converter with a synchronous serial
interface. Typical power dissipation is 8mW at a 100kHz
throughput rate and a +5V supply. The reference voltage
(V

) can be varied between 500mV and VCC/2, providing a

REF

corresponding input voltage range of ±V
includes a shutdown mode which reduces power dissipation
to under 15µW. The ADS8345 is ensured down to 2.7V
operation.

Low-power, high-speed, and an onboard multiplexer make
the ADS8345 ideal for battery-operated systems such as
personal digital assistants, portable multi-channel data log­gers, and measurement equipment. The serial interface also
provides low-cost isolation for remote data acquisition. The
ADS8345 is available in a QSOP-20 or SSOP-20 package
and is ensured over the –40°C to +85°C temperature range.

. The device

REF

CH0
CH1
CH2
CH3

CH4
CH5
CH6
CH7

COM

V

REF

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.

8-Channel

Multiplexer

CDAC

SAR

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Comparator

DCLK

CS

Serial

Interface

and

Control

Copyright © 2001-2003, Texas Instruments Incorporated

SHDN
D

IN

D

OUT

BUSY

ABSOLUTE MAXIMUM RATINGS

+V

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

CC

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

Digital Inputs to GND ........................................................... –0.3V to +6V

Power Dissipation .......................................................................... 250mW

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

CC

ELECTROSTATIC
DISCHARGE SENSITIVITY

This integrated circuit can be damaged by ESD. Texas Instru­ments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.

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 its
published specifications.

PACKAGE/ORDERING INFORMATION

MAXIMUM

INTEGRAL MAXIMUM SPECIFIED

PRODUCT ERROR (LSB) ERROR (%) PACKAGE-LEAD DESIGNATOR

LINEARITY GAIN PACKAGE TEMPERATURE ORDERING TRANSPORT

ADS8345E 8 ±0.05 QSOP-20 DBQ –40°C to +85°C ADS8345E Rails, 100

(1)

RANGE NUMBER MEDIA, QUANTITY

"" " " " "ADS8345E/2K5 Tape and Reel, 2500

ADS8345N 8 ±0.05 SSOP-20 DB –40°C to +85°C ADS8345N Rails, 100

"" " " " "ADS8345N/1K Tape and Reel, 1000

ADS8345EB 6 ±0.024 QSOP-20 DBQ –40°C to +85°C ADS8345EB Rails, 100

"" " " " "ADS8345EB/2K5 Tape and Reel, 2500

ADS8345NB 6 ±0.024 SSOP-20 DB –40°C to +85°C ADS8345NB Rails, 100

"" " " " "ADS8345NB/1K Tape and Reel, 1000

NOTE: (1) For the most current specifications and package information, refer to our web site at www.ti.com.

PIN CONFIGURATION

Top View SSOP

CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7

COM

SHDN

1
2
3
4
5
6
7
8
9

10

ADS8345

+V

20

CC

DCLK

19

CS

18

D

17

IN

16

BUSY

15

D

OUT

14

GND

13

GND

12

+V

CC

11

V

REF

PIN DESCRIPTIONS

PIN NAME DESCRIPTION

1 CH0 Analog Input Channel 0
2 CH1 Analog Input Channel 1
3 CH2 Analog Input Channel 2
4 CH3 Analog Input Channel 3
5 CH4 Analog Input Channel 4
6 CH5 Analog Input Channel 5
7 CH6 Analog Input Channel 6
8 CH7 Analog Input Channel 7
9 COM

10 SHDN Shutdown. When LOW, the device enters a very

11 V

12 +V
13 GND Ground
14 GND Ground
15 D

16 BUSY Busy Output. Busy goes LOW when the D

17 D

18 CS Chip Select Input; Active LOW. Data will not be clocked

19 DCLK External Clock Input. The clock speed determines the

20 +V

Common reference for analog inputs. This pin is typically
connected to V

low-power shutdown mode.
Voltage Reference Input. See the Electrical Character-

REF

istics Table for ranges.
Power Supply, 2.7V to 5.25V

CC

Serial Data Output. Data is shifted on the falling edge of

OUT

DCLK. This output is high impedance when CS is HIGH.

are being read and also when the device is converting.
The Output is high impedance when CS is HIGH.
Serial Data Input. If CS is LOW, data is latched on rising

IN

edge of D

into D

unless CS is LOW. When CS is HIGH, D

IN

high impedance.

conversion rate by the equation f
Power Supply

CC

CLK

.

REF

.

DCLK

IN

= 24 • f

control bits

SAMPLE

OUT

is

.

