TI DAC6571IDBVT

DAC6571
www.ti.com
SLAS406 – DECEMBER 2003
+2.7 V to +5.5 V, I2C INTERFACE, VOLTAGE OUTPUT,
10-BIT DIGITAL-TO-ANALOG CONVERTER
FEATURES
DESCRIPTION
•
•
•
•
•
•
•
The DAC6571 is a low-power, single channel, 10-Bit
buffered voltage output DAC. Its on-chip precision
output amplifier allows rail-to-rail output swing to be
achieved. The DAC6571 utilizes an I2C compatible
two wire serial interface that operates at clock rates
up to 3.4 Mbps with address support of up to two
DAC6571s on the same data bus.
•
•
•
•
Micropower Operation: 125 µA @ 3 V
Fast Update Rate: 188 kSPS
Power-On Reset to Zero
+2.7 V to +5.5 V Power Supply
Specified Monotonic by Design
I2C™ Interface up to 3.4 Mbps
On-Chip Output Buffer Amplifier, Rail-to-Rail
Operation
Double-Buffered Input Register
Address Support for up to Two DAC6571s
Small 6 Lead SOT 23 Package
Operation From -40°C to 105°C
APPLICATIONS
•
•
•
•
•
The output voltage range of the DAC is 0 V to VDD.
The DAC6571 incorporates a power-on-reset circuit
that ensures that the DAC output powers up at zero
volts and remains there until a valid write to the
device takes place. The DAC6571 contains a
power-down feature, accessed via the internal control
register, that reduces the current consumption of the
device to 50 nA at 5 V.
The low power consumption of this part in normal
operation makes it ideally suited for portable battery
operated equipment. The power consumption is less
than 0.7 mW at VDD = 5 V reducing to 1 µW in
power-down mode.
Process Control
Data Acquistion Systems
Closed-Loop Servo Control
PC Peripherals
Portable Instrumentation
DAC7571/6571/5571 are 12/10/8 bit single channel
I2C DACs from the same family. DAC7574/6574/5574
and DAC7573/6573/5573 are 12/10/8 bit quad channel I2C DACs. Also see DAC8571/8574 for
single/quad channel 16-bit I2C DACs.
VDD
GND
Power-On
Reset
Ref (+) REF(−)
10-Bit
DAC
DAC
Register
I2C
Control
Logic
A0
SCL
Output
Buffer
Power Down
Control Logic
VOUT
Resistor
Network
SDA
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
I2C is a trademark of Philips Corporation.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2003, Texas Instruments Incorporated
DAC6571
www.ti.com
SLAS406 – DECEMBER 2003
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated
circuits be handled with appropriate precautions. Failure to observe proper handling and installation
procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision
integrated circuits may be more susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
PACKAGE/ORDERING INFORMATION
PRODUCT
PACKAGE
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
DAC6571
SOT23-6
DBV
-40°C to +105°C
D671
(TOP VIEW)
2
3
D671
1
6
5
4
A0
SCL
SDA
(BOTTOM VIEW)
5
4
YMLL
6
TRANSPORT MEDIA
DAC6571IDBVT
250 Piece Small Tape and Reel
DAC6571IDBVR
3000 Piece Tape and Reel
PIN DESCRIPTION (SOT23-6)
PIN CONFIGURATIONS
VOUT
GND
VDD
ORDERING
NUMBER
PIN
NAME
1
VOUT
Analog output voltage from DAC
2
GND
Ground reference point for all
circuitry on the part
3
VDD
Analog Voltage Supply Input
4
SDA
Serial Data Input
5
SCL
Serial Clock Input
6
A0
LOT
TRACE
CODE:
1
2
DESCRIPTION
Device Address Select
Year (3 = 2003); M onth (1–9 = JAN–SEP; A=OCT,
B=NOV, C=DEC); LL– Random code generated
when assembly is requested
3
Lot Trace Code
ABSOLUTE MAXIMUM RATINGS (1)
UNITS
VDD to GND
-0.3V to +6V
Digital Input voltage to GND
-0.3 V to +VDD + 0.3 V
VOUT to GND
-0.3 V to +VDD + 0.3 V
Operating temperature range
-40°C to + 105°C
Storage temperature range
-65°C to + 150°C
Junction temperature range (TJ max)
+ 150°C
Power dissipation
(TJmax - TA)RΘJA
Thermal impedance, RΘJA
Lead temperature, soldering
(1)
2
240°C/W
Vapor phase (60s)
215°C
Infrared (15s)
220°C
Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. Exposure to absolute
maximum conditions for extended periods may affect device reliability.
