TI DAC8531E/250 Low-power, rail-to-rail output, 16-bit serial input digital-to-analog converter Datasheet

DAC8531
SBAS192B – MARCH 2001 – REVISED JUNE 2003
Low-Power, Rail-to-Rail Output, 16-Bit Serial Input
DIGITAL-TO-ANALOG CONVERTER
FEATURES
DESCRIPTION
● microPower OPERATION: 250µA at 5V
● POWER-ON RESET TO ZERO
● POWER SUPPLY: +2.7V to +5.5V
● ENSURED MONOTONIC BY DESIGN
● SETTLING TIME: 10µs to ±0.003 FSR
● LOW-POWER SERIAL INTERFACE WITH
SCHMITT-TRIGGERED INPUTS
● ON-CHIP OUTPUT BUFFER AMPLIFIER,
RAIL-TO-RAIL OPERATION
● SYNC INTERRUPT FACILITY
● PACKAGES: MSOP-8 and 3x3 SON-8 (same
size as QFN)
The DAC8531 is a low-power, single, 16-bit buffered voltage
output Digital-to-Analog Converter (DAC). Its on-chip precision output amplifier allows rail-to-rail output swing to be
achieved. The DAC8531 uses a versatile three-wire serial
interface that operates at clock rates up to 30MHz and is
compatible with standard SPI™, QSPI™, Microwire™, and
Digital Signal Processor (DSP) interfaces.
The DAC8531 requires an external reference voltage to set
the output range of the DAC. The DAC8531 incorporates a
power-on reset circuit that ensures that the DAC output
powers up at 0V and remains there until a valid write takes
place to the device. The DAC8531 contains a power-down
feature, accessed over the serial interface, that reduces the
current consumption of the device to 200nA at 5V.
The low power consumption of this part in normal operation
makes it ideally suited to portable battery-operated equipment. The power consumption is 2mW at 5V reducing to 1µW
in power-down mode.
APPLICATIONS
●
●
●
●
●
●
PROCESS CONTROL
DATA ACQUISITION SYSTEMS
CLOSED-LOOP SERVO-CONTROL
PC PERIPHERALS
PORTABLE INSTRUMENTATION
PROGRAMMABLE ATTENUATION
The DAC8531 is available in both MSOP-8 and 3x3 SON-8
(same size as QFN) packages.
VDD
VFB
VREF
Ref (+)
VOUT
16-Bit DAC
16
DAC Register
16
SYNC
SCLK
DIN
Shift Register
Power-Down
Control Logic
Resistor
Network
GND
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.
All trademarks are the property of their respective owners.
Copyright © 2001-2003, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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ABSOLUTE MAXIMUM RATINGS(1)
ELECTROSTATIC
DISCHARGE SENSITIVITY
VDD to GND ........................................................................... –0.3V to +6V
Digital Input Voltage to GND ................................. –0.3V to +VDD + 0.3V
VOUT to GND .......................................................... –0.3V to +VDD + 0.3V
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 ........................................................ (TJ max — TA)/θJA
θJA Thermal Impedance ......................................................... 206°C/W
θJC Thermal Impedance .......................................................... 44°C/W
Lead Temperature, Soldering:
Vapor Phase (60s) ............................................................... +215°C
Infrared (15s) ........................................................................ +220°C
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.
NOTE: (1) 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.
PACKAGE/ORDERING INFORMATION
PRODUCT
MINIMUM
RELATIVE
ACCURACY
(LSB)
DIFFERENTIAL
NONLINEARITY
(LSB)
DAC8531E
±64
"
"
DAC8531I
DAC8531I
PACKAGE-LEAD
PACKAGE
DESIGNATOR(1)
SPECIFICATION
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
±1
MSOP-8
DGK
–40°C to +105°C
D31
"
"
"
"
"
DAC8531E/250
DAC8531E/2K5
Tape and Reel, 250
Tape and Reel, 2500
±64
±1
SON-8
DRB
–40°C to +105°C
D31
"
"
"
"
"
"
DAC8531IDRBT
DAC8531IDRBR
Tape and Reel, 250
Tape and Reel, 2500
NOTE: (1) For the most current specifications and package information, refer to our web site at www.ti.com.
