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Preliminary Technical Data
FEATURES
Octal, 12-14-16 Bit Dac with 10ppm/C Max On-Chip Reference in 14-Lead TSSOP AD5628/AD5648/AD5668
Digital Gain and Offset Adjustment Programmable Voltage and Current Sources Programmable Attenuators
VDD AD5628/AD5648/AD5668 INPUT LDAC
REGISTER
Low Power Smallest Pin compatible Octal DACs AD5668: 16 Bits AD5648: 14 Bits AD5628: 12 Bits 12-Bit Accuracy Guaranteed 14/16-Lead TSSOP Package On-chip 1.25/2.5V, 10ppm/C Reference Power-Down to 200 nA @ 5V, 50 nA @ 3V 3V/5V Power Supply Guaranteed Monotonic by Design Power-On-Reset to Zero/Midscale Three Power-Down Functions Hardware /LDAC and /CLR functions Rail-to-Rail Operation Temperature Range -40C to +125C
VREF 1.25/2.5V Ref DAC
REGISTER DAC REGISTER DAC REGISTER STRING DAC A STRING DAC B STRING DAC C STRING DAC D
BUFFER
VOUTA VOUTB VOUTC VOUTD VOUTE VOUTF VOUTG VOUTH
INPUT
REGISTER
BUFFER
INPUT
REGISTER
BUFFER
SCLK INTERFACE LOGIC
INPUT
REGISTER
DAC
REGISTER
BUFFER
SYNC
INPUT
REGISTER
DAC
REGISTER
STRING DAC E
STRING DAC F STRING DAC G STRING DAC H
BUFFER
DIN
INPUT
REGISTER
DAC
REGISTER
BUFFER
INPUT
REGISTER
DAC
REGISTER
BUFFER
INPUT
REGISTER
DAC
REGISTER
BUFFER
POWER-ON RESET
POWER-DOWN LOGIC
APPLICATIONS
ProcessControl Data Acquisition Systems Portable Battery Powered Instruments
LDAC* CLR*
*RU-16 PACKAGE ONLY
GND
Figure 1. Functional Block Diagram
GENERAL DESCRIPTION
The AD5628/48/68 family of devices are low power, octal, 1214-16-bit buffered voltage-out DACs. All devices operate from a single +2.7V to +5.5V, and are guaranteed monotonic by design. The AD5628/48/68 have an on-chip reference with an internal gain of two. The AD56x8-1 has a 1.25V 10ppm/C max reference and the AD56x8-2,-3 have a 2.5V 10ppm/C max reference. The on-board reference is off at power-up allowing the use of an external reference. The internal reference is turned on by writing to the DAC. The part incorporates a power-on-reset circuit that ensures that the DAC output powers up to zero volts (AD56x8-1,-2/) or midscale (AD56683) and remains there until a valid write takes place. The part contains a power-down feature that reduces the current consumption of the device to 200nA at 5V and provides software selectable output loads while in power-down mode for any or all DACs channels.
The outputs of all DACs may be updated simultaneously using the /LDAC function, with the added functionality of selecting through software any number of DAC channels to synchronize. There is also an asynchronous active low /CLR that clears all DACs to a software selectable code - 0 V, midscale or fullscale . The AD5628/48/68 utilizes a versatile three-wire serial interface that operates at clock rates up to 50 MHz and is compatible with standard SPITM, QSPITM, MICROWIRETM and DSP interface standards. Its on-chip precision output amplifier allows rail-to-rail output swing to be achieved.
PRODUCT HIGHLIGHTS
1. 2. 3. 4. 5. Octal 12/14/16-Bit DAC; 12-Bit Accuracy Guaranteed. On-chip 1.25/2.5V, 10ppm/C max Reference. Available in 14/16-lead TSSOP package. Power-On-Reset to Zero volts or Midscale. Power-down capability. When powered down, the DAC typically consumes 50nA at 3V and 200nA at 5V.
Rev. PrA
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 companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. www.analog.com Tel: 781.329.4700 Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved.
