DC979A - Demo Manual

DEMO MANUAL DC979A
LTC2442
24-Bit High Speed 4-Channel
DS ADC with Integrated Amplifier
Description
The LTC®2442 is a 2-/4-channel, high speed, 24-bit ΔΣ
ADC with ten selectable speed/resolution modes from
6.9Hz/200nVRMS to 3.5kHz/25μVRMS. Key DC specifications include 4ppm maximum INL, 5μV offset, 10ppm fullscale 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
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 LTC’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
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
Figure 1. DC979A Demonstration Board
DC979Af
1
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.
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 averaged for the DVM display.
4. Click the COLLECT button to start reading the input
voltage.
Figure 2. QuikEval Software
Hardware Setup
Jumpers
JP1, JP2: Select the source for REF + and REF –, respectively. 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.
2
JP6, JP7: Select the positive and negative supply voltages 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).
DC979Af
DEMO MANUAL DC979A
Hardware Setup
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 connecting 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.)
Experiments
INPUT NOISE
COMMON MODE REJECTION
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 –.
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.
Set the demo software to OSR32768 (6.8 samples per
second) and check the 2X box. Noise should be approximately 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.
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
3
DEMO MANUAL DC979A
Experiments
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.
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
CAP., X7R, 0.1µF, 16V, 20%, 0402
TDK, C1005X7R1C104M
DC979A Required Circuit Components
1
7
C1, C4, C11-C15
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
4
DC979Af
A
B
C
D
COM
CH3
CH2
CH1
CH0
REF-
REF+
C16
4.7UF,10V
0603
VCC
OFF
1
2
VCC
1
2
VCC
5
D2
BAT54S
D1
BAT54S
C9
4.7UF,10V
0603
R12
0
0805
D3
BAT54S
0805
C18
2.2UF,10V
6 CH0
7 CH1
18 -INB
17 OUTB
12 OUTA
13 -INA
10 ADCINB
11 ADCINA
28 COM
8 CH2
9 CH3
30 REF+
31 REF-
VCC
C2
4.7UF,10V
0603
VCC
C20
2.2UF,10V
0805
R11 OPT
0
0805
R8
0
0805
COM
CH3
CH2
CH1
CH0
REF-
REF+
EXT
JP2
REFEXT
GND
JP3
COM
EXT
GND
JP1
REF+
5V
1 VCC
VOUT 2
6 SHDN GND 5
3 C+
C- 4
U6
LTC1983ES6-5
C14
0.1UF
C12
0.1UF
C19
2.2UF,10V
0805
3
3
C10
0.01UF
C6
0.01UF
NC 8
NC 7
VOUT 6
TRIM 5
C5
4.7UF,10V
0603
JP5
AMP SUPPLY
ON
E7
E6
E5
E4
E3
E2
E1
3 NC
C1
0.1UF
4 GND
1 NC
2 VIN
4
MUXOUTA
V-
E15
+10V
E14
GND
E11
-5V
C15
0.1UF
+INB
R10
0
0805
MUXOUTB
+INB 19
+10V
-5V
10K
CS
+INA
R6
MISO
BUSY
SCK
+INA 25
MUXOUTB 26
MUXOUTA 27
INT-EXT/ 3
BUSY 2
FO 34
SDI 33
CS/ 35
SCK 1
SDO 36
R9
0
0805
C4
0.1UF
U1
LTC2442CG
V+
MOSI
R7
51
1
FO
OPT
JP8
C13
0.1UF
R13
10K
2 D
1 CP
VCC
3 I0
1 I1
2 GND
Z 4
VCC
Q 5
Q 3
U5
NL17SZ74US
S 6
VCC 5
3
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
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.
CUSTOMER NOTICE
FO
OPT
U4
NC7SZ157P6X
R1
2
DESIGNER: KIM T.
ENGINEER: MARK T.
APPROVED:
CHECKED:
DRAWN:
APPROVALS
CONTRACT NO.
GND
-5V
+10V
VCC
R2
4.99K
1%
-5V
+10V VCC
R4
4.99K
1%
J1
HD2X7-079-MOLEX
14 NC
11 EESCL
12 EEGND
10 EEVCC
9 EESDA
5 MISO
7 MOSI
6 CS
4 SCK
1 V+
2 5V
V-
V+
VCC
VIN
E13
V-
E12
GND
E10
V+
E9
GND
E8
VCC
E16
VIN
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
JP7
V-
JP6
V+
R3
4.99K
1%
0603
C7 VIN
4.7UF,10V
1
DATE:
A
SIZE
1
SHEET
DC979A-LTC2442CG
Monday, September 26, 2005
DWG NO.
1
OF 1
A
REV
4-CHANNEL, HIGH SPEED, 24-BIT ADC WITH BUFFER
TITLE:
C11
0.1UF
0603
C8
4.7UF,10V
VCC
TECHNOLOGY
SCHEMATIC
3 A2 SCL 6
4 VSS SDA 5
VCC 8
WP 7
U3
24LC025
1 A0
2 A1
JP4
TRIG. MODE
TRIG.
NORMAL
R5
100
2. INSTALL SHUNTS ON JP1-JP7 PIN 1 AND 2.
1. ALL RESISTORS ARE IN OHMS, 0402.
ALL CAPACITORS ARE IN MICROFARADS, 0402.
MOSI
OPT
J2
2
NOTES: UNLESS OTHERWISE SPECIFIED
MISO
SCK
CS
3
Figure 3. DC979A 4-Channel, High Speed, 24-Bit ADC with Buffer
C21
4.7UF,10V
0603
C17
4.7UF,10V
0603
V+
C3
0.01UF
VCC
GND
32
VIN
V24
VCC 29
GND
4
V+ 21
4
2
3
4
5
5
3
1
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
2
GND
4
GND
5
VCC 8
PR 7
CLR
6
GND
13
GND
8
GND
3
U2
LT1236ACS8-5
A
B
C
D
DEMO MANUAL DC979A
Schematic Diagram
DC979Af
5
DEMO MANUAL DC979A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) 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 LTC 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
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
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.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
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 LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
6
DC979Af
Linear Technology Corporation
LT 0613 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2013