AD AD5780 System ready, 18-bit â±1 lsb inl Datasheet

FEATURES
True 18-bit voltage output DAC, ±1 LSB INL
8 nV/√Hz output noise spectral density
0.025 LSB long-term linearity error stability
±0.018 ppm/°C gain error temperature coefficient
2.5 μs output voltage settling time
3.5 nV-sec midscale glitch impulse
Integrated precision reference buffers
Operating temperature range: −40°C to +125°C
4 mm × 5 mm LFCSP package
Wide power supply range of up to ±16.5 V
35 MHz Schmitt triggered digital interface
1.8 V-compatible digital interface
FUNCTIONAL BLOCK DIAGRAM
VCC
SDIN
SYNC
SDO
VREFP
AD5780
IOVCC
SCLK
VDD
INPUT
SHIFT
REGISTER
AND
CONTROL
LOGIC
A1
CLR
18
DAC
REG
18-BIT
DAC
VOUT
6kΩ
POWER-ON RESET
AND CLEAR LOGIC
DGND
VSS
AGND
VREFN
Figure 1.
APPLICATIONS
Medical instrumentation
Test and measurement
Industrial control
Scientific and aerospace instrumentation
Data acquisition systems
Digital gain and offset adjustment
Power supply control
RFB
INV
18
LDAC
RESET
R1 RFB
6.8kΩ 6.8kΩ
09649-001
Data Sheet
System Ready, 18-Bit ±1 LSB INL,
Voltage Output DAC
AD5780
Table 1. Related Devices
Part No.
AD5790
AD5791
AD5781
AD5541A/AD5542A
AD5760
Description
20-bit, 2 LSB accurate DAC
20-bit, 1 ppm accurate DAC
18-bit, 0.5 LSB accurate DAC
16-bit, 1 LSB accurate 5 V DAC
16-bit, 0.5 LSB accurate DAC
GENERAL DESCRIPTION
The AD57801 is a true 18-bit, unbuffered voltage output DAC
that operates from a bipolar supply of up to 33 V. The AD5780
accepts a positive reference input range of 5 V to VDD − 2.5 V
and a negative reference input range of VSS + 2.5 V to 0 V. Both
reference inputs are buffered on chip and external buffers are
not required. The AD5780 offers a relative accuracy specification of ±1 LSB maximum range, and operation is guaranteed
monotonic with a ±1 LSB DNL maximum range specification.
PRODUCT HIGHLIGHTS
The part uses a versatile 3-wire serial interface that operates at
clock rates of up to 35 MHz and is compatible with standard
SPI, QSPI™, MICROWIRE™, and DSP interface standards. The
part incorporates a power-on reset circuit that ensures that the
DAC output powers up to 0 V in a known output impedance
state and remains in this state until a valid write to the device
takes place. The part provides an output clamp feature that
places the output in a defined load state.
Output Amplifier Buffer: AD8675, ADA4898-1, ADA4004-1
1
1.
2.
3.
4.
5.
True 18-bit accuracy.
Wide power supply range of up to ±16.5 V.
−40°C to +125°C operating temperature range.
Low 8 nV/√Hz noise.
Low ±0.018 ppm/°C gain error temperature coefficient.
COMPANION PRODUCTS
External Reference: ADR445
DC-to-DC Design Tool: ADIsimPower™
Additional companion products on the AD5780 product page
Protected by U.S. Patent No. 7,884,747 and 8,089,380.
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2011–2012 Analog Devices, Inc. All rights reserved.
AD5780
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
DAC Architecture....................................................................... 19
Applications....................................................................................... 1
Serial Interface ............................................................................ 19
Functional Block Diagram .............................................................. 1
Hardware Control Pins.............................................................. 20
General Description ......................................................................... 1
On-Chip Registers...................................................................... 21
Product Highlights ........................................................................... 1
AD5780 Features ............................................................................ 24
Companion Products ....................................................................... 1
Power-On to 0 V......................................................................... 24
Revision History ............................................................................... 2
Configuring the AD5780 .......................................................... 24
Specifications..................................................................................... 3
DAC Output State ...................................................................... 24
Timing Characteristics ................................................................ 5
Output Amplifier Configuration.............................................. 24
Absolute Maximum Ratings............................................................ 8
Applications Information .............................................................. 26
ESD Caution.................................................................................. 8
Typical Operating Circuit ......................................................... 26
Pin Configuration and Function Descriptions............................. 9
Evaluation Board ........................................................................ 27
Typical Performance Characteristics ........................................... 10
Outline Dimensions ....................................................................... 28
Terminology .................................................................................... 18
Ordering Guide .......................................................................... 28
Theory of Operation ...................................................................... 19
REVISION HISTORY
3/12—Rev. B to Rev. C
Changes to Data Sheet Title and added Patent 8,089,380 ........... 1
2/12—Rev. A to Rev. B
Deleted Linearity Compensation Section ................................... 24
12/11—Rev. 0 to Rev. A
Edits to Table 2.................................................................................. 3
Changes to Figure 48...................................................................... 17
Changes to DAC Register Section ................................................ 21
Changes to Table 10 and Table 11 ................................................ 22
11/11—Revision 0: Initial Version
Rev. C | Page 2 of 28
Data Sheet
AD5780
SPECIFICATIONS
VDD = 12.5 V to 16.5 V, VSS = −16.5 V to −12.5 V, VREFP = 10 V, VREFN = −10 V, VCC = 2.7 V to 5.5 V, IOVCC = 1.71 V to 5.5 V,
RL = unloaded, CL = unloaded, TMIN to TMAX, unless otherwise noted.
Table 2.
