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DAC8812
SBAS349F – AUGUST 2005 – REVISED JUNE 2016
DAC8812 Dual, Serial-Input 16-Bit Multiplying Digital-to-Analog Converter
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Features
3 Description
The DAC8812 is a dual, 16-bit, current-output digitalto-analog converter (DAC) designed to operate from
a single 2.7-V to 5.5-V supply.
Relative Accuracy: 1 LSB Max
Differential Nonlinearity: 1 LSB Max
2-mA Full-Scale Current ±20%,
With VREF = ±10 V
0.5-μs Settling Time
Midscale or Zero-Scale Reset
Separate 4Q Multiplying Reference Inputs
Reference Bandwidth: 10 MHz
Reference Dynamics: –105-dB THD
SPI™-Compatible 3-Wire Interface:
50 MHz
Double Buffered Registers to Enable
Simultaneous Multichannel Update
Internal Power-On Reset
Industry-Standard Pin Configuration
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 I-to-V precision amplifier.
A double-buffered, serial data interface offers highspeed, 3-wire, SPI and microcontroller compatible
inputs using serial data in (SDI), clock (CLK), and a
chip-select (CS). A common level-sensitive load DAC
strobe (LDAC) input allows simultaneous update of all
DAC outputs from previously loaded input registers.
Additionally, an internal power-on reset forces the
output voltage to zero at system turnon. An MSB pin
allows system reset assertion (RS) to force all
registers to zero code when MSB = 0, or to midscale
code when MSB = 1.
Applications
Device Information(1)
Automatic Test Equipment
Instrumentation
Digitally Controlled Calibration
PART NUMBER
PACKAGE
DAC8812
TSSOP (16)
BODY SIZE (NOM)
5.00 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Space
Space
Space
Functional Block Diagram
VREFA B
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
A0
A1
SDI
RFBA
16
Input
Register
R
DAC A
Register
R
DAC A
IOUTA
AGNDA
RFBB
Input
Register
R
DAC B
Register
R
DAC B
IOUTB
AGNDB
CLK
CS
EN
DAC A
B
Decode
DGND
Power-On
Reset
RS
MSB
LDAC
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
DAC8812
SBAS349F – AUGUST 2005 – REVISED JUNE 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
4
4
4
4
5
6
6
8
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics..........................................
Timing Requirements ................................................
Switching Characteristics ..........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 13
8.1 Overview ................................................................. 13
8.2 Functional Block Diagram ....................................... 13
8.3 Feature Description................................................. 13
8.4 Device Functional Modes........................................ 15
9
Application and Implementation ........................ 18
9.1 Application Information............................................ 18
9.2 Typical Application ................................................. 18
10 Power Supply Recommendations ..................... 19
11 Layout................................................................... 20
11.1 Layout Guidelines ................................................. 20
11.2 Layout Example .................................................... 21
12 Device and Documentation Support ................. 22
12.1
12.2
12.3
12.4
12.5
12.6
Documentation Support ........................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
22
22
22
22
22
22
13 Mechanical, Packaging, and Orderable
Information ........................................................... 22
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision E (March 2016) to Revision F
Page
•
Changed the maximum TA value from 125°C to 85°C in the Recommended Operating Conditions table ........................... 4
•
Changed the name of the input resistance match parameter to Channel-to-channel input resistance match in the
Electrical Characteristics table ............................................................................................................................................... 5
•
Made VREF negative in the equation for VOUT ....................................................................................................................... 14
•
Added the Receiving Notification of Documentation Updates section ................................................................................ 22
Changes from Revision D (January 2016) to Revision E
•
Changed the DAC8812 Timing Diagram image ..................................................................................................................... 7
Changes from Revision C (November 2015) to Revision D
•
Page
Page
Changed the DAC8812 Timing Diagram image to show the setup and hold time with respect to rising edge .................... 7
Changes from Revision B (February 2007) to Revision C
Page
•
Added ESD Ratings table, Timing Requirements and Switching Characteristics tables, Feature Description section,
Device Functional Modes, Application and Implementation section, Power Supply Recommendations section,
Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information
section. .................................................................................................................................................................................. 1
•
Replaced Package/Ordering Information table with Device Comparison table...................................................................... 3
•
Added I/O column to Pin Functions table ............................................................................................................................... 3
2
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SBAS349F – AUGUST 2005 – REVISED JUNE 2016
5 Device Comparison Table
DEVICE
MAXIMUM RELATIVE ACCURACY (LSB)
DAC8812C
±1
DAC8812B
±2
6 Pin Configuration and Functions
PW Package
16-Pin TSSOP
Top View
RFBA
1
16
CLK
VREFA
2
15
LDAC
IOUTA
3
14
MSB
AGNDA
4
13
VDD
AGNDB
5
12
DGND
IOUTB
6
11
CS
VREFB
7
10
RS
RFBB
8
9
SDI
Pin Functions
PIN
NO.
