DC979A - ANALOG DEVICES - Datasheet.Live

DC979Af

DEMO MANUAL DC979A

Description

LTC2442

24-Bit High Speed 4-Channel

ADC with Integrated Amplifier

The LT C

2442 is a 2-/4-channel, high speed, 24-bit ΔS

ADC with ten selectable speed/resolution modes from

6.9Hz/200nVRMS to 3.5kHz/25μVRMS. Key DC specifica-

tions include 4ppm maximum INL, 5μV offset, 10ppm full-

scale error and 20nV/°C offset drift. In the 6.9Hz/200nVRMS

mode, an input normal mode rejection of 50Hz and 60Hz

noise is better than 87dB. The accuracy (offset, full-scale,

linearity, drift) and power dissipation are independent of

the speed selected. The LTC2442 incorporates rail-to-rail

buffer amplifiers for true high impedance inputs.

DC979A is a member of Linear Technology’s QuikEval™

family of demonstration boards. It is designed to allow

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and

QuikEval and SoftSpan are a trademarks of Linear Technology Corporation. All other trademarks

are the property of their respective owners.

BoarD photo

easy evaluation of the LTC2442 and may be connected

directly to the target application’s analog signals while

using the DC590 USB serial controller board and supplied

software to measure performance. The exposed ground

planes allow proper grounding to prototype circuitry. After

evaluating with LT C ’s software, the digital signals can be

connected to the application’s processor/controller for

development of the serial interface.

Design files for this circuit board are available at

http://www.linear.com/demo

Figure 1. DC979A Demonstration Board

DC979Af

DEMO MANUAL DC979A

Quick start proceDure

1. Connect the DC979A to a DC590 USB serial controller

using the supplied 14-conductor ribbon cable.

2. Connect the DC590 to the host PC with a standard

USB A/B cable.

3. Run the QuikEval evaluation software supplied with the

DC590 or download it from www.linear.com/software.

The correct program will be loaded automatically.

4. Click the COLLECT button to start reading the input

voltage.

5. Click the slider at the bottom of the strip chart display

to change the oversample ratio (OSR) which will in

turn change the data output rate.

Tools are available for logging data, changing reference

voltage, changing the number of points in the strip chart

and histogram, and changing the number of points aver-

aged for the DVM display.

harDware setup

JUMPERS

JP1, JP2: Select the source for REF+ and REF–, respect-

ively. REF+ can be 5.00V from the onboard LT

1236

reference (default) or supplied externally. REF– can be

ground (0V, default) or supplied externally.

JP3: Select source for analog COM input, either tied to

ground or supplied externally to the COM turret post.

JP6, JP7: Select the positive and negative supply volt-

ages for the onboard amplifier. Supplies can be VCC and

GND or +10 and –5V from the onboard LTC1983 charge

pump. To use an external power supply, REMOVE JP6

and JP7 and connect the external supply to the V+, GND,

and V– turrets.

JP4: Trigger mode, either normal (default) or externally

triggered (TRIG).

Figure 2. QuikEval Software

DC979Af

DEMO MANUAL DC979A

harDware setup

experiments

JP5: Enable/disable the LTC1983 charge pump power

supply for onboard amplifier. See JP6, JP7 description.

JP8: Trigger Input Signal. Pin 1 is a 5V logic input, Pin 2 is

ground. When triggered mode is selected on JP4, a rising

edge starts a new conversion. Note that since a conversion

cannot be terminated once started, this signal can only be

used to slow down the conversion rate.

CONNECTION TO DC590 SERIAL CONTROLLER

J1 is the power and digital interface connector. Connect to

the DC590 serial controller with the supplied 14-conductor

ribbon cable.

ANALOG CONNECTIONS

Analog signal connections are made via the row of turret

posts along the edge of the board. Also, if you are connect-

ing the board to an existing circuit, the exposed ground

planes along the edges of the board may be used to form

a solid connection between grounds.

GND: Ground turrets are connected directly to the internal

analog ground plane.

VCC: This is the supply for the ADC. Do not draw any power

from this point. External power may be applied to this

point after disabling the switching supply on the DC590.

If the DC590 serial controller is being used, the voltage

must be regulated 5V only, as the isolation circuitry will

also be powered from this supply. See the DC590 Quick

Start guide for details.

REF+, REF–: These turrets are connected to the LTC2442

REF+ and REF– pins. If the onboard reference is being

used, the reference voltage may be monitored from this

point. An external reference may be connected to these

terminals if JP1 and JP2 are configured for external

reference.

Note: The REF+ and REF– terminals are decoupled to

ground with 0.01μF and 4.7μF capacitors in parallel. Thus,

any source connected to these terminals must be able to

drive a capacitive load and have very low impedance at

DC. Examples are series references that require an output

capacitor and C-load stable op amps, such as the LT1219

and LT1368/

CH0-CH3: These are the differential inputs to the LTC2442.