A, B Versions 1
Typ
Max
Parameter
Min
STATIC PERFORMANCE 2
Resolution
Integral Nonlinearity Error (Relative
Accuracy)
18
−0.85
+0.85
−1
−2
−0.25
−1
+1
+2
+0.75
+1
Differential Nonlinearity Error
Long-Term Linearity Error Stability 3
Full-Scale Error
Full-Scale Error Temperature Coefficient
Zero-Scale Error
Zero-Scale Error Temperature
Coefficient
Gain Error
−3
−5.5
−10
−4.8
−10
−20.5
−19
−35
−68
Gain Error Temperature Coefficient
R1, RFB Matching
OUTPUT CHARACTERISTICS
Output Voltage Range
Output Voltage Settling Time
Output Noise Spectral Density
Output Voltage Noise
Midscale Glitch Impulse4
MSB Segment Glitch Impulse4
Output Enabled Glitch Impulse
Digital Feedthrough
DC Output Impedance (Normal Mode)
DC Output Impedance (Output
Clamped to Ground)
0.025
±0.95
±0.675
±0.45
±0.026
±0.325
±0.175
±0.225
±0.025
±2.3
±1.9
±0.9
±0.018
0.015
+3
+0.5
+10
+4.8
+10
+20.5
Unit
Bits
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
ppm/°C
LSB
LSB
LSB
ppm/°C
+19
+35
+68
ppm FSR
ppm FSR
ppm FSR
ppm/°C
%
VREFP
2.5
V
μs
3.5
8
8
1.1
μs
nV/√Hz
nV/√Hz
μV p-p
14
3.5
4
14
3.5
4
57
0.27
3.4
6
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
kΩ
kΩ
VREFN
Rev. C | Page 3 of 28
Test Conditions/Comments
B grade, VREFP = +10 V, VREFN = −10 V,
TA = 25°C
B grade, VREFx = ±10 V, +10 V, and +5 V
A grade, VREFx = ±10 V, +10 V, and +5 V
B grade, VREFx = ±10 V, +10 V, and +5 V
A grade, VREFx = ±10 V, +10 V, and +5 V
After 750 hours at TA = 135°C
VREFP = +10 V, VREFN = −10 V
VREFP = 10 V, VREFN = 0 V
VREFP = 5 V, VREFN = 0 V
VREFP = +10 V, VREFN = −10 V
VREFP = +10 V, VREFN = −10 V
VREFP = 10 V, VREFN = 0 V
VREFP = 5 V, VREFN = 0 V
VREFP = +10 V, VREFN = −10 V
VREFP = +10 V, VREFN = −10 V
VREFP = 10 V, VREFN = 0 V
VREFP = 5 V, VREFN = 0 V
VREFP = +10 V, VREFN = −10 V
10 V step to 0.02%, using the ADA4898-1
buffer in unity-gain mode
500 code step to ±1 LSB 4
At 1 kHz, DAC code = midscale
At 10 kHz, DAC code = midscale
DAC code = midscale, 0.1 Hz to
10 Hz bandwidth
VREFP = +10 V, VREFN = −10 V
VREFP = 10 V, VREFN = 0 V
VREFP = 5 V, VREFN = 0 V
VREFP = +10 V, VREFN = −10 V, see Figure 43
VREFP = 10 V, VREFN = 0 V, see Figure 44
VREFP = 5 V, VREFN = 0 V, see Figure 45
On removal of output ground clamp
AD5780
Parameter
REFERENCE INPUTS
VREFP Input Range
VREFN Input Range
Input Bias Current
Input Capacitance
LOGIC INPUTS
Input Current 5
Input Low Voltage, VIL
Input High Voltage, VIH
Pin Capacitance
LOGIC OUTPUT (SDO)
Output Low Voltage, VOL
Output High Voltage, VOH
High Impedance Leakage Current
High Impedance Output Capacitance
POWER REQUIREMENTS
VDD
VSS
VCC
IOVCC
IDD
ISS
ICC
IOICC
DC Power Supply Rejection Ratio
AC Power Supply Rejection Ratio
Data Sheet
Min
5
VSS + 2.5
−20
−4
A, B Versions 1
Typ
Max
−0.63
−0.63
1
−1
VDD − 2.5
0
+20
+4
Unit
Test Conditions/Comments
V
V
nA
TA = 0°C to 105°C
pF
VREFP, VREFN
+1
0.3 × IOVCC
μA
V
V
pF
IOVCC = 1.71 V to 5.5 V
IOVCC = 1.71 V to 5.5 V
0.4
V
V
μA
pF
0.7 × IOVCC
5
IOVCC − 0.5
±1
3
IOVCC = 1.71 V to 5.5 V, sinking 1 mA
IOVCC = 1.71 V to 5.5 V, sourcing 1 mA
All digital inputs at DGND or IOVCC
7.5
VDD − 33
2.7
1.71
10.3
−10
600
52
±7.5
±1.5
90
90
VSS + 33
−2.5
5.5
5.5
14
−14
900
140
1
V
V
V
V
mA
mA
μA
μA
μV/V
μV/V
dB
dB
IOVCC ≤ VCC
SDO disabled
∆VDD ± 10%, VSS = −15 V
∆VSS ± 10%, VDD = 15 V
∆VDD ± 200 mV, 50 Hz/60 Hz, VSS = −15 V
∆VSS ± 200 mV, 50 Hz/60 Hz, VDD = 15 V
Temperature range: −40°C to +125°C, typical conditions: TA = 25°C, VDD = +15 V, VSS = −15 V, VREFP = +10 V, VREFN = −10 V.
Performance characterized with the AD8675ARZ output buffer.
3
Linearity error refers to both INL error and DNL error, either parameter can be expected to drift by the amount specified after the length of time specified.
4
The AD5780 is configured in the unity-gain mode with a low-pass RC filter on the output. R = 300 Ω, C = 143 pF (total capacitance seen by the output buffer, lead
capacitance, and so forth).
5
Current flowing in an individual logic pin.
2
Rev. C | Page 4 of 28
Data Sheet
AD5780
TIMING CHARACTERISTICS
VCC = 2.7 V to 5.5 V; all specifications TMIN to TMAX, unless otherwise noted.
Table 3.
Parameter
t1 2
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
t14
t15
t16
t17
t18
t19
t20
t21
t22
1
2
Limit 1
IOVCC = 1.71 V to 3.3 V
IOVCC = 3.3 V to 5.5 V
40
28
92
60
15
10
9
5
5
5
2
2
48
40
8
6
9
7
12
7
13
10
20
16
14
11
130
130
130
130
50
50
140
140
0
0
65
60
62
45
0
0
35
35
150
150
Unit
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns typ
ns typ
ns min
ns typ
ns min
ns max
ns max
ns min
ns typ
ns typ
Test Conditions/Comments
SCLK cycle time
SCLK cycle time (readback and daisy-chain modes)
SCLK high time
SCLK low time
SYNC to SCLK falling edge setup time
SCLK falling edge to SYNC rising edge hold time
Minimum SYNC high time
SYNC rising edge to next SCLK falling edge ignore
Data setup time
Data hold time
LDAC falling edge to SYNC falling edge
SYNC rising edge to LDAC falling edge
LDAC pulse width low
LDAC falling edge to output response time
SYNC rising edge to output response time (LDAC tied low)
CLR pulse width low
CLR pulse activation time
SYNC falling edge to first SCLK rising edge
SYNC rising edge to SDO tristate (CL = 50 pF)
SCLK rising edge to SDO valid (CL = 50 pF)
SYNC rising edge to SCLK rising edge ignore
RESET pulse width low
RESET pulse activation time
All input signals are specified with tR = tF = 1 ns/V (10% to 90% of IOVCC) and timed from a voltage level of (VIL + VIH)/2.
Maximum SCLK frequency is 35 MHz for write mode and 16 MHz for readback and daisy-chain modes.
Rev. C | Page 5 of 28
AD5780
Data Sheet
t7
t1
SCLK
1
2
24
t3
t6
t2
t4
t5
SYNC
t9
t8
SDIN
DB23
DB0
t10
t12
t11
LDAC
t13
VOUT
t14
VOUT
t15
CLR
t16
VOUT
t21
RESET
09649-002
t22
VOUT
Figure 2. Write Mode Timing Diagram
t1
t17
SCLK
1
2
24
t3
t6
t20
t7
1
2
24
t2
t5
t4
t5
t17
SYNC
SDIN
t9
DB23
DB0
INPUT WORD SPECIFIES
REGISTER TO BE READ
NOP CONDITION
t18
t19
DB23
SDO
REGISTER CONTENTS CLOCKED OUT
Figure 3. Readback Mode Timing Diagram
Rev. C | Page 6 of 28
DB0
09649-003
t8
Data Sheet
AD5780
SCLK
t20
t1
t17
1
2
24
t3
t6
26
25
48
t2
t5
t4
SYNC
SDIN
t9
DB23
DB0
DB23
DB0
INPUT WORD FOR DAC N – 1
INPUT WORD FOR DAC N
t19
SDO
DB23
DB0
DB23
DB0
INPUT WORD FOR DAC N
UNDEFINED
Figure 4. Daisy-Chain Mode Timing Diagram
Rev. C | Page 7 of 28
t18
09649-004
t8
AD5780
Data Sheet
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted. Transient currents of up to
100 mA do not cause SCR latch-up.
Table 4.
Parameter
VDD to AGND
VSS to AGND
VDD to VSS
VCC to DGND
IOVCC to DGND
Digital Inputs to DGND
VOUT to AGND
VREFP to AGND
VREFN to AGND
DGND to AGND
Operating Temperature Range, TA
Industrial
Storage Temperature Range
Maximum Junction Temperature,
TJ max
Power Dissipation
LFCSP Package
θJA Thermal Impedance
Lead Temperature
Soldering
ESD (Human Body Model)
Rating
−0.3 V to +34 V
−34 V to +0.3 V
−0.3 V to +34 V
−0.3 V to +7 V
−0.3 V to VCC + 3 V or +7 V
(whichever is less)
−0.3 V to IOVCC + 0.3 V or
+7 V (whichever is less)
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
VSS − 0.3 V to +0.3 V
−0.3 V to +0.3 V
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
This device is a high performance integrated circuit with an
ESD rating of 1.6 kV, and it is ESD sensitive. Proper precautions
must be taken for handling and assembly.