NAME
I/O
DESCRIPTION
1
RFBA
I
Establish voltage output for DAC A by connecting to external amplifier output.
2
VREFA
I
DAC A reference voltage input pin. Establishes DAC A full-scale output voltage. Can be tied to VDD pin.
3
IOUTA
O
DAC A current output
4
AGNDA
—
DAC A analog ground
5
AGNDB
—
DAC B analog ground
6
IOUTB
O
DAC B current output
7
VREFB
I
DAC B reference voltage input pin. Establishes DAC B full-scale output voltage. Can be tied to VDD pin.
8
RFBB
I
Establish voltage output for DAC B by connecting to external amplifier output.
9
SDI
I
Serial data input; data loads directly into the shift register.
10
RS
I
Reset pin; active-low input. Input registers and DAC registers are set to all 0s or midscale. Register data =
0x0000 when MSB = 0. Register data = 0x8000 when MSB = 1 for DAC8812.
11
CS
I
Chip-select; active-low input. Disables shift register loading when high. Transfers serial register data to input
register when CS goes high. Does not affect LDAC operation.
12
DGND
—
13
VDD
I
Positive power-supply input. Specified range of operation 2.7 V to 5.5 V.
14
MSB
I
MSB bit sets output to either 0 or midscale during a RESET pulse (RS) or at system power-on. Output
equals zero scale when MSB = 0 and midscale when MSB = 1. MSB pin can be permanently tied to ground
or VDD.
15
LDAC
I
Load DAC register strobe; level-sensitive active-low. Transfers all input register data to the DAC registers.
Asynchronous active-low input. See Table 2 for operation.
16
CLK
I
Clock input. Positive edge clocks data into shift register.
Digital ground
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7 Specifications
7.1 Absolute Maximum Ratings
over operating ambient temperature range (unless otherwise noted) (1)
VDD to GND
MIN
MAX
UNIT
–0.3
7
V
VREFx, RFBx to GND
–18
18
V
Digital logic inputs to GND
–0.3
VDD + 0.3
V
IOUTx to GND
–0.3
VDD + 0.3
V
AGNDx to DGND
–0.3
0.3
V
Input current to any pin except supplies
–50
50
mA
(TJmax – TA) /
RθJA
W
Package power dissipation
Maximum junction temperature (TJmax)
150
°C
Operating temperature
–40
85
°C
Storage temperature, Tstg
–65
150
°C
(1)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
7.2 ESD Ratings
VALUE
Electrostatic
discharge
V(ESD)
(1)
(2)
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±4000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±1000
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Pins listed as ±4000
V may actually have higher performance.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Pins listed as ±1000
V may actually have higher performance.
