Burr Brown Corporation ADS7825UB-1K, ADS7825UB, ADS7825U-1K, ADS7825U, ADS7825PB Datasheet

1

®

ADS7825

CDAC

6kΩ

Internal

+2.5V Ref

Clock

BUSY

DATACLK

SDATA



D7-D0

BYTE

R/C
CS

PWRD

Successive Approximation Register

and Control Logic

Serial

Data

Out

or

Parallel

Data

Out

Comparator

Buffer

Continuous Conversion

Channel

REF

CAP

A0CONTC A1

40kΩ

AIN

2

40kΩ

AIN

1

40kΩ

AIN

0

40kΩ

AIN

3

20kΩ 8kΩ

20kΩ 8kΩ

20kΩ 8kΩ

20kΩ 8kΩ

8

®

4 Channel, 16-Bit Sampling CMOS A/D Converter

FEATURES

● 25µs max SAMPLING AND CONVERSION

● SINGLE +5V SUPPLY OPERATION

● PIN-COMPATIBLE WITH 12-BIT ADS7824

● PARALLEL AND SERIAL DATA OUTPUT

● 28-PIN 0.3" PLASTIC DIP AND SOIC

●

±2.0 LSB max INL

● 50mW max POWER DISSIPATION

● 50µW POWER DOWN MODE

●

±10V INPUT RANGE, FOUR CHANNEL

MULTIPLEXER

● CONTINUOUS CONVERSION MODE

ADS7825

DESCRIPTION

The ADS7825 can acquire and convert 16 bits to
within ±2.0 LSB in 25µs max while consuming only
50mW max. Laser-trimmed scaling resistors provide
the standard industrial ±10V input range and channel­to-channel matching of ±0.1%. The ADS7825 is a
low-power 16-bit sampling A/D with a four channel
input multiplexer, S/H, clock, reference, and a
parallel/serial microprocessor interface. It can be con­figured in a continuous conversion mode to sequen­tially digitize all four channels. The 28-pin ADS7825
is available in a plastic 0.3" DIP and in a SOIC, both
fully specified for operation over the industrial –40°C
to +85°C range.

ADS7825

ADS7825

International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: [phone] • Twx: 910-952-1111

Internet: http://www.burr-brown.com/ • FAXLine: [phone] (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: [phone] • Immediate Product Info: [phone]

www.burr-brown.com/databook/ADS7825.html

©

1996 Burr-Brown Corporation PDS-1304B Printed in U.S.A. October, 1997

2

®

ADS7825

SPECIFICATIONS

ELECTRICAL

At TA = –40°C to +85°C, fS = 40kHz, VS1 = VS2 = V

S =

+5V ±5%, using external reference, CONTC = 0V, unless otherwise specified.

ADS7825P, U ADS7825PB, UB

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

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.

RESOLUTION 16 ✻

(1)

Bits

ANALOG INPUT

Voltage Range ±10V ✻ V
Impedance Channel On or Off 45.7 ✻ kΩ
Capacitance 35 ✻ pF

THROUGHPUT SPEED

Conversion Time 20 ✻ µs
Acquisition Time 5 ✻ µs
Multiplexer Settling Time Includes Acquisition 5 ✻ µs
Complete Cycle (Acquire and Convert) 25 ✻ µs
Complete Cycle (Acquire and Convert) CONTC = +5V 40 ✻ µs
Throughput Rate 40 ✻ kHz

DC ACCURACY

Integral Linearity Error ±3 ±2 LSB

(2)

No Missing Codes 15 16
Transition Noise

(3)

0.8 ✻ LSB

Full Scale Error

(4)

Internal Reference ±0.5 ±0.25 %
Full Scale Error Drift Internal Reference ±7 ±5 ppm/°C
Full Scale Error

(4)

±0.5 ±0.25 %
Full Scale Error Drift ±2 ✻ ppm/°C
Bipolar Zero Error ±10 ✻ mV
Bipolar Zero Error Drift ±2 ✻ ppm/°C
Channel-to-Channel Mismatch ±0.1 ±0.1 %
Power Supply Sensitivity +4.75 < V