AD5628/AD5648/AD5668
TABLE OF CONTENTS
Features .......................................................................................... 1 Applications................................................................................... 1 General Description..................................................................... 1 Product Highlights ....................................................................... 1 AD5628/AD5648/AD5668-Specifications ................................... 3 Timing Characteristics..................................................................... 9 Pin Configuration and Function Descriptions........................... 10 Absolute Maximum Ratings.......................................................... 11 ESD Caution................................................................................ 11 Terminology ................................................................................ 11
Preliminary Technical Data
AD5628/AD5648/AD5668-Typical Performance Characteristics ................................................................................ 13 General Description................................................................... 16 Serial Interface ............................................................................ 16 Microprocessor Interfacing............................................................ Applications ..................................................................................... Outline Dimensions ....................................................................... 23 Ordering Guide ...............................................................................
REVISION HISTORY
Revision 0: Initial Version
Rev.PrA | Page 2 of 24
Preliminary Technical Data AD5628/AD5648/AD5668-SPECIFICATIONS
AD5628/AD5648/AD5668
(VDD = +4.5 V to +5.5 V; RL = 2 k to GND; CL = 200 pF to GND; External REFIN = VDD; all specifications TMIN to TMAX unless otherwise noted) Table 1.
A Grade Parameter STATIC PERFORMANCE3,4 AD5628 Resolution Relative Accuracy Differential Nonlinearity AD5648 Resolution Relative Accuracy Differential Nonlinearity AD5668 Resolution Relative Accuracy Differential Nonlinearity Load Regulation Zero Code Error Zero Code Error Drift3 Full-Scale Error Gain Error Gain Temperature Coefficient Offset Error Offset Temperature Coefficient DC Power Supply Rejection Ratio6 DC Crosstalk6 (Ext Ref) +1 20 -0.15 Min Typ Max Min B Grade Typ Max Unit B Version 1,2 Conditions/Comments
12 0.5 6 1
12 0.5 1 1
Bits LSB LSB
See Figure 4 Guaranteed Monotonic by Design. See Figure 5.
14 2 8 1
14 2 4 1
Bits LSB LSB
See Figure 4 Guaranteed Monotonic by Design. See Figure 5.
16 32 1 2 +9
16 16 1 2 +1 20 -0.15 +9
Bits LSB LSB LSB/mA mV V/C % of FSR % of FSR ppm mV V/C dB V V/mA V V V/mA V
See Figure 4 Guaranteed Monotonic by Design. See Figure 5. VDD=Vref=5V, Midscale Iout=0mA to 15mA sourcing/sinking All Zeroes Loaded to DAC Register. See Figure 8. All Ones Loaded to DAC Register. See Figure 8. of FSR/C
-1.25 1.5
-1.25 1.5
5 1 1.7 -80 9
5 1 1.7 -80 9
VDD 10% RL = 2 k. to GND or VDD Due to Load current change Due to Powering Down (per channel) RL = 2 k. to GND or VDD Due to Load current change Due to Powering Down (per channel)
DC Crosstalk (Int Ref)
6
10 4.5 10 20 4.5 20
10 4.5 10 20 4.5 20
1 2 3
Temperature ranges are as follows: B Version: -40C to +125C, typical at 25C. Linearity calculated using a reduced code range of 485 to 64714. Output unloaded. DC specifications tested with the outputs unloaded unless stated otherwise. 4 Linearity is tested using a reduced code range: AD5628 (Code 48 to Code 4047), AD5648 (Code / to Code /), and AD5668 (Code 485 to 64714). 6 Guaranteed by design and characterization; not production tested. 8 Interface inactive. All DACs active. DAC outputs unloaded. 9 All eight DACs powered down. Specifications subject to change without notice.