7.3 Recommended Operating Conditions
over operating ambient temperature range (unless otherwise noted)
MIN
NOM
MAX
UNIT
VDD
Supply voltage to GND
2.7
5.5
V
TA
Operating ambient temperature
–40
85
°C
7.4 Thermal Information
DAC8812
THERMAL METRIC (1)
PW (TSSOP)
UNIT
16 PINS
RθJA
Junction-to-ambient thermal resistance
100.6
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
32.8
°C/W
RθJB
Junction-to-board thermal resistance
46.8
°C/W
ψJT
Junction-to-top characterization parameter
2
°C/W
ψJB
Junction-to-board characterization parameter
46
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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7.5
SBAS349F – AUGUST 2005 – REVISED JUNE 2016
Electrical Characteristics
VDD = 2.7 V to 5.5 V, IOUTX = Virtual GND, AGNDX = 0 V, VREFA,B = 10 V, TA = full operating temperature range, unless
otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
STATIC PERFORMANCE (1)
Resolution
INL
Relative accuracy
DNL
Differential nonlinearity
IOUTx
Output leakage current
GFSE
Full-scale gain error
TCVFS
Full-scale temperature
coefficient (2)
RFBX
Feedback resistor
REFERENCE INPUT
16
DAC8812B
±2
DAC8812C
±1
±1
Data = 0000h, TA = 25°C
10
Data = 0000h, TA = TA max
20
Data = FFFFh
±0.75
VDD = 5 V
LSB
LSB
nA
mV
1
ppm/°C
5
kΩ
(2)
VREFx
VREFx range
RREFx
Input resistance
–15
4
Channel-to-channel input
resistance match
CREFx
±4
Bits
5
15
V
6
kΩ
1%
Input capacitance
5
pF
ANALOG OUTPUT (2)
IOUTx
Output current
Data = FFFFh
COUTx
Output capacitance
Code-dependent
1.6
2.5
mA
50
pF
LOGIC INPUTS (2)
VIL
Input low voltage
VIH
Input high voltage
IIL
Input leakage current
CIL
Input capacitance
(1)
(2)
VDD = 2.7 V
0.6
VDD = 5 V
0.8
VDD = 2.7 V
2.1
VDD = 5 V
2.4
V
V
1
μA
10
pF
All static performance tests (except IOUT) are performed in a closed-loop system using an external precision OPA277 I-to-V converter
amplifier. The DAC8812 RFB pin is tied to the amplifier output. Typical values represent average readings measured at 25°C.
These parameters are not subject to production testing.
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Electrical Characteristics (continued)
VDD = 2.7 V to 5.5 V, IOUTX = Virtual GND, AGNDX = 0 V, VREFA,B = 10 V, TA = full operating temperature range, unless
otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY CHARACTERISTICS
VDD RANGE
Power supply range
5.5
V
Logic inputs = 0 V, VDD = 4.5 V to 5.5 V
2.7
2
5
μA
Logic inputs = 0 V, VDD = 2.7 V to 3.6 V
1
2.5
μA
0.0275
mW
IDD
Positive supply current
PDISS
Power dissipation
Logic inputs = 0 V
PSS
Power supply sensitivity
ΔVDD = ±5%
AC CHARACTERISTICS (2)
0.006%
(3)
To ±0.1% of full-scale,
Data = 0000h to FFFFh to 0000h
0.3
To ±0.0015% of full-scale,
Data = 0000h to FFFFh to 0000h
0.5
DAC glitch impulse
Data = 7FFFh to 8000h to 7FFFh
5
nV-s
Reference multiplying BW
VREFx = 100 mVRMS, Data = FFFFh, CFB = 3
pF
10
MHz
Feedthrough error
Data = 0000h, VREFx = 100 mVRMS,
f = 100 kHz
–70
dB
Crosstalk error
Data = 0000h, VREFB = 100 mVRMS,
Adjacent channel, f = 100 kHz
–100
dB
QD
Digital feedthrough
CS = 1 and fCLK = 1 MHz
THD
Total harmonic distortion
VREF = 5 VPP, Data = FFFFh, f = 1 kHz
en
Output spot noise voltage
f = 1 kHz, BW = 1 Hz
ts
Output voltage settling time
QG
BW –3 dB
(3)
µs
1
nV-s
–105
dB
12
nV/√Hz
All ac characteristic tests are performed in a closed-loop system using a THS4011 I-to-V converter amplifier.
7.6 Timing Requirements
See Figure 1
MIN
NOM
MAX
UNIT
INTERFACE TIMING (1)
tCH
Clock duration, high
10
ns
tCL
Clock duration, low
10
ns
tCSS
CS to clock setup
0
ns
tCSH
Clock to CS hold
10
ns
tLDAC
Load DAC pulse duration
20
ns
tDS
Data setup
10
ns
tDH
Data hold
10
ns
tLDS
Load setup
5
ns
tLDH
Load hold
25
ns
(1)
All input control signals are specified with tR = tF = 2.5 ns (10% to 90% of 3 V) and timed from a voltage level of 1.5 V.