ELECTRICAL CHARACTERISTICS
VDD = +2.7V to +5.5V. –40°C to +105°C, unless otherwise specified.
DAC8531E
PARAMETER
STATIC PERFORMANCE (1)
Resolution
Relative Accuracy
Differential Nonlinearity
Zero Code Error
Full-Scale Error
Gain Error
Zero Code Error Drift
Gain Temperature Coefficient
OUTPUT CHARACTERISTICS (2)
Output Voltage Range
Output Voltage Settling Time
Slew Rate
Capacitive Load Stability
Code Change Glitch Impulse
Digital Feedthrough
DC Output Impedance
Short-Circuit Current
Power-Up Time
REFERENCE INPUT
Reference Current
CONDITIONS
MIN
TYP
MAX
16
Ensured Monotonic by Design
All Zeroes Loaded to DAC Register
All Ones Loaded to DAC Register
+5
–0.15
±20
±5
0
To ±0.003% FSR
0200H to FD00H
RL = 2kΩ; 0pF < CL < 200pF
RL = 2kΩ; CL = 500pF
8
RL = ∞
RL = 2kΩ
1LSB Change Around Major Carry
VDD = +5V
VDD = +3V
Coming Out of Power-Down Mode
VDD = +5V
Coming Out of Power-Down Mode
VDD = +3V
VREF = VDD = +5V
VREF = VDD = +3.6V
Reference Input Range
Reference Input Impedance
±0.098
±1
+20
–1.25
±1.25
UNITS
Bits
% of FSR
LSB
mV
% of FSR
% of FSR
µV/°C
ppm of FSR/°C
VREF
V
10
µs
12
1
470
1000
20
0.5
1
50
20
µs
V/µs
pF
pF
nV-s
nV-s
Ω
mA
mA
2.5
µs
5
µs
35
20
0
150
45
30
VDD
µA
µA
V
kΩ
NOTES: (1) Linearity calculated using a reduced code range of 485 to 64714; output unloaded. (2) Ensured by design and characterization, not production tested.
2
DAC8531
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SBAS192B
ELECTRICAL CHARACTERISTICS (Cont.)
VDD = +2.7V to +5.5V. –40°C to +105°C, unless otherwise specified.
DAC8531E
PARAMETER
CONDITIONS
LOGIC INPUTS (2)
Input Current
VINL, Input LOW Voltage
VINL, Input LOW Voltage
VINH, Input HIGH Voltage
VINH, Input HIGH Voltage
Pin Capacitance
VDD
VDD
VDD
VDD
POWER REQUIREMENTS
VDD
IDD (normal mode)
VDD = +3.6V to +5.5V
VDD = +2.7V to +3.6V
IDD (all power-down modes)
VDD = +3.6V to +5.5V
VDD = +2.7V to +3.6V
=
=
=
=
MIN
+5V
+3V
+5V
+3V
MAX
UNITS
±1
0.8
0.6
3
µA
V
V
V
V
pF
5.5
V
2.4
2.1
2.7
DAC Active and Excluding Load Current
VIH = VDD and VIL = GND
VIH = VDD and VIL = GND
250
240
400
390
µA
µA
VIH = VDD and VIL = GND
VIH = VDD and VIL = GND
0.2
0.05
1
1
µA
µA
ILOAD = 2mA, VDD = +5V
89
POWER EFFICIENCY
IOUT/IDD
TEMPERATURE RANGE
Specified Performance
–40
%
+105
°C
PIN DESCRIPTION
PIN CONFIGURATIONS
Top View
MSOP-8, SON-8
VDD
1
8
GND
VREF
2
7
DIN
VFB
3
6
SCLK
VOUT
4
5
SYNC
DAC8531
PIN
DAC8531
SBAS192B
TYP
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NAME
DESCRIPTION
1
VDD
Power-Supply Input, +2.7V to +5.5V.
