DAC101C081 [NSC]

12-Bit Micro Power Digital-to-Analog Converter with an I2C-Compatible Interface; 12位微功耗数位类比转换器具有一个I2C兼容接口
DAC101C081
型号: DAC101C081
厂家: National Semiconductor    National Semiconductor
描述:

12-Bit Micro Power Digital-to-Analog Converter with an I2C-Compatible Interface
12位微功耗数位类比转换器具有一个I2C兼容接口

转换器
文件: 总24页 (文件大小:680K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
December 20, 2007  
DAC121C081/ DAC121C085  
12-Bit Micro Power Digital-to-Analog Converter with an  
I2C-Compatible Interface  
General Description  
The DAC121C081 is a 12-bit, single channel, voltage-output  
digital-to-analog converter (DAC) that operates from a +2.7V  
to 5.5V supply. The output amplifier allows rail-to-rail output  
swing and has an 8.5usec settling time. The DAC121C081  
uses the supply voltage as the reference to provide the widest  
dynamic output range and typically consumes 132uA while  
operating at 5.0V. It is available in 6-lead TSOT and LLP  
packages and provides three address options (pin se-  
lectable).  
Features  
Guaranteed Monotonicity to 12-bits  
Low Power Operation: 156 µA max @ 3.3V  
Extended power supply range (+2.7V to +5.5V)  
I2C-Compatible 2-wire Interface which supports standard  
(100kHz), fast (400kHz), and high speed (3.4MHz) modes  
Rail-to-Rail Voltage Output  
Very small 6-pin TSOT and LLP Packages  
As an alternative, the DAC121C085 provides nine I2C ad-  
dressing options and uses an external reference. It has the  
same performance and settling time as the DAC121C081. It  
is available in an 8-lead MSOP.  
The DAC121C081 and DAC121C085 use a 2-wire, I2C-com-  
patible serial interface that operates in all three speed modes,  
including high speed mode (3.4MHz). An external address  
selection pin allows up to three DAC121C081 or nine  
DAC121C085 devices per 2-wire bus. Pin compatible alter-  
natives to the DAC121C081 are available that provide addi-  
tional address options.  
Key Specifications  
Resolution  
INL  
12 bits  
±8 LSB (max)  
+0.6 / -0.5 LSB (max)  
8.5 µs (max)  
DNL  
Settling Time  
Zero Code Error  
Full-Scale Error  
Supply Power  
+10 mV (max)  
−0.7 %FS (max)  
Normal  
380 µW (3V) / 730 µW (5V) typ  
0.5 µW (3V) / 0.9 µW (5V) typ  
Power Down  
The DAC121C081 and DAC121C085 each have a 16-bit reg-  
ister that controls the mode of operation, the power-down  
condition, and the output voltage. A power-on reset circuit  
ensures that the DAC output powers up to zero volts. A power-  
down feature reduces power consumption to less than a  
microWatt. Their low power consumption and small packages  
make these DACs an excellent choice for use in battery op-  
erated equipment. Each DAC operates over the extended  
industrial temperature range of −40°C to +125°C.  
Applications  
Industrial Process Control  
Portable Instruments  
Digital Gain and Offset Adjustment  
Programmable Voltage & Current Sources  
Test Equipment  
The DAC121C081 and DAC121C085 are each part of a fam-  
ily of pin compatible DACs that also provide 8 and 10 bit  
resolution. For 8-bit DACs see the DAC081C081 and  
DAC081C085. For 10-bit DACs see the DAC101C081 and  
DAC101C085.  
Pin-Compatible Alternatives  
All devices are fully pin and function compatible.  
Resolution TSOT-6 and LLP-6 MSOP-8 Package w/  
Packages  
External Reference  
12-bit  
10-bit  
8-bit  
DAC121C081  
DAC101C081  
DAC081C081  
DAC121C085  
DAC101C085  
DAC081C085  
Connection Diagrams  
30004901  
30004902  
30004910  
I2C® is a registered trademark of Phillips Corporation.  
© 2007 National Semiconductor Corporation  
300049  
www.national.com  
Ordering Information  
Order Code  
Temperature Range  
−40°C TA +125°C  
−40°C TA +125°C  
−40°C TA +125°C  
−40°C TA +125°C  
−40°C TA +125°C  
−40°C TA +125°C  
Package  
TSOT  
Top Mark  
X84C  
X84C  
X87  
DAC121C081CIMK  
DAC121C081CIMKX  
DAC121C081CISD  
DAC121C081CISDX  
DAC121C085CIMM  
DAC121C085CIMMX  
DAC121C08XEB  
TSOT Tape-and-Reel  
LLP  
LLP Tape-and-Reel  
MSOP  
X87  
X90C  
X90C  
MSOP Tape-and-Reel  
Evaluation Board  
Block Diagram  
30004903  
www.national.com  
2
Pin Descriptions  
Symbol  
Type  
Equivalent Circuit  
Description  
Analog Output Voltage.  
VOUT  
Analog Output  
Power supply input. For the TSOT and LLP versions, this  
supply is used as the reference. Must be decoupled to  
GND.  
VA  
Supply  
Ground  
GND  
Ground for all on-chip circuitry.  
Serial Data bi-directional connection. Data is clocked into  
or out of the internal 16-bit register relative to the clock  
edges of SCL. This is an open drain data line that must be  
pulled to the supply (VA) by an external pull-up resistor.  
Digital  
Input/Output  
SDA  
Serial Clock Input. SCL is used together with SDA to  
control the transfer of data in and out of the device.  
SCL  
Digital Input  
Tri-state Address Selection Input. Sets the two Least  
Significant Bits (A1 & A0) of the 7-bit slave address. (see  
Table 1)  
Digital Input,  
three levels  
ADR0  
Digital Input,  
three levels  
Tri-state Address Selection Input. Sets Bits A6 & A3 of the  
7-bit slave address. (see Table 1)  
ADR1  
VREF  
Unbufferred reference voltage. For the MSOP-8, this  
supply is used as the reference. VREF must be free of noise  
and decoupled to GND.  
Supply  
Ground  
Exposed die attach pad can be connected to ground or left  
floating. Soldering the pad to the PCB offers optimal  
thermal performance and enhances package self-  
alignment during reflow.  