S

< +5.25 ±8 ✻ LSB

AC ACCURACY

Spurious-Free Dynamic Range

(5)

f

IN

= 1kHz 90 ✻ dB

Total Harmonic Distortion f

IN

= 1kHz –90 ✻ dB

Signal-to-(Noise+Distortion) f

IN

= 1kHz 83 86 dB

Signal-to-Noise f

IN

= 1kHz 83 86 dB

Channel Separation

(6)

f

IN

= 1kHz 100 120 ✻✻ dB
–3dB Bandwidth 2 ✻ MHz
Useable Bandwidth

(7)

90 ✻ kHz

SAMPLING DYNAMICS

Aperture Delay 40 ✻ ns
Transient Response

(8)

FS Step 5 ✻ µs

Overvoltage Recovery

(9)

1 ✻ µs

REFERENCE

Internal Reference Voltage 2.48 2.5 2.52 ✻✻ ✻ V
Internal Reference Source Current 1 ✻ µA

(Must use external buffer)

External Reference Voltage Range 2.3 2.5 2.7 ✻✻✻ V

for Specified Linearity

External Reference Current Drain V

REF

= +2.5V 100 ✻ µA

DIGITAL INPUTS

Logic Levels

V

IL

–0.3 +0.8 ✻✻V

V

IH

+2.4 VS +0.3V ✻✻V

I

IL

±10 ✻ µA

I

IH

±10 ✻ µA

DIGITAL OUTPUTS

Data Format Parallel in two bytes; Serial ✻
Data Coding Binary Two's Complement ✻

V

OL

I

SINK

= 1.6mA +0.4 ✻ V

V

OH

I

SOURCE

= 500µA+4 ✻ V

Leakage Current High-Z State, V

OUT

= 0V to V

S

±5 ✻ µA

Output Capacitance High-Z State 15 ✻ pF

3

®

ADS7825

VS1
V

S2


PWRD
CONTC
BUSY
CS
R/C
BYTE
PAR/SER
A0
A1
D0
D1
D2

AGND1

AIN

0



AIN

1



AIN

2



AIN

3


CAP
REF

AGND2

D7
D6
D5
D4
D3

DGND

1
2
3
4
5
6
7
8

9
10
11
12
13
14

28
27
26
25
24
23
22
21
20
19
18
17
16
15

ADS7825




TRI-STATE
TRI-STATE
TRI-STATE

EXT/INT

SYNC

TAG
SDATA
DATACLK

DIGITAL TIMING

Bus Access Time PAR/SER = +5V 83 ✻ ns
Bus Relinquish Time PAR/SER = +5V 83 ✻ ns
Data Clock PAR/SER = 0V

Internal Clock (Output only when EXT/INT LOW 0.5 1.5 ✻✻MHz

transmitting data)

External Clock EXT/INT HIGH 0.1 10 ✻✻MHz

POWER SUPPLIES

V

S1

= VS2 = V

S

+4.75 +5 +5.25 ✻✻✻ V

Power Dissipation f

S

= 40kHz 50 ✻ mW

PWRD HIGH 50 ✻ µW

TEMPERATURE RANGE

Specified Performance –40 +85 ✻✻ °C
Storage –65 +150 ✻✻ °C
Thermal Resistance (

θ

JA

)
Plastic DIP 75 ✻ °C/W
SOIC 75 ✻ °C/W

NOTES: (1) An asterik (✻) specifies same value as grade to the left. (2) LSB means Least Significant Bit. For the 16-bit, ±10V input ADS7825, one LSB is 305µV. (3)
Typical rms noise at worst case transitions and temperatures. (4) Full scale error is the worst case of –Full Scale or +Full Scale untrimmed deviation from ideal first and
last code transitions, divided by the transition voltage (not divided by the full-scale range) and includes the effect of offset error. (5) All specifications in dB are referred
to a full-scale ±10V input. (6) A full scale sinewave input on one channel will be attenuated by this amount on the other channels. (7) Useable Bandwidth defined as
Full-Scale input frequency at which Signal-to-(Noise+Distortion) degrades to 60dB, or 10 bits of accuracy. (8) The ADS7825 will accurately acquire any input step if given
a full acquisition period after the step. (9) Recovers to specified performance after 2 x FS input overvoltage, and normal acquisitions can begin.

SPECIFICATIONS (CONT)

ELECTRICAL

At TA = –40°C to +85°C, fS = 40kHz, VS1 = VS2 = V

S =

+5V ±5%, using external reference, CONTC = 0V, unless otherwise specified.