Rev. PrA| Page 3 of 24
AD5628/AD5648/AD5668
A Grade Parameter OUTPUT CHARACTERISTICS6 Output Voltage Range Capacitive Load Stability DC Output Impedance Short Circuit Current Power-Up Time REFERENCE INPUTS3 Reference Input voltage Reference Current Reference Input Range Reference Input Impedance REFERENCE OUTPUT Output Voltage 2.495 AD5628/AD5648/AD5668x2/3 Reference TC Reference Output Impedance LOGIC INPUTS3 Input Current VINL, Input Low Voltage VINH, Input High Voltage Pin Capacitance POWER REQUIREMENTS VDD IDD (Normal Mode)8 VDD=4.5 V to +5.5 V IDD (All Power-Down Modes)9 VDD=4.5 V to +5.5 V POWER EFFICIENCY IOUT/IDD 2.5 2.505 2.495 2.5 2.505 V 0 14.6 VDD 35 45 VDD 0 14.6 VDD 35 45 VDD V A k Min Typ Max Min B Grade Typ Max Unit
Preliminary Technical Data
B Version 1,2 Conditions/Comments
0 2 10 0.5 30 4
VDD
0 2 10 0.5 30 4
VDD
V pF pF mA s
RL= RL=2 k VDD=+5V Coming out of Power-Down Mode. VDD=+5V 1% for specified performance VREF = VDD = +5.5V (per DAC channel) Per DAC channel
10 2 2
10
ppm/C k
1 0.8 2 3 4.5 2 5.5 4 4.5 2 2 3
1 0.8
A V V pF V mA
VDD=+5 V VDD=+5 V
5.5 4
All Digital Inputs at 0 or VDD DAC Active and Excluding Load Current VIH=VDD and VIL=GND
0.2 89
1
0.2 89
1
A %
VIH=VDD and VIL=GND ILOAD=2 mA, VDD=+5 V
Rev.PrA | Page 4 of 24
Preliminary Technical Data
specifications TMIN to TMAX unless otherwise noted)
AD5628/AD5648/AD5668
AC CHARACTERISTICS1 (VDD = +4.5 V to +5.5 V; RL = 2 k to GND; CL = 200 pF to GND; External REFIN = VDD; all
B Version 1 Conditions/Comments 1/4 to 3/4 scale settling to 2LSB 1/4 to 3/4 scale settling to 2LSB 1/4 to 3/4 scale settling to 2LSB
Parameter Output Voltage Settling Time AD5628 AD5648 AD5668 Settling Time for 1LSB Step Slew Rate Digital-to-Analog Glitch Impulse Channel -to-Channel Isolation Digital Feedthrough Digital Crosstalk Analog Crosstalk DAC-to-DAC Crosstalk Multiplying Bandwidth Total Harmonic Distortion Output Noise Spectral Density Output Noise
2
Min
Typ 6 7 8 1.5 5 100 0.1 0.5 1 3 200 -80 120 100 15
Max 8 9 10
Unit s s s V/s nV-s dB nV-s nV-s nV-s nV-s kHz dB nV/Hz nV/Hz Vp-p
1 LSB Change Around Major Carry. See Figure 21.
VREF = 2V 0.1 V p-p. VREF = 2V 0.1 V p-p. Frequency = 10kHz DAC code=8400H, 1kHz DAC code=8400H, 10kHz 0.1Hz to 10Hz;
NOTES by design and characterization; not production tested. the Terminology section. 3Temperature range (Y Version): -40C to +125C; typical at +25C. Specifications subject to change without notice.
1Guaranteed 2See
Rev. PrA| Page 5 of 24
AD5628/AD5648/AD5668
AD5628/AD5648/AD5668-SPECIFICATIONS
Preliminary Technical Data
(VDD = +2.7 V to +3.6 V; RL = 2 k to GND; CL = 200 pF to GND; External REFIN = VDD ; all specifications TMIN to TMAX unless otherwise noted) Table 2.
A Grade Parameter STATIC PERFORMANCE3,4 AD5628 Resolution Relative Accuracy Differential Nonlinearity AD5648 Resolution Relative Accuracy Differential Nonlinearity AD5668 Resolution Relative Accuracy Differential Nonlinearity Load Regulation Min Typ Max Min B Grade Typ Max Unit B Version 1,1 Conditions/Comments
12 0.5 6 1
12 0.5 1 1
Bits LSB LSB
See Figure 4 Guaranteed Monotonic by Design. See Figure 5.