PAD  
(LLP only)  
Package Pinouts  
VOUT  
VA  
2
VREF  
N/A  
N/A  
7
GND  
SDA  
SCL  
ADR0  
ADR1  
N/A  
N/A  
2
PAD (LLP only)  
TSOT  
LLP  
1
6
8
3
4
5
4
3
4
5
2
3
6
1
1
N/A  
7
5
MSOP-8  
6
N/A  
3
www.national.com  
Absolute Maximum Ratings  
(Notes 1, 2)  
Operating Ratings (Notes 1, 2)  
Operating Temperature Range  
−40°C TA +125°C  
Supply Voltage, VA  
+2.7V to 5.5V  
+1.0V to VA  
0.0V to 5.5V  
0 to 1500 pF  
If Military/Aerospace specified devices are required,  
please contact the National Semiconductor Sales Office/  
Distributors for availability and specifications.  
Reference Voltage, VREFIN  
Digital Input Voltage (Note 7)  
Output Load  
Supply Voltage, VA  
−0.3V to +6.5V  
−0.3V to +6.5V  
±10 mA  
Voltage on any Input Pin  
Package Thermal Resistances  
Input Current at Any Pin (Note 3)  
Package Input Current (Note 3)  
Power Consumption at TA = 25°C  
Package  
θJA  
±20 mA  
6-Lead TSOT  
6-Lead LLP  
250°C/W  
190°C/W  
240°C/W  
See (Note 4)  
ESD Susceptibility (Note 5)  
Human Body Model  
Machine Model  
2500V  
250V  
8-Lead MSOP  
Charge Device Model (CDM)  
1000V  
Soldering  
process  
must  
comply  
with  
National  
Semiconductor's Reflow Temperature Profile specifications.  
Refer to www.national.com/packaging. (Note 6)  
Junction Temperature  
Storage Temperature  
+150°C  
−65°C to +150°C  
Electrical Characteristics  
Values shown in this table are design targets and are subject to change before product release.  
The following specifications apply for VA = +2.7V to +5.5V, VREF = VA, CL = 200 pF to GND, input code range 48 to 4047. Boldface  
limits apply for TMIN TA TMAX and all other limits are at TA = 25°C, unless otherwise specified.  
Typical  
(Note 9)  
Limits  
(Note 9)  
Units  
(Limits)  
Symbol  
Parameter  
Conditions  
STATIC PERFORMANCE  
Resolution  
12  
12  
Bits (min)  
Bits (min)  
Monotonicity  
+2.2  
−1.5  
+0.18  
−0.12  
+1.1  
−0.1  
−0.2  
−20  
+8  
LSB (max)  
LSB (min)  
LSB (max)  
LSB (min)  
mV (max)  
%FSR (max)  
%FSR (max)  
µV/°C  
INL  
Integral Non-Linearity  
−8  
+0.6  
−0.5  
+10  
−0.7  
−0.7  
DNL  
Differential Non-Linearity  
IOUT = 0  
IOUT = 0  
ZE  
FSE  
GE  
Zero Code Error  
Full-Scale Error  
Gain Error  
All ones Loaded to DAC register  
ZCED  
Zero Code Error Drift  
VA = 3V  
VA = 5V  
−0.7  
−1.0  
ppm FSR/°C  
ppm FSR/°C  
TC GE Gain Error Tempco  
ANALOG OUTPUT CHARACTERISTICS (VOUT  
)
0
VREF  
V (min)  
V (max)  
DAC121C085  
DAC121C081  
Output Voltage Range(Note 10)  
0
VA  
V (min)  
V (max)  
VA = 3V, IOUT = 200 µA  
1.3  
7.0  
mV  
mV  
V
ZCO  
FSO  
IOS  
Zero Code Output  
VA = 5V, IOUT = 200 µA  
VA = 3V, IOUT = 200 µA  
2.984  
4.989  
56  
Full Scale Output  
VA = 5V, IOUT = 200 µA  
V
VA = 3V, VOUT = 0V, Input Code = FFFh.  
VA = 5V, VOUT = 0V, Input Code = FFFh.  
VA = 3V, VOUT = 3V, Input Code = 000h.  
VA = 5V, VOUT = 5V, Input Code = 000h.  
mA  
mA  
mA  
mA  
Output Short Circuit Current  
(ISOURCE  
Output Short Circuit Current  
(ISINK  
)
69  
−52  
−75  
IOS  
IO  
)
Continuous Output  
Current (Note 10)  
Available on the DAC output  
11  
mA (max)  
www.national.com  
4
Typical  
(Note 9)  
Limits  
(Note 9)  
Units  
(Limits)  
Symbol  
Parameter  
Conditions  
1500  
1500  
7.5  
pF  
pF  
RL = ∞  
RL = 2kΩ  
CL  
Maximum Load Capacitance  
DC Output Impedance  
ZOUT  
REFERENCE INPUT CHARACTERISTICS- (DAC121C085 only)  
Input Range Minimum  
0.2  
1.0  
VA  
V (min)  
V (max)  
kΩ  
VREF  
Input Range Maximum  
Input Impedance  
120  
LOGIC INPUT CHARACTERISTICS (SCL, SDA)  
VIH  
VIL  
0.7 x VA  
0.3 x VA  
±1  
Input High Voltage  
Input Low Voltage  
Input Current  
V (min)  
V (max)  
µA (max)  
pF (max)  
V (min)  
IIN  
CIN  
Input Pin Capacitance (Note 10)  
Input Hysteresis  
3
VHYST  
0.1 x VA  
LOGIC INPUT CHARACTERISTICS (ADR0, ADR1)  
VIH  
VIL  
IIN  
VA- 0.8V  
0.5  
Input High Voltage  
Input Low Voltage  
Input Current  
V (min)  
V (max)  
µA (max)  
±1  
LOGIC OUTPUT CHARACTERISTICS (SDA)  
ISINK = 3 mA  
ISINK = 6 mA  
0.4  
0.6  
V (max)  
V (max)  
VOL  
IOZ  
Output Low Voltage  
High-Impedence Output  
Leakage Current  
±1  
µA (max)  
5
www.national.com  
Typical  
(Note 9)  
Limits  
(Note 9)  
Units  
(Limits)  
Symbol  
Parameter  
Conditions  
POWER REQUIREMENTS  
Supply Voltage Minimum  
Supply Voltage Maximum  
2.7  
5.5  
V (min)  
V (max)  
VA  
Normal -- VOUT set to midscale. 2-wire interface quiet (SCL = SDA = VA). (output unloaded)  
VA = 2.7V to 3.6V  
IST_VA-1 VA DAC121C081 Supply Current  
105  
132  
86  
156  
214  
118  
152  
43  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µW  
VA = 4.5V to 5.5V  
VA = 2.7V to 3.6V  
IST_VA-5 VA DAC121C085 Supply Current  
VA = 4.5V to 5.5V  
98  
VA = 2.7V to 3.6V  
37  
VREF Supply Current  
IST_VREF  
(DAC121C085 only)  
VA = 4.5V to 5.5V  
VA = 3.0V  
53  
61  
380  
730  
Power Consumption  
(VA & VREF for DAC121C085)  
