National Semiconductor DAC121C085 Manual de usuario

1 http://www.national.com

National Semiconductor

Dec. 19, 2007

Rev - 1.0

CMC

Evaluation Board User's Guide

DAC121C08XEB, DAC101C08XEB, DAC081C08XEB

Micro Power Digital-to-Analog Converter (DAC)

with an I

C-Compatible Interface

12-bit 10-bit 8-bit

DAC121C085/

DAC121C081

DAC101C085/

DAC101C081

DAC081C085/

DAC081C081

2 http://www.national.com

Table of Contents

1.0 Introduction ........................................................................................................... 3

2.0 Board Assembly.................................................................................................... 4

3.0 Quick Start............................................................................................................ 4

3.1 Stand-Alone Mode..................................................................................... 4

3.2 Computer Mode......................................................................................... 5

4.0 Functional Description........................................................................................... 6

4.1 Jumper Settings ........................................................................................ 6

4.2 I

C Interface .............................................................................................. 6

4.3 DAC Reference Circuitry ........................................................................... 6

4.4 Analog Output ........................................................................................... 7

4.5 Power Supply Connections........................................................................ 7

5.0 Software Operation and Settings .......................................................................... 8

6.0 Evaluation Board Specifications............................................................................ 9

7.0 Hardware Schematic............................................................................................. 10

8.0 Evaluation Board Bill of Materials.......................................................................... 11

A1.0 Summary Tables of Test Points, Jumpers, and Connectors ............................... 12

3 http://www.national.com

1.0 Introduction

The DAC121C08XEB Design Kit (consisting of the

DAC Evaluation Board and this User's Guide) is

designed to ease evaluation and

design-in of National Semiconductor’s

DAC121C081/DAC121C085 family of Digital-to-

Analog Converters (DACs). The Micro-Power

DACs feature Rail-to-Rail Output and an I

C-

Compatible interface. This User’s Guide supports

all three resolutions of the DAC family. The

evaluation board comes with the full-featured

MSOP-8 version of the DAC. For the 12-bit

resolution, the DAC121C085 is used. For the 10-

bit resolution, the DAC101C085 is used. For the

8-bit resolution, the DAC081C085 is used. All the

devices in the family (DAC121C085,

DAC101C085, and DAC081C085) will be referred

to as the DAC121C085 in this document.

The evaluation board can be used in either of two

modes. In the Stand-Alone mode, suitable test

equipment, such as a pattern generator and signal

analyzer, can be used with the board to evaluate

the DAC121C085 performance.

In the Computer mode, data capture and

evaluation is simplified by connecting this board to

National Semiconductor’s Data Capture Board

(order number WAVEVSN BRD 4.4). The Data

Capture (WV4) Board is connected to a personal

computer running WaveVision software through a

USB port. The WaveVision4 software runs on

Microsoft Windows, and the latest version can be

downloaded from the web at

http://www.national.com/adc.

Note: WaveVision Software version 4.4 or later is

required to evaluate this part with the WV4

Evaluation System.

The WaveVision software allows the user to drive

the DAC121C085 with a variety of preset

waveforms and custom waveforms. The software

also allows the user to configure the I

C serial

Interface.

Data transmitted to the DAC121C085, via the

C interface, is converted to an analog waveform

by U1, the DAC121C085.

Figure 1: Component and Test Point Locations

WV4 Connector

JP10

3P3V Select

JP9

Select

JP4

Output Load

JP5

dd Select

DAC121C085

WV4S

Connector

Input

JP7

REF

Select

OUT

4 http://www.national.com

2.0 Board Assembly

The DAC121C08XEB evaluation board comes

fully assembled and ready for use. Refer to the Bill

of Materials for a description of components, to

Figure 1 for major component placement, and to

Figure 12 for the Evaluation Board schematic.

3.0 Quick Start

The evaluation board may be used in the Stand-

Alone mode or Computer mode. In Stand-Alone

mode, a Pattern Generator is used to interface to

the DAC’s I

C Interface. In Computer Mode, a

WaveVision4 Board is used to drive the DAC’s I

interface. In either case, a Signal Analyzer is used

to evaluate the analog output signal.

3.1 Stand-Alone Mode

Refer to Figure 1 for locations of test points and

major components.

1. Connect a clean analog (not switching) +5V

power source to Power Connector J2 on the

DAC121C08XEB board. Ground the middle

terminal and connect +5V to the bottom

terminal closest to JP9.

