National Semiconductor DAC121C085 User manual

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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
2
C-Compatible Interface
12-bit 10-bit 8-bit
DAC121C085/
DAC121C081
DAC101C085/
DAC101C081
DAC081C085/
DAC081C081

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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
2
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

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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
2
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
2
C serial
Interface.
Data transmitted to the DAC121C085, via the
I
2
C interface, is converted to an analog waveform
by U1, the DAC121C085.
Figure 1: Component and Test Point Locations
J3
WV4 Connector
JP10
3P3V Select
JP9
V
A
Select
JP4
Output Load
JP5
A
dd Select
U1
DAC121C085
J1
WV4S
Connector
J2
V
A
Input
JP7
V
REF
Select
J4
V
OUT

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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
2
C Interface. In Computer Mode, a
WaveVision4 Board is used to drive the DAC’s I
2
C
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
2
C
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
2
C
speed ranges. Ensure the I
2
C master device
is configured to drive 5V CMOS logic.
5. Connect the I
2
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
2
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
2
C address
0x0C by default with pins A0 and A1 floating.
Change the I
2
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
2
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
J3
WV4
14
12
10
8
6
13
11
9
5
7
4
2
3
1
SD
A

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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
I
2
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.
J1
WV4S
SDA
(
DAC
)
1
3
5
7
9
11
13
2
4
6
8
10
12
14
GND
N
/C
SDA
(
EEPROM
)
+3.3V
SCL
(EEPROM)
GND
+5V
N
/C
SCL
(
DAC
)

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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
2
C Address Select (See Below)
JP6 Enable V
REF
supply to the DAC.
JP7 Use external
V
REF
from J2. Set V
REF
= V
A
JP8 Enable V
A
supply to the DAC.
JP9 Use V
A
from the
WV4 board
Use external V
A
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
V
OUT
to GND
Address
Jumper JP5 (I
2
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
2
C Interface
The DAC supports all three I
2
C speeds, including
Hs-Mode (3.4MHz). In Hs-Mode the maximum
DAC conversion rate is 188.9kHz. The board is
designed with 1kΩI
2
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
2
C bus.
In Computer Mode, the I
2
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
2
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
2
C
interface depends on the analog supply voltage
(V
A
). 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
2
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
A
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
A
. V
A
is
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
.

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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
V
A
on the DAC board. To set V
REF
=V
A
, 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
A
externally, connect a DC
voltage supply to connector J2. Connect GND to
the center terminal and V
A
to the bottom terminal.
Place a jumper across pins 2 and 3 of JP9 to
select V
A
_REMOTE. This voltage (V
A
) can be set
anywhere from +2.7V to +5.5V. The source of
V
REF
is controlled by the JP7 jumper. To set
V
REF
=V
A
, short pins 2 & 3. To use an external
V
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
A
and V
REF
are as follows:
•For V
A
= +3.3V, I = 7mA
•For V
A
= +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
V
OUT
V
OUT
A
GND
V
REF
V
A
R
emo
t
e

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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
2
C Interface speed as seen in
Figure 7. Standard mode, Fast Mode, and
High Speed mode are supported.
Figure 7: I
2
C Speed Select
7. Configure the I
2
C address of the DAC. The
DAC121C085 will respond to I
2
C address
0x0C by default with pins A0 and A1 floating
(no jumpers on JP5). Change the I
2
C slave
address of the DAC by adding jumpers to JP5.
Refer to Table 1 for a detailed description of
the I
2
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
2
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

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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
2
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
I
2
C Interface Speed: 100 kHz, 400kHz, or 3.4 MHz
Analog Output
AC Coupled
Output Range:
-(V
A
/2) to (V
A
/2)
Impedance: User Selectable: 2KΩ, 200pF, or ∞.

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7.0 Hardware Schematic
Figure 12: DAC121C08XEB Evaluation Board Schematic
SCLHS_E SCLHS_E SDA SCL SDA_DUT SCL_DUT
SCLSDA
SDA_DUT
SCL_DUT
VOUT
1
TP6
3P3V_REMOTE
1
TP4 VA
1
2
JP6 I_VREF
C11
0.1uF
2 4 6 8 10 12 14
1 3 5 7 9
11 13
J1 WV4S
1 2 3
JP7 VREF
1
TP1 AGND
2
4
1
3
JP4 HEADER 4X2_0
1 2 3
JP10 3P3V
C6
NS
C9 1uF
R7
1K
A0
1
A1
2
A2
3
GND
4SDA 5
SCL 6
WP 7
VCC 8
U3 24C02
C4
0.1uF
C5
1uF
R11 510
A0
1
A1
2
SCL
3
SDA
4
VREF 7
VOUT 8
VA 6
GND 5
U1 DAC121C085
C2
0.1uF
1 2 3 4 5 6 7
JP5
ADDRESS SELECT
1
TP7 AGND
1
TP5 AGND
1 2 3
J2 VIN
C1
200pF
D2
RED LE D
2 4 6 8
10
1 3 5 7 9 1112 1314
J3 WV4
R1 2K
C8
0.1uF
1
TP3 AGND
1
2
J5 LED
C10
0.1uF
D1 RED LED
R6 1K
C3
1uF
C7 1uF
1
2
3
JP9 VA SELECT
L1 100uH
OE
1
A
2
GND
3Y4
VCC 5
U2 NC7SZ126P5X_NL
1
2
JP8 I_VA
R8 51 R9 51
1
TP2 AGND
1
2
4 3
5
J4 VOUT
R10 510
VA
5P0V_WV
VA
3P3V_WV 5P0V_WV
3P3V
3P3V 3P3V
VA
VA
VA
3P3V_WV
VA
VA_REMOTE
AGND
VOU T
VA A0 AGND VA A1 AGND
VREF AGND
VREF_EXT VREF=VA
3P3V
WV4 WV4S
VA
3P3V
WV REM
3P3V
AGND VA
AGND
AGND
AGND
AGN D
REM
WV
CR
VOUT
VA