PST  
VA = 5.0V  
µW  
Continuous Operation -- 2-wire interface actively addressing the DAC and writing to the DAC register. (output unloaded)  
VA = 2.7V to 3.6V  
VA = 4.5V to 5.5V  
VA = 2.7V to 3.6V  
VA = 4.5V to 5.5V  
VA = 2.7V to 3.6V  
VA = 4.5V to 5.5V  
VA = 2.7V to 3.6V  
VA = 4.5V to 5.5V  
VA = 2.7V to 3.6V  
VA = 4.5V to 5.5V  
VA = 3.0V  
134  
192  
225  
374  
101  
142  
193  
325  
33.5  
49.5  
480  
1.06  
810  
2.06  
220  
300  
320  
500  
155  
220  
235  
410  
55  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µA (max)  
µW  
fSCL=400kHz  
fSCL=3.4MHz  
fSCL=400kHz  
fSCL=3.4MHz  
ICO_VA-1 VA DAC121C081 Supply Current  
ICO_VA-5 VA DAC121C085 Supply Current  
VREF Supply Current  
ICO_VREF  
(DAC121C085 only)  
71.4  
fSCL=400kHz  
fSCL=3.4MHz  
VA = 5.0V  
mW  
Power Consumption  
PCO  
(VA & VREF for DAC121C085)  
VA = 3.0V  
µW  
VA = 5.0V  
mW  
Power Down -- 2-wire interface quiet (SCL = SDA = VA) after PD mode written to DAC register. (output unloaded)  
VA = 2.7V to 3.6V  
VA = 4.5V to 5.5V  
VA = 3.0V  
0.13  
0.15  
0.5  
1.52  
3.25  
µA (max)  
µA (max)  
µW  
Supply Current  
(VA & VREF for DAC121C085)  
All Power Down  
Modes  
IPD  
Power Consumption  
(VA & VREF for DAC121C085)  
All Power Down  
Modes  
PPD  
VA = 5.0V  
0.9  
µW  
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6
A.C. and Timing Characteristics  
Values shown in this table are design targets and are subject to change before product release.  
The following specifications apply for VA = +2.7V to +5.5V, VREF = VA, RL = Infinity, CL = 200 pF to GND. Boldface limits apply  
for TMIN TA TMAX and all other limits are at TA = 25°C, unless otherwise specified.  
Limits  
(Notes 9,  
13)  
Typical  
(Note 9)  
Units  
(Limits)  
Symbol  
Parameter  
Conditions (Note 13)  
400h to C00h code change  
Output Voltage Settling Time  
(Note 10)  
ts  
SR  
6
8.5  
µs (max)  
RL = 2k, CL = 200 pF  
Output Slew Rate  
1
V/µs  
nV-sec  
nV-sec  
kHz  
Glitch Impulse  
Code change from 800h to 7FFh  
12  
Digital Feedthrough  
Multiplying Bandwidth(Note 12)  
0.5  
160  
VREF = 2.5V ± 0.1Vpp  
VREF = 2.5V ± 0.1Vpp  
input frequency = 10kHz  
VA = 3V  
Total Harmonic Distortion(Note 12)  
Wake-Up Time  
70  
dB  
0.8  
0.5  
µsec  
µsec  
tWU  
VA = 5V  
DIGITAL TIMING SPECS (SCL, SDA)  
Standard Mode  
Fast Mode  
High Speed Mode, Cb = 100pF  
High Speed Mode, Cb = 400pF  
100  
400  
3.4  
1.7  
KHz (max)  
KHz (max)  
MHz (max)  
MHz (max)  
fSCL  
Serial Clock Frequency  
SCL Low Time  
Standard Mode  
Fast Mode  
High Speed Mode, Cb = 100pF  
High Speed Mode, Cb = 400pF  
4.7  
1.3  
160  
320  
us (min)  
us (min)  
ns (min)  
ns (min)  
tLOW  
Standard Mode  
Fast Mode  
High Speed Mode, Cb = 100pF  
High Speed Mode, Cb = 400pF  
4.0  
0.6  
60  
us (min)  
us (min)  
ns (min)  
ns (min)  
tHIGH  
SCL High Time  
120  
Standard Mode  
Fast Mode  
High Speed Mode  
250  
100  
10  
ns (min)  
ns (min)  
ns (min)  
tSU;DAT  
Data Setup Time  
0
3.45  
us (min)  
us (max)  
Standard Mode  
0
0.9  
us (min)  
us (max)  
Fast Mode  
tHD;DAT  
Data Hold Time  
0
70  
ns (min)  
ns (max)  
High Speed Mode, Cb = 100pF  
High Speed Mode, Cb = 400pF  
0
150  
ns (min)  
ns (max)  
Standard Mode  
Fast Mode  
High Speed Mode  
4.7  
0.6  
160  
us (min)  
us (min)  
ns (min)  
Setup time for a start or a repeated  
start condition  
tSU;STA  
Standard Mode  
Fast Mode  
High Speed Mode  
4.0  
0.6  
160  
us (min)  
us (min)  
ns (min)  
Hold time for a start or a repeated start  
condition  
tHD;STA  
Bus free time between a stop and start Standard Mode  
4.7  
1.3  
us (min)  
us (min)  
tBUF  
condition  
Fast Mode  
Standard Mode  
Fast Mode  
High Speed Mode  
4.0  
0.6  
160  
us (min)  
us (min)  
ns (min)  
tSU;STO  
Setup time for a stop condition  
7
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Limits  
(Notes 9,  
13)  
Typical  
(Note 9)  
Units  
(Limits)  
Symbol  
Parameter  
Conditions (Note 13)  
Standard Mode  
1000  
20+0.1Cb  
300  
ns (max)  
ns (min)  
ns (max)  
Fast Mode  
trDA  
Rise time of SDA signal  
10  
80  
ns (min)  
ns (max)  
High Speed Mode, Cb = 100pF  
20  
160  
ns (min)  
ns (max)  
High Speed Mode, Cb = 400pF  
Standard Mode  
250  
20+0.1Cb  
250  
ns (max)  
ns (min)  
ns (max)  
Fast Mode  
tfDA  
trCL  
trCL1  
tfCL  
Fall time of SDA signal  
10  
80  
ns (min)  
ns (max)  
High Speed Mode, Cb = 100pF  
20  
160  
ns (min)  
ns (max)  
High Speed Mode, Cb = 400pF  
Standard Mode  
1000  
20+0.1Cb  
300  
ns (max)  
ns (min)  
ns (max)  
Fast Mode  
Rise time of SCL signal  
10  
40  
ns (min)  
ns (max)  
High Speed Mode, Cb = 100pF  
20  
80  
ns (min)  
ns (max)  
High Speed Mode, Cb = 400pF  
Standard Mode  
1000  
20+0.1Cb  
300  
ns (max)  
ns (min)  
ns (max)  
Fast Mode  
Rise time of SCL signal after a  
repeated start condition and after an  
acknowledge bit.  