ESD CAUTION
−40°C to +125°C
−65°C to +150°C
150°C
(TJ max − TA)/θJA
31.0°C/W
JEDEC industry standard
J-STD-020
1.6 kV
Rev. C | Page 8 of 28
Data Sheet
AD5780
24 INV
23 DNC
22 DNC
21 DNC
20 RFB
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
1
2
3
4
5
6
7
AD5780
TOP VIEW
(Not to Scale)
19
18
17
16
15
14
13
AGND
VSS
VSS
VREFN
DGND
SYNC
SCLK
NOTES
1. DNC = DO NOT CONNECT. DO NOT CONNECT TO THIS PIN.
2. NEGATIVE ANALOG SUPPLY CONNECTION (VSS).
A VOLTAGE IN THE RANGE OF –16.5 V TO –2.5 V
CAN BE CONNECTED. VSS SHOULD BE DECOUPLED
TO AGND. THE PADDLE CAN BE LEFT ELECTRICALLY
UNCONNECTED PROVIDED THAT A SUPPLY
CONNECTION IS MADE AT THE VSS PINS. IT IS
RECOMMENDED THAT THE PADDLE BE THERMALLY
CONNECTED TO A COPPER PLANE FOR ENHANCED
THERMAL PERFORMANCE.
09649-005
VCC 8
IOVCC 9
DNC 10
SDO 11
SDIN 12
VOUT
VREFP
VDD
RESET
VDD
CLR
LDAC
Figure 5. Pin Configuration
Table 5. Pin Function Descriptions
Pin No.
1
2
3, 5
Mnemonic
VOUT
VREFP
VDD
4
6
RESET
CLR
7
LDAC
8
9
VCC
IOVCC
10, 21,
22, 23
11
12
DNC
SDO
SDIN
13
SCLK
14
SYNC
15
16
17, 18
DGND
VREFN
VSS
19
20
24
EPAD
AGND
RFB
INV
VSS
Description
Analog Output Voltage.
Positive Reference Voltage Input. A voltage in the range of 5 V to VDD − 2.5 V can be connected to this pin.
Positive Analog Supply Connection. A voltage in the range of 7.5 V to 16.5 V can be connected to this pin. VDD must be
decoupled to AGND.
Active Low Reset. Asserting this pin returns the AD5780 to its power-on status.
Active Low Input. Asserting this pin sets the DAC register to a user defined value (see Table 12) and updates the DAC
output. The output value depends on the DAC register coding that is being used, either binary or twos complement.
Active Low Load DAC Logic Input. This pin is used to update the DAC register and, consequently, the analog output.
When tied permanently low, the output is updated on the rising edge of SYNC. If LDAC is held high during the write cycle,
the input register is updated, but the output update is held off until the falling edge of LDAC. Do not leave the LDAC pin
unconnected.
Digital Supply. Voltage range is from 2.7 V to 5.5 V. VCC should be decoupled to DGND.
Digital Interface Supply. Digital threshold levels are referenced to the voltage applied to this pin. Voltage range is from
1.71 V to 5.5 V.
Do Not Connect. Do not connect to these pins.
Serial Data Output.
Serial Data Input. This device has a 24-bit input shift register. Data is clocked into the register on the falling edge of the
serial clock input.
Serial Clock Input. Data is clocked into the input shift register on the falling edge of the serial clock input. Data can be
transferred at rates of up to 35 MHz.
Level Triggered Control Input (Active Low). This is the frame synchronization signal for the input data. When SYNC goes
low, it enables the input shift register, and data is then transferred in on the falling edges of the following clocks. The DAC
is updated on the rising edge of SYNC.
Ground Reference Pin for Digital Circuitry.
Negative Reference Voltage Input.
Negative Analog Supply Connection. A voltage in the range of −16.5 V to −2.5 V can be connected to this pin.
VSS must be decoupled to AGND.
Ground Reference Pin for Analog Circuitry.
Feedback Connection for External Amplifier. See the AD5780 Features section for further details.
Inverting Input Connection for External Amplifier. See the AD5780 Features section for further details.
Negative Analog Supply Connection (VSS). A voltage in the range of −16.5 V to −2.5 V can be connected to this pin. VSS
must be decoupled to AGND. The paddle can be left electrically unconnected provided that a supply connection is made
at the VSS pins. It is recommended that the paddle be thermally connected to a copper plane for enhanced thermal
performance.
Rev. C | Page 9 of 28
AD5780
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
0.4
0.4
AD8675 OUTPUT BUFFER
TA = 25°C
0.3
AD8675 OUTPUT BUFFER
TA = 25°C
0.3
0.2
0.2
0.1
0
INL (LSB)
0
–0.1
–0.4
–0.5
50000
100000
150000
200000
250000
300000
DAC CODE
Figure 6. Integral Nonlinearity Error vs. DAC Code, ±10 V Span
0.6
–0.7
09649-006
0
50000
100000
150000
200000
250000
300000
Figure 9. Integral Nonlinearity Error vs. DAC Code, 5 V Span, ×2 Gain Mode
0.5
AD8675 OUTPUT BUFFER
TA = 25°C
0.4
0.4
0.3
0.3
0.2
0.2
DNL (LSB)
INL (LSB)
0
DAC CODE
AD8675 OUTPUT BUFFER
TA = 25°C
0.5
VREFP = +5V
VREFN = 0V
VDD = +15V
VSS = –15V
–0.6
09649-009
VREFP = +10V
VREFN = –10V
VDD = +15V
VSS = –15V
–0.3
0.1
0
0.1
0
–0.1
–0.1
–0.2
–0.2
VREFP = +10V
VREFN = 0V
VDD = +15V
VSS = –15V
0
50000
100000
150000
200000
250000
300000
DAC CODE
–0.4
50000
100000
150000
200000
250000
300000
Figure 10. Differential Nonlinearity Error vs. DAC Code, ±10 V Span
0.7
AD8675 OUTPUT BUFFER
TA = 25°C
0.6
0
DAC CODE
Figure 7. Integral Nonlinearity Error vs. DAC Code, 10 V Span
0.8
VREFP = +10V
VREFN = –10V
VDD = +15V
VSS = –15V
–0.3
09649-007
–0.3
–0.4
–0.2
–0.3
–0.2
–0.4
–0.1
09649-010
INL (LSB)
0.1
AD8675 OUTPUT BUFFER
TA = 25°C
0.5
0.4
0.3
DNL (LSB)
0
–0.2
0.1
–0.1
–0.4
–0.3
–0.6
–1.0
0
50000
100000
150000
200000
250000
300000
DAC CODE
VREFP = +10V
VREFN = 0V
VDD = +15V
VSS = –15V
–0.5
Figure 8. Integral Nonlinearity Error vs. DAC Code, 5 V Span
–0.7
0
50000
100000
150000
200000
250000
300000
DAC CODE
Figure 11. Differential Nonlinearity Error vs. DAC Code, 10 V Span