They may be configured either as single-ended inputs

with respect to the COM pin, or adjacent pairs may be

configured as differential inputs (CH0-CH1, CH2-CH3.)

INPUT NOISE

Solder a short wire from CH0 to CH1. Ensure that the

buffer amplifiers are in their active region of operation by

either biasing the inputs to mid-supply with a 10kΩ to

10kΩ divider when the buffer amplifier is powered from

VCC and ground, or tie the inputs to ground and select

+10 and –5V for V+ and V –.

Set the demo software to OSR32768 (6.8 samples per

second) and check the 2X box. Noise should be approxi-

mately 0.04ppm of VREF (200nV.) Next, select different

oversample ratios. Measured noise for each oversample

ratio should be close to the values given in the LTC2442

data sheet.

COMMON MODE REJECTION

Tie the two inputs (still connected together from the previ

ous experiment) to ground through a short wire and

note the indicated voltage. Tie the inputs to REF+; the

difference should be less than 5μV due to the 120dB

CMRR of the LTC2442.

Select +10 and –5V for V+ and V – for this experiment. If

the common mode voltage is limited to GND + 0.25V to

VCC – 0.25V, this test may be performed with the amplifier

supplies set to ground and VCC.

DC979Af

DEMO MANUAL DC979A

parts List

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

DC979A Required Circuit Components

1 7 C1, C4, C11-C15 CAP., X7R, 0.1µF, 16V, 20%, 0402 TDK, C1005X7R1C104M

2 8 C2, C5, C7, C8, C9, C16, C17, C21 CAP., X5R, 4.7µF, 10V, 20%, 0603 TDK, C1608X5R0J475M

3 3 C3, C6, C10 CAP., X7R, 0.01µF, 25V, 10%, 0402 AVX, 04023C103KAT1A

4 3 C18, C19, C20 CAP., X5R, 2.2µF, 10V, 20%, 0805 TDK, C2012X5R1A225M

5 3 D1, D2, D3 DIODE, SCHOTTKY, SOT23 DIODE INC., BAT54S

6 16 E1-E16 TESTPOINT, TURRET, 0.064" MILL-MAX, 2308-2

7 7 JP1-JP7 JMP, 3-PIN, 1 ROW, 0.079" SAMTEC, TMM-103-02-L-S

8 7 FOR JP1-JP7, PIN 1 AND PIN 2 SHUNT, 0.079" CENTER SAMTEC, 2SN-BK-G

9 0 JP8 JMP, 2-PIN, 1 ROW, 0.100" COMM CON., 3801S-02G2

10 1 J1 HEADER, 2×7 PIN, 0.079" MOLEX, 87831-1420

11 0 J2 CONN, 5-PIN, GOLD, STRAIGHT CONNEX, 132134

12 0 R1 RES., 0402 OPT

13 3 R2, R3, R4 RES., CHIP, 4.99k, 1/16W, 1%, 0402 AAC, CR05-4991FM

14 1 R5 RES., CHIP, 100, 1/16W, 5%, 0402 VISHAY, CRCW0402101J

15 2 R6, R13 RES., CHIP, 10k, 1/16W, 5%, 0402 AAC, CR05-103JM

16 1 R7 RES., CHIP, 51, 1/16W, 5%, 0402 AAC, CR05-510JM

17 4 R8, R9, R10, R12 RES., CHIP, 0, 1/16W, 5%, 0805 AAC, CJ10-000M

18 0 R11 RES., CHIP, 0, 1/16W, 5%, 0805 OPT

19 1 U1 I.C., LTC2442CG, SSOP36G LINEAR TECHNOLOGY, LTC2442CG

20 1 U2 I.C., LT1236ACS8-5, SO8 LINEAR TECHNOLOGY, LT1236ACS8-5

21 1 U3 I.C., 24LC025, TSSOP8 MICROCHIP, 24LC025-I/ST

22 1 U4 IC, NON-INVERTING MULTIPLEXER, SC70 FAIRCHILD, NC7SZ157P6X

23 1 U5 IC, SINGLE D, FLIP-FLOP, US8 ON SEMI., NL17SZ74US

24 1 U6 I.C., LTC1983ES6-5, SOT23-6 LINEAR TECHNOLOGY, LTC1983ES6-5

INPUT NORMAL MODE REJECTION

The LTC2442’s SINC4 digital filter is trimmed to strongly

reject both 50Hz and 60Hz line noise when operated with

the internal conversion clock and oversample ratio 32768

(6.8 samples per second.) To measure input normal

mode rejection, connect COM to a 2.5V source such as

an LT1790-2.5 reference or a power supply. Connect any

other input (CH0-CH3) to the same supply through a 10k

resistor. Apply a 10Hz, 2V peak-to-peak sine wave to the

input through a 1µF capacitor.

Select OSR32768 (6.8 samples per second) and 2X mode

in the demo software and start taking data. The input noise

will be quite large, and the graph of output vs time should

show large variations.