10  
80  
ns (min)  
ns (max)  
High Speed Mode, Cb = 100pF  
20  
160  
ns (min)  
ns (max)  
High Speed Mode, Cb = 400pF  
Standard Mode  
300  
20+0.1Cb  
300  
ns (max)  
ns (min)  
ns (max)  
Fast Mode  
Fall time of a SCL signal  
10  
40  
ns (min)  
ns (max)  
High Speed Mode, Cb = 100pF  
High Speed Mode, Cb = 400pF  
20  
80  
ns (min)  
ns (max)  
Capacitive load for each bus line (SCL  
and SDA)  
Cb  
400  
pF (max)  
Pulse Width of spike suppressed  
(Notes 11, 10)  
Fast Mode  
High Speed Mode  
50  
10  
ns (max)  
ns (max)  
tSP  
toutz  
Fast Mode  
High Speed Mode  
87  
38  
270  
60  
ns (max)  
ns (max)  
SDA output delay (see Section 1.9)  
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is  
functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed  
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test  
conditions. Operation of the device beyond the maximum Operating Ratings is not recommended.  
Note 2: All voltages are measured with respect to GND = 0V, unless otherwise specified.  
Note 3: When the input voltage at any pin exceeds 5.5V or is less than GND, the current at that pin should be limited to 10 mA. The 20 mA maximum package  
input current rating limits the number of pins that can safely exceed the power supplies with an input current of 10 mA to two.  
Note 4: The absolute maximum junction temperature (TJmax) for this device is 150°C. The maximum allowable power dissipation is dictated by TJmax, the  
junction-to-ambient thermal resistance (θJA), and the ambient temperature (TA), and can be calculated using the formula PDMAX = (TJmax − TA) / θJA. The values  
for maximum power dissipation will be reached only when the device is operated in a severe fault condition (e.g., when input or output pins are driven beyond  
the operating ratings, or the power supply polarity is reversed).  
Note 5: Human body model is a 100 pF capacitor discharged through a 1.5 kresistor. Machine model is a 220 pF capacitor discharged through 0 . Charge  
device model simulates a pin slowly acquiring charge (such as from a device sliding down the feeder in an automated assembler) then rapidly being discharged.  
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8
Note 6: Reflow temperature profiles are different for lead-free packages.  
Note 7: The inputs are protected as shown below. Input voltage magnitudes up to 5.5V, regardless of VA, will not cause errors in the conversion result. For  
example, if VA is 3V, the digital input pins can be driven with a 5V logic device.  
30004904  
Note 8: To guarantee accuracy, it is required that VA and VREF be well bypassed.  
Note 9: Typical figures are at TJ = 25°C, and represent most likely parametric norms. Test limits are guaranteed to National's AOQL (Average Outgoing Quality  
Level).  
Note 10: This parameter is guaranteed by design and/or characterization and is not tested in production.  
Note 11: Spike suppression filtering on SCL and SDA will supress spikes that are less than 50ns for standard-fast mode and less than 10ns for hs-mode.  
Note 12: Applies to the Multiplying DAC configuration. In this configuration, the reference is used as the analog input. The value loaded in the DAC Register will  
digitally attenuate the signal at Vout.  
Note 13: Cb refers to the capacitance of one bus line. Cb is expressed in pF units.  
MAXIMUM LOAD CAPACITANCE is the maximum capaci-  
Specification Definitions  
tance that can be driven by the DAC with output stability  
maintained.  
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of  
the maximum deviation from the ideal step size of 1 LSB,  
which is VREF / 4096 = VA / 4096.  
MONOTONICITY is the condition of being monotonic, where  
the DAC has an output that never decreases when the input  
code increases.  
DIGITAL FEEDTHROUGH is a measure of the energy inject-  
ed into the analog output of the DAC from the digital inputs  
when the DAC output is not updated. It is measured with a  
full-scale code change on the data bus.  
MOST SIGNIFICANT BIT (MSB) is the bit that has the largest  
value or weight of all bits in a word. Its value is 1/2 of VA.  
MULTIPLYING BANDWIDTH is the frequency at which the  
output amplitude falls 3dB below the input sine wave on  
VREFIN with a full-scale code loaded into the DAC.  
FULL-SCALE ERROR is the difference between the actual  
output voltage with a full scale code (FFFh) loaded into the  
DAC and the value of VA x 4095 / 4096.  
POWER EFFICIENCY is the ratio of the output current to the  
total supply current. The output current comes from the power  
supply. The difference between the supply and output cur-  
rents is the power consumed by the device without a load.  
GAIN ERROR is the deviation from the ideal slope of the  
transfer function. It can be calculated from Zero and Full-  
Scale Errors as GE = FSE - ZE, where GE is Gain error, FSE  
is Full-Scale Error and ZE is Zero Error.  
SETTLING TIME is the time for the output to settle to within  
1/2 LSB of the final value after the input code is updated.  
GLITCH IMPULSE is the energy injected into the analog out-  
put when the input code to the DAC register changes. It is  
specified as the area of the glitch in nanovolt-seconds.  
TOTAL HARMONIC DISTORTION (THD) is the measure of  
the harmonics present at the output of the DACs with an ideal  
sine wave applied to VREFIN. THD is measured in dB.  
INTEGRAL NON-LINEARITY (INL) is a measure of the de-  
viation of each individual code from a straight line through the  
input to output transfer function. The deviation of any given  
code from this straight line is measured from the center of that  
code value. The end point method is used. INL for this product  
is specified over a limited range, per the Electrical Tables.  