2
VREF
Reference Voltage Input
3
VFB
Feedback connection for the output amplifier.
4
VOUT
Analog output voltage from DAC. The output amplifier has rail-to-rail operation.
5
SYNC
Level-triggered control input (active LOW). This is
the frame sychronization signal for the input data.
When SYNC goes LOW, it enables the input shift
register and data is transferred in on the falling
edges of the following clocks. The DAC is updated
following the 24th clock cycle unless SYNC is taken
HIGH before this edge, in which case the rising
edge of SYNC acts as an interrupt and the write
sequence is ignored by the DAC8531.
6
SCLK
Serial Clock Input. Data can be transferred at rates
up to 30MHz.
7
DIN
Serial Data Input. Data is clocked into the 24-bit
input shift register on the falling edge of the serial
clock input.
8
GND
Ground reference point for all circuitry on the part.
3
TIMING CHARACTERISTICS(1, 2)
VDD = +2.7V to +5.5V; all specifications –40°C to +105°C unless otherwise noted.
DAC8531E
PARAMETER
t1
(3)
t2
t3
t4
t5
t6
t7
t8
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNITS
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
50
33
ns
ns
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
13
13
ns
ns
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
22.5
13
ns
ns
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
0
0
ns
ns
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
5
5
ns
ns
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
4.5
4.5
ns
ns
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
0
0
ns
ns
VDD = 2.7V to 3.6V
VDD = 3.6V to 5.5V
50
33
ns
ns
SCLK Cycle Time
SCLK HIGH Time
SCLK LOW Time
SYNC to SCLK Rising
Edge Setup Time
Data Setup Time
Data Hold Time
SCLK Falling Edge to
SYNC Rising Edge
Minimum SYNC HIGH Time
NOTES: (1) All input signals are specified with tR = tF = 5ns (10% to 90% of VDD) and timed from a voltage level of (VIL + VIH)/2. (2) See Serial Write Operation timing
diagram, below. (3) Maximum SCLK frequency is 30MHz at VDD = +3.6V to +5.5V and 20MHz at VDD = +2.7V to +3.6V.
SERIAL WRITE OPERATION
t1
SCLK
t8
t3
t4
t2
t7
SYNC
t6
t5
DIN
4
DB23
DB0
DAC8531
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SBAS192B
TYPICAL CHARACTERISTICS: VDD = 5V
At TA = +25°C, VDD = 5V, unless otherwise noted.
NOTE: All references to IDD include IREF current.
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+25°C)
LE (LSB)
64
48
32
16
0
–16
–32
–48
–64
2.0
1.5
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
DLE (LSB)
DLE (LSB)
LE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(–40°C)
64
48
32
16
0
–16
–32
–48
–64
2.0
1.5
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
Digital Input Code
Digital Input Code
DLE (LSB)
ZERO-SCALE ERROR vs TEMPERATURE
20
64
48
32
16
0
–16
–32
–48
–64
15
10
2.0
1.5
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
Error (mV)
LE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+105°C)
5
0
–5
–10
–15
–20
–40
0
40
80
120
Temperature (°C)
Digital Input Code
FULL-SCALE ERROR vs TEMPERATURE
IDD HISTOGRAM
20
2000
15
1500
5
Frequency
Error (mV)
10
0
–5
–10
1000
500
–15
–20
–40
0
0
40
80
120
100 130
Temperature (°C)
IDD (µA)
DAC8531
SBAS192B
160 190 220 250 280 310 340 370 400
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5
TYPICAL CHARACTERISTICS: VDD = 5V (Cont.)
At TA = +25°C, VDD = 5V, unless otherwise noted.
NOTE: All references to IDD include IREF current.
SOURCE AND SINK CURRENT CAPABILITY
SUPPLY CURRENT vs DIGITAL INPUT CODE
5
500
DAC Loaded with FFFFH
400
3
IDD (µA)
VOUT (V)
4
2
1
300
200
100
DAC Loaded with 0000H
0
0
0
5
10
15
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
ISOURCE/SINK (mA)
Digital Input Code
POWER-SUPPLY CURRENT vs TEMPERATURE
SUPPLY CURRENT vs SUPPLY VOLTAGE
350
350
300
300
250
250
200
200
IDD (µA)
Quiescent Current (µA)
VREF tied to VDD.
