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DEMO MANUAL DC1792A
Description
LTC2756
Serial 18-Bit SoftSpan IOUT DAC
Demonstration circuit 1792A features the LTC2756 18-bit
SoftSpan™, IOUT DAC. The digital interface is a simple,
4-wire Serial Peripheral Interface (SPI) interface, aug-
mented with separate CLEAR and LDAC pins that reset
the output to zero and load the DAC code, respectively.
This device features six output ranges: 0V to 5V, 0V to
10V, ±5V, ±10V, ±2.5V, and –2.5V to 7.5V. These ranges
are programmable through the SPI interface or through L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks
and SoftSpan and QuikEval are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
BoarD photo
separate span control pins if SoftSpan operation is not
needed. Voltage input offset and gain adjustment pins
facilitate trimming of residual DC errors without impacting
the excellent temperature stability of this device.
Design files for this circuit board are available at
http://www.linear.com/demo
DAC
OUTPUT
ANALOG POWER SUPPLY
(NORMALLY ±15V)
RIBBON CABLE TO
DC590 CONTROLLER
Connect a low noise ±15V power supply to the AMPV+
and AMPV– turret posts at the left side of the DC1792A
board. Connect J1 to a DC590 USB serial controller us-
ing the supplied 14-conductor ribbon cable. Connect
DC590 to a host PC with a standard USB A/B cable.
Run the evaluation software supplied with the DC590,
or download it from www.linear.com/software. The cor-
rect control panel will be loaded automatically, shown in
Quick start proceDure
Figure 2. The software automatically sets the LTC2756
outputs according to the entries in the control panel. A
square wave option is available to test settling time. MSPAN
jumper should be set to 0 if software span control is desired.
Setting MSPAN high (1) causes the S2, S1, S0 pins to set
the span according to the table printed on the board, and
the corresponding span should be selected in software to
ensure that the calculated DAC code is correct.
Figure 1. Connection Diagram
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DEMO MANUAL DC1792A
Quick start proceDure
Figure 2. Software Screenshot
VCC: Select source for 5V VCC supply. Set to 5V for sup-
ply by onboard LTC6655 reference (recommended). Set
to REG to be supplied by regulated supply from DC590
Controller and remove the jumper to supply externally.
VREF: Select source for reference. Set to 5V to use onboard
LTC6655 reference or select EXT to drive externally through
the VREF jumper.
CLR: Asynchronous Clear Input. Tie to 0 to set all DAC
outputs to 0V.
LDAC: Asynchronous DAC Load Input. Tie to 0 to update
all DACS if _CS is high.
RFLAG: Reset Flag Output. Remove jumper and probe
middle pin for RFLAG status.
Analog Connections (Turret Posts)
VOUT: DAC Voltage Output.
VREF: DAC Reference Voltage. If the onboard LTC6655
reference is selected, the voltage may be measured at these
points. If a remote reference is selected, then an external
reference must be applied to these points.
VOSADJ: DAC offset adjust input, use only if VOSA jumper
set to EXT. Nominal input range is ±5V, which will provide
±2048LSB of offset adjustment.
GEADJ: Gain Adjust Pin. This voltage control pin can be
used to null gain error or to compensate for reference
errors. The gain error change expressed in LSB is the
same for any output range. Nominal range is ±5V, which
will provide ±2048LSB of gain adjustment.
Power and Ground Connections
Analog Power: AMPV+, AMPV–, and GND turret posts
are the analog supplies for the onboard DAC amplifiers.
These should be connected to a well regulated, low noise
±15V power supply.
VCC: Connection to VCC. See schematic and description
for VCC jumper.
Grounding: Separate power and signal grounds are pro-
vided. Signal GND is the turret closest to VOUT, use this
for measurement ground and output return. Power GND
is between AMPV+ and AMPV– turrets.
Additional software documentation may be available from
the Help menu item, as features may be added periodically.
HARDWARE SET-UP
Jumpers
MSPAN: Manual Span Control Pin. MSPAN is used to
configure the LTC2756 for operation in a single, fixed
output range. If MSPAN is 1 (high) it will be configured
for single span use. If MSPAN is low it will be set through
the QuikEval
™
Software. Default position is 0 (low).
S0, S1, S2: Used to set the fixed output range if MSPAN
is 1 (high).
Table 1. MSPAN Configuration
S2 S1 S0 SPAN
0 0 0 0V to 5V
0 0 1 0V to 10V
0 1 0 ±5V
0 1 1 ±10V
1 0 0 ±2.5V
1 0 1 –2.5V to 7.5V
GEADJ: Gain Adjust Pin. If no adjustments are required,
select GND. Selecting EXT. connects the pin to the turret
allowing external adjustment to null gain error or com-
pensate for reference errors.