DAC6571
www.ti.com
SLAS406 – DECEMBER 2003
ELECTRICAL CHARACTERISTICS
VDD = +2.7 V to +5.5 V; RL = 2 kΩ to GND; CL = 200 pF to GND; all specifications -40°C to +105°C unless otherwise noted.
PARAMETER
CONDITIONS
DAC6571
MIN
TYP
MAX
UNITS
STATIC PERFORMANCE (1)
Resolution
10
Bits
Relative accuracy
Differential nonlinearity
Assured monotonic by design
±2
LSB
±0.5
LSB
Zero code error
All zeroes loaded to DAC register
5
20
mV
Full-scale error
All ones loaded to DAC register
-0.15
-1.25
% of FSR
±1.25
% of FSR
Gain error
Zero code error drift
±7
µV/°C
Gain temperature coefficient
±3
ppm of FSR/°C
OUTPUT CHARACTERISTICS (2)
Output voltage range
Output voltage settling time
0
1/4 Scale to 3/4 scale change (400H to C00H) ;
RL = ∞
7
Slew rate
Capacitive load stability
Code change glitch impulse
9
µs
1
V/µs
pF
RL = ∞
470
1000
pF
1 LSB Change around major carry
20
nV-s
0.5
nV-s
DC output impedance
Power-up time
V
RL = 2kΩ
Digital feedthrough
Short-circuit current
VDD
VDD = +5V
VDD = +3V
1
Ω
50
mA
20
mA
Coming out of power-down mode, VDD = +5V
2.5
µs
Coming out of power-down mode, VDD = +3V
5
µs
LOGIC INPUTS (2)
Input current
VINL, Input low voltage
VINH, Input high voltage
VDD = +3V
VDD = +5V
±1
µA
0.3×VDD
V
0.7×VD
V
D
Pin capacitance
3
pF
5.5
V
POWER REQUIREMENTS
VDD
2.7
IDD (normal operation)
DAC active and excluding load current
VDD = +3.6V to +5.5V
VIH = VDD and VIL = GND
155
200
µA
VDD = +2.7V to +3.6V
VIH = VDD and VIL = GND
125
160
µA
IDD (all power-down modes)
VDD = +3.6 V to +5.5V
VIH = VDD and VIL = GND
0.2
1
µA
VDD = +2.7V to +3.6V
VIH = VDD and VIL = GND
0.05
1
µA
ILOAD = 2mA, VDD = +5V
93
POWER EFFICIENCY
IOUT/IDD
(1)
(2)
%
Linearity calculated using a reduced code range of 12 to 1012; output unloaded.
Specified by design and characterization, not production tested.
3
DAC6571
www.ti.com
SLAS406 – DECEMBER 2003
TIMING CHARACTERISTICS
SYMBOL
fSCL
tBUF
tHD; tSTA
tLOW
tHIGH
tSU; tSTA
tSU; tDAT
tHD; tDAT
tRCL
tRCL1
tFCL
PARAMETER
SCL Clock Frequency
Bus Free Time Between a STOP
and START Condition
Hold Time (Repeated) START
Condition
LOW Period of the SCL Clock
HIGH Period of the SCL Clock
Setup Time for a Repeated
START Condition
Data Setup Time
Data Hold Time
Rise Time of SCL Signal
Rise Time of SCL Signal After a
Repeated START Condition and
After an Acknowledge BIT
Fall Time of SCL Signal
TEST CONDITIONS
MAX
UNITS
Standard mode
100
kHz
Fast mode
400
kHz
High-speed mode, CB - 100pF max
3.4
MHz
High-Speed mode, CB - 400pF max
1.7
Rise Time of SDA Signal
MHz
4.7
µs
Fast mode
1.3
µs
Standard mode
4.0
µs
Fast mode
600
ns
High-speed mode
160
ns
Standard mode
4.7
µs
Fast mode
1.3
µs
High-speed mode, CB - 100pF max
160
ns
High-speed mode, CB - 400pF max
320
ns
Standard mode
4.0
µs
Fast mode
600
ns
High-speed mode, CB - 100pF max
60
ns
High-speed mode, CB - 400pF max
120
ns
Standard mode
4.7
µs
Fast mode
600
ns
High-speed mode
160
ns
Standard mode
250
ns
Fast mode
100
ns
High-speed mode
10
Standard mode
0
3.45
µs
Fast mode
0
0.9
µs
High-speed mode, CB - 100pF max
0
70
ns
High-speed mode, CB - 400pF max
0
150
ns
Standard mode
20 ×0.1CB
1000
ns
Fast mode
4
Fall Time of SDA Signal
ns
20 ×0.1CB
300
ns
High-speed mode, CB - 100pF max
10
40
ns
High-speed mode, CB - 400pF max
20
80
ns
Standard mode
