DA
C8
820
DAC8820
www.ti.com
SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
16-Bit, Parallel Input Multiplying Digital-to-Analog Converter
FEATURES
APPLICATIONS
•
•
•
•
•
•
•
•
•
•
•
1
2
•
•
•
•
•
•
•
±0.5 LSB DNL
±1 LSB INL
16-Bit Monotonic
Low Noise: 10 nV/√Hz
Low Power: IDD = 2 µA
Analog Power Supply: +2.7 V to +5.5 V
1.66 mA Full-Scale Current,
with VREF = 10 V
Settling Time: 0.5 µs
4-Quadrant Multiplying Reference
Reference Bandwidth: 8 MHz
Reference Input: ±15 V
Reference Dynamics: –105 dB THD
SSOP-28 Package
Industry-Standard Pin Configuration
Automatic Test Equipment
Instrumentation
Digitally Controlled Calibration
Industrial Control PLCs
DESCRIPTION
The DAC8820, a multiplying digital-to-analog
converter (DAC), is designed to operate from a single
2.7 V to 5.5 V supply.
The applied external reference input voltage VREF
determines the full-scale output current. An internal
feedback resistor (RFB) provides temperature tracking
for the full-scale output when combined with an
external, current-to-voltage (I/V) precision amplifier.
A
parallel
interface
offers
high-speed
communications. The DAC8820 is packaged in a
space-saving SSOP-28 package and has an
industry-standard pinout.
VDD
R1
RCOM
R1
DAC8820
REF
R2
ROFS
RFB
ROFS
RFB
D0
¼
D15
DAC
Parallel Bus
Input
Register
AGND
WR
RST
LDAC
IOUT
DAC
Register
Control
Logic
DGND
1
2
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.
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 © 2005–2008, Texas Instruments Incorporated
DAC8820
www.ti.com
SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
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.
ORDERING INFORMATION (1)
PRODUCT
RELATIVE
ACCURACY
(LSB)
DIFFERENTIAL
NONLINEARITY
(LSB)
PACKAGELEAD
(DESIGNATOR)
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
DAC8820IB
±2
±1
DB-28 (SSOP)
–40°C to +85°C
DAC8820
DAC8820IC
±1
±1
DB-28 (SSOP)
–40°C to +85°C
DAC8820
(1)
ORDERING
NUMBER
TRANSPORT MEDIA,
QUANTITY
DAC8820IBDB
Tubes, 48
DAC8820IBDBR
Tape and Reel, 2000
DAC8820ICDB
Tubes, 48
DAC8820ICDBR
Tape and Reel, 2000
For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS (1)
Over operating free-air temperature range (unless otherwise noted)
DAC8820
UNIT
–0.3 to +7
V
Digital input voltage to GND
–0.3 to +VDD + 0.3
V
V (IOUT) to GND
–0.3 to +VDD + 0.3
V
±25
V
Operating temperature range
–40 to +85
°C
Storage temperature range
–65 to +150
°C
+125
°C
(TJ max – TA) / RθJA
W
VDD to GND
REF, ROFS, RFB, R1, RCOM to AGND, DGND
Junction temperature range (TJ max)
Power dissipation
55
°C/W
Human Body Model (HBM)
4000
V
Charged Device Model (CDM)
1000
V
Thermal impedance, RθJA
ESD rating
(1)
2
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.
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Copyright © 2005–2008, Texas Instruments Incorporated
Product Folder Link(s): DAC8820
DAC8820
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
ELECTRICAL CHARACTERISTICS
All specifications at –40°C to +85C, VDD = +2.7 V to +5.5 V, IOUT = virtual GND, GND = 0 V, VREF = 10 V, and TA = full
operating temperature, unless otherwise noted.