WAKE-UP TIME is the time for the output to exit power-down  
mode. This time is measured from the rising edge of SCL  
during the ACK bit of the lower data byte to the time the output  
voltage deviates from the power-down voltage of 0V.  
ZERO CODE ERROR is the output error, or voltage, present  
at the DAC output after a code of 000h has been entered.  
LEAST SIGNIFICANT BIT (LSB) is the bit that has the small-  
est value or weight of all bits in a word. This value is  
LSB = VREF / 2n  
where VREF is the supply voltage for this product, and "n" is  
the DAC resolution in bits, which is 12 for the DAC121C081.  
9
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Transfer Characteristic  
30004905  
FIGURE 1. Input / Output Transfer Characteristic  
Timing Diagrams  
30004960  
FIGURE 2. Serial Timing Diagram  
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10  
Typical Performance Characteristics VREF = VA, fSCL = 3.4MHz, TA = 25C, Input Code Range 48 to  
4047, unless otherwise stated.  
INL  
DNL  
30004920  
30004921  
INL/DNL vs Temperature at VA = 3.0V  
INL/DNL vs Temperature at VA = 5.0V  
30004922  
30004923  
INL/DNL vs VREFIN at VA = 3.0V  
INL/DNL vs VREFIN at VA = 5.0V  
30004924  
30004925  
11  
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INL/DNL vs VA  
Zero Code Error vs. VA  
30004926  
30004928  
30004929  
30004927  
30004936  
30004930  
Zero Code Error vs. Temperature  
Full Scale Error vs. VA  
Full Scale Error vs. Temperature  
Total Supply Current vs. VA  
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12  
VREF Supply Current vs. VA  
Total Supply Current vs. Temperature @ VA = 3V  
30004932  
30004931  
Total Supply Current vs. Temperature @ VA = 5V  
5V Glitch Response  
30004934  
30004933  
Power-On Reset  
30004935  
13  
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1.0 Functional Description  
1.1 DAC SECTION  
1.2 OUTPUT AMPLIFIER  
The DAC121C081 is fabricated on a CMOS process with an  
architecture that consists of switches and resistor strings that  
are followed by an output buffer.  
The output amplifier is rail-to-rail, providing an output voltage  
range of 0V to VA when the reference is VA. All amplifiers,  
even rail-to-rail types, exhibit a loss of linearity as the output  
approaches the supply rails (0V and VA, in this case). For this  
reason, linearity is specified over less than the full output  
range of the DAC. However, if the reference is less than VA,  
there is only a loss in linearity in the lowest codes. The output  
capabilities of the amplifier are described in the Electrical Ta-  
bles.  
For simplicity, a single resistor string is shown in Figure 3.  
This string consists of 4096 equal valued resistors with a  
switch at each junction of two resistors, plus a switch to  
ground. The code loaded into the DAC register determines  
which switch is closed, connecting the proper node to the  
amplifier. The input coding is straight binary with an ideal out-  
put voltage of:  
The output amplifiers are capable of driving a load of 2 kin  
parallel with 1500 pF to ground or to VA. The zero-code and  
full-scale outputs for given load currents are available in the  
Electrical Characteristics Table.  
VOUT = VREF x (D / 4096)  
where D is the decimal equivalent of the binary code that is  
loaded into the DAC register. D can take on any integer value  
between 0 and 4095. This configuration guarantees that the  
DAC is monotonic.  
1.3 REFERENCE VOLTAGE  
The DAC121C081 uses the supply (VA) as the reference.  
With that said, VA must be treated as a reference. The Analog  
output will only be as clean as the reference (VA). It is rec-  
ommended that the reference be driven by a voltage source  
with low output impedance.  
The DAC121C085 comes with an external reference supply  
pin (VREF). For the DAC121C085, it is important that VREF be  
kept as clean as possible.  
The Applications section describes a handful of ways to drive  
the reference appropriately. Refer to Section 2.1 for details.  
30004907  
FIGURE 3. DAC Resistor String  
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14  
1.4 SERIAL INTERFACE  
master is writing data, the slave ACKs after every data byte  
is successfully received. When the master is reading data, the  
master ACKs after every data byte is received to let the slave  
know it wants to receive another data byte. When the master  
wants to stop reading, it NACKs after the last data byte and  
creates a Stop condition on the bus.  
The I2C-compatible interface operates in all three speed  
modes. Standard mode (100kHz) and Fast mode (400kHz)  
are functionally the same and will be referred to as Standard-  
Fast mode in this document. High-Speed mode (3.4MHz) is  
an extension of Standard-Fast mode and will be referred to  
as Hs-mode in this document. The following diagrams de-  
scribe the timing relationships of the clock (SCL) and data  
(SDA) signals. Pull-up resistors or current sources are re-  
quired on the SCL and SDA busses to pull them high when  
they are not being driven low. A logic zero is transmitted by  
driving the output low. A logic high is transmitted by releasing  
the output and allowing it to be pulled-up externally. The ap-  
propriate pull-up resistor values will depend upon the total bus  
capacitance and operating speed.  
All communication on the bus begins with either a Start con-  
dition or a Repeated Start condition. The protocol for starting  
the bus varies between Standard-Fast mode and Hs-mode.  
In Standard-Fast mode, the master generates a Start condi-  
tion by driving SDA from high to low while SCL is high. In Hs-  
mode, starting the bus is more complicated. Please refer to  
section 1.4.3 for the full details of a Hs-mode Start condition.  
A Repeated Start is generated to either address a different  
device, or switch between read and write modes. The master  
generates a Repeated Start condition by driving SDA low  
while SCL is high. Following the Repeated Start, the master  
sends out the slave address and a read/write bit as shown in  
Figure 4. The bus continues to operate in the same speed  
mode as before the Repeated Start condition.  
1.4.1 Basic I2C Protocol  
The I2C interface is bi-directional and allows multiple devices  
to operate on the same bus. To facilitate this bus configura-  
tion, each device has a unique hardware address which is  
referred to as the "slave address." To communicate with a  
particular device on the bus, the controller (master) sends the  
slave address and listens for a response from the slave. This  
response is referred to as an acknowledge bit. If a slave on  
the bus is addressed correctly, it Acknowledges(ACKs) the  
master by driving the SDA bus low. If the address doesn't  
match a device's slave address, it Not-acknowledges  
(NACKs) the master by letting SDA be pulled high. ACKs also  
occur on the bus when data is being transmitted. When the  
All communication on the bus ends with a Stop condition. In  
either Standard-Fast mode or Hs-Mode, a Stop condition oc-  
curs when SDA is pulled from low to high while SCL is high.  