7.7 Switching Characteristics
over operating ambient temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
INTERFACE TIMING
tPD
6
Clock to SDO propagation delay
2
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20
ns
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SDI
SBAS349F – AUGUST 2005 – REVISED JUNE 2016
A1
A0
DB15
DB1
DB0
tDS
tDH
CLK
18
1
tCL
tCH
tCSH
tCSS
CS
tLDH
tLDS
LDAC
tLDAC
Figure 1. DAC8812 Timing Diagram
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7.8 Typical Characteristics
7.8.1 Channel A—5 V
At TA = 25°C, VDD = 5 V, unless otherwise noted
1.0
0.6
0.6
0.4
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-0.8
-1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
Figure 2. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = -40°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 3. Differential Nonlinearity vs Digital Input Code
TA = -40°C
0.8
INL (LSB)
0
-0.2
-0.6
0
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 4. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = +85°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 5. Differential Nonlinearity vs Digital Input Code
TA = +85°C
0.8
INL (LSB)
0.2
-0.4
-1.0
-1.0
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 6. Integral Nonlinearity vs Digital Input Code
8
TA = +25°C
0.8
DNL (LSB)
INL (LSB)
1.0
TA = +25°C
0.8
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 7. Differential Nonlinearity vs Digital Input Code
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7.8.2 Channel B—5 V
At TA = 25°C, VDD = 5 V, unless otherwise noted
1.0
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
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
Figure 8. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = -40°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 9. Differential Nonlinearity vs Digital Input Code
TA = -40°C
0.8
INL (LSB)
0.2
-0.4
-1.0
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 10. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = +85°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 11. Differential Nonlinearity vs Digital Input Code
TA = +85°C
0.8
INL (LSB)
TA = +25°C
0.8
DNL (LSB)
INL (LSB)
1.0
TA = +25°C
0.8
-1.0
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 12. Integral Nonlinearity vs Digital Input Code
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 13. Differential Nonlinearity vs Digital Input Code
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7.8.3 Channel A and B—5 V
At TA = 25°C, VDD = 5 V, unless otherwise noted
180
VDD = +5.0V
140
6
0
−6
− 12
− 18
− 24
− 30
− 36
− 42
− 48
− 54
− 60
− 66
− 72
− 78
− 84
− 90
− 96
− 102
− 108
− 114
10
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
5.0
0x0000
1 00
10k
10 0k
1M
10M
100 M
Figure 15. Reference Multiplying Bandwidth
Code: 7FFFh to 8000h
Output Voltage (5V/div)
Figure 14. Supply Current vs Logic Input Voltage
Output Voltage (50mV/div)
1k
Bandwidth (H z )
Logic Input Voltage (V)
Voltage Output Settling
Trigger Pulse
LDAC Pulse
Time (0.2ms/div)
Time (0.1ms/div)
Figure 16. DAC Glitch
10
0xFFFF
0x8000
0x4000
0x2000
0x1000
0x0800
0x0400
0x0200
0x0100
0x0080
0x0040
0x0020
0x0010
0x0008
0x0004
0x0002
0x0001
Attenuation (dB)
Supply Current, IDD (mA)
160
Figure 17. DAC Settling Time
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At TA = 25°C, VDD = 5 V, unless otherwise noted
7.8.4 Channel A—2.7 V
At TA = 25°C, VDD = 2.7 V, unless otherwise noted
1.0
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
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
Figure 18. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = -40°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 19. Differential Nonlinearity vs Digital Input Code
TA = -40°C
0.8
INL (LSB)
0.2
-0.4
-1.0
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 20. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = +85°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 21. Differential Nonlinearity vs Digital Input Code
TA = +85°C
0.8
INL (LSB)
TA = +25°C
0.8
DNL (LSB)
INL (LSB)
1.0
TA = +25°C
0.8
-1.0
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 22. Integral Nonlinearity vs Digital Input Code