DAC8820
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
STATIC PERFORMANCE
Resolution
16
Bits
Relative accuracy
DAC8820IB
±2
LSB
Relative accuracy
DAC8820IC
±1
LSB
±1
LSB
nA
Differential nonlinearity
±0.5
Output leakage current
Data = 0000h, TA = +25°C
5
Output leakage current
Data = 0000h, TA = TMAX
10
nA
Full-scale gain error
Unipolar, data = FFFFh
2
±16
LSB
Bipolar, data = FFFFh
2
±16
LSB
1
2
ppm/°C
TA = +25°C
±5
LSB
TA = TMAX
±8
LSB
±2.0
LSB/V
Full-scale temperature coefficient
Bipolar zero scale error
PSRR
Power-supply rejection ratio; VDD = 5 V ±10%
±0.2
OUTPUT CHARACTERISTICS (1)
Output current
Output capacitance
Code dependent
1.66
mA
50
pF
REFERENCE INPUT
VREF Range
–15
RREF
Input resistance (unipolar)
4.5
Input capacitance
LOGIC INPUTS AND OUTPUT
Input leakage current
Input capacitance
7.5
kΩ
pF
R1/R2 resistance (bipolar)
9
12
15
kΩ
Feedback and offset resistance
9
12
15
kΩ
VIL VDD = +2.7 V
0.6
V
VIL VDD = +5 V
0.8
V
ROFS, RFB
Input high voltage
V
5
R1/R2
Input low voltage
6
15
(1)
VIH VDD = +2.7 V
2.1
VIH VDD = +5 V
2.4
IIL
V
V
0.001
CIL
1
µA
8
pF
INTERFACE TIMING, VDD = +5.0V (1) (See Figure 40 and Table 1)
tDS Data to WR setup time
20
ns
tDH Data to WR hold time
0
ns
tWR WR pulse width
20
ns
tLDAC LDAC pulse width
20
ns
Data setup time
tRST RST pulse width
20
ns
Data hold time
tLWD WR to LDAC delay time
0
ns
35
ns
INTERFACE TIMING, VDD = +2.7V (1) (See Figure 40 and Table 1)
tDS Data to WR setup time
tDH Data to WR hold time
0
ns
tWR WR pulse width
35
ns
tLDAC LDAC pulse width
35
ns
Data setup time
tRST RST pulse width
35
ns
Data hold time
tLWD WR to LDAC delay time
0
ns
(1)
Specified by design and characterization; not production tested.
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DAC8820
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
ELECTRICAL CHARACTERISTICS (continued)
All specifications at –40°C to +85C, VDD = +2.7 V to +5.5 V, IOUT = virtual GND, GND = 0 V, VREF = 10 V, and TA = full
operating temperature, unless otherwise noted.
DAC8820
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
POWER REQUIREMENTS
VDD
2.7
IDD (normal operation)
Logic inputs = 0 V
VDD = +4.5 V to +5.5 V
VIH = VDD and VIL = GND
VDD = +2.7 V to +3.6 V
VIH = VDD and VIL = GND
5.5
V
5
µA
3
5
µA
1
2.5
µA
AC CHARACTERISTICS (2)
Output current settling time
0.5
µs
Reference multiplying BW
VREF = 5 VPP, Data = FFFFh
8
MHz
DAC glitch impulse
VREF = 0 V to 10 V,
Data = 7FFFh to 8000h to 7FFFh
2
nV–s
Feedthrough error VOUT/VREF
Data = 0000h, VREF = 10 kHz, ±10 VPP
–70
dB
Digital feedthrough
LDAC = Logic low, VREF = –10 V to + 10 V
Any code change
1
nV–s
Total harmonic distortion
VREF = 6 VRMS, Data = FFFFh, f = 1 kHz
–105
dB
10
nV/√Hz
Output spot noise voltage
(2)
Specified by design and characterization; not production tested.
TERMINAL FUNCTIONS
PIN ASSIGNMENTS
REF
1
28
RST
RCOM
2
27
D0
R1
3
26
D1
R OFS
4
25
D2
RFB
5
24
IOUT
6
AGND
7
LDAC
PIN #
NAME
1
REF
Reference input and 4-quadrant resistor
(R2).
2
RCOM
Center tap of two 4-quadrant resistors
(R1 and R2).
3
R1
4
ROFS
Bipolar offset resistor
D3
5
RFB
Internal matching feedback resistor
23
VDD
6
IOUT
DAC current output
22
DGND
7
AGND
Analog ground
8
21
D4
LDAC
WR
9
20
D5
Digital input load DAC control. When
LDAC is high, data is loaded from input
register into a DAC register, updating the
DAC output.
D15
10
19
D6
D14
11
18
D7
D13
12
17
D8
D12
13
16
D9
D11
14
15
D10
DAC8820
8
4
DESCRIPTION
9
WR
10–21
D15–D4
22
DGND
23
VDD
24–27
D3–D0
28
RST
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4-quadrant resistor (R1).