Rev. C | Page 10 of 28
09649-011
VREFP = +5V
VREFN = 0V
VDD = +15V
VSS = –15V
–0.8
09649-008
INL (LSB)
0.2
Data Sheet
AD5780
0.40
0.4
0.35
0.3
0.30
DNL ERROR (LSB)
0.5
0.1
0
–0.1
VREFP = +5V
VREFN = 0V
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
TA = 25°C
0.20
0.15
0.10
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
0
50000
100000
150000
200000
250000
300000
DAC CODE
0
–0.05
–40
09649-012
–0.3
0.6
0.5
0
20
40
60
80
100
TEMPERATURE (°C)
0.4
VREFP = +5V
VREFN = 0V
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
TA = 25°C
–20
Figure 15. Differential Nonlinearity Error vs. Temperature
Figure 12. Differential Nonlinearity Error vs. DAC Code, 5 V Span
0.3
INL MAX
0.2
INL ERROR (LSB)
0.4
0.3
DNL (LSB)
0.25
0.05
–0.2
–0.4
±10V SPAN MIN DNL
+10V SPAN MIN DNL
+5V SPAN MIN DNL
09649-015
DNL (LSB)
0.2
±10V SPAN MAX DNL
+10V SPAN MAX DNL
+5V SPAN MAX DNL
0.2
0.1
0.1
TA = 25°C
VREFP = +10V
VREFN = –10V
AD8675 OUTPUTBUFFER
0
–0.1
0
–0.2
–0.1
–0.3
0
50000
100000
150000
200000
250000
300000
DAC CODE
Figure 13. Differential Nonlinearity Error vs. DAC Code, 5 V Span,
×2 Gain Mode
±10V SPAN MAX INL
+10V SPAN MAX INL
+5V SPAN MAX INL
0.7
–0.4
12.5
09649-013
13.5
14.0
14.5
15.0
15.5
16.0
16.5
VDD/|VSS| (V)
Figure 16. Integral Nonlinearity Error vs. Supply Voltage, ±10 V Span
±10V SPAN MIN INL
+10V SPAN MIN INL
+5V SPAN MIN INL
0.4
0.5
INL MAX
INL ERROR (LSB)
0.2
0.3
0.1
0
TA = 25°C
VREFP = 5V
VREFN = 0V
AD8675 OUTPUTBUFFER
–0.2
–0.1
INL MIN
–0.4
–0.3
–0.5
–40
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–20
0
20
40
60
80
TEMPERATURE (°C)
100
09649-014
INL ERROR (LSB)
13.0
–0.6
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
16.5
VDD/|VSS| (V)
Figure 17. Integral Nonlinearity Error vs. Supply Voltage, 5 V Span
Figure 14. Integral Nonlinearity Error vs. Temperature
Rev. C | Page 11 of 28
09649-017
–0.2
09649-016
INL MIN
AD5780
Data Sheet
0.35
4
ZERO-SCALE ERROR (LSB)
3
0.10
0.05
13.5
14.0
14.5
0
15.0
15.5
16.0
16.5
VDD/|VSS| (V)
–2
7.5
8.5
9.5
10.5
11.5
12.5
Figure 18. Differential Nonlinearity Error vs. Supply Voltage, ±10 V Span
0
0.30
–0.1
MIDSCALE ERROR (LSB)
DNL ERROR (LSB)
0.15
TA = 25°C
VREFP = 5V
VREFN = 0V
AD8675 OUTPUT BUFFER
0.10
0.05
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
16.5
–0.2
–0.3
–0.4
VDD/|VSS| (V)
–0.6
12.5
09649-019
–0.05
7.5
0.1
0
–0.1
–0.2
14.0
15.5
16.0
16.5
0.5
0
–0.5
–1.0
–1.5
–0.4
13.5
15.0
1.0
–0.3
13.0
14.5
1.5
0.2
–0.5
12.5
14.0
2.0
TA = 25°C
VREFP = +10V
VREFN = –10V
AD8675 OUTPUT BUFFER
MIDSCALE ERROR (LSB)
0.3
13.5
Figure 22. Midscale Error vs. Supply Voltage, ±10 V Span
14.5
15.0
15.5
16.0
16.5
VDD/|VSS| (V)
09649-020
ZERO-SCALE ERROR (LSB)
0.4
13.0
VDD/|VSS| (V)
Figure 19. Differential Nonlinearity Error vs. Supply Voltage, 5 V Span
0.5
16.5
–0.5
DNL MIN
0
15.5
TA = 25°C
VREFP = +10V
VREFN = –10V
AD8675 OUTPUT BUFFER
DNL MAX
0.20
14.5
Figure 21. Zero-Scale Error vs. Supply Voltage, 5 V Span
0.35
0.25
13.5
VDD/|VSS| (V)
09649-021
13.0
09649-018
–0.05
12.5
1
–1
DNL MIN
0
2
09649-022
0.15
TA = 25°C
VREFP = +10V
VREFN = –10V
AD8675 OUTPUT BUFFER
Figure 20. Zero-Scale Error vs. Supply Voltage, ±10 V Span
TA = 25°C
VREFP = 5V
VREFN = 0V
AD8675 OUTPUT BUFFER
–2.0
7.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
VDD/|VSS| (V)
Figure 23. Midscale Error vs. Supply Voltage, 5 V Span
Rev. C | Page 12 of 28
16.5
09649-023
DNL ERROR (LSB)
0.25
0.20
TA = 25°C
VREFP = 5V
VREFN = 0V
AD8675 OUTPUT BUFFER
DNL MAX
0.30
Data Sheet
1.40
0.35
GAIN ERROR (LSB)
FULL-SCALE ERROR (LSB)
0.40
1.45
0.30
0.25
0.20
0.15
1.35
1.30
1.25
1.20
1.15
1.10
0.10
TA = 25°C
V
= 5V
1.05 VREFP = 0V
REFN
AD8675 OUTPUT BUFFER
1.00
7.5
8.5
9.5
10.5 11.5
0
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
VDD/|VSS| (V)
09649-024
0.05
0.5
15.5
16.5
10.0
0.3
TA = 25°C
VREFP = 5V
VREFN = 0V
AD8675 OUTPUT BUFFER
INL MAX
0.2
0.1
0
–0.5
–1.0
–1.5
0
TA = 25°C
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–0.1
–0.2
–2.0
INL MIN
–0.3
–2.5
8.5
9.5
10.5
11.5
12.5
13.5
14.5
15.5
16.5
VDD/|VSS| (V)
–0.4
5.0
09649-025
–3.0
7.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
Figure 28. Integral Nonlinearity Error vs. Reference Voltage
0.35
0.25
5.5
VREFP /|VREFN | (V)
Figure 25. Full-Scale Error vs. Supply Voltage, 5 V Span
0.30
TA = 25°C
VREFP = +10V
VREFN = –10V
AD8675 OUTPUT BUFFER
INL MAX
0.25
0.20
DNL ERROR (LSB)
0.15
0.05
–0.05
0.15
0.10
TA = 25°C
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
0.05
INL MIN
0
–0.25
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
VDD/|VSS| (V)
16.5
–0.05
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
VREFP /|VREFN | (V)
Figure 29. Differential Nonlinearity Error vs. Reference Voltage
Figure 26. Gain Error vs. Supply Voltage, ±10 V Span
Rev. C | Page 13 of 28
09649-029
–0.15
09649-026
GAIN ERROR (LSB)
14.5
Figure 27. Gain Error vs. Supply Voltage, 5 V Span
INL ERROR (LSB)
FULL-SCALE ERROR (LSB)
1.0
13.5
VDD/|VSS| (V)
Figure 24. Full-Scale Error vs. Supply Voltage, ±10 V Span
1.5
12.5
09649-027
0.45
1.50
TA = 25°C
VREFP = +10V
VREFN = –10V
AD8675 OUTPUT BUFFER
09649-028
0.50
AD5780
AD5780
Data Sheet
–1.0
0
TA = 25°C
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–1.1
–1.2
TA = 25°C
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–0.10
GAIN ERROR (LSB)
–0.15
–0.20
–0.25
–1.3
–1.4
–1.5
–1.6