2. Make the following required jumper

connections, see Table 1 for more details:

•JP9 - pins 2 & 3

•JP7 - pins 2 & 3

•JP6 - pins 1 & 2

•JP8 - pins 1 & 2

3. Turn on the power source.

4. Configure a pattern generator or other I

master device to interface to the

DAC121C085. Refer to the timing diagrams

in the datasheet for further timing details. The

DAC supports any of the three standard I

speed ranges. Ensure the I

C master device

is configured to drive 5V CMOS logic.

5. Connect the I

C master device to Serial

Interface Header J3 (WV4). Refer to Figure 2

below for connection details. NOTE: The

board comes with pull-up resistors (R6 and

R7). Any other pull-ups on the I

C bus must

be disabled.

Figure 2: J3 (WV4) Interface Header

6. The Analog Output signal can be seen DC

coupled at J5, or AC coupled at SMA

connector J4. See the board schematic of

Figure 12 for details.

7. Select the desired output load by adding

jumpers to JP4. Connect a jumper across the

two left pins near the “C” to add a 200pF load

capacitance to ground. Connect a jumper

across the two right side pins near the “R” to

add a 2kΩresistive load. See Table 1 for

jumper configurations.

8. The DAC121C085 will respond to I

C address

0x0C by default with pins A0 and A1 floating.

Change the I

C slave address of the DAC by

adding jumpers to JP5. A0 is controlled by

pins 1,2, & 3 of JP5. A1 is controlled by pins

5, 6, & 7. Refer to Table 1 for a detailed

description of the I

C Slave address settings.

NOTE: Jumper Setting changes to the pin-

configurable slave address will not take effect

until the DAC is power-cycled.

SCL

WV4

5 http://www.national.com

3.2 Computer Mode

Refer to Figure 1 for locations of test points and

major components. The board comes configured

for “plug-and-play” WaveVision evaluation.

1. Run the WaveVision 4 program, version 4.4 or

higher is required to interface to the WV4

board. While the program is loading, continue

below.

2. Connect a USB cable between the WV4 board

and the PC running the WaveVision 4

software.

3. Make the following required jumper

connections, see Table 1 for more details:

•JP9 - pins 1 & 2

•JP7 - pins 2 & 3

•JP6 - pins 1 & 2

•JP8 - pins 1 & 2

•JP10 - pins 1 & 2

4. Connect the J1 header on the

DAC121C08XEB evaluation board to the WV4

serial connector (J7) on the WV4 board.

Refer to Figure 3 for the serial connection and

Figure 4 for the J1 header pin out.

Note: J1 on the DAC121C08XEB is

intentionally stuffed on the bottom side of the

board.

Figure 3: WV4 to DAC121C08XEB Connection

Figure 4: J1 (WV4S) Header

5. Perform step 7 of section 3.1 to configure the

loading of the analog output (V

OUT

6. Perform step 8 of section 3.1 to configure the

C slave address of the DAC.

7. Connect a clean (not switching) +5.0V power

source with a 350mA current limit to power

connector J1 on the WV4 board. Turn on the

power supply.

8. Refer to Section 5.0 on Software Operation

and Settings to setup the WaveVision 4

software.

WV4S

SDA

(

DAC

)

GND

SDA

(

EEPROM

)

+3.3V

SCL

(EEPROM)

GND

+5V

SCL

(

DAC

)

6 http://www.national.com

4.0 Functional Description

4.1 Jumper Settings

Table 1 describes the function of the various

jumpers on the DAC121C08XEB evaluation

board. The evaluation board schematic is shown

in Figure 12.

Jumper

Pins 1 & 2 Pins 2 & 3

JP4 V

OUT

Load Select (See Below)

JP5 I

C Address Select (See Below)

JP6 Enable V

REF

supply to the DAC.

JP7 Use external

REF

from J2. Set V

REF

= V

JP8 Enable V

supply to the DAC.

JP9 Use V

from the

WV4 board

Use external V

from J2.

JP10

Use 3.3V supply

from the WV4

board

Use external

3.3V supply from

TP6.

Jumper JP4 (V

OUT

Load Select)

Left side

pins near

“C”

Connect a 200pF load capacitance

from V

OUT

to GND

Right side

pins near

“R”

Connect a 2kΩload resistance from

OUT

to GND

Address

Jumper JP5 (I

C Address Select)

0x0C No jumpers

0x0D Short pins 2 & 3.

0x0E Short pins 1 & 2.

0x08 Short pins 6 & 7.

0x09 Short pins 2 & 3 and pins 6 & 7.

0x0A Short pins 1 & 2 and pins 6 & 7.

0x4C Short pins 5 & 6.

0x4D Short pins 2 & 3 and pins 5 & 6.

0x4E Short pins 1 & 2 and pins 5 & 6.