14 2 8 1
14 2 4 1
Bits LSB LSB
See Figure 4 Guaranteed Monotonic by Design. See Figure 5.
16 32 1 4
16 16 1 4
Bits LSB LSB LSB/mA
Zero Code Error Zero Code Error Drift1 Full-Scale Error Gain Error Gain Temperature Coefficient Offset Error Offset Temperature Coefficient DC Power Supply Rejection Ratio6 DC Crosstalk6 (Ext Ref)
+1 20 -0.15
+9
+1 20 -0.15
+9
mV V/C % of FSR % of FSR ppm mV V/C dB V V/mA V V V/mA V
See Figure 4 Guaranteed Monotonic by Design. See Figure 5. VDD=Vref=3V, Midscale Iout=0mA to 7.5mA sourcing/sinking All Zeroes Loaded to DAC Register. See Figure 8. All Ones Loaded to DAC Register. See Figure 8. of FSR/C
-1.25 0.7
-1.25 0.7
5 1 1.7 -80 9
5 1 1.7 -80 9
VDD 10% RL = 2 k. to GND or VDD Due to Load current change Due to Powering Down (per channel) RL = 2 k. to GND or VDD Due to Load current change Due to Powering Down (per channel)
10 4.5 10 20 4.5 20
10 4.5 10 20 4.5 20
DC Crosstalk6 (Int Ref)
OUTPUT CHARACTERISTICS6 Output Voltage Range Capacitive Load Stability
0 2
VDD
0 2
Rev.PrA | Page 6 of 24
VDD
V pF
RL=
Preliminary Technical Data
10 0.5 30 5 10 0.5 30 5
AD5628/AD5648/AD5668
pF mA s RL=2 k VDD=+3V Coming Out of Power-Down Mode. VDD=+3V 1% for specified performance VREF = VDD = +3.6V (per DAC channel) Per DAC channel
DC Output Impedance Short Circuit Current Power-Up Time REFERENCE INPUTS3 Reference Input voltage Reference Current Reference Input Range Reference Input Impedance REFERENCE OUTPUT Output Voltage 1.248 AD5628/AD5648/AD5668x1 Reference TC Reference Output Impedance LOGIC INPUTS3 Input Current VINL, Input Low Voltage VINH, Input High Voltage Pin Capacitance POWER REQUIREMENTS VDD IDD (Normal Mode)8 VDD=2.7 V to +3.6 V IDD (All Power-Down Modes)9 VDD=2.7 V to +3.6 V POWER EFFICIENCY IOUT/IDD 0
VDD 20 20 VDD 14.6 0
VDD 20 20 VDD 14.6
V A
k
1.25
1.252
1.248
1.25
1.252
V
10 2 2
10
ppm/C k
1 0.8 2 3 2.7 3.6 2.7 2 3
1 0.8
A V V pF V
VDD=+3 V VDD=+3 V
3.6
2
4
2
4
mA
All Digital Inputs at 0 or VDD DAC Active and Excluding Load Current VIH=VDD and VIL=GND
0.2 89
1
0.2 89
1
A %
VIH=VDD and VIL=GND ILOAD=2 mA, VDD=+5 V
AC CHARACTERISTICS1
(VDD = +2.7 V to +3.6 V; RL = 2 k to GND; CL = 200 pF to GND; External REFIN = VDD; all specifications TMIN to TMAX unless otherwise noted)
Parameter2 Output Voltage Settling Time AD5628 AD5648 AD5668 Settling Time for 1LSB Step Slew Rate Digital-to-Analog Glitch Impulse Channel -to-Channel Isolation Digital Feedthrough Min Typ 6 7 8 1.5 10 100 0.5 Max 8 9 10 Unit s s s V/s nV-s dB nV-s
Rev. PrA| Page 7 of 24
B Version 1 Conditions/Comments 1/4 to 3/4 scale settling to 2LSB 1/4 to 3/4 scale settling to 2LSB 1/4 to 3/4 scale settling to 2LSB