–1.7
–0.30
–1.8
–0.35
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
VREFP /|VREFN | (V)
–2.0
5.0
5.5
–0.5
–0.6
–0.7
–0.8
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
VREFP /|VREFN | (V)
9.5
10.0
1.0
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–20
0
20
40
60
80
100
TEMPERATURE (°C)
Figure 34. Full-Scale Error vs. Temperature
0.6
TA = 25°C
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
±10V SPAN
+10V SPAN
+5V SPAN
0.4
0.2
MIDSCALE ERROR (LSB)
1.5
1.3
1.1
0
–0.2
–0.4
–0.6
–0.8
0.9
–1.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
VREFP /|VREFN | (V)
10.0
09649-032
FULL-SCALE ERROR (LSB)
9.0
1.2
Figure 31. Midscale Error vs. Reference Voltage
1.7
8.5
1.4
0.6
–40
09649-031
6.0
8.0
±10V SPAN
+10V SPAN
+5V SPAN
0.8
–0.9
5.5
7.5
1.6
FULL-SCALE ERROR (LSB)
MIDSCALE ERROR (LSB)
1.8
TA = 25°C
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–0.4
0.7
5.0
7.0
Figure 33. Gain Error vs. Reference Voltage
–0.2
–1.0
5.0
6.5
VREFP /|VREFN | (V)
Figure 30. Zero-Scale Error vs. Reference Voltage
–0.3
6.0
09649-034
5.5
09649-033
–1.9
09649-030
–0.40
5.0
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–1.2
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
Figure 35. Midscale Error vs. Temperature
Figure 32. Full-Scale Error vs. Reference Voltage
Rev. C | Page 14 of 28
100
09649-035
ZERO-SCALE ERROR (LSB)
–0.05
Data Sheet
1.0
0.010
±10V SPAN
+10V SPAN
+5V SPAN
0.5
0.008
IDD
0.006
0
0.004
–0.5
IDD/ISS (mA)
–1.0
–1.5
0.002
0
–0.002
–0.004
–2.0
–0.006
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
0
20
40
60
80
100
TEMPERATURE (°C)
–0.010
–20
Figure 36. Zero-Scale Error vs. Temperature
0
VOUT (V)
0
–2.0
–4
–3.0
–6
0
20
40
60
80
100
TEMPERATURE (°C)
–10
–1
700
0
1
2
3
4
5
5
Figure 40. Rising Full-Scale Voltage Step
6
IOVCC = 5V, LOGIC VOLTAGE
INCREASING
IOVCC = 5V, LOGIC VOLTAGE
DECREASING
IOVCC = 3V, LOGIC VOLTAGE
INCREASING
IOVCC = 3V, LOGIC VOLTAGE
DECREASING
VDD = +15V
VSS = –15V
VREFP = +10V
VREFN = –10V
ADA4808-1 BUFFERED
LOAD = 10MΩ || 20pF
4
2
VOUT (V)
0
500
400
–2
–4
300
–6
200
–8
100
0
0
1
2
3
4
LOGIC INPUT VOLTAGE (V)
5
6
–10
–1
09649-038
IOICC (µA)
600
20
TIME (µs)
Figure 37. Gain Error vs. Temperature
800
15
–8
VDD = +15V
VSS = –15V
AD8675 OUTPUT BUFFER
–3.5
TA = 25°C
10
VDD = +15V
VSS = –15V
VREFP = +10V
VREFN = –10V
ADA4808-1 BUFFERED
LOAD = 10MΩ || 20pF
–2
–2.5
09649-037
GAIN ERROR (LSB)
–1.5
900
0
5
VDD/VSS (V)
4
2
–20
–5
6
–1.0
–4.0
–40
–10
Figure 39. Power Supply Currents vs. Power Supply Voltages
±10V SPAN
+10V SPAN
+5V SPAN
–0.5
–15
09649-039
–20
09649-040
–3.0
–40
ISS
–0.008
09649-036
–2.5
09649-041
ZERO-SCALE ERROR (LSB)
AD5780
0
1
2
3
4
TIME (µs)
Figure 41. Falling Full-Scale Voltage Step
Figure 38. IOICC vs. Logic Input Voltage
Rev. C | Page 15 of 28
AD5780
Data Sheet
6
10
VREFP = 5V
VREFN = 0V
UNITY-GAIN MODE
ADA4898-1 OUTPUT BUFFER
RC LOW-PASS FILTER
9
5
OUTPUT GLITCH (nV-s)
8
6
5
4
3
VREFP = +10V
VREFN = –10V
RC LOW-PASS FILTER
UNITY-GAIN MODE
ADA4898-1 OUTPUT BUFFER
0
–1
0
1
2
3
4
3
2
1
5
TIME (µs)
0
09649-047
1
09649-042
2
4
16384
65536
114688
163840
212992
262144
311296
360448
409600
458752
507904
557056
606208
655360
704512
753664
802816
851968
901120
950272
999424
VOUT (mV)
7
NEGATIVE
POSITIVE
CODE
Figure 42. 500 Code Step Settling Time
Figure 45. 6 MSB Segment Glitch Energy for 5 V VREF
55
NEGATIVE
VREFP = +10V
POSITIVE
VREFN = –10V
UNITY-GAIN MODE
ADA4898-1 OUTPUT BUFFER
20
RC LOW-PASS FILTER
POSITIVE
NEGATIVE
CODE CHANGE CODE CHANGE
±10V SPAN
+10V SPAN
+5V SPAN
45
35
OUTPUT GLITCH (mV)
OUTPUT GLITCH (nV-s)
25
15
10
25
15
5
–5
5
–1
800
OUTPUT VOLTAGE (nV)
2.5
2.0
1.5
1.0
MIDSCALE CODE LOADED
OUTPUT UNBUFFERED
200
0
–200
–400
0.5
–600
CODE
09649-044
0
TA = 25°C
VDD = +15V
600 VSS = –15V
VREFP = +10V
VREFN = –10V
400
Figure 44. 6 MSB Segment Glitch Energy for 10 V VREF
0
1
2
3
4
5
6
TIME (Seconds)
7
8
9
10
Figure 47. Voltage Output Noise, 0.1 Hz to 10 Hz Bandwidth
Rev. C | Page 16 of 28
09649-045
3.0
16384
65536
114688
163840
212992
262144
311296
360448
409600
458752
507904
557056
606208
655360
704512
753664
802816
851968
901120
950272
999424
OUTPUT GLITCH (nV-s)
3.5
3
Figure 46. Midscale Peak-to-Peak Glitch for ±10 V
NEGATIVE
POSITIVE
VREFP = 10V
VREFN = 0V
UNITY-GAIN MODE
ADA4898-1
OUTPUT BUFFER
RC LOW-PASS FILTER
2
1
TIME (µs)
Figure 43. 6 MSB Segment Glitch Energy for ±10 V VREF
4.0
0
09649-046
CODE
–25
09649-043
0
16384
49152
81920
114688
147456
180224
212992
245760
278528
311296
344064
376832
409600
442368
475136
507904
540672
573440
606208
638976
671744
704512
737280
770048
802816
835584
868352
901120
933888
966656
999424
1032192
–15
Data Sheet
AD5780
200
VDD = +15V
VSS = –15V
VREFP = +10V
VREFN = –10V
VDD = +15V
VSS = –15V
VREFP = +10V
VREFN = –10V
UNITY GAIN
ADA4898-1
180
OUTPUT VOLTAGE (mV)
160
10
140
120
100
80
60
40
20
1
10
100
1k
FREQUENCY (Hz)
10k
–20
0
1
2
3
TIME (µs)
4
5
Figure 49. Glitch Impulse on Removal of Output Clamp
Figure 48. Noise Spectral Density vs. Frequency
Rev. C | Page 17 of 28
6
09649-048
0
1
0.1
09649-055
NSD (nV/√Hz)
100
AD5780
Data Sheet
TERMINOLOGY
Relative Accuracy
Relative accuracy, or integral nonlinearity (INL), is a measure of
the maximum deviation, in LSB, from a straight line passing
through the endpoints of the DAC transfer function. A typical
INL error vs. code plot is shown in Figure 6.