150
150
100
100
50
50
0
–40
0
40
80
0
120
2.7
3.2
3.7
4.2
Temperature (°C)
4.7
5.2
5.7
VDD (V)
POWER-DOWN CURRENT vs SUPPLY VOLTAGE
SUPPLY CURRENT vs LOGIC INPUT VOLTAGE
100
700
90
600
80
500
60
IDD (µA)
IDD (nA)
70
+105°C
50
–40°C
40
400
300
30
20
200
+25°C
10
0
100
2.7
3.2
3.7
4.2
4.7
5.2
5.7
VDD (V)
6
0
1
2
3
4
5
VLOGIC (V)
DAC8531
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SBAS192B
TYPICAL CHARACTERISTICS: VDD = 5V (Cont.)
At TA = +25°C, VDD = 5V, unless otherwise noted.
FULL-SCALE SETTLING TIME
FULL-SCALE SETTLING TIME
Scope Trigger (5.0V/div)
Scope Trigger (5.0V/div)
Large-Signal Output (1.0V/div)
Small-Signal Error (1mV/div)
Small-Signal Error (1mV/div)
Full-Scale Code Change
FFFFH to 0000H
Output Loaded with
2kΩ and 200pF to GND
Full-Scale Code Change
0000H to FFFFH
Output Loaded with
2kΩ and 200pF to GND
Large-Signal Output (1.0V/div)
Time (2µs/div)
Time (2µs/div)
HALF-SCALE SETTLING TIME
HALF-SCALE SETTLING TIME
Scope Trigger (5.0V/div)
Scope Trigger (5.0V/div)
Large-Signal Output (1.0V/div)
Small-Signal Error (1mV/div)
Small-Signal Error (1mV/div)
Large-Signal Output (1V/div)
Half-Scale Code Change
4000H to C000H
Output Loaded with
2kΩ and 200pF to GND
Half-Scale Code Change
C000H to 4000H
Output Loaded with
2kΩ and 200pF to GND
Time (2µs/div)
Time (2µs/div)
EXITING POWER-DOWN
(8000H Loaded)
POWER-ON RESET TO 0V
Loaded with 2kΩ to VDD.
Scope Trigger (5.0V/div)
VDD (2V/div)
Output (1.0V/div)
VOUT (1V/div)
Time (2µs/div)
Time (50µs/div)
DAC8531
SBAS192B
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7
TYPICAL CHARACTERISTICS: VDD = 5V (Cont.)
At TA = +25°C, VDD = 5V, unless otherwise noted.
VOUT (50mV/div)
CODE CHANGE GLITCH
Glitch Waveform (50mV/div)
Time (2µs/div)
TYPICAL CHARACTERISTICS: VDD = 2.7V
At TA = +25°C, VDD = 2.7V, unless otherwise noted.
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+25°C)
LE (LSB)
64
48
32
16
0
–16
–32
–48
–64
2.0
1.5
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
DLE (LSB)
DLE (LSB)
LE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(–40°C)
64
48
32
16
0
–16
–32
–48
–64
2.0
1.5
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
Digital Input Code
Digital Input Code
DLE (LSB)
ZERO-SCALE ERROR vs TEMPERATURE
20
64
48
32
16
0
–16
–32
–48
–64
15
10
2.0
1.5
1.0
0.5
0.0
–0.5
–1.0
–1.5
–2.0
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
Error (mV)
LE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+105°C)
0
–5
–10
–15
–20
–40
0
40
80
120
Temperature (°C)
Digital Input Code
8
5
DAC8531
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SBAS192B
TYPICAL CHARACTERISTICS: VDD = 2.7V
At TA = +25°C, VDD = 2.7V, unless otherwise noted.
NOTE: All references to IDD include IREF current.