1 LSB Change Around Major Carry. See Figure 21.
AD5628/AD5648/AD5668
Preliminary Technical Data
Digital Crosstalk Analog Crosstalk DAC-to-DAC Crosstalk Multiplying Bandwidth Total Harmonic Distortion Output Noise Spectral Density Output Noise
NOTES
1Guaranteed 2See
0.5 1 3 200 -80 120 100 15
nV-s nV-s nV-s kHz dB nV/Hz nV/Hz Vp-p
VREF = 2V 0.1 V p-p. VREF = 2V 0.1 V p-p. Frequency = 10kHz DAC code=8400H, 1kHz DAC code=8400H, 10kHz 0.1Hz to 10Hz;
by design and characterization; not production tested. the Terminology section. 3Temperature range (Y Version): -40C to +125C; typical at +25C. Specifications subject to change without notice.
Rev.PrA | Page 8 of 24
Preliminary Technical Data TIMING CHARACTERISTICS
AD5628/AD5648/AD5668
All input signals are specified with tr = tf = 1 ns/V (10% to 90% of VDD) and timed from a voltage level of (VIL + VIH)/2. See Figure 2. (VDD = +2.7 V to +5.5 V; all specifications TMIN to TMAX unless otherwise noted)
Parameter t1 1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13 t14 t15 Limit at TMIN, TMAX VDD = 2.7 V to 3.6 V VDD= 3.6 V to 5.5 V 20 11 9 13 4 4 0 25 13 0 20 20 20 0 tbd 20 9 9 13 4 4 0 20 13 0 20 20 20 0 tbd 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 min ns min Conditions/Comments SCLK Cycle Time SCLK High Time SCLK Low Time SYNC to SCLK Falling Edge Setup Time Data Setup Time Data Hold Time SCLK Falling Edge to SYNC Rising Edge Minimum SYNC High Time SYNC Rising Edge to SCLK Fall Ignore SCLK Falling Edge to SYNC Fall Ignore LDAC Pulsewidth Low SCLK Falling Edge to LDAC Rising Edge /CLR Pulse Width Low SCLK Falling Edge to LDAC Falling Edge /CLR Pulse Activation Time (AD5380?)
t10
t1
t9
SCLK t8 SYNC t6 t5 DIN DB31 DB0 t14 LDAC1 t12 LDAC2 t13 t11 t4 t3 t2 t7
CLR
NOTES 1. ASYNCHRONOUS LDAC UPDATE MODE. 2. SYNCHRONOUS LDAC UPDATE MODE.
Figure 2. Serial Write Operation
1
3Maximum SCLK frequency is 50 MHz at VDD = +2.7 V to +5.5 V Rev. PrA| Page 9 of 24
AD5628/AD5648/AD5668
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
SYNC 1 VDD 2 VOUTA 3 VOUTC 4 VOUTE 5 VOUTG 6 VREF 7 14 SCLK LDAC 1 SYNC 2 VDD 3 VOUTA 4 VOUTC 5 VOUTE 6 VOUTG 7 VREF 8
Preliminary Technical Data
16 SCLK
AD5628 AD5648 AD5668
13 DIN 12 GND 11 VOUTB
AD5628 AD5648 AD5668
15 DIN 14 GND
TOP VIEW (Not to Scale) 10 VOUTD 9 VOUTF 8 VOUTH
13 VOUTB TOP VIEW (Not to Scale) 12 VOUTD 11 VOUTF 10 VOUTH 9 CLR
Figure 3. 14-Lead TSSOP (RU-14)
Figure 4. 16-Lead TSSOP (RU-16)
Table 2. Pin Function Descriptions Pin No. 1 Mnemonic /LDAC Function Pulsing this pin low allows any or all DAC registers to be updated if the input registers have new data. This allows simultaneous update of all DAC outputs. Alternatively, this pin can be tied permanently low. Active Low-Control Input. This is the frame synchronization signal for the input data. When SYNC goes low, it powers on the SCLK and DIN buffers and enables the input shift register. Data is transferred in on the falling edges of the following 32 clocks. If SYNC is taken high before the 32nd falling edge, the rising edge of SYNC acts as an interrupt and the write sequence is ignored by the device. Power Supply Input. These parts can be operated from 2.5 V to 5.5 V, and the supply should be decoupled with a 10 F capacitor in parallel with a 0.1 F capacitor to GND. Analog Output Voltage from DAC A. The output amplifier has rail-to-rail operation. Analog Output Voltage from DAC B. The output amplifier has rail-to-rail operation. Analog Output Voltage from DAC C. The output amplifier has rail-to-rail operation. Analog Output Voltage from DAC D. The output amplifier has rail-to-rail operation. Reference Input/Output Pin
Active Low Control Input that Loads Software selectable code - Zero, midscale, fullscale - to All Input and DAC Registers. Therefore, the outputs also go to selected code. Default clears the output to 0V.