20 ×0.1CB
1000
ns
Fast mode
20 ×0.1CB
300
ns
High-speed mode, CB - 100pF max
10
80
ns
High-speed mode, CB - 400pF max
20
160
ns
Standard mode
20 ×0.1CB
300
ns
Fast mode
20 ×0.1CB
300
ns
10
40
ns
High-speed mode, CB - 100pF max
20
80
ns
Standard mode
20 ×0.1CB
1000
ns
Fast mode
20 ×0.1CB
300
ns
10
80
ns
High-speed mode, CB - 100pF max
High-speed mode, CB - 400pF max
tFDA
TYP
Standard mode
High-speed mode, CB - 400pF max
tRDA
MIN
20
160
ns
Standard mode
20 ×0.1CB
300
ns
Fast mode
20 ×0.1CB
300
ns
High-speed mode, CB - 100pF max
10
80
ns
High-speed mode, CB - 400pF max
20
160
ns
DAC6571
www.ti.com
SLAS406 – DECEMBER 2003
TIMING CHARACTERISTICS (continued)
SYMBOL
PARAMETER
tSU; tSTO
Setup Time for STOP Condition
CB
Capacitive Load for SDA and SCL
tSP
Pulse Width of Spike Suppressed
VNH
VNL
Noise Margin at the HIGH Level
for Each Connected Device
(Including Hysteresis)
Noise Margin at the LOW Level for
Each Connected Device
(Including Hysteresis)
TEST CONDITIONS
MIN
Standard mode
4.0
TYP
MAX
UNITS
µs
Fast mode
600
ns
High-speed mode
160
ns
400
pF
Fast mode
50
ns
High-speed mode
10
ns
Standard mode
Fast mode
0.2VDD
V
0.1VDD
V
High-speed mode
Standard mode
Fast mode
High-speed mode
5
DAC6571
www.ti.com
SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +5 V
At TA = +25°C, +VDD = +5 V, unless otherwise noted.
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR
vs
CODE (-40°C)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR
vs
CODE (+25 ° C )
2
2
0
−1
0
−1
−2
0.5
DLE − LSB
−2
0.5
0.25
0
−0.25
0.25
0
−0.25
−0.5
−0.5
0
128
256
384
512
640
Digital Input Code
768
896
VDD = 5 V at 25°C
1
LE − LSB
LE − LSB
DLE − LSB
VDD = 5 V at −40°C
1
1024
0
128
256
384
512
640
Digital Input Code
Figure 1.
16
VDD = 5 V, TA = 25°C
VDD = 5 V at 105°C
1
LE − LSB
1024
TYPICAL TOTAL UNADJUSTED ERROR
2
0
Output Error (mV)
8
−1
−2
0.5
DLE − LSB
896
Figure 2.
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR
vs
CODE (+105° C)
0.25
0
−8
0
−0.25
−16
0
−0.5
0
128
256
384
512
640
768
896
1024
128
256
384
512
640
Digital Input Code
Digital Input Code
Figure 4.
ZERO-SCALE ERROR
vs
TEMPERATURE
FULL-SCALE ERROR
vs
TEMPERATURE
896
1024
30
VDD = 5 V
VDD = 5 V
20
Full-Scale Error − mV
20
Zero-Scale Error − mV
768
Figure 3.
30
10
0
−10
−20
10
0
−10
−20
−30
−50 −40 −30 −20 −10 0
10 20 30 40 50 60 70 80 90 100 110
T − Temperature − C
Figure 5.
6
768
−30
−50 −40 −30 −20 −10 0
10 20 30 40 50 60 70 80 90 100 110
T − Temperature − C
Figure 6.
DAC6571
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SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +5 V (continued)
At TA = +25°C, +VDD = +5 V, unless otherwise noted.
IDD HISTOGRAM
SOURCE AND SINK CURRENT CAPABILITY
2500
5
VDD = 5 V
DAC Loaded with 3FF
4
1500
1000
H
3
V O U T (V)
f − Frequency − Hz
2000
2
500
1
DAC Loaded with 00 H
200
190
180
170
160
150
140
130
120
110
100
90
80
0
0
0
IDD − Supply Current − A
5
10
15
ISOURCE/SINK (mA)
Figure 7.
Figure 8.
SUPPLY CURRENT
vs
CODE
SUPPLY CURRENT
vs
TEMPERATURE
500
300
VDD = 5 V
I DD − Supply Current − µ A
I DD − Supply Current − µ A
VDD = 5 V
400
300
200
100
250
200
150
100
50
0
−50 −40 −30 −20 −10 0 10 20 30 40 50 60 70 80 90 100 110
T − Temperature − C
0
0H
BH
80H 100H 180H 200H 280H 300H 380H 3F3H 3FFH
Code
Figure 9.