Table 1: Jumper Configurations

4.2 I

C Interface

The DAC supports all three I

C speeds, including

Hs-Mode (3.4MHz). In Hs-Mode the maximum

DAC conversion rate is 188.9kHz. The board is

designed with 1kΩI

C pull-up resistors on both

the SDA and SCL lines (R6 & R7). Also, series

resistors for SCL and SDA are designed into the

board (R8 & R9). The board is shipped with 51Ω

series resistors which can be increased to

interface to a noisy I

C bus.

In Computer Mode, the I

C interface is driven by

the WaveVision4 board. The WaveVision4

software allows the user to drive the DAC121C085

with various digitized signals. Refer to Section 5.0

“Software Operation and Settings” for further

information.

In Stand-Alone Mode, the I

C interface must be

driven by an external device. See section 1.4.5 of

the DAC121C081/DAC121C085 datasheet for a

typical write sequence timing diagram.

The maximum digital input level of the I

interface depends on the analog supply voltage

). The interface operates at normal CMOS

logic levels. See the Electrical Characteristics

section of the datasheet for further details.

The SDA signal is accessible by connecting to

pin 2 of the WV4 connector (J3). The SCL signal

is accessible by connecting to pin 6 of J3.

Please refer to section 1.4 of the datasheet for a

detailed description of the I

C interface. Refer to

the Philips I2C Specification for further details.

4.3 DAC Reference Circuitry

The reference voltage for the DAC121C085 is

selected by JP7. (See Table 1 for details.) The

reference can either be selected as the V

supply

or an externally supplied voltage (J2). The analog

output range of the DAC121C085 can be scaled

by adjusting the reference voltage (V

REF

). The

lower the V

REF

, the smaller the output range. V

REF

can be set anywhere from 1.0V to V

. V

independent of V

REF

and can be set anywhere

from +2.7V to +5.5V. In any case, V

REF

has little

to no PSRR and must be as clean as possible to

reduce noise feedthrough on V

OUT

7 http://www.national.com

4.4 Analog Output

The analog output of this Eval board is available in

two places. For a DC coupled output, pin 1 of J5

provides V

OUT

and pin 2 provides AGND. An AC

coupled output is provided by the SMA connector

(J4). See Figure 5 below for details.

If using a spectrum analyzer to look at the output

of the DAC, the AC coupled output (J4) is

recommended.

For very low frequency (i.e. less than 1kHz), use

J5 to see the output signal DC coupled. For an

AC coupled output at low frequencies, simply

replace the AC coupling capacitor at C9 with a

larger capacitor. Use the J4 SMA to look at the

AC coupled output.

Figure 5: Analog Output

4.5 Power Supply Connections

In Computer mode, the board can be powered by

either an external supply or the local WaveVision4

board supply. In Stand-alone mode, the

Evaluation Board must be powered by an external

supply.

If you wish to use the local supply from the

WaveVision4 Board, place a jumper across pins 1

and 2 of JP9. This connection will supply +5V to

on the DAC board. To set V

REF

, simply

short pins 2 & 3 of JP7. For WaveVision to

recognize the board, the 3P3V supply must be

enabled as well. Do this by placing a jumper

across pins 1 and 2 of JP10. The board comes

configured to use the local supply. The default

jumper settings are shown in Figure 1.

If you wish to supply V

externally, connect a DC

voltage supply to connector J2. Connect GND to

the center terminal and V

to the bottom terminal.

Place a jumper across pins 2 and 3 of JP9 to

select V

_REMOTE. This voltage (V

) can be set

anywhere from +2.7V to +5.5V. The source of

REF

is controlled by the JP7 jumper. To set

REF

, short pins 2 & 3. To use an external

REF

from the top terminal of J2, short pins 1 & 2.

Refer to Figure 6 for a diagram of the power

supply connections.

Figure 6: Power Supply Connections

Typical supply currents when applying an external

supply to V

and V

REF

are as follows:

•For V

= +3.3V, I = 7mA

•For V

= +5.0V, I = 12mA

Note: These values are specified for a

continuously operating DAC in High Speed Mode,

driving a full-scale sinewave output. The majority

of this current is for powering devices external to

the DAC121C085 such as the pull-up resistors

and the LED.

AC Coupled

OUT

GND

REF

emo

8 http://www.national.com

5.0 Software Operation and Settings

The WaveVision4 software is included with the

WaveVision4 board and the latest version can be

downloaded from National's web site at

http://www.national.com/adc. WaveVision4

software version 4.4 or later is required to evaluate

this device with the WV4 system.

To install this software, follow the procedure in the

WaveVision4 Board User's Guide. Once the

software is installed, run it and set it up as follows:

Note: Before continuing, ensure that the

WaveVision Hardware is setup according to

Section 3.2.