2
/SYNC
3 4 13 5 12 8 9 6 11 7 10 14 15 16
VDD VOUTA VOUTB VOUTC VOUTD VREF /CLR VOUTE VOUTF VOUTG VOUTH GND DIN SCLK
Analog Output Voltage from DAC E. The output amplifier has rail-to-rail operation. Analog Output Voltage from DAC F. The output amplifier has rail-to-rail operation. Analog Output Voltage from DAC G. The output amplifier has rail-to-rail operation. Analog Output Voltage from DAC H. The output amplifier has rail-to-rail operation. Ground Reference Point for All Circuitry on the Part. Serial Data Input. This device has a 32-bit 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 up to 50 MHz.
Rev.PrA | Page 10 of 24
Preliminary Technical Data ABSOLUTE MAXIMUM RATINGS
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 listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. (TA = +25C unless otherwise noted)
Parameter VDD to GND Digital Input Voltage to GND Rating -0.3 V to +7 V -0.3 V to VDD + 0.3 V
AD5628/AD5648/AD5668
VOUT to GND Operating Temperature Range Industrial (B Version) Storage Temperature Range Junction Temperature (TJ Max) TSSOP Package Power Dissipation JA Thermal Impedance Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) -0.3 V to VDD + 0.3 V -40C to +105C -65C to +150C +150C (TJ Max-TA)/JA 150.4C/W +215C +220C
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
TERMINOLOGY
Relative Accuracy For the DAC, relative accuracy or Integral Nonlinearity (INL) is a measure of the maximum deviation, in LSBs, from a straight line passing through the endpoints of the DAC transfer function. A typical INL vs. code plot can be seen in Figure 2. Differential Nonlinearity Differential Nonlinearity (DNL) 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 by design. A typical DNL vs. code plot can be seen in Figure 3.
(0000Hex) is loaded to the DAC register. Ideally the output should be 0 V. The zero-code error is always positive in the AD56x8 because the output of the DAC cannot go below 0 V. It is due to a combination of the offset errors in the DAC and output amplifier. Zero-code error is expressed in mV. A plot of zero-code error vs. temperature can be seen in Figure 6. Gain Error This is a measure of the span error of the DAC. It is the deviation in slope of the DAC transfer characteristic from ideal expressed as a percent of the full-scale range. Zero-Code Error Drift This is a measure of the change in zero-code error with a change in temperature. It is expressed in V/C. Gain Error Drift
Offset Error Offset error is a measure of the difference between VOUT (actual) and VOUT (ideal) expressed in mV in the linear region of the transfer function. Offset error is measured on the AD5668 with Code ??? loaded into the DAC register. This is a measure of the offset error of the DAC and the output amplifier (see Figures 2 and 3). It can be negative or positive, and is expressed in mV. Zero-Code Error Zero-code error is a measure of the output error when zero code
This is a measure of the change in gain error with changes in temperature. It is expressed in (ppm of full-scale range)/C. Full-Scale Error Full-scale error is a measure of the output error when full-scale code (FFFF Hex) is loaded to the DAC register. Ideally the output should be VDD - 1 LSB. Full-scale error is expressed in percent of full-scale range. A plot of full-scale error vs. temperature can be seen in Figure 6. Total Unadjusted Error Total Unadjusted Error (TUE) is a measure of the output error
Rev. PrA| Page 11 of 24
AD5628/AD5648/AD5668