Write control digital input. Active low.
When WR is taken to logic low, data is
loaded from the digital input pins (D0–D15)
into a16-bit input register.
Digital input data bits. D15 is MSB.
Digital ground
Positive power supply
Digital Input data bits. D0 is LSB.
Reset. Active low. When RST is taken to
logic low, the DAC register is set to zero
code, resulting in the DAC output being
set to 0 V.
Copyright © 2005–2008, Texas Instruments Incorporated
Product Folder Link(s): DAC8820
DAC8820
www.ti.com
SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS: VDD = +5 V
At TA = +25°C, unless otherwise noted.
LINEARITY ERROR
vs DIGITAL INPUT CODE
1.0
1.0
TA = +25°C
VREF = +10V
0.8
0.6
0.6
0.4
0.4
0.2
0
-0.2
0
-0.2
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
0
1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 1.
Figure 2.
LINEARITY ERROR
vs DIGITAL INPUT CODE
DIFFERENTIAL LINEARITY ERROR
vs DIGITAL INPUT CODE
1.0
TA = -40° C
VREF = +10V
0.8
TA = -40° C
VREF = +10V
0.8
0.6
0.6
0.4
0.4
DNL (LSB)
INL (LSB)
0.2
-0.4
-1.0
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
-1.0
0
1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 3.
Figure 4.
LINEARITY ERROR
vs DIGITAL INPUT CODE
DIFFERENTIAL LINEARITY ERROR
vs DIGITAL INPUT CODE
1.0
TA = +85°C
VREF = +10V
0.8
TA = +85°C
VREF = +10V
0.8
0.6
0.6
0.4
0.4
DNL (LSB)
INL (LSB)
TA = +25°C
VREF = +10V
0.8
DNL (LSB)
INL (LSB)
DIFFERENTIAL LINEARITY ERROR
vs DIGITAL INPUT CODE
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
-1.0
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
Figure 5.
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 6.
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DAC8820
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS: VDD = +5 V (continued)
At TA = +25°C, unless otherwise noted.
SUPPLY CURRENT
vs LOGIC INPUT VOLTAGE
REFERENCE MULTIPLYING BANDWIDTH
UNIPOLAR MODE
180
140
0xFFFF
0x8000
0x4000
0x2000
0x1000
0x0800
0x0400
0x0200
0x0100
0x0080
0x0040
0x0020
0x0010
0x0008
0x0004
0x0002
0x0001
Attenuation (dB)
Supply Current, IDD (mA)
VDD = +5.0V
120
100
80
60
40
VDD = +2.7V
20
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0x0000
10
5.0
100
1k
10M
100M
REFERENCE MULTIPLYING BANDWIDTH
BIPOLAR MODE
REFERENCE MULTIPLYING BANDWIDTH
BIPOLAR MODE
10k
100k
1M
10M
100M
Attenuation (dB)
Attenuation (dB)
1k
6
0
-6
-12
-18
-24
-30
-36
-42
-48
-54
-60
-66
-72
-78
-84
-90
-96
-102
-108
-114
Codes from
Midscale to
Zero Scale
10
100
1k
10k
100k
1M
10M
0x0000
0x4000
0x6000
0x5000
0x4800
0x4400
0x4200
0x4100
0x4080
0x4040
0x4020
0x4010
0x4008
0x4004
0x4002
0x4001
0x8000
Digital Code
100
Digital Code
0xFFFF
0xC000
0xA000
0x9000
0x8800
0x8400
0x8200
0x8100
0x8080
0x8040
0x8020
0x8010
0x8008
0x8004
0x8002
0x8001
0x8000
100M
Bandwidth (Hz)
Figure 9.
Figure 10.
MIDSCALE DAC GLITCH
MIDSCALE DAC GLITCH
VREF = +10V
VREF = +10V
Code: 7FFFh to 8000h
LDAC Pulse
Output Voltage (20mV)
Output Voltage (20mV)
1M
Figure 8.
Bandwidth (Hz)
Code: 8000h to 7FFFh
LDAC Pulse
Time (0.5ms)
Time (0.5ms)
Figure 11.
6
100k
Figure 7.