2

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ADS8345

SBAS177C

ELECTRICAL CHARACTERISTICS: +5V

At TA = –40°C to +85°C, +VCC = +5V, V

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
RESOLUTION 16 ✻ Bits

ANALOG INPUT

Full-Scale Input Span Positive Input-Negative Input –V
Absolute Input Range +IN –0.2

Capacitance 25 ✻ pF
Leakage Current ±1 ✻ µA

SYSTEM PERFORMANCE

No Missing Codes 14 15 Bits
Integral Linearity Error ±8 ±6LSB
Bipolar Error ±2 ±1mV
Bipolar Error Match 48 ✻✻LSB
Gain Error ±0.05 ±0.024 %
Gain Error Match 1.0 4 ✻✻ LSB
Noise 20 ✻ µVrms
Power-Supply Rejection +4.75V < V

SAMPLING DYNAMICS

Conversion Time 16 ✻ CLK Cycles
Acquisition Time 4.5 ✻ CLK Cycles
Throughput Rate 100 ✻ kHz
Multiplexer Settling Time 500 ✻ ns
Aperture Delay 30 ✻ ns
Aperture Jitter 100 ✻ ps
Internal Clock Frequency SHDN = V
External Clock Frequency 0.024 2.4 ✻✻MHz

DYNAMIC CHARACTERISTICS

Total Harmonic Distortion

(2)

Signal-to-(Noise + Distortion) V
Spurious-Free Dynamic Range V
Channel-to-Channel Isolation V

REFERENCE INPUT

Range 0.5 +VCC/2 ✻✻V
Resistance DCLK Static 5 ✻ GΩ
Input Current 40 100 ✻✻ µA

DIGITAL INPUT/OUTPUT

Logic Family CMOS ✻
Logic Levels

V

IH

V

IL

V

OH

V

OL

Data Format Binary Two’s Complement ✻

POWER-SUPPLY REQUIREMENTS

+V

CC

Quiescent Current 1.5 2.0 ✻✻ mA

Power Dissipation 7.5 10 ✻✻ mW

TEMPERATURE RANGE

Specified Performance –40 +85 ✻✻°C

= +2.5V, f

REF

= 100kHz, and f

SAMPLE

CLK

= 24 • f

= 2.4MHz, unless otherwise noted.

SAMPLE

ADS8345E, N ADS8345EB, NB

REF

–IN –0.2

< 5.25V 3 ✻ LSB

CC

DD

2.4 ✻ MHz

+V

REF

+VCC + 0.2
+VCC + 0.2

✻✻V
✻✻V
✻✻V

Data Transfer Only 0 2.4 ✻✻MHz

VIN = 5Vp-p at 10kHz –96 ✻ dB

= 5Vp-p at 10kHz 85 ✻ dB

IN

= 5Vp-p at 10kHz 98 ✻ dB

IN

= 5Vp-p at 10kHz 105 ✻ dB

IN

DCLK Static 0.001 3 ✻✻ µA

| IIH | ≤ +5µA 3.0 5.5 ✻✻V
| IIL | ≤ +5µA –0.3 +0.8 ✻✻V

IOH = –250µA 3.5 ✻ V

IOL = 250µA 0.4 ✻ V

Specified Performance 4.75 5.25 ✻✻V

f

= 10kHz 1.2 ✻ mA

SAMPLE

Power-Down Mode

(3)

, CS = +V

CC

3 ✻ µA

(1)

(1)

✻ Same specifications as ADS8345E, N.
NOTES: (1) LSB means Least Significant Bit. With V

(PD1 = PD0 = 0) active or SHDN = GND.

ADS8345

SBAS177C

equal to +2.5V, one LSB is 76µV. (2) First nine harmonics of the test frequency. (3) Auto power-down mode

REF

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3

ELECTRICAL CHARACTERISTICS: +2.7V

At TA = –40°C to +85°C, +VCC = +2.7V, V

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
RESOLUTION 16 ✻ Bits

ANALOG INPUT

Full-Scale Input Span Positive Input-Negative Input –V
Absolute Input Range +IN –0.2

Capacitance 25 ✻ pF
Leakage Current ±1 ✻ µA

SYSTEM PERFORMANCE

No Missing Codes 14 15 Bits
Integral Linearity Error ±8 ±6LSB
Bipolar Error ±1.0 ±0.5 mV
Bipolar Error Match 24 ✻✻LSB
Gain Error ±0.05 ±0.024 % of FSR
Gain Error Match 14 ✻✻ LSB
Noise 20 ✻ µVrms
Power-Supply Rejection +2.7 < V