Differential Nonlinearity (DNL)
Differential nonlinearity is the difference between the measured
change and the ideal 1 LSB change between any two adjacent
codes. A specified differential nonlinearity of ±1 LSB maximum
ensures monotonicity. This DAC is guaranteed monotonic. A
typical DNL error vs. code plot is shown in Figure 10.
Linearity Error Long-Term Stability
Linearity error long-term stability is a measure of the stability of
the linearity of the DAC over a long period of time. It is specified in LSB for a time period of 500 hours and 1000 hours at an
elevated ambient temperature.
Zero-Scale Error
Zero-scale error is a measure of the output error when zero-scale
code (0x00000) is loaded to the DAC register. Ideally, the output
voltage should be VREFN. Zero-scale error is expressed in LSBs.
Zero-Scale Error Temperature Coefficient
Zero-scale error temperature coefficient is a measure of the
change in zero-scale error with a change in temperature. It is
expressed in ppm FSR/°C.
Full-Scale Error
Full-scale error is a measure of the output error when full-scale
code (0x3FFFF) is loaded to the DAC register. Ideally, the
output voltage should be VREFP − 1 LSB. Full-scale error is
expressed in LSBs.
Full-Scale Error Temperature Coefficient
Full-scale error temperature coefficient is a measure of the
change in full-scale error with a change in temperature. It is
expressed in ppm FSR/°C.
Gain Error
Gain error is a measure of the span error of the DAC. It is the
deviation in slope of the DAC transfer characteristic from the
ideal, expressed in ppm of the full-scale range.
Gain Error Temperature Coefficient
Gain error temperature coefficient is a measure of the change
in gain error with a change in temperature. It is expressed in
ppm FSR/°C.
Output Voltage Settling Time
Output voltage settling time is the amount of time it takes for
the output voltage to settle to a specified level for a specified
change in voltage. For fast settling applications, a high speed
buffer amplifier is required to buffer the load from the 3.4 kΩ
output impedance of the AD5780, in which case, it is the
amplifier that determines the settling time.
Digital-to-Analog Glitch Impulse
Digital-to-analog glitch impulse is the impulse injected into the
analog output when the input code in the DAC register changes
state. It is specified as the area of the glitch in nV-sec and is
measured when the digital input code is changed by 1 LSB at
the major carry transition (see Figure 49).
Output Enabled Glitch Impulse
Output enabled glitch impulse is the impulse injected into the
analog output when the clamp to ground on the DAC output is
removed. It is specified as the area of the glitch in nV-sec (see
Figure 49).
Digital Feedthrough
Digital feedthrough is a measure of the impulse injected into
the analog output of the DAC from the digital inputs of the
DAC but is measured when the DAC output is not updated. It is
specified in nV-sec and measured with a full-scale code change
on the data bus, that is, from all 0s to all 1s, and vice versa.
Total Harmonic Distortion (THD)
Total harmonic distortion is the ratio of the rms sum of the
harmonics of the DAC output to the fundamental value. Only
the second to fifth harmonics are included.
DC Power Supply Rejection Ratio
DC power supply rejection ratio is a measure of the rejection of
the output voltage to dc changes in the power supplies applied
to the DAC. It is measured for a given dc change in power
supply voltage and is expressed in μV/V.
AC Power Supply Rejection Ratio (AC PSRR)
AC power supply rejection ratio is a measure of the rejection of
the output voltage to ac changes in the power supplies applied
to the DAC. It is measured for a given amplitude and frequency
change in power supply voltage and is expressed in decibels.
Midscale Error
Midscale error is a measure of the output error when midscale
code (0x20000) is loaded to the DAC register. Ideally, the output
voltage should be (VREFP – VREFN)/2 + VREFN. Midscale error is
expressed in LSBs.
Rev. C | Page 18 of 28
Data Sheet
AD5780
THEORY OF OPERATION
R
2R
VREFP
R
R
VOUT
2R
2R ...
2R
2R
2R ...
2R
S0
S1 ...
S11
E62
E61...
E0
VREFN
12-BIT R-2R LADDER
DAC ARCHITECTURE
09649-049
The AD5780 is a high accuracy, fast settling, single, 18-bit,
serial input, voltage output DAC. It operates from a VDD supply
voltage of 7.5 V to 16.5 V and a VSS supply of −16.5 V to −2.5 V.
Data is written to the AD5780 in a 24-bit word format via a 3-wire
serial interface. The AD5780 incorporates a power-on reset
circuit that ensures the DAC output powers up to 0 V with the
VOUT pin clamped to AGND through a ~6 kΩ internal resistor.
SIX MSBs DECODED INTO
63 EQUAL SEGMENTS
Figure 50. DAC Ladder Structure Serial Interface
The architecture of the AD5780 consists of two matched DAC
sections. A simplified circuit diagram is shown in Figure 50.
The six MSBs of the 18-bit data-word are decoded to drive
63 switches, E0 to E62. Each of these switches connects one
of 63 matched resistors to either the buffered VREFP or buffered
VREFN voltage. The remaining 12 bits of the data-word drive
the S0 to S11 switches of a 12-bit voltage mode R-2R ladder
network.
SERIAL INTERFACE
The AD5780 has a 3-wire serial interface (SYNC, SCLK, and
SDIN) that is compatible with SPI, QSPI, and MICROWIRE
interface standards, as well as most DSPs (see Figure 2 for a
timing diagram).
Input Shift Register
The input shift register is 24 bits wide. Data is loaded into the
device MSB first as a 24-bit word under the control of a serial
clock input, SCLK, which can operate at up to 35 MHz. The
input register consists of a R/W bit, three address bits, and
20 data bits as shown in Table 6. The timing diagram for this
operation is shown in Figure 2.
Table 6. Input Shift Register Format
MSB
DB23
R/W
LSB
DB22
DB21
Register address
DB20
DB19 to DB0
Register data
Table 7. Decoding the Input Shift Register
R/W
X
0
0
0
0
1
1
1
1
1
0
0
0
0
1
0
0
0
Register Address
0
0
0
1
1
0
1
1
0
0
0
1
1
0
1
1
Description
No operation (NOP). Used in readback operations.
Write to the DAC register.
Write to the control register.
Write to the clearcode register.
Write to the software control register.
Read from the DAC register.
Read from the control register.
Read from the clearcode register.
X is don’t care.
Rev. C | Page 19 of 28
AD5780
Data Sheet
Standalone Operation
CONTROLLER
The serial interface works with both a continuous and noncontinuous serial clock. A continuous SCLK source can be used
only if SYNC is held low for the correct number of clock cycles.
SERIAL CLOCK
SCLK
CONTROL OUT
SYNC
DATA OUT
In gated clock mode, a burst clock containing the exact number
of clock cycles must be used, and SYNC must be taken high after
the final clock to latch the data. The first falling edge of SYNC
starts the write cycle. Exactly 24 falling clock edges must be
applied to SCLK before SYNC is brought high again. If SYNC is
brought high before the 24th falling SCLK edge, the data written
is invalid. If more than 24 falling SCLK edges are applied before
SYNC is brought high, the input data is also invalid.
AD5780*
SDIN
DATA IN
SDO
SDIN
AD5780*
SCLK
SYNC
The input shift register is updated on the rising edge of SYNC.