Codes from
Full-scale to
Midscale
10
10k
Bandwidth (Hz)
Logic Input Voltage (V)
6
0
-6
-12
-18
-24
-30
-36
-42
-48
-54
-60
-66
-72
-78
-84
-90
-96
-102
-108
-114
Digital Code
6
0
-6
-12
-18
-24
-30
-36
-42
-48
-54
-60
-66
-72
-78
-84
-90
-96
-102
-108
-114
160
Figure 12.
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DAC8820
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS: VDD = +5 V (continued)
At TA = +25°C, unless otherwise noted.
FULL-SCALE ERROR
vs TEMPERATURE
4.8
3.8
BIPOLAR-ZERO ERROR
vs TEMPERATURE
1.5
VREF = +10V
1.0
Bipolar-Zero Error (mV)
2.8
Full-Scale Error (mV)
VREF = +10V
1.8
0.8
0
-0.8
-1.8
-2.8
0.5
0
-0.5
-1.0
-3.8
-1.5
-4.8
-60
-40
-20
0
20
40
60
80
100
-60
Temperature (°C)
-40
-20
0
20
40
60
80
100
Temperature (°C)
Figure 13.
Figure 14.
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DAC8820
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS: VDD = +2.7 V
At TA = +25°C, unless otherwise noted.
LINEARITY ERROR
vs DIGITAL INPUT CODE
1.0
1.0
TA = +25°C
VREF = +10V
0.8
0.6
0.6
0.4
0.4
0.2
0
-0.2
0
-0.2
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
0
1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 15.
Figure 16.
LINEARITY ERROR
vs DIGITAL INPUT CODE
DIFFERENTIAL LINEARITY ERROR
vs DIGITAL INPUT CODE
1.0
TA = -40° C
VREF = +10V
0.8
TA = -40° C
VREF = +10V
0.8
0.6
0.6
0.4
0.4
DNL (LSB)
INL (LSB)
0.2
-0.4
-1.0
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
-1.0
0
1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 17.
Figure 18.
LINEARITY ERROR
vs DIGITAL INPUT CODE
DIFFERENTIAL LINEARITY ERROR
vs DIGITAL INPUT CODE
1.0
TA = +85°C
VREF = +10V
0.8
TA = +85°C
VREF = +10V
0.8
0.6
0.6
0.4
0.4
DNL (LSB)
INL (LSB)
TA = +25°C
VREF = +10V
0.8
DNL (LSB)
INL (LSB)
DIFFERENTIAL LINEARITY ERROR
vs DIGITAL INPUT CODE
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
-1.0
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
Figure 19.
8
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 20.
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS: VDD = +2.7 V (continued)
At TA = +25°C, unless otherwise noted.
DAC GLITCH
DAC GLITCH
Output Voltage (20mV)
VREF = +10V
Output Voltage (20mV)
VREF = +10V
Code: 7FFFh to 8000h
LDAC Pulse
Code: 8000h to 7FFFh
LDAC Pulse
Time (0.5ms)
4.8
3.8
Time (0.5ms)
Figure 21.
Figure 22.
FULL-SCALE ERROR
vs TEMPERATURE
BIPOLAR-ZERO ERROR
vs TEMPERATURE
1.5
VREF =+ 10V
1.0
Bipolar-Zero Error (mV)
2.8
Full-Scale Error (mV)
VREF = +10V
1.8
0.8
0
-0.8
-1.8
-2.8
0.5
0
-0.5
-1.0
-3.8
-1.5
-4.8
-60
-40
-20
0
20
40
60
80
100
-60
Temperature (°C)
-40
-20
0
20
40
60
80
100
Temperature (°C)
Figure 23.
Figure 24.
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS
At TA = +25°C, unless otherwise noted.
IDD vs TEMPERATURE
DAC SETTLING TIME
5.0
4.5
Output Voltage (5V/div)
4.0
IDD (µA)
3.5
3.0
5.0V
2.5
2.0
1.5
Unipolar Mode
Voltage Output Settling
1.0
Trigger Pulse
2.7V
0.5
0
−40
−20
0
20
40
60
80
Time (0.5ms/div)
100
Temperature (_ C)
1.0
Figure 26.
INTEGRAL NONLINEARITY vs VREF
UNIPOLAR MODE
INTEGRAL NONLINEARITY vs VREF
BIPOLAR MODE
1.0
VDD = 5V
0.8
0.6
0.6
0.4
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-0.8
-8
-4
-2
0
2
4
6
8
-1.0
10
-10
-6
-4
-2
0
2
4
6
VREF (V)
Figure 28.