ADS7825P, U ADS7825PB, UB

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

ELECTROSTATIC
DISCHARGE SENSITIVITY

This integrated circuit can be damaged by ESD. Burr-Brown
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 MINIMUM SIGNAL­DRAWING TEMPERATURE MAXIMUM INTEGRAL TO-(NOISE + DISTORTION)

PRODUCT PACKAGE NUMBER

(1)

RANGE LINEARITY ERROR (LSB) RATIO (dB)

ADS7825P Plastic Dip 246 –40°C to +85°C ±383
ADS7825PB Plastic Dip 246 –40°C to +85°C ±286
ADS7825U SOIC 217 –40°C to +85°C ±383
ADS7825UB SOIC 217 –40°C to +85 °C ±286

NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book.

PACKAGE/ORDERING INFORMATION

ABSOLUTE MAXIMUM RATINGS

TOP VIEW DIP/SOIC

PIN CONFIGURATION

Analog Inputs: AIN0, AIN1, AIN2, AIN3..............................................±15V

REF ................................... (AGND2 –0.3V) to (V

S

+ 0.3V)

CAP ........................................Indefinite Short to AGND2,

Momentary Short to V

S

VS1 and VS2 to AGND2........................................................................... 7V

V

S1

to VS2.......................................................................................... ±0.3V

Difference between AGND1, AGND2 and DGND............................. ±0.3V

Digital Inputs and Outputs.......................................... –0.3V to (V

S

+ 0.3V)

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

Internal Power Dissipation .............................................................825mW

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

Maximum Input Current to Any Pin ................................................. 100mA

4

®

ADS7825

PIN # NAME I/O DESCRIPTION

PIN ASSIGNMENTS

1 AGND1 Analog Ground. Used internally as ground reference point.
2 AIN

0

Analog Input Channel 0. Full-scale input range is ±10V.

3 AIN

1

Analog Input Channel 1. Full-scale input range is ±10V.

4 AIN

2

Analog Input Channel 2. Full-scale input range is ±10V.

5 AIN

3

Analog Input Channel 3. Full-scale input range is ±10V.
6 CAP Internal Reference Output Buffer. 2.2µF Tantalum to ground.
7 REF Reference Input/Output. Outputs +2.5V nominal. If used externally, must be buffered to maintain ADS7825 accuracy.

Can also be driven by external system reference. In both cases, bypass to ground with a 2.2µF Tantalum capacitor.
8 AGND2 Analog Ground.
9 D7 O Parallel Data Bit 7 if PAR/SER HIGH; Tri-state if PAR/SER LOW. See Table I.

10 D6 O Parallel Data Bit 6 if PAR/SER HIGH; Tri-state if PAR/SER LOW. See Table I.
11 D5 O Parallel Data Bit 5 if PAR/SER HIGH; Tri-state if PAR/SER LOW. See Table I.
12 D4 I/O Parallel Data Bit 4 if PAR/SER HIGH; if PAR/SER LOW, a LOW level input here will transmit serial data on SDATA from

the previous conversion using the internal serial clock; a HIGH input here will transmit serial data using an external serial

clock input on DATACLK (D2). See Table I.

13 D3 O Parallel Data Bit 3 if PAR/SER HIGH; SYNC output if PAR/SER LOW. See Table I.
14 DGND Digital Ground.
15 D2 I/O Parallel Data Bit 2 if PAR/SER HIGH; if PAR/SER LOW, this will output the internal serial clock if EXT/INT (D4) is LOW;

will be an input for an external serial clock if EXT/INT (D4) is HIGH. See Table I.

16 D1 O Parallel Data Bit 1 if PAR/SER HIGH; SDATA serial data output if PAR/SER LOW. See Table I.
17 D0 I/O Parallel Data Bit 0 if PAR/SER HIGH; TAG data input if PAR/SER LOW. See Table I.
18 A1 I/O Channel Address. Input if CONTC LOW, output if CONTC HIGH. See Table I.
19 A0 I/O Channel Address. Input if CONTC LOW, output if CONTC HIGH. See Table I.
20 PAR/SER I Select Parallel or Serial Output. If HIGH, parallel data will be output on D0 thru D7. If LOW, serial data will be output on

SDATA. See Table I and Figure 1.