After a Stop condition, the bus remains idle until a master  
generates a Start condition.  
Please refer to the Phillips I2C® Specification (Version 2.1  
Jan, 2000) for a detailed description of the serial interface.  
30004911  
FIGURE 4. Basic Operation.  
1.4.2 Standard-Fast Mode  
output updates to reflect the contents of the 16-bit DAC reg-  
ister. Next, the master either sends another pair of data bytes,  
generates a Stop condition to end communication, or gener-  
ates a Repeated Start condition to communicate with another  
device on the bus.  
In Standard-Fast mode, the master generates a start condi-  
tion by driving SDA from high to low while SCL is high. The  
Start condition is always followed by a 7-bit slave address and  
a Read/Write bit. After these eight bits have been transmitted  
by the master, SDA is released by the master and the  
DAC121C081 either ACKs or NACKs the address. If the slave  
address matches, the DAC121C081 ACKs the master. If the  
address doesn't match, the DAC121C081 NACKs the master.  
For a read operation, the DAC121C081 sends out the upper  
eight data bits of the DAC register. This is followed by an ACK  
by the master. Next, the lower eight data bits of the DAC reg-  
ister are sent to the master. The master then produces a  
NACK by letting SDA be pulled high. The NACK is followed  
by a master-generated Stop condition to end communication  
on the bus, or a Repeated Start to communicate with another  
device on the bus.  
For a write operation, the master follows the ACK by sending  
the upper eight data bits to the DAC121C081. Then the  
DAC121C081 ACKs the transfer by driving SDA low. Next,  
the lower eight data bits are sent by the master. The  
DAC121C081 then ACKs the transfer. At this point, the DAC  
15  
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1.4.3 High-Speed (Hs) Mode  
address to the DAC121C081, and communication continues  
as shown above in the "Basic Operation" Diagram (see Figure  
4).  
For Hs-mode, the sequence of events to begin communica-  
tion differ slightly from Standard-Fast mode. Figure 5 de-  
scribes this in further detail. Initially, the bus begins running  
in Standard-Fast mode. The master generates a Start condi-  
tion and sends the 8-bit Hs master code (00001XXX) to the  
DAC121C081. Next, the DAC121C081 responds with a  
NACK. Once the SCL line has been pulled to a high level, the  
master switches to Hs-mode by increasing the bus speed and  
generating a Repeated Start condition (driving SDA low while  
SCL is pulled high). At this point, the master sends the slave  
When the master generates a Repeated Start condition while  
in Hs-mode, the bus stays in Hs-mode awaiting the slave ad-  
dress from the master. The bus continues to run in Hs-mode  
until a Stop condition is generated by the master. When the  
master generates a Stop condition on the bus, the bus must  
be started in Standard-Fast mode again before increasing the  
bus speed and switching to Hs-mode. ns16705  
30004912  
FIGURE 5. Beginning Hs-Mode Communication  
1.4.4 I2C Slave (Hardware) Address  
DAC121C085's on the 2-wire bus. When the bus is addressed  
by the broadcast address, all the DAC121C081's and  
DAC121C085's will respond and update synchronously. Fig-  
ure 6 and Figure 7 describe how the master device should  
address the DAC via the I2C-Compatible interface.  
The DAC has a seven-bit I2C slave address. For the MSOP-8  
version of the DAC, this address is configured by the ADR0  
and ADR1 address selection inputs. For the DAC121C081,  
the address is configured by the ADR0 address selection in-  
put. ADR0 and ADR1 can be grounded, left floating, or tied to  
VA. If desired, the address selection inputs can be set to VA/  
2 rather than left floating. The state of these inputs sets the  
address the DAC responds to on the I2C bus (see Table 1).  
In addition to the selectable slave address, there is also a  
broadcast address (1001000) for all DAC121C081's and  
Keep in mind that the address selection inputs (ADR0 and  
ADR1) are only sampled until the DAC is correctly addressed  
with a non-broadcast address. At this point, the ADR0 and  
ADR1 inputs TRI-STATE and the slave address is "locked".  
Changes to ADR0 and ADR1 will not update the selected  
slave address until the device is power-cycled.  
TABLE 1. Slave Addresses  
DAC121C081  
DAC121C085 (MSOP-8)  
(TSOT & LLP) *  
Slave Address  
[A6 - A0]  
ADR1  
Floating  
Floating  
Floating  
GND  
GND  
GND  
VA  
ADR0  
Floating  
GND  
VA  
ADR0  
Floating  
0001100  
0001101  
0001110  
0001000  
0001001  
0001010  
1001100  
1001101  
1001110  
1001000  
GND  
VA  
Floating  
GND  
VA  
---------------  
---------------  
---------------  
---------------  
---------------  
---------------  
Floating  
GND  
VA  
VA  
VA  
--------------- Broadcast Address ---------------  
* Pin-compatible alternatives to the DAC121C081 options are available with additional address options.  
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16  
1.4.5 Writing to the DAC Register  
either sends the upper byte of the next data word to be con-  
verted by the DAC, generates a Stop condition to end com-  
munication, or generates a Repeated Start condition to begin  
communication with another device on the bus. Until gener-  
ating a Stop condition, the master can continuously write the  
upper and lower data bytes to the DAC register. This allows  
for a maximum DAC conversion rate of 188.9 kilo-conver-  
sions per second in Hs-mode.  
To write to the DAC, the master addresses the part with the  
correct slave address (A6-A0) and writes a "zero" to the read/  
write bit. If addressed correctly, the DAC returns an ACK to  
the master. The master then sends out the upper data byte.  
The DAC responds by sending an ACK to the master. Next,  
the master sends the lower data byte to the DAC. The DAC  
responds by sending an ACK again. At this point, the master  
30004964  
FIGURE 6. Typical Write to the DAC Register  
1.4.6 Reading from the DAC Register  
DAC sends the lower data byte to the master. Assuming only  
one 16-bit data word is read, the master sends a NACK after  
receiving the lower data byte. At this point, the master either  
generates a Stop condition to end communication, or a Re-  
peated Start condition to begin communication with another  
device on the bus.  