DIFFERENTIAL NONLINEARITY vs VREF
UNIPOLAR MODE
DIFFERENTIAL NONLINEARITY vs VREF
BIPOLAR MODE
1.0
VDD = 5V
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
-0.6
-0.8
-0.8
-4
-2
0
2
4
6
8
10
8
10
-0.2
-0.4
-6
VDD = 2.7V
0
-0.6
-8
10
0.2
-0.4
-1.0
8
VDD = 5V
0.8
VDD = 2.7V
-10
-8
VREF (V)
0.8
DNL (LSB)
-6
Figure 27.
1.0
10
0
-0.2
-0.6
-1.0
VDD = 2.7V
0.2
-0.4
-10
VDD = 5V
0.8
VDD = 2.7V
INL (LSB)
INL (LSB)
Figure 25.
-1.0
-10
-8
-6
-4
-2
0
2
VREF (V)
VREF (V)
Figure 29.
Figure 30.
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6
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SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, unless otherwise noted.
INTEGRAL NONLINEARITY vs VDD
UNIPOLAR MODE
1.0
0.4
INL (LSB)
0.4
0.2
0
-0.2
0
-0.2
-0.4
-0.6
-0.6
-0.8
-0.8
1.0
2.3
2.8
3.3
3.8
4.3
4.8
-1.0
5.3 5.5
4.3
4.8
5.3 5.5
DIFFERENTIAL NONLINEARITY vs VDD
BIPOLAR MODE
1.0
DNL (LSB)
0.4
0
-0.2
0
-0.2
-0.4
-0.6
-0.6
-0.8
-0.8
2.8
3.3
3.8
4.3
4.8
-1.0
5.3 5.5
VREF = 2.5V
0.2
-0.4
2.3
VREF = 10V
0.8
0.2
-65
3.8
DIFFERENTIAL NONLINEARITY vs VDD
UNIPOLAR MODE
0.4
-55
3.3
VDD (V)
0.6
-45
2.8
Figure 32.
VREF = 2.5V
1.8
2.3
VDD(V)
0.6
-1.0
1.8
Figure 31.
VREF = 10V
0.8
VREF = 2.5V
0.2
-0.4
1.8
2.3
2.8
3.3
3.8
4.3
4.8
5.3 5.5
VDD (V)
VDD (V)
Figure 33.
Figure 34.
BIPOLAR MULTIPLYING MODE THD
vs FREQUENCY
BIPOLAR MULTIPLYING MODE THD
vs FREQUENCY
500kHz Filter
80kHz Filter
30kHz Filter
Code FFFFh
VREF = 6VRMS
VDD = +5V
Two OPA627s
C1 = 20pF
-75
-85
-95
-105
-115
-45
Total Harmonic Distortion (dB)
INL (LSB)
0.6
1.8
VREF = 10V
0.8
VREF = 2.5V
0.6
-1.0
DNL (LSB)
1.0
VREF = 10V
0.8
Total Harmonic Distortion (dB)
INTEGRAL NONLINEARITY vs VDD
BIPOLAR MODE
-55
-65
500kHz Filter
80kHz Filter
30kHz Filter
Code 0000h
VREF = 6VRMS
VDD = +5V
Two OPA627s
C1 = 20pF
-75
-85
-95
-105
-115
10
100
1000
10k 20k 30k
10
Frequency (Hz)
100
1000
10k 20k 30k
Frequency (Hz)
Figure 35.
Figure 36.
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, unless otherwise noted.
UNIPOLAR MULTIPLYING MODE THD
vs FREQUENCY
Total Harmonic Distortion (dB)
-45
-55
-65
500kHz Filter
80kHz Filter
30kHz Filter
Code FFFFh
VREF = 6VRMS
VDD = +5V
One OPA627
C1 = 20pF
-75
-85
-95
-105
-115
10
100
1000
10k 20k 30k
Frequency (Hz)
Figure 37.