taking the various offset and gain errors into account. A typical TUE vs. code plot can be seen in Figure 4. 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 normally specified as the area of the glitch in nV secs and is measured when the digital input code is changed by 1 LSB at the major carry transition (7FFF Hex to 8000 Hex). See Figure 19. DC Power Supply Rejection Ratio (PSRR) This indicates how the output of the DAC is affected by changes in the supply voltage. PSRR is the ratio of the change in VOUT to a change in VDD for full-scale output of the DAC. It is measured in dB. VREF is held at 2 V and VDD is varied 10%. DC Crosstalk This is the dc change in the output level of one DAC in response to a change in the output of another DAC. It is measured with a fullscale output change on one DAC while monitoring another DAC kept at midscale. It is expressed in V. Reference Feedthrough This is the ratio of the amplitude of the signal at the DAC output to the reference input when the DAC output is not being updated (i.e., LDAC is high). It is expressed in dB. Channel-to-Channel Isolation This is the ratio of the amplitude of the signal at the output of one DAC to a sine wave on the reference input of another DAC. It is measured in dB. Major-Code Transition Glitch Energy Major-code transition glitch energy is the energy of the impulse injected into the analog output when the code in the DAC register changes state. It is normally specified as the area of the glitch in nV-s and is measured when the digital code is changed by 1 LSB at the major carry transition (011 . . . 11 to 100 . . . 00 or 100 . . . 00 to 011 . . . 11). Digital Feedthrough Digital feedthrough is a measure of the impulse injected into the
Preliminary Technical Data
analog output of a DAC from the digital input pins of the device, but is measured when the DAC is not being written to (SYNC held high). It is specified in nV-s and is measured with a fullscale change on the digital input pins, i.e., from all 0s to all 1s and vice versa. Digital Crosstalk This is the glitch impulse transferred to the output of one DAC at midscale in response to a full-scale code change (all 0s to all 1s and vice versa) in the input register of another DAC. It is measured in standalone mode and is expressed in nV-s. Analog Crosstalk This is the glitch impulse transferred to the output of one DAC due to a change in the output of another DAC. It is measured by loading one of the input registers with a full-scale code change (all 0s to all 1s and vice versa) while keeping LDAC high. Then pulse LDAC low and monitor the output of the DAC whose digital code was not changed. The area of the glitch is expressed in nV-s. DAC-to-DAC Crosstalk This is the glitch impulse transferred to the output of one DAC due to a digital code change and subsequent output change of another DAC. This includes both digital and analog crosstalk. It is measured by loading one of the DACs with a full-scale code change (all 0s to all 1s and vice versa) with LDAC low and monitoring the output of another DAC. The energy of the glitch is expressed in nV-s. Multiplying Bandwidth The amplifiers within the DAC have a finite bandwidth. The multiplying bandwidth is a measure of this. A sine wave on the reference (with full-scale code loaded to the DAC) appears on the output. The multiplying bandwidth is the frequency at which the output amplitude falls to 3 dB below the input. Total Harmonic Distortion This is the difference between an ideal sine wave and its attenuated version using the DAC. The sine wave is used as the reference for the DAC, and the THD is a measure of the harmonics present on the DAC output. It is measured in dB.