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 23. Differential Nonlinearity vs Digital Input Code
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7.8.5 Channel B—2.7 V
At TA = 25°C, VDD = 2.7 V, unless otherwise noted
1.0
0.6
0.6
0.4
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-0.8
-1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
0
Figure 24. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = -40°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 25. Differential Nonlinearity vs Digital Input Code
TA = -40°C
0.8
INL (LSB)
0
-0.2
-0.6
0
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 26. Integral Nonlinearity vs Digital Input Code
1.0
1.0
TA = +85°C
0.8
0.6
0.4
0.4
DNL (LSB)
0.6
0.2
0
-0.2
0.2
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 27. Differential Nonlinearity vs Digital Input Code
TA = +85°C
0.8
INL (LSB)
0.2
-0.4
-1.0
-1.0
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 28. Integral Nonlinearity vs Digital Input Code
12
TA = +25°C
0.8
DNL (LSB)
INL (LSB)
1.0
TA = +25°C
0.8
0
8192 16384 24576 32768 40960 49152 57344 65535
Code
Figure 29. Differential Nonlinearity vs Digital Input Code
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8 Detailed Description
8.1 Overview
The DAC8812 contains two 16-bit, current-output, digital-to-analog converters (DACs). Each DAC has its own
independent multiplying reference input. The DAC8812 uses a 3-wire, SPI-compatible serial data interface, with a
configurable asynchronous RS pin for midscale (MSB = 1) or zero-scale (MSB = 0) preset. In addition, an LDAC
strobe enables two channel simultaneous updates for hardware synchronized output voltage changes.
8.2 Functional Block Diagram
VREFA B
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
A0
A1
SDI
RFBA
16
Input
Register
DAC A
Register
R
IOUTA
DAC A
R
AGNDA
RFBB
Input
Register
DAC B
Register
R
DAC B
R
IOUTB
AGNDB
CLK
EN
CS
DAC A
B
Decode
Power-On
Reset
DGND
RS
MSB
LDAC
8.3 Feature Description
8.3.1 Digital-to-Analog Converters
The DAC8812 contains two current-steering R-2R ladder DACs. Figure 30 shows a typical equivalent DAC. Each
DAC contains a matching feedback resistor for use with an external I-to-V converter amplifier. The RFBX pin is
connected to the output of the external amplifier. The IOUTX pin is connected to the inverting input of the external
amplifier. The AGNDX pin should be Kelvin-connected to the load point in the circuit requiring the full 16-bit
accuracy.
VDD
R
R
R
VREFX
RFBX
2R
2R
2R
R
5 kW
S2
S1
IOUTX
AGNDX
DGND
Digital interface connections omitted for clarity.
Switches S1 and S2 are closed, VDD must be powered.
Figure 30. Typical Equivalent DAC Channel
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Feature Description (continued)
The DAC is designed to operate with both negative or positive reference voltages. The VDD power pin is only
used by the logic to drive the DAC switches on and off. Note that a matching switch is used in series with the
internal 5 kΩ feedback resistor. If users are attempting to measure the value of RFB, power must be applied to
VDD in order to achieve continuity. The DAC output voltage is determined by VREF and the digital data (D)
according to Equation 1:
D
VOUT = - VREF ´
65 536
(1)
Note that the output polarity is opposite of the VREF polarity for dc reference voltages.
The DAC is also designed to accommodate ac reference input signals. The DAC8812 accommodates input
reference voltages in the range of –15 V to 15 V. The reference voltage inputs exhibit a constant nominal input
resistance of 5 kΩ, ±20%. On the other hand, DAC outputs IOUTA and B are code-dependent and produce
various output resistances and capacitances.
The choice of external amplifier should take into account the variation in impedance generated by the DAC8812
on the amplifiers' inverting input node. The feedback resistance, in parallel with the DAC ladder resistance,
dominates output voltage noise. For multiplying mode applications, an external feedback compensation
capacitor, CFB (4 pF to 20 pF typical), may be needed to provide a critically damped output response for step
changes in reference input voltages.