THEORY OF OPERATION
The DAC8820 is a multiplying, single-channel current output, 16-bit DAC. The architecture, illustrated in
Figure 38, is an R-2R ladder configuration with the three MSBs segmented. Each 2R leg of the ladder is either
switched to GND or to the IOUT terminal. The IOUT terminal of the DAC is held at a virtual GND potential by the
use of an external I/V converter op amp. The R-2R ladder is connected to an external reference input (VREF) that
determines the DAC full-scale current. The R-2R ladder presents a code independent load impedance to the
external reference of 6 kΩ ±25%. The external reference voltage can vary in a range of –15 V to +15 V, thus
providing bipolar IOUT current operation. By using an external I/V converter op amp and the RFB resistor in the
DAC8820, an output voltage range of –VREF to +VREF can be generated.
R
R
VREF
R
¼
2R
2R
2R
2R
2R
2R
2R
2R
2R
2R
2R
2R
RFB
IOUT
GND
¼
¼
Figure 38. Equivalent R-2R DAC Circuit
The DAC output voltage is determined by VREF and the digital data (D) according to Equation 1:
D
V OUT + *VREF
65536
(1)
Each DAC code determines the 2R-leg switch position to either GND or IOUT. The external I/V converter op amp
noise gain will also change because the DAC output impedance (as seen looking into the IOUT terminal) changes
versus code. Because of this, the external I/V converter op amp must have a sufficiently low offset voltage such
that the amplifier offset is not modulated by the DAC IOUT terminal impedance change. External op amps with
large offset voltages can produce INL errors in the transfer function of the DAC8820 because of offset
modulation versus DAC code. For best linearity performance of the DAC8820, an op amp (OPA277) is
recommended, as shown in Figure 39. This circuit allows VREF to swing from –10 V to +10 V.
12
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VDD
U1
VDD ROFS RFB
+15 V
U2
VREF
V+
IOUT
DAC8820
VOUT
OPA277
V−
GND
−15 V
Figure 39. Voltage Output Configuration
tWR
WR
DATA
tDS
tDH
tLWD
LDAC
tLDAC
tRST
RST
Figure 40. DAC8820 Timing Diagram
Table 1. Function of Control Inputs
CONTROL INPUTS
RST
WR
LDAC
REGISTER OPERATION
0
X
X
Asynchronous operation. The DAC register is set to zero code, resulting in the DAC output being set
to 0 V. The DAC input register contents are not reset by the RST signal.
1
0
0
Load the input register with all 16 data bits.
1
1
1
Load the DAC register with the contents of the input register.
1
0
1
The input and DAC register are transparent.
LDAC and WR are tied together and programmed as a pulse. The 16 data bits are loaded into the
input register on the falling edge of the pulse and then loaded into the DAC register on the rising
edge of the pulse.
1
1
1
0
No register operation.
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APPLICATION INFORMATION
Multiplying Mode THD vs Frequency
Figure 35 and Figure 36 show the DAC8820 bipolar 4-quadrant multiplying mode total harmonic distortion (THD)
versus frequency. Figure 35 shows the bipolar multiplying mode THD with the DAC8820 set to a full-scale code
of FFFFh. Figure 36 shows the bipolar multiplying mode THD with the DAC8820 set to a minus full scale code of
0000h. In both graphs, two OPA627s are used for both the DAC output op amp and the reference inverting
amplifier. A 6 VRMS sine wave is used for the reference input VREF and is swept in frequency from 10 Hz to 30
kHz. The THD levels versus frequency are illustrated at various DAC output filtering levels using an external
ac-coupled low-pass filter.
Figure 37 illustrates the DAC8820 unipolar 2-quadrant multiplying mode THD versus frequency. The DAC8820 is
set to a full-scale code of FFFFh. A single OPA627 is used for the DAC output op amp.
Stability Circuit
For a current-to-voltage (I/V) design, as shown in Figure 41, the DAC8820 current output (IOUT) and the
connection with the inverting node of the op amp should be as short as possible and laid out according to correct
printed circuit board (PCB) layout design. For each code change there is a step function. If the gain bandwidth
product (GBP) of the op amp is limited and parasitic capacitance is excessive at the inverting node, then gain
peaking is possible. Therefore, a compensation capacitor C1 (4 pF to 20 pF, typ) can be added to the design for
circuit stability, as shown in Figure 41.