FULL-SCALE ERROR vs TEMPERATURE
IDD HISTOGRAM
20
2000
15
1500
5
Frequency
Error (mV)
10
0
–5
–10
1000
500
–15
0
–20
–40
0
40
80
120
100 130
160 190 220 250 280 310 340 370 400
Temperature (°C)
IDD (µA)
SUPPLY CURRENT vs DIGITAL INPUT CODE
SOURCE AND SINK CURRENT CAPABILITY
500
3.0
2.5
400
DAC Loaded with FFFFH
IDD (µA)
VOUT (V)
2.0
1.5
300
200
1.0
100
0.5
DAC Loaded with 0000H
0
0.0
0
5
10
0000H 2000H 4000H 6000H 8000H A000H C000H E000H FFFFH
15
Digital Input Code
ISOURCE/SINK (mA)
SUPPLY CURRENT vs LOGIC INPUT VOLTAGE
200
300
180
250
160
IDD (µA)
Quiescent Current (µA)
POWER SUPPLY CURRENT vs TEMPERATURE
350
200
150
140
120
100
100
50
80
0
–40
0
40
80
120
0
DAC8531
SBAS192B
0.5
1
1.5
2
2.5
3
VLOGIC (V)
Temperature (°C)
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9
TYPICAL CHARACTERISTICS: VDD = 2.7V (Cont.)
At TA = +25°C, VDD = 2.7V, unless otherwise noted.
FULL-SCALE SETTLING TIME
FULL-SCALE SETTLING TIME
Scope Trigger (5.0V/div)
Scope Trigger (5.0V/div)
Large-Signal Output (1.0V/div)
Small-Signal Error (1mV/div)
Small-Signal Error (1mV/div)
Large-Signal Output (1.0V/div)
Full-Scale Code Change
0000H to FFFFH
Output Loaded with
2kΩ and 200pF to GND
Full-Scale Code Change
FFFFH to 0000H
Output Loaded with
2kΩ and 200pF to GND
Time (2µs/div)
Time (2µs/div)
HALF-SCALE SETTLING TIME
HALF-SCALE SETTLING TIME
Scope Trigger (5.0V/div)
Scope Trigger (5.0V/div)
Large-Signal Output (1.0V/div)
Small-Signal Error (1mV/div)
Small-Signal Error (1mV/div)
Large-Signal Output (1.0V/div)
Half-Scale Code Change
4000H to C000H
Output Loaded with
2kΩ and 200pF to GND
Half-Scale Code Change
C000H to 4000H
Output Loaded with
2kΩ and 200pF to GND
Time (2µs/div)
Time (2µs/div)
POWER-ON RESET to 0V
EXITING POWER-DOWN
(8000H Loaded)
Loaded with 2kΩ to VDD.
Scope Trigger (5.0V/div)
VDD (1V/div)
Output (1.0V/div)
VOUT (1V/div)
Time (50µs/div)
10
Time (2µs/div)
DAC8531
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SBAS192B
TYPICAL CHARACTERISTICS: VDD = 2.7V (Cont.)
At TA = +25°C, VDD = 2.7V, unless otherwise noted.
VOUT (20mV/div)
CODE CHANGE GLITCH
Glitch Waveform (20mV/div)
Time (2µs/div)
RESISTOR STRING
THEORY OF OPERATION
DAC SECTION
The architecture consists of a string DAC followed by an
output buffer amplifier. Figure 1 shows a block diagram of the
DAC architecture.
Figure 2 shows the resistor string section. It is simply 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 output amplifier by closing one
of the switches connecting the string to the amplifier. It is
ensured monotonic because it is a string of resistors.
VDD
DAC Register
VFB
R
VOUT
REF (+)
Resistor String
REF(–)
Output
Amplifier
R
GND
R
To Output
Amplifier
FIGURE 1. DAC8531 Architecture.
The input coding to the DAC8531 is straight binary, so the
ideal output voltage is given by:
VOUT = VREF •
D
65536
R
where D = decimal equivalent of the binary code that is
loaded to the DAC register; it can range from 0 to 65535.