Figure 10.
SUPPLY CURRENT
vs
SUPPLY VOLTAGE
POWER-DOWN CURRENT
vs
SUPPLY VOLTAGE
300
90
80
200
70
150
IDD (nA)
I DD − Supply Current − µ A
100
250
100
60
+105°C
50
–40°C
40
30
50
20
0
2.7
3.2
3.7
4.2
4.7
VDD − Supply Voltage − V
5.2
5.7
+25°C
10
0
2.7
3.2
3.7
4.2
4.7
5.2
5.7
VDD (V)
Figure 11.
Figure 12.
7
DAC6571
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SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +5 V (continued)
At TA = +25°C, +VDD = +5 V, unless otherwise noted.
SUPPLY CURRENT
vs
LOGIC INPUT VOLTAGE
FULL-SCALE SETTLING TIME
CLK (5V/div)
2500
IDD (µA)
2000
VOUT (1V/div)
1500
1000
Full−Scale Code Change
00H to 3FF H
Output Loaded with
2 KΩ and 200pF to GND
500
0
Time (1µs/div)
0
1
2
3
4
5
VLOGIC (V)
Figure 13.
Figure 14.
FULL-SCALE SETTLING TIME
HALF-SCALE SETTLING TIME
CLK (5V/div)
CLK (5V/div)
VOUT (1V/div)
Full−Scale Code Change
1023 to 0
Output Loaded with
2 k and 200 pF to GND
Half−Scale Code Change
256 to 768
Output Loaded with
2kΩ and 200pF to GND
VOUT (1V/div)
Time 1 s/div
Time (1µs/div)
Figure 15.
Figure 16.
HALF-SCALE SETTLING TIME
POWER-ON RESET TO 0V
C LK (5 V/div)
H alf−S ca le C o de C ha nge
768 to 256
Loaded with 2kΩ to VDD.
O utpu t Lo ad ed w ith
2kΩ an d 20 0pF to G N D
VDD (1V/div)
V O U T (1V /div)
VOUT (1V/div)
Time
(1µs /d iv)
Time (20µs/div)
Figure 17.
8
Figure 18.
DAC6571
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SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +5 V (continued)
At TA = +25°C, +VDD = +5 V, unless otherwise noted.
EXITING POWER-DOWN
(512 Loaded)
CODE CHANGE GLITCH
Loa ded w ith 2 kΩ
and 2 00p F to G N D .
C ode C hang e:
512 to 511
VOUT (20mV/div)
CLK (5V/div)
VOUT (1V/div)
Time (0.5 µs/div)
Time (5µs/div)
Figure 19.
Figure 20.
9
DAC6571
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SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +2.7V
At TA = +25°C, +VDD = +2.7V, unless otherwise noted.
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR
vs
CODE (-40 °C)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR
vs
CODE (+25 °C)
2
VDD = 2.7 V at 25°C
VDD = 2.7 V at −40°C
1
LE − LSB
LE − LSB
2
0
−1
0
−1
−2
−2
0.5
DLE − LSB
0.5
DLE − LSB
1
0.25
0
−0.25
0.25
0
−0.25
−0.5
−0.5
0
128
256
384
512
640
768
896
0
1024
128
256
640
Figure 22.
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR
vs
CODE (+105 °C)
OUTPUT ERROR
vs
CODE (+25 °C)
768
896
1024
16
VDD = 2.7 V at 105°C
1
VDD = 2.7 V, TA = 25°C
0
8
−1
Output Error (mV)
LE − LSB
512
Figure 21.
2
−2
0.5
DLE − LSB
384
Digital Input Code
Digital Input Code
0.25
0
0
−8
−0.25
−0.5
0
128
256
384
512
640
Digital Input Code
Figure 23.
10
768
896
1024
−16
0
128
256
384
512
640
Digital Input Code
Figure 24.
768
896
1024
DAC6571
www.ti.com
SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +2.7V (continued)
At TA = +25°C, +VDD = +2.7V, unless otherwise noted.
ZERO-SCALE ERROR
vs
TEMPERATURE
FULL-SCALE ERROR
vs
TEMPERATURE
30
30
VDD = 2.7 V
VDD = 2.7 V
20
Full-Scale Error − mV
Zero-Scale Erro − mV
20
10
0
−10
−20
10
0
−10
−20
−30
−50 −40 −30 −20 −10 0
−30
10 20 30 40 50 60 70 80 90 100 110
−50 −40−30 −20 −10 0
T − Temperature − C
10 20 30 40 50 60 70 80 90 100 110
T − Temperature − C
Figure 25.
Figure 26.