VDD
U1
VDD ROFS RFB
C1
VREF
VREF
DAC8820
IOUT
OPA277
GND
VOUT
U2
Figure 41. Gain Peaking Prevention Circuit with Compensation Capacitor
Bipolar Output Circuit
The DAC8820, as a 4-quadrant multiplying DAC, can be used to generate a bipolar output. The polarity of the
full-scale output (IOUT) is the inverse of the input reference voltage at VREF.
Using a dual op amp, such as the OPA2277, full 4-quadrant operation can be achieved with minimal
components. Figure 42 demonstrates a ±10 VOUT circuit with a fixed +10 V reference.
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V OUT +
SBAS358D – AUGUST 2005 – REVISED FEBRUARY 2008
ǒ32,D768 *1Ǔ
V REF
(2)
VREF
U1
OPA2277
VDD
R1
RCOM
R1
DAC8820
REF
R2
ROFS
RFB
ROFS
RFB
D0
¼
D15
DAC
Parallel Bus
Input
Register
C1
IOUT
DAC
Register
U2
OPA2277
VOUT
AGND
WR
RST
LDAC
Control
Logic
DGND
Figure 42. Bipolar Output Circuit
Programmable Current Source Circuit
A DAC8820 can be integrated into the circuit in Figure 43 to implement an improved Howland current pump for
precise V/I conversions. Bidirectional current flow and high-voltage compliance are two features of the circuit.
With a matched resistor network, the load current of the circuit is shown by Equation 3:
(R2)R3) ń R1
IL +
V REF D
R3
(3)
The value of R3 in the previous equation can be reduced to increase the output current drive of U3. U3 can drive
±20 mA in both directions with voltage compliance limited up to 15 V by the U3 voltage supply. Elimination of the
circuit compensation capacitor (C1) in the circuit is not suggested as a result of the change in the output
impedance (ZO), according to Equation 4:
R1ȀR3(R1)R2)
ZO +
R1(R2Ȁ)R3Ȁ) * R1Ȁ(R2)R3)
(4)
As shown in Equation 4, ZO with matched resistors is infinite and the circuit is optimum for use as a current
source. However, if unmatched resistors are used, ZO is positive or negative with negative output impedance
being a potential cause of oscillation. Therefore, by incorporating C1 into the circuit, possible oscillation problems
are eliminated. The value of C1 can be determined for critical applications; for most applications, however, a
value of several pF is suggested.
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R2′
15 kΩ
C1
10 pF
VDD
R1′
150 kΩ
U3
R3′
50 kΩ
U1
U2
VREF
VREF
IOUT
DAC8820
VOUT
OPA277
C2
10 pF
VDD ROFS RFB
R1
150 kΩ
R2
15 kΩ
R3
50 Ω
IL
OPA277
LOAD
GND
Figure 43. Programmable Bidirectional Current Source Circuit
Cross-Reference
The DAC8820 has an industry-standard pinout. Table 2 provides the cross-reference information.
Table 2. Cross-Reference
PRODUCT
BIT
INL (LSB)
DNL (LSB)
SPECIFIED
TEMPERATURE
RANGE
DAC8820IBDB
16
±2
±1
–40°C to +85°C
SSOP-28
SSOP-28
LTC1597BIG
DAC8820ICDB
16
±1
±1
–40°C to +85°C
SSOP-28
SSOP-28
LTC1597AIG
16
PACKAGE
DESCRIPTION
PACKAGE
OPTION
CROSSREFERENCE
PART
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Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (June 2006) to Revision D .................................................................................................... Page
•
•
•
•
Changed front page block diagram........................................................................................................................................ 1
Changed pin 28 description text in Terminal Functions table................................................................................................ 4
Changed first row description text in Table 1 ...................................................................................................................... 13
Changed Figure 42 ............................................................................................................................................................. 15
Changes from Revision B (March 2006) to Revision C .................................................................................................. Page
•
•
Changed from "voltage-to-current" to "current-to-voltage"..................................................................................................... 1
Added bipolar zero scale error specification.......................................................................................................................... 3
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
DAC8820IBDB
ACTIVE
SSOP
DB
28
50
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8820
DAC8820IBDBR
ACTIVE
SSOP
DB
28
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8820
DAC8820ICDB
ACTIVE
SSOP
DB
28
50
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8820
DAC8820ICDBG4
ACTIVE
SSOP
DB
28
50
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8820
DAC8820ICDBR
ACTIVE
SSOP
DB
28
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8820
(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.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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