VOSADJ: Offset Adjustment Selection for DAC. If no
offset adjustment is required, select GND. Selecting EXT
connects the offset pin to the turret allowing external
adjustment of offset.
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DEMO MANUAL DC1792A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 11 C1, C2, C3, C5, C6, C11, C13, C15,
C18, C19, C20
CAP., X7R, 10µF, 10V, 20% 1206 TDK, C3216X5R1A106M
2 5 C4, C36, C37, C40, C41 CAP., X7R, 0.1µF, 10V, 10% 0603 AVX, 0603ZC104KAT2A
3 3 C7, C10, C21 CAP., X7R, 0.01µF, 10V, 10% 0603 AVX, 0603ZC103KAT2A
4 0 C34(OPT.) CAP., 0603
5 1 C31 CAP., C0G, 100pF, 10V, 10% 0603 AVX, 06033A101KAT2A
6 0 C29, C35(OPT.) CAP., 1206
7 1 C30 CAP., C0G, 100pF, 10V, 10% 1206 AVX, 1206ZC101KAT
8 2 C32, C33 CAP., X7R, 1µF, 10V, 10% 1206 AVX, 1206ZC105KAT2A
9 3 D1, D2, D3 DIODE, BAT54C, SOT23 DIODE/ZETEX, BAT54CTA
10 1 J1 CONNECTOR, HD2X7-079 MOLEX, 87831-1420
11 11 JP1–JP11 3-PIN 0.079 SINGLE ROW HEADER SAMTEC, TMM103-02-L-S
12 14 XJP1–XJP11 SHUNT, .079" CENTER SAMTEC, 2SN-BK-G
13 1 JP12 0.1" JUMPER SHUNT, SOLDER DOWN SAMTEC, JL-100-25-T
14 1 R1 RES., CHIP, 88.7k, 1/16W, 1% 0603 VISHAY, CRCW060388K7KFEA
15 1 R2 RES., CHIP, 10.0k, 1/16W, 1% 0603 NIC, NRC06F1002TRF
16 3 R3, R4, R5 RES., CHIP, 4.99k, 1/16W, 1% 0603 NIC, NRC06F4991TRF
17 3 R22, R25, R30 RES., CHIP, 1k, 1/16W, 5% 0603 VISHAY, CRCW06031K00JNEA
18 9 R11–R17, R23, R24 RES., CHIP, 10k, 1/16W, 5% 0603 NIC, NRC06J1002TRF
19 0 R26, R29, R31–R34(OPT.) RES., CHIP, 0603
20 1 R27 RES., CHIP, 4.02k, 1/16W, 1% 0603 VISHAY, CRCW06034K02KFEA
21 1 R28 RES., CHIP, 10, 1/16W, 5% 0603 VISHAY, CRCW060310R0JNEA
22 11 E1–E11 Turret, Testpoint MILL-MAX, 2308-2-00-44
23 1 U1 IC., LTC2756ACG, SSOP28 LINEAR, LTC2756ACG#TRPBF
24 1 U2 IC., LTC6655CHMS8-5, MSOP-8 LINEAR, LTC6655CHMS8-5#TRPBF
25 0 U3(OPT) IC., SO-8
26 1 U4 IC., 24LC025, TSSOP-8 MICROCHIP, 24LC025 I /ST
27 1 U5 IC., LT1761ES5-5, SOT23-5 LINEAR, LT1761ES5-5#TRPBF
28 1 U6 IC., LT1964ES5-5, SOT23-5 LINEAR, LT1964ES5-5#TRPBF
29 1 U7 IC., LT1012ACS8, SO-8 LINEAR, LT1012ACS8#TRPBF
30 1 U9 IC., LT1360CS8, SO-8 LINEAR, LT1360CS8#TRPBF
31 1 U8 IC., LTC2054CS5, TSOT23-5 LINEAR, LTC2054CS5#TRPBF
32 1 U10 IC., LT1761ES5-BYP, SOT23-5 LINEAR, LT1761ES5-BYP#TRPBF
33 1 U11 IC., LTC6244CDD, 8-PIN 3 × 3, DD LINEAR, LTC6244CDD#TRPBF
34 4 MH1–MH4 STAND-OFF, NYLON 0.25" KEYSTONE, 8831(SNAP ON)
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DEMO MANUAL DC1792A
schematic Diagram
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DEMO MANUAL DC1792A
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.
schematic Diagram
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DEMO MANUAL DC1792A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2012
LT 0412 • PRINTED IN USA
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
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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.).
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.
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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 applica-
tion engineer.
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Copyright © 2004, Linear Technology Corporation