R
FIGURE 2. Resistor String.
DAC8531
SBAS192B
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11
OUTPUT AMPLIFIER
The output buffer amplifier is capable of generating rail-to-rail
voltages on its output which gives an output range of
0V to VDD. It is capable of driving a load of 2kΩ in parallel with
1000pF to GND. The source and sink capabilities of the
output amplifier can be seen in the typical curves. The slew
rate is 1V/µs with a full-scale settling time of 8µs with the
output unloaded.
The inverting input of the output amplifier is brought out to the
VFB pin. This allows for better accuracy in critical applications
by tying the VFB point and the amplifier output together
directly at the load. Other signal conditioning circuitry
may also be connected between these points for specific
applications.
SERIAL INTERFACE
SYNC buffer draws more current when the SYNC signal is
HIGH than it does when it is LOW, SYNC should be idled
LOW between write sequences for lowest power operation of
the part. As mentioned above, it must be brought HIGH again
just before the next write sequence.
INPUT SHIFT REGISTER
The input shift register is 24 bits wide, as shown in Figure 3.
The first six bits are “don’t cares”. The next two bits (PD1 and
PD0) are control bits that control which mode of operation the
part is in (normal mode or any one of three power-down
modes). There is a more complete description of the various
modes in the Power-Down Modes section. The next 16 bits
are the data bits. These are transferred to the DAC register
on the 24th falling edge of SCLK.
SYNC INTERRUPT
The DAC8531 has a three-wire serial interface (SYNC,
SCLK, and DIN), which is compatible with SPI, QSPI, and
Microwire interface standards as well as most DSPs. See the
Serial Write Operation timing diagram for an example of a
typical write sequence.
The write sequence begins by bringing the SYNC line LOW.
Data from the DIN line is clocked into the 24-bit shift register
on the falling edge of SCLK. The serial clock frequency can
be as high as 30MHz, making the DAC8531 compatible with
high-speed (DSPs). On the 24th falling edge of the serial
clock, the last data bit is clocked in and the programmed
function is executed (i.e., a change in DAC register contents
and/or a change in the mode of operation).
At this point, the SYNC line may be kept LOW or brought
HIGH. In either case, it must be brought HIGH for a minimum
of 33ns before the next write sequence so that a falling edge
of SYNC can initiate the next write sequence. Since the
In a normal write sequence, the SYNC line is kept LOW for
at least 24 falling edges of SCLK and the DAC is updated on
the 24th falling edge. However, if SYNC is brought HIGH
before the 24th falling edge, this acts as an interrupt to the
write sequence. The shift register is reset and the write
sequence is seen as invalid. Neither an update of the DAC
register contents or a change in the operating mode occurs,
as shown in Figure 4.
POWER-ON RESET
The DAC8531 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 0V; it
remains there 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 output of the DAC while it is in the
process of powering up.
DB23
X
DB0
X
X
X
X
X
PD1
PD0 D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
FIGURE 3. Data Input Register.
24th Falling Edge
24th Falling Edge
CLK
SYNC
DIN
DB23
DB0
DB23
Invalid Write Sequence:
SYNC HIGH before 24th Falling Edge
DB0
Valid Write Sequence: Output Updates
on the 24th Falling Edge
FIGURE 4. SYNC Interrupt Facility.
12
DAC8531
www.ti.com
SBAS192B
POWER-DOWN MODES
The DAC8531 supports four separate modes of operation.
These modes are programmable by setting two bits (PD1
and PD0) in the control register. Table I shows how the state
of the bits corresponds to the mode of operation of the
device.
PD1 (DB17)
PD0 (DB16)
0
0
OPERATING MODE
Normal Operation
—
—
Power-Down Modes
0
1
Output 1kΩ to GND
1
0
Output 100kΩ to GND
1
1
High-Z
TABLE I. Modes of Operation for the DAC8531.