IDD HISTOGRAM
SOURCE AND SINK CURRENT CAPABILITY
3
2500
VDD = 2.7 V
V D D = + 3V
D AC Lo ad ed w ith 3FFH
2
1500
VOUT (V)
f − Frequency − Hz
2000
1000
1
500
190
200
180
170
160
150
140
130
120
110
90
80
0
100
D AC Lo ade d w ith 000 H
0
IDD − Supply Current − A
0
5
10
15
I S O U R C E /S IN K (m A)
Figure 27.
Figure 28.
SUPPLY CURRENT
vs
CODE
SUPPLY CURRENT
vs
9 TEMPERATURE
500
300
VDD = 2.7 V
250
I DD − Supply Current − µ A
I DD − Supply Current − µ A
VDD = 2.7 V
400
300
200
100
0
0H
BH
80H 100H 180H 200H 280H 300H 380H 3F3H 3FFH
Code
Figure 29.
200
150
100
50
0
−50 −40 −30 −20 −10 0
10 20 30 40 50 60 70 80 90 100 110
T − Temperature − C
Figure 30.
11
DAC6571
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SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +2.7V (continued)
At TA = +25°C, +VDD = +2.7V, unless otherwise noted.
SUPPLY CURRENT
vs
LOGIC INPUT VOLTAGE
FULL SCALE SETTLING TIME
2500
C LK (2.7V /div)
IDD (µA)
2000
1500
1000
F ull−S c ale C o de C h an ge
000 H to 3 FF H
O utpu t L oad ed w ith
500
2 kΩ an d 200 pF to G N D
V O U T (1V /div )
0
Tim e (1 µ s/d iv )
1
0
2
3
4
5
VLOGIC (V)
Figure 31.
Figure 32.
FULL SCALE SETTLING TIME
HALF SCALE SETTLING TIME
CLK (2.7V/div)
CLK (2.7V/div)
Full−Scale Code Change
3FFH to 000H
Output Loaded with
2kΩ and 200pF to GND
VOUT (1V/div)
Half−Scale Code Change
256 to 768
VOUT (1V/div)
Output Loaded with
2 kΩ and 200 pF to GND
Time (1 µs/div)
Time (1µs/div)
Figure 33.
HALF SCALE SETTLING TIME
Figure 34.
POWER ON RESET 0 V
POWER-ON RESET to 0V
C LK (2.7V /div)
H alf−Sca le C ode C ha nge
768 to 256
V O U T (1V/d iv)
O u tp ut Lo aded w ith
2 kΩ and 200 pF to GND
Time (1 µs/div)
Figure 35.
12
Time (20µs/div)
Figure 36.
DAC6571
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SLAS406 – DECEMBER 2003
TYPICAL CHARACTERISTICS: VDD = +2.7V (continued)
At TA = +25°C, +VDD = +2.7V, unless otherwise noted.
EXITING-POWER DOWN (512 Loaded)
CODE CHANGE GLITCH
H
Loa de d w ith 2k and 2 00pF to G N D .
CLK (2.7V/div)
C ode C hange :
VOUT (1V/div)
Time (5µs/div)
Figure 37.
VOUT (20mV/div)
512 to 511
Time (0.5 µs/div)
Figure 38.
13
DAC6571
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SLAS406 – DECEMBER 2003
THEORY OF OPERATION
D/A SECTION
The architecture of the DAC6571 consists of a string DAC followed by an output buffer amplifier.Figure 39 shows
a generalized block diagram of the DAC architecture.
VDD
50 k
50 k
70 k
_
Ref+
Resistor String
Ref−
DAC Register
+
VOUT
GND
Figure 39. R-String DAC Architecture
The input coding to the DAC6571 is unsigned binary, which gives the ideal output voltage as:
V OUT Where D = decimal equivalent of the binary code that is loaded to the DAC register; it can range from 0 to 1023.
RESISTOR STRING
The resistor string section is shown in Figure 40. It is basically a divide-by-2 resistor, followed by a string of
resistors, each of value R. The code loaded into the DAC register determines at which node on the string the
voltage is tapped off to be fed into the ouptupt amplifier by closing one of the switches connecting the string to
the amplifier. Because the acrhitecture consists of a string of resistors, it is specified monotonic.
To Output
Amplifier
VDD
GND
R
R
R
R
Figure 40. Typical Resistor String
Output Amplifier
The output buffer amplifier is a gain-of-2 amplifier, capable of generating rail-to-rail voltages on its output, which
gives an output range of 0 V to VDD. It is capable of driving a load of 2 kΩ in parallel with 1000 pF to GND. The
source and sink capabilities of the output amplifier can be seen in the typical characteristics curves. The slew
rate is 1 V/µs with a half-scale settling time of 7 µs with the output unloaded.