For another serial transfer to take place, SYNC must be brought
low again. After the end of the serial data transfer, data is
automatically transferred from the input shift register to the
addressed register. When the write cycle is complete, the output
can be updated by taking LDAC low while SYNC is high.
SDO
SDIN
AD5780*
SCLK
SYNC
Daisy-Chain Operation
A continuous SCLK source can be used only if SYNC is held
low for the correct number of clock cycles. In gated clock mode,
a burst clock containing the exact number of clock cycles must
be used, and SYNC must be taken high after the final clock to
latch the data.
In any one daisy-chain sequence, do not mix writes to the DAC
register with writes to any of the other registers. All writes to the
daisy-chained parts must be either writes to the DAC registers
or writes to the control, clearcode, or software control register.
SDO
*ADDITIONAL PINS OMITTED FOR CLARITY.
09649-050
For systems that contain several devices, the SDO pin can be
used to daisy-chain several devices together. Daisy-chain mode
can be useful in system diagnostics and in reducing the number
of serial interface lines. The first falling edge of SYNC starts the
write cycle. SCLK is continuously applied to the input shift register
when SYNC is low. If more than 24 clock pulses are applied, the
data ripples out of the shift register and appears on the SDO
line. This data is clocked out on the rising edge of SCLK and
is valid on the falling edge. By connecting the SDO of the first
device to the SDIN input of the next device in the chain, a
multidevice interface is constructed. Each device in the system
requires 24 clock pulses. Therefore, the total number of clock
cycles must equal 24 × N, where N is the total number of
AD5780 devices in the chain. When the serial transfer to all
devices is complete, SYNC is taken high. This latches the input
data in each device in the daisy chain and prevents any further
data from being clocked into the input shift register. The serial
clock can be a continuous or a gated clock.
Figure 51. Daisy-Chain Block Diagram
Readback
The contents of all the on-chip registers can be read back via
the SDO pin. Table 7 outlines how the registers are decoded.
After a register has been addressed for a read, the next 24 clock
cycles clock the data out on the SDO pin. The clocks must be
applied while SYNC is low. When SYNC is returned high, the
SDO pin is placed in tristate. For a read of a single register, the
NOP function can be used to clock out the data. Alternatively,
if more than one register is to be read, the data of the first
register to be addressed can be clocked out at the same time
that the second register to be read is being addressed. The SDO
pin must be enabled to complete a readback operation. The
SDO pin is enabled by default.
HARDWARE CONTROL PINS
Load DAC Function (LDAC)
After data has been transferred into the input register of the
DAC, there are two ways to update the DAC register and DAC
output. Depending on the status of both SYNC and LDAC, one
of two update modes is selected: synchronous DAC update or
asynchronous DAC update.
Synchronous DAC Update
In this mode, LDAC is held low while data is being clocked into
the input shift register. The DAC output is updated on the rising
edge of SYNC.
Rev. C | Page 20 of 28
Data Sheet
AD5780
Asynchronous DAC Update
In this mode, LDAC is held high while data is being clocked
into the input shift register. The DAC output is asynchronously
updated by taking LDAC low after SYNC has been taken high.
The update now occurs on the falling edge of LDAC.
is high) until a new value is loaded to the DAC register. The
output cannot be updated with a new value while the CLR pin is
low. A clear operation can also be performed by setting the CLR
bit in the software control register (see Table 13).
ON-CHIP REGISTERS
Reset Function (RESET)
DAC Register
The AD5780 can be reset to its power-on state by two means:
either by asserting the RESET pin or by using the reset function
in the software control register (see Table 13). If the RESET pin
is not used, hardwire it to IOVCC.
Table 9 outlines how data is written to and read from the DAC
register.
Asynchronous Clear Function (CLR)
VOUT =
The CLR pin is an active low clear that allows the output to be
cleared to a user defined value. The 18-bit clearcode value is
programmed to the clearcode register (see Table 12). It is
necessary to maintain CLR low for a minimum amount of time
to complete the operation (see Figure 2). When the CLR signal
is returned high, the output remains at the clear value (if LDAC
The following equation describes the ideal transfer function of
the DAC:
(VREFP − VREFN ) × D + V
218
REFN
where:
VREFN is the negative voltage applied at the VREFN input pin.
VREFP is the positive voltage applied at the VREFP input pin.
D is the 18-bit code programmed to the DAC.
Table 8. Hardware Control Pins Truth Table
LDAC
CLR
RESET
X1
X1
0
0
1
X1
X1
0
1
0
1
0
1
0
0
X
X
1
1
1
1
1
1
1
1
1
1
1
1
0
1
0
1
Function
The AD5780 is in reset mode. The device cannot be programmed.
The AD5780 is returned to its power-on state. All registers are set to their default values.
The DAC register is loaded with the clearcode register value, and the output is set accordingly.
The output is set according to the DAC register value.
The DAC register is loaded with the clearcode register value, and the output is set accordingly.
The output is set according to the DAC register value.
The output remains at the clearcode register value.
The output remains set according to the DAC register value.
The output remains at the clearcode register value.
The DAC register is loaded with the clearcode register value and the output is set accordingly.
The DAC register is loaded with the clearcode register value and the output is set accordingly.
The output remains at the clearcode register value.
The output is set according to the DAC register value.
X is don’t care.
Table 9. DAC Register
MSB
DB23
R/W
DB22
R/W
0
1
LSB
DB21
DB20
Register address
0
1
DB19 to DB2
DAC register data
DB1
DB0
18 bits of data
X1
X1
X is don’t care.
Rev. C | Page 21 of 28
X
AD5780
Data Sheet
Control Register
is asserted. The output value depends on the DAC coding that is
being used, either binary or twos complement. The default
register value is 0.
The control register controls the mode of operation of the
AD5780.
Clearcode Register
The clearcode register sets the value to which the DAC output is
set when the CLR pin or CLR bit in the software control register
Table 10. Control Register
MSB
DB23
R/W
DB22 DB21 DB20
Register address
DB19 to DB11
DB10
LSB
R/W
0
Reserved
Reserved
1
0
DB9
DB8
DB7
DB6 DB5
DB4
Control register data
0000
SDODIS
BIN/2sC
DB3
DB2
DB1
DB0
DACTRI
OPGND
RBUF
Reserved
Table 11. Control Register Functions
Bit Name
Reserved
RBUF
OPGND
DACTRI
BIN/2sC
SDODIS
R/W
Description
These bits are reserved and should be programmed to zero.
Output amplifier configuration control.
0: the internal amplifier, A1, is powered up and Resistors RFB and R1 are connected in series as shown in Figure 54. This allows
an external amplifier to be connected in a gain of two configuration. See the AD5780 Features section for further details.
1: (default) the internal amplifier, A1, is powered down and Resistors RFB and R1 are connected in parallel, as shown in Figure 53,
so that the resistance between the RFB and INV pins is 3.4 kΩ, equal to the resistance of the DAC. This allows the RFB and INV
pins to be used for input bias current compensation for an external unity-gain amplifier. See the AD5780 Features section for
further details.
Output ground clamp control.
0: the DAC output clamp to ground is removed, and the DAC is placed in normal mode.
1: (default) the DAC output is clamped to ground through a ~6 kΩ resistance, and the DAC is placed in tristate mode.
Resetting the part puts the DAC in OPGND mode, where the output ground clamp is enabled and the DAC is tristated. Setting
the OPGND bit to 1 in the control register overrules any write to the DACTRI bit
DAC tristate control.
0: the DAC is in normal operating mode.
1: (default) the DAC is in tristate mode.
DAC register coding selection.
0: (default) the DAC register uses twos complement coding.
1: the DAC register uses offset binary coding.
SDO pin enable/disable control.
0: (default) the SDO pin is enabled.
1: the SDO pin is disabled (tristate).
Read/write select bit.
0: AD5780 is addressed for a write operation.