21 BYTE I Byte Select. Only used with parallel data, when PAR/SER HIGH. Determines which byte is available on D0 thru D7.

Changing BYTE with CS LOW and R/C HIGH will cause the data bus to change accordingly. LOW selects the 8 MSBs;

HIGH selects the 8 LSBs. See Figures 2 and 3

22 R/C I Read/Convert Input. With CS LOW, a falling edge on R/C puts the internal sample/hold into the hold state and starts a

conversion. With CS LOW, a rising edge on R/C enables the output data bits if PAR/SER HIGH, or starts transmission

of serial data if PAR/SER LOW and EXT/INT HIGH.

23 CS I Chip Select. Internally OR'd with R/C. With CONTC LOW and R/C LOW, a falling edge on CS will initiate a conversion.

With R/C HIGH, a falling edge on CS will enable the output data bits if PAR/SER HIGH, or starts transmission of serial

data if PAR/SER LOW and EXT/INT HIGH.

24 BUSY O Busy Output. Falls when conversion is started; remains LOW until the conversion is completed and the data is latched

into the output register. In parallel output mode, output data will be valid when BUSY rises, so that the rising edge

can be used to latch the data.

25 CONTC I Continuous Conversion Input. If LOW, conversions will occur normally when initiated using CS and R/C; if HIGH,

acquisition and conversions will take place continually, cycling through all four input channels, as long as CS, R/C and

PWRD are LOW. See Table I. For serial mode only.

26 PWRD I Power Down Input. If HIGH, conversions are inhibited and power consumption is significantly reduced. Results from the

previous conversion are maintained in the output register. In the continuous conversion mode, the multiplexer address

channel is reset to channel 0.

27 V

S2

Supply Input. Nominally +5V. Connect directly to pin 28. Decouple to ground with 0.1µF ceramic and 10µF Tantalum

capacitors.

28 V

S1

Supply Input. Nominally +5V. Connect directly to pin 27.

5

®

ADS7825

TYPICAL PERFORMANCE CURVES

At TA = +25°C, fS = 40kHz, VS1 = VS2 = +5V, using internal reference, unless otherwise noted.

FREQUENCY SPECTRUM

(8192 Point FFT; f

IN

= 1.02kHz, –0.5dB)

0
–10
–20
–30
–40
–50
–60
–70
–80
–90

–100
–110
–120
–130

0 5 10 15 20

Amplitude (dB)

Frequency (kHz)

–60.0
–70.0
–80.0

–90.0
–100.0
–110.0
–120.0
–130.0
–140.0

CROSSTALK vs INPUT FREQUENCY

(Active Channel Amplitude = –0.1dB)

100 1k

Active Channel Input Frequency (Hz)

Resulting Amplitude on Selected Channel (dB)



(Input Grounded)

10k 100k

Adjacent Channels, Worst Pair

Non-Adjacent Channels

Adjacent Channels

Measurement Limit

ADJACENT CHANNEL CROSSTALK, WORST PAIR

(8192 Point FFT; AIN

3

= 1.02kHz, –0.1dB; AIN2 = AGND)

0
–10
–20
–30
–40
–50
–60
–70
–80
–90

–100
–110
–120
–130

0 5 10 15 20

Amplitude (dB)

Frequency (kHz)

ADJACENT CHANNEL CROSSTALK, WORST PAIR

(8192 Point FFT; AIN

3

= 10.1kHz, –0.1dB; AIN2 = AGND )

0
–10
–20
–30
–40
–50
–60
–70
–80
–90

–100
–110
–120
–130

0 5 10 15 20

Amplitude (dB)

Frequency (kHz)

100

90

80

70

60

50

40

30

100

Input Signal Frequency (Hz)

SINAD (dB)

SIGNAL-TO-(NOISE + DISTORTION)

vs INPUT FREQUENCY (f

IN

= –0.1dB)

1k 10k 100k

100

90
80
70
60
50
40
30
20
10

0

Input Signal Frequency (kHz)

SINAD (dB)

SIGNAL-TO-(NOISE + DISTORTION)

vs INPUT FREQUENCY AND INPUT AMPLITUDE

2 4 6 8 10 12 14 16 18 20

0dB

–20dB

–60dB