I2C Interface
I2C is a 2-wire serial interface developed by Philips Semiconductor (see I2C-Bus Specification, Version 2.1,
January 2000). The bus consists of a data line (SDA) and a clock line (SCL) with pullup structures. When the bus
is idle, both SDA and SCL lines are pulled high. All the I2C compatible devices connect to the I2C bus through
open drain I/O pins, SDA and SCL. A master device, usually a microcontroller or a digital signal processor,
controls the bus. The master is responsible for generating the SCL signal and device addresses. The master also
generates specific conditions that indicate the START and STOP of data transfer. A slave device receives and/or
transmits data on the bus under control of the master device.
14
DAC6571
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SLAS406 – DECEMBER 2003
THEORY OF OPERATION (continued)
The DAC6571 works as a slave and supports the following data transfer modes, as defined in the I2C-Bus
Specification: standard mode (100 kbps), fast mode (400 kbps), and high-speed mode (3.4 Mbps). The data
transfer protocol for standard and fast modes is exactly the same, therefore they are referred to as F/S-mode in
this document. The protocol for high-speed mode is different from the F/S-mode, and it is referred to as
HS-mode. The DAC6571 supports 7-bit addressing; 10-bit addressing and general call address are not
supported.
F/S-Mode Protocol
•
•
•
•
The master initiates data transfer by generating a start condition. The start condition is when a high-to-low
transition occurs on the SDA line while SCL is high, as shown in Figure 41. All I2C-compatible devices should
recognize a start condition.
The master then generates the SCL pulses, and transmits the 7-bit address and the read/write direction bit
R/W on the SDA line. During all transmissions, the master ensures that data is valid. A valid data condition
requires the SDA line to be stable during the entire high period of the clock pulse (see Figure 42). All devices
recognize the address sent by the master and compare it to their internal fixed addresses. Only the slave
device with a matching address generates an acknowledge (see Figure 43) by pulling the SDA line low
during the entire high period of the ninth SCL cycle. Upon detecting this acknowledge, the master knows that
communication link with a slave has been established.
The master generates further SCL cycles to either transmit data to the slave (R/W bit 1) or receive data from
the slave (R/W bit 0). In either case, the receiver needs to acknowledge the data sent by the transmitter. So
an acknowledge signal can either be generated by the master or by the slave, depending on which one is the
receiver. 9-bit valid data sequences consisting of 8-bit data and 1-bit acknowledge can continue as long as
necessary.
To signal the end of the data transfer, the master generates a stop condition by pulling the SDA line from low
to high while the SCL line is high (see Figure 41). This releases the bus and stops the communication link
with the addressed slave. All I2C compatible devices must recognize the stop condition. Upon the receipt of a
stop condition, all devices know that the bus is released, and they wait for a start condition followed by a
matching address.
HS-Mode Protocol
•
•
•
When the bus is idle, both SDA and SCL lines are pulled high by the pullup devices.
The master generates a start condition followed by a valid serial byte containing HS master code 00001XXX.
This transmission is made in F/S-mode at no more than 400 Kbps. No device is allowed to acknowledge the
HS master code, but all devices must recognize it and switch their internal setting to support 3.4 Mbps
operation.
The master then generates a repeated start condition (a repeated start condition has the same timing as the
start condition). After this repeated start condition, the protocol is the same as F/S-mode, except that
transmission speeds up to 3.4 Mbps are allowed. A stop condition ends the HS-mode and switches all the
internal settings of the slave devices to support the F/S-mode. Instead of using a stop condition, repeated
start conditions should be used to secure the bus in HS-mode.
SDA
SDA
SCL
SCL
S
P
Start
Condition
Stop
Condition
Figure 41. START and STOP Conditions
15
DAC6571
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SLAS406 – DECEMBER 2003
THEORY OF OPERATION (continued)
SDA
SCL
Data Line
Stable;
Data Valid
Change of Data Allowed
Figure 42. Bit Transfer on the I2C Bus
Data Output
by Transmitter
Not Acknowledge
Data Output
by Receiver
Acknowledge
SCL From
Master
1
2
8
9
S
Clock Pulse for
Acknowledgement
START
Condition
Figure 43. Acknowledge on the I2C Bus
Recognize START or
REPEATED START
Condition
Recognize STOP or
REPEATED START
Condition
Generate ACKNOWLEDGE
Signal
P
SDA
MSB
Acknowledgement
Signal From Slave
Sr
Address
R/W
SCL
S
or
Sr
START or
Repeated START
Condition
1
2
7
8
9
ACK
1
2
9
ACK
Sr
or
P
Clock Line Held Low While
Interrupts are Serviced
STOP or
Repeated START
Condition
Figure 44. Bus Protocol
16
3-8
DAC6571
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SLAS406 – DECEMBER 2003
THEORY OF OPERATION (continued)
DAC6571 I2C Update Sequence
The DAC6571 requires a start condition, a valid I2C address, a control-MSB byte, and an LSB byte for a single
update. After the receipt of each byte, DAC6571 acknowledges by pulling the SDA line low during the high period
of a single clock pulse. A valid I2C address selects the DAC6571. The CTRL/MSB byte sets the operational
mode of the DAC6571, and the 4 most significant bits. The DAC6571 then receives the LSB byte containing 6
least significant data bits. DAC6571 performs an update on the falling edge of the acknowledge signal that
follows the LSB byte.