To read from the DAC register, the master addresses the part  
with the correct slave address (A6-A0) and writes a "one" to  
the read/write bit. If addressed correctly, the DAC returns an  
ACK to the master. Next, the DAC sends out the upper data  
byte. The master responds by sending an ACK to the DAC to  
indicate that it wants to receive another data byte. Then the  
30004963  
FIGURE 7. Typical Read from the DAC Register  
17  
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1.5 DAC REGISTER  
1.8 POWER-DOWN MODES  
The DAC register, Figure 8, has sixteen bits. The first two bits  
are always zero. The next two bits determine the mode of  
operation (normal mode or one of three power-down modes).  
The final twelve bits of the shift register are the data bits. The  
data format is straight binary (MSB first, LSB last), with twelve  
0's corresponding to an output of 0V and twelve 1's corre-  
sponding to a full-scale output of VA - 1 LSB. When writing to  
the DAC Register, VOUT will update on the rising edge of the  
ACK following the lower data byte.  
The DAC121C081 has three power-down modes. In power-  
down mode, the supply current drops to 0.13µA at 3V and  
0.15µA at 5V (typ). The DAC121C081 is put into power-down  
mode by writing a one to PD1 and/or PD0. The outputs can  
be set to high impedance, terminated by 2.5 kto GND, or  
terminated by 100 kto GND (see Figure 8).  
The bias generator, output amplifier, resistor string, and other  
linear circuitry are all shut down in any of the power-down  
modes. When the DAC121C081 is powered down, the value  
written to the DAC register, including the power-down bits, is  
saved. While the DAC is in power-down, the saved DAC reg-  
ister contents can be read back. When the DAC is brought out  
of power-down mode, the DAC register contents will be over-  
written and VOUT will be updated with the new 12-bit data  
value.  
The time to exit power-down (Wake-Up Time) is typically  
0.8µsec at 3V and 0.5µsec at 5V.  
30004908  
1.9 ADDITIONAL TIMING INFORMATION: toutz  
FIGURE 8. DAC Register Contents  
The toutz specification is provided to aid the design of the I2C  
bus. After the SCL bus is driven low by the I2C master, the  
SDA bus will be held for a short time by the DAC121C081.  
This time is referred to as toutz. The following figure illustrates  
the relationship between the fall of SCL, at the 30% threshold,  
to the time when the DAC begins to transition the SDA bus.  
The toutz specification only applies when the DAC is in control  
of the SDA bus. The DAC is only in control of the bus during  
an ACK by the DAC121C081 or a data byte read from the  
DAC (see Figure 7).  
1.6 POWER-ON RESET  
The power-on reset circuit controls the output voltage of the  
DAC during power-up. Upon application of power, the DAC  
register is filled with zeros and the output voltage is 0 Volts.  
The output remains at 0V until a valid write sequence is made  
to the DAC.  
When resetting the device, it is crutial that the VA supply be  
lowered to a maximum of 200mV before the supply is raised  
again to power-up the device. Dropping the supply to within  
200mV of GND during a reset will ensure the ADC performs  
as specified.  
1.7 SIMULTANEOUS RESET  
The broadcast address allows the I2C master to write a single  
word to multiple DACs simultaneously. Provided that all of the  
DACs exist on a single I2C bus, every DAC will update when  
the broadcast address is used to address the bus. This fea-  
ture allows the master to reset all of the DACs on a shared  
I2C bus to a specific digital code. For instance, if the master  
writes a power-down code to the bus with the broadcast ad-  
dress, all of the DACs will power-down simultaneously.  
30004965  
FIGURE 9. Data Output Timing  
The toutz specification is typically 87nsec in Standard-Fast  
Mode and 38nsec in Hs-Mode.  
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18  
2.1.2 LM4050  
2.0 Applications Information  
Available with accuracy of 0.44%, the LM4050 shunt refer-  
ence is also a good choice as a reference for the  
DAC121C081. It is available in 4.096V and 5V versions and  
comes in a space-saving 3-pin SOT23.  
2.1 USING REFERENCES AS POWER SUPPLIES  
While the simplicity of the DAC121C081 implies ease of use,  
it is important to recognize that the path from the reference  
input (VA for the DAC121C081 & VREF for the DAC121C085)  
to VOUT will have essentially zero Power Supply Rejection  
Ratio (PSRR). Therefore, it is necessary to provide a noise-  
free supply voltage to the reference. In order to use the full  
dynamic range of the DAC121C085, the supply pin (VA) and  
VREF can be connected together and share the same supply  
voltage. Since the DAC121C081 consumes very little power,  
a reference source may be used as the supply voltage. The  
advantages of using a reference source over a voltage regu-  
lator are accuracy and stability. Some low noise regulators  
can also be used. Listed below are a few reference and power  
supply options for the DAC121C081. When using the  
DAC121C081, it is important to treat the analog supply (VA)  
as the reference.  
2.1.1 LM4132  
The LM4132, with its 0.05% accuracy over temperature, is a  
good choice as a reference source for the DAC121C081. The  
4.096V version is useful if a 0 to 4.095V output range is de-  
sirable or acceptable. Bypassing the LM4132 VIN pin with a  
0.1µF capacitor and the VOUT pin with a 2.2µF capacitor will  
improve stability and reduce output noise. The LM4132  
comes in a space-saving 5-pin SOT23.  
30004914  
FIGURE 11. The LM4050 as a power supply  
The minimum resistor value in the circuit of Figure 11 must  
be chosen such that the maximum current through the  
LM4050 does not exceed its 15 mA rating. The conditions for  
maximum current include the input voltage at its maximum,  
the LM4050 voltage at its minimum, and the DAC121C081  
drawing zero current. The maximum resistor value must allow  
the LM4050 to draw more than its minimum current for regu-  
lation plus the maximum DAC121C081 current in full opera-  
tion. The conditions for minimum current include the input  
voltage at its minimum, the LM4050 voltage at its maximum,  
the resistor value at its maximum due to tolerance, and the  
DAC121C081 draws its maximum current. These conditions  
can be summarized as  
R(min) = ( VIN(max) − VZ(min) ) /IZ(max)  
and  
30004913  
FIGURE 10. The LM4132 as a power supply  
R(max) = ( VIN(min) − VZ(max) ) / ( (IDAC(max) + IZ(min) )  
where VZ(min) and VZ(max) are the nominal LM4050 output  
voltages ± the LM4050 output tolerance over temperature, IZ  
(max) is the maximum allowable current through the LM4050,  
IZ(min) is the minimum current required by the LM4050 for  
proper regulation, and IDAC(max) is the maximum  
DAC121C081 supply current.  