SAMPLING DYNAMICS

Conversion Time 16 ✻ CLK Cycles
Acquisition Time 4.5 ✻ CLK Cycles
Throughput Rate 100 ✻ kHz
Multiplexer Settling Time 500 ✻ ns
Aperture Delay 30 ✻ ns
Aperture Jitter 100 ✻ ps
Internal Clock Frequency SHDN = V
External Clock Frequency 0.024 2.4 ✻✻MHz

DYNAMIC CHARACTERISTICS

Total Harmonic Distortion

(2)

Signal-to-(Noise + Distortion) V
Spurious-Free Dynamic Range V
Channel-to-Channel Isolation V

REFERENCE INPUT

Range 0.5 +VCC/2 ✻✻V
Resistance DCLK Static 5 ✻ GΩ
Input Current 13 40 ✻✻ µA

DIGITAL INPUT/OUTPUT

Logic Family CMOS ✻
Logic Levels

V

IH

V

IL

V

OH

V

OL

Data Format Binary Two’s Complement ✻

POWER-SUPPLY REQUIREMENTS

+V

CC

Quiescent Current 1.2 1.85 ✻✻ mA

Power Dissipation 3.2 5 ✻✻ mW

TEMPERATURE RANGE

Specified Performance –40 +85 ✻✻°C

= +1.25V, f

REF

= 100kHz, and f

SAMPLE

CLK

= 24 • f

= 2.4MHz, unless otherwise noted.

SAMPLE

ADS8345E, N ADS8345EB, NB

REF

–IN –0.2

< +3.3V 3 ✻ LSB

CC

DD

2.4 ✻ MHz

+V

REF

+VCC + 0.2
+VCC + 0.2

✻✻V
✻✻V
✻✻V

When used with Internal Clock 0.024 2.0 ✻✻MHz

Data Transfer Only 0 2.4 ✻✻MHz

VIN = 2.5Vp-p at 1kHz –95 ✻ dB

= 2.5Vp-p at 1kHz 81 ✻ dB

IN

= 2.5Vp-p at 1kHz 95 ✻ dB

IN

= 2.5Vp-p at 10kHz 108 ✻ dB

IN

DCLK Static 0.001 3 ✻✻ µA

| I

| ≤ +5µA+V

IH

| I

| ≤ +5µA –0.3 +0.8 ✻✻V

IL

IOH = –250µA+V

IOL = 250µA 0.4 ✻ V

• 0.7 5.5 ✻✻V

CC

• 0.8 ✻ V

CC

Specified Performance 2.7 3.6 ✻✻V

f

= 10kHz 950 ✻ µA

SAMPLE

Power-Down Mode

(3)

, CS = +V

CC

3 ✻ µA

(1)

✻ Same specifications as ADS8345E, N.
NOTES: (1) LSB means Least Significant Bit. With V

mode (PD1 = PD0 = 0) active or SHDN = GND.

4

equal to +1.25V, one LSB is 38µV. (2) First nine harmonics of the test frequency. (3) Auto power-down

REF

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ADS8345

SBAS177C

TYPICAL CHARACTERISTICS: +5V

CHANGE IN SIGNAL-TO-(NOISE + DISTORTION)

vs TEMPERATURE

–50 –25 0 20 50 75 100

Temperature (°C)

Delta from +25°C (dB)

0.2

0.0

–0.2

–0.4

–0.6

–0.8

0.4
fIN = 4.956kHz, –0.2dB

At TA = +25°C, +VCC = +5V, V

= +2.5V, f

REF

= 100kHz, and f

SAMPLE

DCLK

= 24 • f

SAMPLE

= 2.4MHz, unless otherwise noted.

FREQUENCY SPECTRUM

(4096 Point FFT; f

0

–20

–40

–60

–80

Amplitude (dB)

–100

–120

–140

0 1020304050

SIGNAL-TO-NOISE RATIO AND

SIGNAL-TO-(NOISE + DISTORTION)

100

90

80

vs INPUT FREQUENCY

= 1.001kHz, –0.2dB)

IN

Frequency (kHz)

SNR

SINAD

FREQUENCY SPECTRUM

(4096 Point FFT; f

0

–20

–40

–60

–80

Amplitude (dB)

–100

–120

–140

0 1020304050

SPURIOUS-FREE DYNAMIC RANGE

AND TOTAL HARMONIC DISTORTION

110

100

90

80

SFDR (dB)

vs INPUT FREQUENCY

= 9.985kHz, –0.2dB)