For the first update, DAC6571 requires a start condition, a valid I2C address, a CTRL/MSB byte, an LSB byte.
For all consecutive updates, DAC6571 needs a CTRL/MSB byte, and an LSB byte.
Using the I2C high-speed mode (fscl= 3.4 MHz), the clock running at 3.4 MHz, each 10-bit DAC update other than
the first update can be done within 18 clock cycles (CTRL/MSB byte, acknowledge signal, LSB byte,
acknowledge signal), at 188.88 KSPS. Using the fast mode (fscl= 400 kHz), clock running at 400 kHz, maximum
DAC update rate is limited to 22.22 KSPS. Once a stop condition is received, DAC6571 releases the I2C bus and
awaits a new start condition.
Address Byte
MSB
1
LSB
0
0
1
1
0
A0
0
The address byte is the first byte received following the START condition from the master device. The first six
bits (MSBs) of the address are factory preset to 100110. The next bit of the address is the device select bit A0.
The A0 address input can be connected to VDD or digital GND, or can be actively driven by TTL/CMOS logic
levels. The device address is set by the state of this pin during the power-up sequence of the DAC6571. Up to 2
devices (DAC6571) can be connected to the same I2C-Bus without requiring additional glue logic.
Broadcast Address Byte
MSB
1
LSB
0
0
1
0
0
0
0
Broadcast addressing is also supported by DAC6571. Broadcast addressing can be used for synchronously
updating or powering down multiple DAC6571 devices. Using the broadcast address, DAC6571 responds
regardless of the state of the address pin A0.
Control - Most Significant Byte
Most Significant Byte CTRL/MSB[7:0] consists of two zeros, two power-down bits, and four most significant bits
of 10-bit unsigned binary D/A conversion data.
Least Significant Byte
Least Significant Byte LSB[7:0] consists of the 6 least significant bits of the 10-bit unsigned binary D/A
conversion data, followed by 2 don't care bits. DAC6571 updates at the falling edge of the acknowledge signal
that follows the LSB[0] bit.
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DAC6571
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SLAS406 – DECEMBER 2003
Standard-and Fast-Mode:
S SLAVE ADDRESS
0
A
Ctrl/MS-Byte
A LS-Byte
A/A
P
Data Transferred
(n* Words + Acknowledge)
Word = 16 Bit
”0” (write)
From Master to DAC6571
DAC6571 I2C-SLAVE ADDRESS:
From DAC6571 to Master
MSB
A =
A =
S =
Sr =
P =
LSB
1
Acknowledge (SDA LOW)
Not Acknowledge (SDA HIGH)
START Condition
Repeated START Condition
STOP Condition
0
0
1
1
0
A0
0
Factory Preset
A0 = I2C Address Pin
High-Speed-Mode (HS-Mode):
F/S-Mode
S
HS-Mode
HS-Master Code
A Sr Slave Address
0
A
Ctrl/MS-Byte
HS-Mode Master Code:
A/A
P
HS-Mode Continues
Sr Slave Address
MSB
LSB
0
0
0
1
X
X
0
Ctrl/MS-Byte:
LS-Byte:
MSB
0
A LS-Byte
Data Transferred
(n* Words + Acknowledge)
Word = 16 Bit
”0” (write)
0
F/S-Mode
0
PD1 PD2
D9
D8
D7
LSB
MSB
D6
D5
LSB
D4
D3
D2
D1
D0
X
X
D9 − D0 = Data Bits
Figure 45. Master Transmitter Addressing DAC6571 as a Slave Receiver With a 7-Bit Address
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DAC6571
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SLAS406 – DECEMBER 2003
POWER-ON RESET
The DAC6571 contains a power-on reset circuit that controls the output voltage during power-up. On power-up,
the DAC register is filled with zeros and the output voltage is 0 V. It remains at a zero-code output until a valid
write sequence is made to the DAC. This is useful in applications where it is important to know the state of the
DAC output while it is in the process of powering up.
POWER-DOWN MODES
The DAC6571 contains four separate modes of operation. These modes are programmable via two bits (PD1
and PD0). Table 1 shows how the state of these bits correspond to the mode of operation.