Figure 15 shows the gain vs frequency performance at various attenuation settings using a 3 pF external
feedback capacitor connected across the IOUTX and RFBX pins. In order to maintain good analog performance,
power-supply bypassing of 0.01 μF, in parallel with 1 μF, is recommended. Under these conditions, clean power
supply with low ripple voltage capability should be used. Switching power supplies is usually not suitable for this
application due to the higher ripple voltage and PSS frequency-dependent characteristics. It is best to derive the
DAC8812 5-V supply from the system analog supply voltages (do not use the digital 5-V supply); see Figure 31.
15 V
2R
5V
+
Analog
Power
Supply
R
VDD
R
R
R
RFBX
VREFX
2R
2R
2R
R
5 kW
15 V
S2
S1
IOUTX
VCC
VOUT
A1
+
AGNDX
VEE
Load
DGND
DGND
Digital interface connections omitted for clarity.
Switches S1 and S2 are closed, VDD must be powered.
Figure 31. Recommended Kelvin-Sensed Hookup
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VREF A B
CS
EN
VDD
CLK
SDI
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
A0
A1
RFBB
16
DAC A
Register R
Input
Register R
DAC A
IOUTA
AGNDA
RFBB
DAC B
Register R
Input
Register R
DAC B
IOUTB
AGNDB
DAC A
B
Set
MSB
Decode
Set
MSB
Poweron
Reset
DGND
MSB
LDAC
RS
Figure 32. System-Level Digital Interfacing
8.3.2 Power-On Reset
When the VDD power supply is turned on, an internal reset strobe forces all the Input and DAC registers to the
zero-code state or midscale, depending on the MSB pin voltage. The VDD power supply should have a smooth
positive ramp without drooping, in order to have consistent results, especially in the region of VDD = 1.5 V to
2.3 V. The DAC register data stays at zero or midscale setting until a valid serial register data load takes place.
8.3.2.1 ESD Protection Circuits
All logic-input pins contain back-biased ESD protection zener diodes connected to ground (DGND) and VDD as
shown in Figure 33.
VDD
DIGITAL
INPUTS
250 W
DGND
Figure 33. Equivalent ESD Protection Circuits
8.4 Device Functional Modes
8.4.1 Serial Data Interface
The DAC8812 uses a 3-wire (CS, SDI, CLK) SPI-compatible serial data interface. Serial data of the DAC8812 is
clocked into the serial input register in an 18-bit data-word format. MSB bits are loaded first. Table 1 defines the
18 data-word bits for the DAC8812.
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Device Functional Modes (continued)
Data is placed on the SDI pin, and clocked into the register on the positive clock edge of CLK subject to the data
setup and data hold time requirements specified in the Interface Timing specifications of the Electrical
Characteristics. Data can only be clocked in while the CS chip select pin is active low. For the DAC8812, only
the last 18 bits clocked into the serial register are interrogated when the CS pin returns to the logic high state.
Because most microcontrollers output serial data in 8-bit bytes, three right-justified data bytes can be written to
the DAC8812. Keeping the CS line low between the first, second, and third byte transfers will result in a
successful serial register update.
When the data is properly aligned in the shift register, the positive edge of the CS initiates the transfer of new
data to the target DAC register, determined by the decoding of address bits A1 and A0. For the DAC8812,
Table 1, Table 2, Table 3, and Figure 1 define the characteristics of the software serial interface.
Table 1. Serial Input Register Data Format, Data Loaded MSB First (1)
Bit
B17
(MSB)
B16
B15
B14
B13
B12
B11
B10
B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
(LSB)
Data
A1
A0
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
(1)
Only the last 18 bits of data clocked into the serial register (address + data) are inspected when the CS line positive edge returns to
logic high. At this point an internally-generated load strobe transfers the serial register data contents (bits D15-D0) to the decoded DACinput-register address determined by bits A1 and A0. Any extra bits clocked into the DAC8812 shift register are ignored; only the last 18
bits clocked in are used. If double-buffered data is not needed, the LDAC pin can be tied logic low to disable the DAC registers.