Next, slowly increase the frequency to 55Hz. The noise

should be almost undetectable in the graph.

Change the OSR to 16384 (13.75 samples per second) the

noise will increase substantially, as the first notch at this

OSR is at 110Hz. Increase the signal generator frequency

to 110Hz, the noise will drop again.

experiments

DC979Af

DEMO MANUAL DC979A

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Figure 3. DC979A 4-Channel, High Speed, 24-Bit ADC with Buffer

schematic Diagram

D D

C C

B B

A A

1. ALL RESISTORS ARE IN OHMS, 0402.

ALL CAPACITORS ARE IN MICROFARADS, 0402.

NOTES: UNLESS OTHERWISE SPECIFIED

2. INSTALL SHUNTS ON JP1-JP7 PIN 1 AND 2.

DC979A-LTC2442CG

Monday, September 26, 2005 1 1

4-CHANNEL, HIGH SPEED, 24-BIT ADC WITH BUFFER

KIM T.

MARK T.

SCHEMATIC

SIZE

DATE:

DWG NO. REV

SHEET OF

TITLE:

CONTRACT NO.

APPROVALS

DRAWN:

CHECKED:

APPROVED:

ENGINEER:

DESIGNER:

TECHNOLOGY

Fax: (408)434-0507

Milpitas, CA 95035

Phone: (408)432-1900

1630 McCarthy Blvd.

LTC Confidential-For Customer Use Only

CUSTOMER NOTICE

LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A

CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;

HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO

VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL

APPLICATION. COMPONENT SUBSTITUTION AND PRINTED

CIRUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT

PERFORMANCE OR RELIABILITY. CONTACT LINEAR

TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.

THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND

SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.

CSREF+

MOSI

CH0

SCK

CH2

COM

CH1

CH3

MISO

REF-

VCC V+ VIN

VCC

V+

V-

VCC

-5V

VCC

-5V

V-

VCC

VIN

+10V

VCC VCC V+

VIN

C10

0.01UF

C15

0.1UF

JP6

V+

+10V

VCC

4.7UF,10V

0603

R10

0805

CH0

E14

GND

NC7SZ157P6X

VCC

GND

C14

0.1UF

JP3

COM

GND

EXT

JP1

REF+

EXT

R11

0805

OPT

0.01UF

4.99K

HD2X7-079-MOLEX

MOSI

EESDA

V+

SCK

EEVCC

MISO

EESCL

EEGND

GND

E11

-5V

MUXOUTA

4.7UF,10V

0603

JP8

OPT

LTC2442CG

1918

CH0

CH1

CH2

BUSY

INT-EXT/

GND

V+

V-

+INA

MUXOUTB

MUXOUTA

COM

SCK

CH3

ADCINB

ADCINA

OUTA

-INA

+INB-INB

OUTB

SDO

CS/

SDI

GND

REF-

REF+

VCC

C12

0.1UF

C16

4.7UF,10V

0603 JP7

V-

-5V

GND

0.1UF

100

LTC1983ES6-5

1 2

C-

GND

VCC VOUT

C+

SHDN

NL17SZ74US

6 7

CLR PR

VCCGND

R12

0805

C18

2.2UF,10V

0805

MUXOUTB

0805

JP4

TRIG. MODE

TRIG.

NORMAL

BAT54S

1 3

MISO

VCC

MOSI

4.99K

CH1

REF-

R6 10K

LT1236ACS8-5

4 5

VIN

GND TRIM

VOUT

C11

0.1UF

24LC025

SDA

VCCA0

VSS

SCL

C17

4.7UF,10V

0603

C20

2.2UF,10V

0805

JP5

OFF

AMP SUPPLY

+INA

CH2

BUSY

4.7UF,10V

0603

BAT54S

1 3

E10

V+

4.7UF,10V

0603

BAT54S

1 3

0.1UF

4.99K

R13

10K

4.7UF,10V

0603

C13

0.1UF

CH3

C21

4.7UF,10V

0603

0805

E13

V-

+INB

REF+

GND

E12

GND

COM

C19

2.2UF,10V

0805

R1 OPT

0.01UF

OPT

E15

+10V

JP2

REF-

GND

EXT

SCK

E16

VIN

DC979Af

DEMO MANUAL DC979A

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

 LINEAR TECHNOLOGY CORPORATION 2013

LT 0613 • PRINTED IN USA

DEMONSTRATION BOARD IMPORTANT NOTICE

Linear Technology Corporation (LT C ) provides the enclosed product(s) under the following AS IS conditions:

This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT

OR EVALUATION PURPOSES ONLY and is not provided by LT C for commercial use. As such, the DEMO BOARD herein may not be complete

in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety

measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union

directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.

If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date

of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU

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arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all

appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or

agency certified (FCC, UL, CE, etc.).

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observe good laboratory practice standards. Common sense is encouraged.

This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LT C applica-

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Milpitas, CA 95035