When both bits are set to 0, the part works normally with its
typical current consumption of 250µA at 5V. However, for the
three power-down modes, the supply current falls to 200nA
at 5V (50nA at 3V). 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 part is known
while the part is in power-down mode. There are three
different options. The output is connected internally to GND
through a 1kΩ resistor, a 100kΩ resistor, or it is left opencircuited (High-Z). The output stage is illustrated in Figure 5.
MICROPROCESSOR
INTERFACING
DAC8531 TO 8051 INTERFACE
Figure 6 shows a serial interface between the DAC8531 and
a typical 8051-type microcontroller. The setup for the interface is as follows: TXD of the 8051 drives SCLK of the
DAC8531, while RXD drives the serial data line of the part.
The SYNC signal is derived from a bit-programmable pin on
the port. In this case, port line P3.3 is used. When data is to
be transmitted to the DAC8531, P3.3 is taken LOW. The
8051 transmits data only in 8-bit bytes; thus only eight falling
clock edges occur in the transmit cycle. To load data to the
DAC, P3.3 is left LOW after the first eight bits are transmitted
and a second write cycle is initiated to transmit the second
byte of data. P3.3 is taken HIGH following the completion of
the third write cycle. The 8051 outputs the serial data in a
format which has the LSB first. The DAC8531 requires its
data with the MSB as the first bit received. The 8051 transmit
routine must therefore take this into account, and “mirror” the
data as needed.
80C51/80L51(1)
DAC8531(1)
P3.3
SYNC
TXD
SCLK
RXD
DIN
NOTE: (1) Additional pins omitted for clarity.
VFB
Resistor
String DAC
Amplifier
FIGURE 6. DAC8531 to 80C51/80L51 Interface.
VOUT
DAC8531 TO Microwire INTERFACE
Power-Down
Circuitry
Figure 7 shows an interface between the DAC8531 and any
Microwire compatible device. Serial data is shifted out on the
falling edge of the serial clock and is clocked into the
DAC8531 on the rising edge of the SK signal.
Resistor
Network
FIGURE 5. Output Stage During Power-Down.
MicrowireTM
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 to exit
power-down is typically 2.5µs for VDD = 5V, and 5µs
for VDD = 3V. See the Typical Characteristics for more
information.
DAC8531(1)
CS
SYNC
SK
SCLK
SO
DIN
NOTE: (1) Additional pins omitted for clarity.
Microwire is a registered trademark of National Semiconductor.
FIGURE 7. DAC8531 to Microwire Interface.
DAC8531
SBAS192B
www.ti.com
13
DAC8531 TO 68HC11 INTERFACE
Figure 8 shows a serial interface between the DAC8531 and
the 68HC11 microcontroller. SCK of the 68HC11 drives the
SCLK of the DAC8531, while the MOSI output drives the
serial data line of the DAC. The SYNC signal is derived from
a port line (PC7), similar to what was done for the 8051.
power supply is quite noisy or if the system supply voltages
are at some value other than 5V. The REF02 will output a
steady supply voltage for the DAC8531. If the REF02 is
used, the typical current it needs to supply to the DAC8531
is 250µA. This is with no load on the output of the DAC.
When the DAC output is loaded, the REF02 also needs to
supply the current to the load. The total current required (with
a 5kΩ load on the DAC output) is:
250µA + (5V/ 5kΩ) = 1.29mA
DAC8531(1)
68HC11(1)
PC7
SYNC
SCK
SCLK
MOSI
The load regulation of the REF02 is typically 0.005%/mA,
which results in an error of 322µV for the 1.29mA current
drawn from it. This corresponds to a 4.2LSB error.
DIN
NOTE: (1) Additional pins omitted for clarity.
BIPOLAR OPERATION USING THE DAC8531
FIGURE 8. DAC8531 to 68HC11 Interface.
The 68HC11 should be configured so that its CPOL bit is a
0 and its CPHA bit is a 1. This configuration causes data
appearing on the MOSI output to be valid on the falling edge
of SCK. When data is being transmitted to the DAC, the
SYNC line is taken LOW (PC7). Serial data from the 68HC11
is transmitted in 8-bit bytes with only eight falling clock edges
occurring in the transmit cycle. Data is transmitted MSB first.