Table 2. Control Logic Truth Table (1)
CS
CLK
LDAC
RS
MSB
H
X
H
H
X
No effect
Latched
Latched
L
L
H
H
X
No effect
Latched
Latched
L
↑+
H
H
X
Shift register data advanced one bit
Latched
Latched
L
H
H
H
X
No effect
Latched
Latched
↑+
L
H
H
X
No effect
Selected DAC updated with current SR contents
Latched
H
X
L
H
X
No effect
Latched
Transparent
H
X
H
H
X
No effect
Latched
Latched
H
X
↑+
H
X
No effect
Latched
Latched
H
X
H
L
0
No effect
Latched data = 0000h
Latched data = 0000h
H
X
H
L
H
No effect
Latched data = 8000h
Latched data = 8000h
(1)
SERIAL SHIFT REGISTER
INPUT REGISTER
DAC REGISTER
↑+ = Positive logic transition; X = Don't care
Table 3. Address Decode
16
A1
A0
0
0
DAC DECODE
None
0
1
DAC A
1
0
DAC B
1
1
DAC A and DAC B
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Figure 34 shows the equivalent logic interface for the key digital control pins for the DAC8812.
To Input Register
Address
Decoder
CS
A
B
EN
CLK
Shift Register
SDI
Figure 34. DAC8812 Equivalent Logic Interface
Two additional pins, RS and MSB, provide hardware control over the preset function and DAC register loading. If
these functions are not needed, the RS pin can be tied to logic high. The asynchronous input RS pin forces all
input and DAC registers to either the zero-code state (MSB = 0), or the midscale state (MSB = 1).
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
This design features one channel of the DAC8812 followed by a four-quadrant circuit for multiplying DACs. The
circuit conditions the current output of an MDAC into a symmetrical bipolar voltage. The design uses an op amp
in a transimpedance configuration to convert the MDAC current into a voltage, followed by an additional amplifier
in a summing configuration to apply an offset voltage.
9.2 Typical Application
Transimpedance Stage
Gain and Offset Stage
RG2
VREF
REFIN RFB
IOUT
RG1
+
MDAC
RFB2
A1 VDAC
VOUT
+
A2
Figure 35. Four-Quadrant Multiplying Application Circuit
9.2.1 Design Requirements
Using a multiplying DAC requires a transimpedance stage using an amplifier with minimal input offset voltage.
The tolerance of the external resistors varies depending on the goals of the application, but for optimal
performance with the DAC8812 the tolerance should be 0.1% for all of the external resistors. The summing stage
amplifier also requires low input-offset voltage and enough slew rate for the output range desired.
9.2.2 Detailed Design Procedure
The first stage of the design converts the current output of the MDAC (IOUT) to a voltage (VOUT) using an amplifier
in a transimpedance configuration. A typical MDAC features an on-chip feedback resistor sized appropriately to
match the ratio of the resistor values used in the DAC R-2R ladder. This resistor is available using the input
shown in Figure 35 called RFB on the MDAC. The MDAC reference and the output of the transimpedance stage
are then connected to the inverting input of the amplifier in the summing stage to produce the output that is
defined by Equation 2.
æ R FB2 VREF ´ Code ö æ R FB2
ö
VOUT (Code ) = ç
V
´
÷
ç
´
÷
REF
ç R G1
÷ ç R G2
÷
2 bits
è
ø è
ø
(2)
9.2.3 Application Curves
Figure 36 shows the output voltage vs code of this design, and Figure 37 shows the output error vs code. Notice
that the error gets worse as the output code increases because the contribution of the DAC gain error increases
with code.
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Typical Application (continued)
10
0.014
8
0.012
Output Error (%FSR)
Output Voltage (V)
6
4
2
0
-2
-4
0.01
0.008
0.006
0.004
-6
0.002
-8
-10
0
0
8192 16384 24576 32768 40960 49152 57344 65536
Input Code (Decimal)
D001
0
Figure 36. Input Code vs Output Voltage
8192 16384 24576 32768 40960 49152 57344 65536
Input Code (Decimal)
D002
Figure 37. Input Code vs Output Error
10 Power Supply Recommendations
This device can operate within the specified supply voltage range of 2.7 V to 5.5 V. The power applied to VDD
should be well-regulated and low-noise. In order to further minimize noise from the power supplies, a strong
recommendation is to include a 100-pF to 1-nF capacitor and a 0.1-μF to 1-μF bypass capacitor very close to the
VDD pin. The current consumption of the VDD pin, the short-circuit current limit, and the load current for these
devices are listed in the Electrical Characteristics table. Choose a power supply for these devices to meet the
aforementioned current requirements.