1. From the WaveVision main menu, go to

Settings, then Capture Settings to open the

System Settings dialog.

2. Under board type, select WaveVision4 (USB).

3. Turn on the power to both boards, then click

on the "Reset" button and await the firmware

download. After the firmware has

downloaded, WaveVision will open up a

control panel window for the DAC121C08XEB.

4. Click on the "Close" button to close the

System Settings Dialog.

5. Navigate to the DAC121C08XEB Evaluation

Board window.

6. Configure the I

C Interface speed as seen in

Figure 7. Standard mode, Fast Mode, and

High Speed mode are supported.

Figure 7: I

C Speed Select

7. Configure the I

C address of the DAC. The

DAC121C085 will respond to I

C address

0x0C by default with pins A0 and A1 floating

(no jumpers on JP5). Change the I

C slave

address of the DAC by adding jumpers to JP5.

Refer to Table 1 for a detailed description of

the I

C address settings. The address in

Figure 8 must match the address configured

by A0 and A1.

NOTE: Jumper Setting changes to the pin-

configured slave address will not take effect

until the DAC is power-cycled.

Figure 8: I

C Address

8. Perform register level control of the DAC by

writing 16-bit words to the DAC Data Register.

To write the DAC, simply type a 16-bit hex

value into the “Manual DAC Control” field and

press Enter or click the “Write DAC Register”

button. See Figure 9.

Figure 9: Manual DAC Control

9. To put the DAC into power-down mode, select

a power-down option from the “Power-down

Mode” box and click the “Set Mode” button.

Figure 10: DAC Power-down Control

9 http://www.national.com

10. Configure the digital waveform to be

converted by the DAC as seen in Figure 11.

Please see the WaveVision4 User’s Manual

for detailed instructions. The ability to drive

preset waveforms or custom data is provided.

Figure 11: Waveform Configuration

11. Press the “Start” button to begin driving the

digital waveform to the DAC.

The WaveVision4 Board will continuously send the

waveform out to the DAC over the I

C interface

until the “Stop” button is pressed. Please refer to

Section 4.4 for details on measuring the Analog

Output of the DAC.

The Digital Waveform is plotted in the main

WaveVision window for added convienience. This

waveform may be further analyzed by clicking on

the magnifying glass icon, then clicking and

dragging across a specific area of the plot for

better data inspection. See the WaveVision4

Board User's Guide for details.

If this board is used in conjunction with the

WaveVision4 Data Capture Board and

WaveVision software, a USB cable is needed to

connect WaveVision4 Board to the host computer.

See the WaveVision4 Board User's Guide for

details.

6.0 Evaluation Board Specifications

Board Size: 2.8" x 2.0" (7.2 cm x 5.1 cm)

Power Requirements Min: +2.7V , 6mA Max: +5.5V, 16mA

C Interface Speed: 100 kHz, 400kHz, or 3.4 MHz

Analog Output

AC Coupled

Output Range:

-(V

/2) to (V

/2)

Impedance: User Selectable: 2KΩ, 200pF, or ∞.

10 http://www.national.com

7.0 Hardware Schematic

Figure 12: DAC121C08XEB Evaluation Board Schematic

SCLHS_E

SDA SCL

SDA_DUT

SCL_DUT

SCLSDA

SDA_DUT

SCL_DUT

VOUT

TP6

3P3V_REMOTE

TP4

JP6

I_VREF

C11

0.1uF

WV4S

JP7

VREF

TP1

AGND

JP4

HEADER 4X2_0

JP10

3P3V

C9 1uF

GND

4SDA 5

SCL 6

WP 7

VCC 8

24C02

0.1uF

1uF

R11

510

SCL

SDA

VREF 7

VOUT 8

VA 6

GND 5

DAC121C085

0.1uF

JP5

ADDRESS SELECT

TP7

AGND

TP5

AGND

VIN

200pF

RED LE D

1112

1314

WV4

0.1uF

TP3

AGND

LED

C10

0.1uF

RED LED

1uF

JP9

VA SELECT

L1 100uH

GND

3Y4

VCC 5

NC7SZ126P5X_NL

JP8

I_VA

R8 51

R9 51

TP2

AGND

4 3

VOUT

R10

510

5P0V_WV

3P3V_WV 5P0V_WV

3P3V

3P3V 3P3V

3P3V_WV

VA_REMOTE

AGND

VOU T

AGND

VREF

AGND

VREF_EXT

VREF=VA

3P3V

WV4

WV4S

3P3V

REM

3P3V

AGND VA

AGND

AGN D

REM

VOUT

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