IN

Frequency (kHz)

SFDR

THD

(1)

–110

–100

–90

–80

THD (dB)

70

SNR and SINAD (dB)

60

15.0

14.5

14.0

13.5

13.0

12.5

12.0

Effective Number of Bits

11.5

11.0

101 100

Frequency (kHz)

EFFECTIVE NUMBER OF BITS

vs INPUT FREQUENCY

101 100

Frequency (kHz)

70

NOTE: (1) First Nine Harmonics
of the Input Frequency

60

–70

–60

101 100

Frequency (kHz)

ADS8345

SBAS177C

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5

TYPICAL CHARACTERISTICS: +5V (Cont.)

At TA = +25°C, +VCC = +5V, V

= +2.5V, f

REF

= 100kHz, and f

SAMPLE

DCLK

= 24 • f

= 2.4MHz, unless otherwise noted.

SAMPLE

3

INTEGRAL LINEARITY ERROR vs CODE

2

1

0

ILE (LSB)

–1

–2

–3

8000

H

SUPPLY CURRENT vs TEMPERATURE

1.7

1.6

1.5

1.4

Supply Current (mA)

1.3

C000

H

0000

H

Output Code

4000

DIFFERENTIAL LINEARITY ERROR vs CODE

3

2

1

0

DLE (LSB)

–1

–2

–3

7FFF

H

H

8000

H

C000

0000

H

H

4000

7FFF

H

H

Output Code

CHANGE IN BPZ vs TEMPERATURE

4

3

2

1

0

Delta from 25°C (LSBs)

–1

1.2
–50 –25 0 25 50 75 100

Temperature (°C)

CHANGE IN GAIN vs TEMPERATURE

1.0

0.5

0

Delta from 25°C (LSBs)

–0.5

–50 –25 0 25 50 75 100

Temperature (°C)

–2

–50 –25 0 25 50 75 100

Temperature (°C)

WORST-CASE CHANNEL-TO-CHANNEL

BPZ MATCH vs TEMPERATURE

5.0

4.5

4.0

3.5

3.0

BPZ Match (LSBs)

2.5

2.0
–50 –25 0 25 50 75 100

Temperature (°C)

6

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ADS8345

SBAS177C

TYPICAL CHARACTERISTICS: +5V (Cont.)

COMMON-MODE REJECTION vs FREQUENCY

0.1 1 10 100
Frequency (kHz)

CMRR (dB)

100

90

80

70

60

50

VCM = 2Vp-p Sinewave Centered Around V

REF

At TA = +25°C, +VCC = +2.5V, V

WORST-CASE CHANNEL-TO-CHANNEL

0.5

0.4

0.3

Gain Match (LSBs)

0.2

0.1
–50 –25 0 25 50 75 100

GAIN MATCH vs TEMPERATURE

= +2.5V, f

REF

Temperature (°C)

SAMPLE

= 100kHz, and f

DCLK

= 24 • f

= 2.4MHz, unless otherwise noted.

SAMPLE

TYPICAL CHARACTERISTICS: +2.7V

At TA = +25°C, +VCC = +2.7V, V

= +1.25V, f

REF

= 100kHz, and f

SAMPLE

DCLK

= 24 • f

= 2.4MHz, unless otherwise noted.

SAMPLE

FREQUENCY SPECTRUM

(4096 Point FFT; f

0

–20

–40

–60

–80

Amplitude (dB)

–100

–120

–140

0 1020304050

Frequency (kHz)

SIGNAL-TO-NOISE RATIO AND

SIGNAL-TO-(NOISE + DISTORTION)

95

85

75

65

SNR and SINAD (dB)

55

ADS8345

SBAS177C

vs INPUT FREQUENCY

Frequency (kHz)

= 1.001kHz, –0.2dB)

IN

SNR

SINAD

101 100

Amplitude (dB)

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FREQUENCY SPECTRUM

(4096 Point FFT; f

0

–20

–40

–60

–80

–100

–120

–140

0 1020304050

SPURIOUS-FREE DYNAMIC RANGE

AND TOTAL HARMONIC DISTORTION

100

90

80

70

SFDR (dB)

60

NOTE: (1) First Nine Harmonics
of the Input Frequency

50

vs INPUT FREQUENCY

= 9.985kHz, –0.2dB)

IN

Frequency (kHz)

SFDR

(1)

THD

101 100

Frequency (kHz)

–100

–90

–80

–70

–60

–50

THD (dB)

7