Linear Technology LTC2668 Quick setup guide

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DEMO MANUAL DC2025A

DESCRIPTION

16-Channel 16-Bit/12-Bit

±10V VOUT SoftSpan DACs with

10ppm/°C Max Reference

Demonstration circuit 2025A features the LT C

2668,

16-channel16-Bit/12-Bit±10VVOUT SoftSpan™DACswith

10ppm/°C max reference in a 6mm × 6mm QFN package.

This device features per-channel SoftSpan configuration

with five output ranges: 0V to 5V, 0V to 10V, ±2.5V, ±5V,

and ±10V. A toggle feature allows any or all DACs to switch

betweentwoprogrammedcodesviaasingleSPIcommand

or by the TGP input pin. The versatile SPI interface can

operate on any logic level between 1.71V and 5.5V, for

easy interface to lower voltage microcontrollers or FPGAs.

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

SoftSpan and QuikEval are trademarks of Analog Devices, Inc. All other trademarks are the

property of their respective owners.

DC2025A-A is populated with the 16-bit version of the

LTC2668. DC2025A-B is populated with the 12-bit version

for lower resolution applications.

Design files for this circuit board are available at

http://www.linear.com/demo/DC2025A

Figure 1. Connection Diagram

SIGNAL

GROUND

MEASURE REF VOLTAGE,

MUX OUTPUT

SIGNAL

GROUND

DAC

OUTPUTS

–

DAC

OUTPUTS

OVERTEMPERATURE

OUTPUT

SEE TEXT. LDAC, TGP, CLR

PULLED TO OVP W/5kΩ

DAC

OUTPUTS

ANALOG SUPPLIES

(±15V ALLOWS ALL

SOFTSPAN RANGES)

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DEMO MANUAL DC2025A

QUICK START PROCEDURE

Download and install QuikEval™ from:

http://www.linear.com/designtools/software/#Data

Connect a DC590 controller or DC2026 Linduino with

DC590emulatorfirmwaretotheDC2025Awith thesupplied

ribbon cable. Connect low-noise analog power supplies

as shown in Figure 1. A±15V supply will allow all of the

SoftSpan ranges to be used, refer to the LTC2668 data

sheet for other supply options if not all SoftSpan ranges

are used.

Connect the controller to the host PC’s USB port and run

QuikEval. The DC2025A software will be downloaded and

installed, after which a jumper setting window will appear

as shown in Figure 2. The default settings are internal

reference, SoftSpan operation with 0V to 5V range, 0V

output on power-up. If the jumpers on the board have been

changed to a different configuration, select the appropri-

ate options in the pull-down menus to match the board.

Click OK and the main dialog will appear. The control panel

gives access to all of the LTC2668’s functionality includ-

ing per-channel SoftSpan ranges, toggling, Power-Down,

etc. Detailed instructions are provided in the Help menu.

Figure 2. Jumper Settings Dialog

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DEMO MANUAL DC2025A

Figure 3. Main Control Panel

QUICK START PROCEDURE

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DEMO MANUAL DC2025A

QUICK START PROCEDURE

External Connections

J1: Interface connector to DC590 controller or Linduino.

Provides OVP power, SPI interface, and board identifica-

tion.

V–, GND, V+:Analog supplies, connected to the LTC2668

V+and V–pins. Nominally ±15V for operation in all Soft-

Span ranges. Refer to the data sheet for other supply

configurations.

GND: Four additional ground posts and exposed ground

plane around board edge allow solid connection to pro-

totype circuitry and measurement equipment.

AVP:Analog supply voltage. Normally supplied by an on-

board LT1761-5 fixed 5V regulator that is powered from

the V+supply. For single 5V supply applications, AVP

may be tied directly to V+and supplied with 4.5V to 5.5V.

OVP: Digital interface power. No connection to this pin is

required when used with a DC590 or Linduino controller.

If another controller is used, connect to digital supply that

powers the SPI bus controller (1.71 to 5.5V).

REF: Connection to the REF pin. In internal reference

mode, the reference voltage may be monitored at this

point. Placing REF_SEL jumper in the EXT position allows

an external reference to be connected to this point.

MUX: Monitor Mux output. Allows surveying the DAC

outputs under software control. Must be measured with

a high impedance meter (output impedance is nominally

2.1kΩ).

VOUT0 to VOUT15: DAC outputs.

CLR:Asynchronous clear input (pulled high to OVP with

a4.99k resistor). Pull to ground to reset the DAC to the

power-on reset value (determined by MSPx pins.)

TGP: Toggle input (pulled high to OVP with a 4.99k resis-

tor). A high level on this pin enables software toggling. See

data sheet for a complete description of toggle operation.

LDAC:Asynchronous DAC update. If CS/LD is high at the

falling edge of LDAC, DAC outputs will be updated with

the contents of the input registers. If CS/LD is low when

LDAC goes low, the DAC registers are updated after CS/

LD returns high.

OVRTMP:Overtemperature pin (pulled high to OVP with a

4.99k resistor). The LTC2668 pulls this pin low if the die

temperature exceeds approximately 160°C. It is released

on the next rising edge of CS/LD.

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DEMO MANUAL DC2025A

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.

QUICK START PROCEDURE

Table 1

MSP2 MSP1 MSP0 OUTPUT RANGE RESET CODE MANUAL SPAN SoftSpan

0 0 0 ±10V Mid-Scale X

0 0 1 ±5V Mid-Scale X

0 1 0 ±2.5V Mid-Scale X

0 1 1 0V to 10V Zero-Scale X

1 0 0 0V to 10V Mid-Scale X

1 0 1 0V to 5V Zero-Scale X

1 1 0 0V to 5V Mid-Scale X

1 1 1 0V to 5V Zero-Scale X

Jumpers

REF_SEL (JP1): Selects internal or external reference

mode. (See data sheet description of REFCOMP pin.)

MSP0, MSP1, MSP2 (JP2, JP3, JP4): Manual Span

control. Setting all jumpers to the 1 position (Default)

selects SoftSpan operation, with a power-up default span

of 0V to 5V, and reset to Zero-Scale. Other options are

listed in Table 1.

LEDs

OVRTMP: Lights when OVRTMP pin asserts, indicating an

overtemperature state. (Note that LED will light if positive

analog supply is present and OVP is not. OVP is normally

supplied by the controller.)

Test Points

The SPI bus is available on a row of through-hole test

points next to J1 that may be used to monitor the bus or

to drive the bus with an external controller.

EEGND, WP: For factory use only.

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DEMO MANUAL DC2025A

 LINEAR TECHNOLOGY CORPORATION 2014

LT 0617 REV A • 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

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 LT C 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. LT C assumes no liability for applications assistance,

customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.

LT C 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 LT C applica-

tion engineer.

Mailing Address:

Linear Technology

1630 McCarthy Blvd.

Milpitas, CA 95035

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