Table 1. Modes of Operation for the DAC6571
PD1
PD0
0
0
OPERATING MODE
Normal Operation
0
1
1kΩ to AGND, PWD
1
0
100kΩ to AGND, PWD
1
1
High Impedance, PWD
When both bits are set to 0, the device works normally with normal power consumption of 150 µA at 5V.
However, for the three power-down modes, the supply current falls to 200 nA at 5 V (50 nA at 3 V). Not only
does the supply current fall but the output stage is also internally switched from the output of the amplifier to a
resistor network of known values. This has the advantage that the output impedance of the device is known while
in power-down mode. There are three different options: The output is connected internally to AGND through a 1
kΩ resistor, a 100 kΩ resistor, or it is left open-circuited (high impedance). The output stage is illustrated in
Figure 46.
Amplifier
Resistor
String DAC
VOUT
Powerdown
Circuitry
Resistor
Network
Figure 46. Output Stage During Power-Down
All linear circuitry is shut down when the power-down mode is activated. However, the contents of the DAC
register are unaffected when in power-down. The time required to exit power down is typically 2.5 µs for AVDD =
5 V and 5 µs for AVDD = 3V. See the Typical Characteristics for more information.
CURRENT CONSUMPTION
The DAC6571 typically consumes 150 µA at VDD = 5 V and 120 µA at VDD = 3 V. Additional current consumption
can occur due to the digital inputs if VIH << VDD. For most efficient power operation, CMOS logic levels are
recommended at the digital inputs to the DAC. In power-down mode, typical current consumption is 200 nA.
DRIVING RESISTIVE AND CAPACITIVE LOADS
The DAC6571 output stage is capable of driving loads of up to 1000 pF while remaining stable. Within the offset
and gain error margins, the DAC6571 can operate rail-to-rail when driving a capacitive load. When the outputs of
the DAC are driven to the positive rail under resistive loading, the PMOS transistor of each Class-AB output
stage can enter into the linear region. When this occurs, the added IR voltage drop deteriorates the linearity
performance of the DAC. This may occur within approximately the top 20 mV of the DAC's digital input-to-voltage
output transfer characteristic.
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DAC6571
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SLAS406 – DECEMBER 2003
OUTPUT VOLTAGE STABILITY
The DAC6571 exhibits excellent temperature stability of 5 ppm/°C typical output voltage drift over the specified
temperature range of the device. This enables the output voltage to stay within a ±25 µV window for a ±1°C
ambient temperature change. Combined with good dc noise performance and true 10-bit differential linearity, the
DAC6571 becomes a perfect choice for closed-loop control applications.
APPLICATIONS
USING REF02 AS A POWER SUPPLY FOR THE DAC6571
Due to the extremely low supply current required by the DAC6571, a possible configuration is to use a REF02 +5
V precision voltage reference to supply the required voltage to the DAC6571's supply input as well as the
reference input, as shown in Figure 47. This is especially useful if the power supply is quite noisy or if the system
supply voltages are at some value other than 5 V. The REF02 will output a steady supply voltage for the
DAC6571. If the REF02 is used, the current it needs to supply to the DAC6571 is 140 µA typical. When a DAC
output is loaded, the REF02 also needs to supply the current to the load. The total typical current required (with a
5 mW load on a given DAC output) is: 140 µA + (5 mW/5 V) = 1.14 mA.
The load regulation of the REF02 is typically (0.005%×VDD)/mA, which results in an error of 0.285 mV for the
1.14 mA current drawn from it. This corresponds to a 0.05 LSB error for a 0 V to 5 V output range.
15 V
REF02
5V
1.14 mA
I2C
Interface
A0
SCL
DAC6571
VOUT = 0 V to 5 V
SDA
Figure 47. REF02 as Power Supply to DAC6571
LAYOUT
A precision analog component requires careful layout, adequate bypassing, and clean, well-regulated power
supplies.
The power applied to VDD should be well regulated and low noise. Switching power supplies and DC/DC
converters will often have high-frequency glitches or spikes riding on the output voltage. In addition, digital
components can create similar high-frequency spikes as their internal logic switches states. This noise can easily
couple into the DAC output voltage through various paths between the power connections and analog output.
As with the GND connection, VDD should be connected to a +5V power supply plane or trace that is separate
from the connection for digital logic until they are connected at the power entry point. In addition, the 1 µF to 10
µF and 0.1 µF bypass capacitors are strongly recommended. In some situations, additional bypassing may be
required, such as a 100µF electrolytic capacitor or even a Pi filter made up of inductors and capacitors—all
designed to essentially low-pass filter the +5V supply, removing the high-frequency noise.
20
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