1: AD5780 is addressed for a read operation.
Table 12. Clearcode Register
MSB
DB23
R/W
DB22
R/W
0
1
LSB
DB21
DB20
Register address
1
1
DB19 to DB2
Clearcode register data
DB1
DB0
18 bits of data
X1
X1
X is don’t care.
Rev. C | Page 22 of 28
X
Data Sheet
AD5780
Software Control Register
This is a write only register in which writing a 1 to a particular bit has the same effect as pulsing the corresponding pin low.
Table 13. Software Control Register
MSB
DB23
R/W
DB22
0
1
1
2
LSB
DB21
DB20
Register address
0
0
DB19 to DB3
Reserved
DB2
DB1
Software control register data
Reset
CLR 1
DB0
LDAC 2
The CLR function has no effect when the LDAC pin is low.
The LDAC function has no effect when the CLR pin is low.
Table 14. Software Control Register Functions
Bit Name
LDAC
CLR
Reset
Description
Setting this bit to 1 updates the DAC register and consequently the DAC output.
Setting this bit to 1 sets the DAC register to a user defined value (see Table 12) and updates the DAC output. The output
value depends on the DAC register coding that is being used, either binary or twos complement.
Setting this bit to 1 returns the AD5780 to its power-on state.
Rev. C | Page 23 of 28
AD5780
Data Sheet
AD5780 FEATURES
POWER-ON TO 0 V
Unity-Gain Configuration
The AD5780 contains a power-on reset circuit that, as well as
resetting all registers to their default values, controls the output
voltage during power-up. Upon power-on, the DAC is placed in
tristate (its reference inputs are disconnected), and its output is
clamped to AGND through a ~6 kΩ resistor. The DAC remains
in this state until programmed otherwise via the control register.
This is a useful feature in applications where it is important to
know the state of the DAC output while it is in the process of
powering up.
Figure 52 shows an output amplifier configured for unity gain.
In this configuration, the output spans from VREFN to VREFP.
VREFP
A1
RFB
R1
RFB
6.8kΩ 6.8kΩ
INV
18-BIT
DAC
AD8675,
ADA4898-1,
ADA4004-1
VOUT
VOUT
CONFIGURING THE AD5780
DAC OUTPUT STATE
The DAC output can be placed in one of three states, controlled
by the DACTRI and OPGND bits of the control register, as
shown in Table 15.
Table 15. Output State Truth Table
DACTRI
0
0
1
1
OPGND
0
1
0
1
Output State
Normal operating mode.
Output is clamped via ~6 kΩ to AGND.
Output is in tristate.
Output is clamped via ~6 kΩ to AGND.
AD5780
09649-051
After power-on, the AD5780 must be configured to put it into
normal operating mode before programming the output. To
do this, the control register must be programmed. The DAC
is removed from tristate by clearing the DACTRI bit, and the
output clamp is removed by clearing the OPGND bit. At this
point, the output goes to VREFN unless an alternative value is first
programmed to the DAC register.
VREFN
Figure 52. Output Amplifier in Unity-Gain Configuration
A second unity-gain configuration for the output amplifier is
one that removes an offset from the input bias currents of the
amplifier. It does this by inserting a resistance in the feedback
path of the amplifier that is equal to the output resistance of the
DAC. The DAC output resistance is 3.4 kΩ. By connecting R1
and RFB in parallel, a resistance equal to the DAC resistance is
available on chip. Because the resistors are all on one piece of
silicon, they are temperature coefficient matched. To enable this
mode of operation, the RBUF bit of the control register must be
set to Logic 1. Figure 53 shows how the output amplifier is
connected to the AD5780. In this configuration, the output
amplifier is in unity gain and the output spans from VREFN to
VREFP. This unity-gain configuration allows a capacitor to be
placed in the amplifier feedback path to improve dynamic
performance.
VREFP
OUTPUT AMPLIFIER CONFIGURATION
RFB
R1
6.8kΩ
RFB
6.8kΩ
INV
18-BIT
DAC
VOUT
AD5780
VREFN = 0V
10pF
VOUT
AD8675,
ADA4898-1,
ADA4004-1
09649-049
There are a number of different ways that an output amplifier
can be connected to the AD5780, depending on the voltage
references applied and the desired output voltage span.
Figure 53. Output Amplifier in Unity Gain with Amplifier Input Bias Current
Compensation
Rev. C | Page 24 of 28
Data Sheet
AD5780
VREFP
Figure 54 shows an output amplifier configured for a gain of
two. The gain is set by the internal matched 6.8 kΩ resistors,
which are exactly twice the DAC resistance, having the effect
of removing an offset from the input bias current of the external
amplifier. In this configuration, the output spans from 2 × VREFN −
VREFP to VREFP. This configuration is used to generate a bipolar
output span from a single-ended reference input, with VREFN =
0 V. For this mode of operation, the RBUF bit of the control
register must be cleared to Logic 0.
A1
R1
RFB
RFB
10pF
6.8kΩ 6.8kΩ
INV
18-BIT
DAC
VOUT
VOUT
AD8675,
ADA4898-1,
ADA4004-1
AD5780
VREFN
Figure 54. Output Amplifier in Gain-of-Two Configuration
Rev. C | Page 25 of 28
09649-050
Gain of Two Configuration (×2 Gain Mode)
AD5780
Data Sheet
APPLICATIONS INFORMATION
TYPICAL OPERATING CIRCUIT
09649-054
Figure 55. Typical Operating Circuit
Rev. C | Page 26 of 28
Data Sheet
Figure 55 shows a typical operating circuit for the AD5780
using an AD8675 as an output buffer. Because the output
impedance of the AD5780 is 3.4 kΩ, an output buffer is
required for driving low resistive, high capacitive loads.
EVALUATION BOARD
An evaluation board is available for the AD5780 to aid
designers in evaluating the high performance of the part
with minimum effort. The AD5780 evaluation kit includes a
AD5780
populated and tested AD5780 printed circuit board (PCB). The
evaluation board interfaces to the USB port of a PC. Software is
available with the evaluation board to allow the user to easily
program the AD5780. The software runs on any PC that has
Microsoft® Windows® XP (SP2), Vista (32-bit or 64-bit), or
Windows 7 installed. The AD5780 user guide, UG-256, is
available, which gives full details on the operation of the
evaluation board.
Rev. C | Page 27 of 28
AD5780
Data Sheet
OUTLINE DIMENSIONS
2.75
2.65
2.50
4.00 BSC
PIN 1
INDICATOR
20
PIN 1
INDICATOR
1
19
0.50
BSC
5.00 BSC
3.75
3.65
3.50
EXPOSED
PAD
7
13
1.00
0.90
0.80
SEATING
PLANE
0.30
0.25
0.20
0.50
0.40
0.30
0.05 MAX
0.02 NOM
COPLANARITY
0.08
0.20 REF
8
12
BOTTOM VIEW
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
122409-B
TOP VIEW
(Chamfer 0.225)
24
Figure 56. 24-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
4 mm × 5 mm Body, Very Thin Quad
(CP-24-5)
Dimensions shown in millimeters
ORDERING GUIDE
Model 1
AD5780ACPZ
AD5780ACPZ-REEL7
AD5780BCPZ
AD5780BCPZ-REEL7
EVAL-AD5780SDZ
1
Temperature Range
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
INL
±2 LSB
±2 LSB
±1 LSB
±1 LSB
Z = RoHS Compliant Part.
©2011–2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D09649-0-3/12(C)
Rev. C | Page 28 of 28
Package Description
24-Lead LFCSP_VQ
24-Lead LFCSP_VQ
24-Lead LFCSP_VQ
24-Lead LFCSP_VQ
Evaluation Board
Package Option
CP-24-5
CP-24-5
CP-24-5
CP-24-5