19  
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2.1.3 LP3985  
2.2 BIPOLAR OPERATION  
The LP3985 is a low noise, ultra low dropout voltage regulator  
with a 3% accuracy over temperature. It is a good choice for  
applications that do not require a precision reference for the  
DAC121C081. It comes in 3.0V, 3.3V and 5V versions,  
among others, and sports a low 30 µV noise specification at  
low frequencies. Since low frequency noise is relatively diffi-  
cult to filter, this specification could be important for some  
applications. The LP3985 comes in a space-saving 5-pin  
SOT23 and 5-bump micro SMD packages.  
The DAC121C081 is designed for single supply operation and  
thus has a unipolar output. However, a bipolar output may be  
obtained with the circuit in Figure 14. This circuit will provide  
an output voltage range of ±5 Volts. A rail-to-rail amplifier  
should be used if the amplifier supplies are limited to ±5V.  
30004917  
FIGURE 14. Bipolar Operation  
30004915  
The output voltage of this circuit for any code is found to be  
VO = (VA x (D / 4096) x ((R1 + R2) / R1) - VA x R2 / R1)  
FIGURE 12. Using the LP3985 regulator  
where D is the input code in decimal form. With VA = 5V and  
R1 = R2,  
An input capacitance of 1.0µF without any ESR requirement  
is required at the LP3985 input, while a 1.0µF ceramic ca-  
pacitor with an ESR requirement of 5mto 500mis required  
at the output. Careful interpretation and understanding of the  
capacitor specification is required to ensure correct device  
operation.  
VO = (10 x D / 4096) - 5V  
A list of rail-to-rail amplifiers suitable for this application are  
indicated in Table 2.  
TABLE 2. Some Rail-to-Rail Amplifiers  
2.1.4 LP2980  
Typ ISUPPLY  
AMP  
PKGS  
Typ VOS  
The LP2980 is an ultra low dropout regulator with a 0.5% or  
1.0% accuracy over temperature, depending upon grade. It is  
available in 3.0V, 3.3V and 5V versions, among others.  
DIP-8  
SOT23-5  
LMC7111  
0.9 mV  
25 µA  
SO-8  
SOT23-5  
LM7301  
LM8261  
0.03 mV  
0.7 mV  
620 µA  
1 mA  
SOT23-5  
30004916  
FIGURE 13. Using the LP2980 regulator  
Like any low dropout regulator, the LP2980 requires an output  
capacitor for loop stability. This output capacitor must be at  
least 1.0µF over temperature, but values of 2.2µF or more will  
provide even better performance. The ESR of this capacitor  
should be within the range specified in the LP2980 data sheet.  
Surface-mount solid tantalum capacitors offer a good combi-  
nation of small size and ESR. Ceramic capacitors are attrac-  
tive due to their small size but generally have ESR values that  
are too low for use with the LP2980. Aluminum electrolytic  
capacitors are typically not a good choice due to their large  
size and have ESR values that may be too high at low tem-  
peratures.  
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20  
2.3 DSP/MICROPROCESSOR INTERFACING  
2.3.2 Interfacing to a Hs-mode Bus  
Interfacing the DAC121C081 to microprocessors and DSPs  
is quite simple. The following guidelines are offered to simplify  
the design process.  
Interfacing to a Hs-mode bus is very similar to interfacing to  
a Standard-Fast mode bus. In Hs-mode, the specified rise  
time of SCL is shortened. To create a faster rise time, the  
master device (microcontroller) can drive the SCL bus high  
and low. In other words, the microcontroller can drive the line  
high rather than leaving it to the pull-up resistor. It is also pos-  
sible to decrease the value of the pull-up resistors or increase  
the pull-up current to meet the tighter timing specs. Please  
refer to the I2C Specification for further details.  
2.3.1 Interfacing to the 2-wire Bus  
Figure 15 shows  
a microcontroller interfacing to the  
DAC121C081 via the 2-wire bus. Pull-up resistors (Rp)  
should be chosen to create an appropriate bus rise time and  
to limit the current that will be sunk by the open-drain outputs  
of the devices on the bus. Please refer to the I2C Specification  
for further details. Typical pull-up values to use in Standard-  
Fast mode bus applications are 2kto 10k. SCL and SDA  
series resisters (RS) near the DAC121C081 are optional. If  
high-voltage spikes are expected on the 2-wire bus, series  
resistors should be used to filter the voltage on SDA and SCL.  
The value of the series resistance must be picked to ensure  
the VIL threshold can be achieved. If used, RS is typically  
51Ω.  
2.4 LAYOUT, GROUNDING, AND BYPASSING  
For best accuracy and minimum noise, the printed circuit  
board containing the DAC121C081 should have separate  
analog and digital areas. The areas are defined by the loca-  
tions of the analog and digital power planes. Both of these  
planes should be located on the same board layer. There  
should be a single ground plane. A single ground plane is  
preferred if digital return current does not flow through the  
analog ground area. Frequently a single ground plane design  
will utilize a "fencing" technique to prevent the mixing of ana-  
log and digital ground current. Separate ground planes should  
only be utilized when the fencing technique is inadequate.  
The separate ground planes must be connected in one place,  
preferably near the DAC121C081. Special care is required to  
guarantee that digital signals with fast edge rates do not pass  
over split ground planes. They must always have a continu-  
ous return path below their traces.  
The DAC121C081 power supply should be bypassed with a  
4.7µF and a 0.1µF capacitor as close as possible to the device  
with the 0.1µF right at the device supply pin. The 4.7µF ca-  
pacitor should be a tantalum type and the 0.1µF capacitor  
should be a low ESL, low ESR type. The power supply for the  
DAC121C081 should only be used for analog circuits.  
Avoid crossover of analog and digital signals and keep the  
clock and data lines on the component side of the board.  
These clock and data lines should have controlled  
impedances.  
30004909  
FIGURE 15. Serial Interface Connection Diagram  
21  
www.national.com  
Physical Dimensions inches (millimeters) unless otherwise noted  
6-Lead TSOT  
Order Numbers DAC121C081CIMK  
NS Package Number MK06A  
6-Lead LLP  
Order Numbers DAC121C081CISD  
NS Package Number SDB06A  
www.national.com  
22  
8-Lead MSOP  
Order Numbers DAC121C085CIMM  
NS Package Number MUA08A  
23  
www.national.com  
Notes  
For more National Semiconductor product information and proven design tools, visit the following Web sites at:  
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www.national.com/contacts  
www.national.com/quality/green  
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www.national.com/lvds  
Green Compliance  
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Quality and Reliability www.national.com/quality  
LVDS  
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