In order to load data to the DAC8531, PC7 is left LOW after
the first eight bits are transferred, then a second and third
serial write operation is performed to the DAC and PC7 is
taken HIGH at the end of this procedure.
The output voltage for any input code can be calculated as
follows:

 R2  
 D   R1 + R 2 
VO = VREF • 
 •
 – VREF • 



R
65536


 R1  

1
where D represents the input code in decimal (0–65535).
With VREF = 5V, R1 = R2 = 10kΩ:
 10 • D 
VO = 
 – 5V
 65536 
APPLICATIONS
USING REF02 AS A POWER SUPPLY FOR
THE DAC8531
Due to the extremely low supply current required by the
DAC8531, an alternative option is to use a REF02 +5V
precision voltage reference to supply the required voltage to
the part, as shown in Figure 9. This is especially useful if the
This is an output voltage range of ±5V with 0000H corresponding to a –5V output and FFFFH corresponding to a +5V
output. Similarly, using VREF = 2.5V, ±2.5V output voltage
raw can be achieved.
LAYOUT
A precision analog component requires careful layout, adequate bypassing, and clean, well-regulated power supplies.
+15
As the DAC8531 offers single-supply operation, it will often
be used in close proximity with digital logic, microcontrollers,
microprocessors, and digital signal processors. The more
digital logic present in the design and the higher the switching speed, the more difficult it will be to keep digital noise
from appearing at the output.
+5V
REF02
285µA
SYNC
Three-Wire
Serial
Interface
The DAC8531 has been designed for single-supply operation
but a bipolar output range is also possible using the circuit in
Figure 10. The circuit shown will give an output voltage range
of ±VREF. Rail-to-rail operation at the amplifier output is achievable using an OPA703 as the output amplifier.
SCLK
DAC8531
VOUT = 0V to 5V
DIN
Due to the single ground pin of the DAC8531, all return
currents, including digital and analog return currents, must
flow through the GND pin. Ideally, GND would be connected
directly to an analog ground plane. This plane would be
separate from the ground connection for the digital components until they were connected at the power-entry point of
the system.
FIGURE 9. REF02 as a Power Supply to the DAC8531.
14
DAC8531
www.ti.com
SBAS192B
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 1µF to 10µF and 0.1µF
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 lowpass filter the +5V supply, removing the high-frequency
noise.
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.
R2
10kΩ
VREF
+5V
R1
10kΩ
OPA703
VFB
VREF
10µF
DAC8531
0.1µF
±5V
VOUT
–5V
Three-Wire
Serial
Interface
FIGURE 10. Bipolar Operation with the DAC8531.
DAC8531
SBAS192B
www.ti.com
15
PACKAGE DRAWINGS
DGK (R-PDSO-G8)
PLASTIC SMALL-OUTLINE PACKAGE
0,38
0,25
0,65
8
0,08 M
5
0,15 NOM
3,05
2,95
4,98
4,78
Gage Plane
0,25
1
0°– 6°
4
3,05
2,95
0,69
0,41
Seating Plane
1,07 MAX
0,15
0,05
0,10
4073329/C 08/01
NOTES: A.
B.
C.
D.
16
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Body dimensions do not include mold flash or protrusion.
Falls within JEDEC MO-187
DAC8531
www.ti.com
SBAS192B
PACKAGE DRAWINGS (Cont.)
DAC8531
SBAS192B
www.ti.com
17
PACKAGE OPTION ADDENDUM
www.ti.com
19-May-2004
PACKAGING INFORMATION
ORDERABLE DEVICE
STATUS(1)
PACKAGE TYPE
PACKAGE DRAWING
PINS
PACKAGE QTY
DAC8531E/250
ACTIVE
VSSOP
DGK
8
250
DAC8531E/2K5
ACTIVE
VSSOP
DGK
8
2500
DAC8531IDRBR
ACTIVE
SON
DRB
8
3000
DAC8531IDRBT
ACTIVE
SON
DRB
8
250
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
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