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11 Layout
11.1 Layout Guidelines
A precision analog component requires careful layout, adequate bypassing, and clean, well-regulated power
supplies. The DAC8812 offers single-supply operation, and is often 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 is to keep digital noise from appearing at the output. This
device has three ground pins: two for analog ground (AGNDA and AGNDB) and one for digital ground (DGND),
which are pinned out on opposite sides of the device. Ideally, the analog grounds would be connected directly to
an analog ground plane, and similarly the digital ground connected to a digital ground plane. These planes would
be separated until they were connected at the power-entry point of the system. The power applied to VDD should
be well-regulated and low-noise. Switching power supplies and dc-dc converters 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. VDD should be connected to a power-supply
plane or trace that is separate from the connection for digital logic until the analog and digital supplies are
connected at the power-entry point. In addition, adding both a 100-pF to 1-nF capacitor and a 0.1-μF to 1-μF
bypass capacitor is strongly recommended. In some situations, additional bypassing may be required, such as a
100-μF electrolytic capacitor or even a pi filter made up of inductors and capacitors – all designed essentially to
provide low-pass filtering for the supply and remove the high-frequency noise.
The compensation capacitors shown on the layout in Figure 38 are not required for normal operation of the DAC.
However, overshoot of the amplifier output voltage on large code changes is possible. This can be mitigated by
using a compensation capacitor between the IOUTx and RFBx nodes, as shown implemented here.
Performance of the DAC8812 can be compromised by grounding and PCB lead trace resistance. The 16-bit
DAC8812 with a 10-V full-scale range has an LSB size of 153 µV. The ladder and associated reference and
analog ground currents for a given channel can be as high as 2 mA. With this 2-mA current level, a series wiring
and connector resistance of only 76 mΩ causes 1 LSB of voltage drop. The preferred PCB layout for the
DAC8812 is to have all AGNDx pins connected directly to an analog ground plane at the device. The
noninverting input for the transimpedance amplifier of each channel should also either connect directly to the
analog ground plane or have an individual sense trace back to the AGNDx pin connection. The feedback resistor
trace to the transimpedance amplifier should also be kept short and have low resistance in order to prevent IR
drops from contributing to gain error. Therefore, it is important to place the transimpedance amplifier as close to
the DAC as possible. This attention to wiring and placement ensures the optimal performance of the DAC8812.
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11.2 Layout Example
Digital
Interface
AGNDA
MSB
IOUTA
VREFA
RFBA
Amplifier
Compensation
Capacitor
VSS
AGNDB
VDD
CLK
GND
IOUTB
DGND
LDAC
Compensation
Capacitor
IOUT A
VREFB
VOUT B
DAC
GND
CS
Power Capacitors
RFBB
IOUT A
RS
VOUT A
SDI
VCC
REF B
REF A
Digital
Interface
Figure 38. DAC8812 Layout Example
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
For related documentation see the following:
DAC8811 16-Bit, Serial Input Multiplying Digital-to-Analog Converter
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.4 Trademarks
E2E is a trademark of Texas Instruments.
SPI is a trademark of Motorola, Inc.
All other trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
12.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the mostcurrent data available for the designated devices. This data is subject to change without notice and without
revision of this document. For browser-based versions of this data sheet, see the left-hand navigation pane.
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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)
DAC8812IBPW
ACTIVE
TSSOP
PW
16
90
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8812
DAC8812IBPWR
ACTIVE
TSSOP
PW
16
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8812
DAC8812ICPW
ACTIVE
TSSOP
PW
16
90
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8812
DAC8812ICPWG4
ACTIVE
TSSOP
PW
16
90
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8812
DAC8812ICPWR
ACTIVE
TSSOP
PW
16
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
DAC8812
(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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