Rev.PrA | Page 12 of 24
Preliminary Technical Data
AD5628/AD5648/AD5668
AD5628/AD5648/AD5668-TYPICAL PERFORMANCE CHARACTERISTICS
Figure 4. Typical INL Plot Figure 7. INL Error and DNL Error vs. Temperature
Figure 5. Typical DNL Plot
Figure 8. Zero-Scale Error and Full-Scale Error vs. Temperature
Figure 6. Typical Total Unadjusted Error Plot Figure 9. IDD Histogram with VDD=3V and VDD=5V
Rev. PrA| Page 13 of 24
AD5628/AD5648/AD5668
Preliminary Technical Data
Figure 10. Source and Sink Current Capability with VDD=3V
Figure 13. Supply Current vs. Temperature
Figure 11. Source and Sink Current Capability with VDD=5 V
Figure 14. Supply Current vs. Supply Voltage
Figure 12. Supply Current vs. Code
Figure 15. Power-Down Current vs. Supply Voltage
Rev.PrA | Page 14 of 24
Preliminary Technical Data
AD5628/AD5648/AD5668
Figure 19. Power-On Reset to 0V Figure 16. Supply Current vs. Logic Input Voltage
Figure 20. Exiting Power-Down (800 Hex Loaded) Figure 17. Full-Scale Settling Time
Figure 21. Digital-to-Analog Glitch Impulse Figure 18. Half-Scale Settling Time
Rev. PrA| Page 15 of 24
AD5628/AD5648/AD5668
GENERAL DESCRIPTION
D/A Section The AD5628/AD5648/AD5668 DACs are fabricated on a CMOS process. The architecture consists of a string DAC followed by an output buffer amplifier. The parts include an internal 1.25/2.5V, 10ppm/C reference with an internal gain of two. Figure 22 shows a block diagram of the DAC architecture.
VDD REF (+) DAC REGISTER RESISTOR STRING REF () OUTPUT AMPLIFIER (Gain=2) VOUT
Preliminary Technical Data
GND
Figure 22. DAC Architecture
Since the input coding to the DAC is straight binary, the ideal output voltage is given by:
D VOUT = Vref (ext ) x 2^ N VOUT D = 2 Vref (int) x 2^ N
Resistor String
Figure 23. Resistor String
where D = decimal equivalent of the binary code that is loaded to the DAC register; 0 - 4095 for AD5628 (12 bit) 0 - 16383 for AD5648 (14 bit) 0 - 65535 for AD5668 (16 bit) N = the DAC resolution
The resistor string section is shown in Figure 23. It is simply a string of resistors, each of value R. The code loaded to the DAC register determines at which node on the string the voltage is tapped off to be fed into the output amplifier. The voltage is tapped off by closing one of the switches connecting the string to the amplifier. Because it is a string of resistors, it is guaranteed monotonic. Output Amplifier The output buffer amplifier is capable of generating rail-to-rail voltages on its output which gives an output range of 0 V to VDD. It is capable of driving a load of 2 k in parallel with 1000 pF to GND. The source and sink capabilities of the output amplifier can be seen in Figure 10 and Figure 11. The slew rate is 1.5 V/s with a half-scale settling time of 8 s with the output unloaded.
SERIAL INTERFACE
The AD5628/AD5648/AD5668 has a three-wire serial interface (SYNC, SCLK and DIN), which is compatible with SPI, QSPI and MICROWIRE interface standards as well as most DSPs. See Figure 2 for a timing diagram of a typical write sequence. The write sequence begins by bringing the SYNC line low. Data from the DIN line is clocked into the 32-bit shift register on the falling edge of SCLK. The serial clock frequency can be as high as 50 MHz, making the AD5628/AD5648/AD5668 compatible with high speed DSPs. On the 32nd falling clock edge, the last data bit is clocked in and the programmed function is executed
Rev.PrA | Page 16 of 24
Preliminary Technical Data
(i.e., a change in DAC register contents and/or a change in the mode of operation). At this stage, the SYNC line may be kept low or be brought high. In either case, it must be brought high for a minimum of 50 ns before the next write sequence so that a falling edge of SYNC can initiate the next write sequence. Since the SYNC buffer draws more current when VIN = 2V than it does when VIN = 0.8 V, SYNC should be idled low between write sequences for even lower power operation of the part. As is mentioned above, however, it must be brought high again just before the next write sequence.
AD5628/AD5648/AD5668
Input Shift Register The input shift register is 32 bits wide (see Figure 24). The first four bits are "don't cares." The next four bits are the Command bits C3-C0, (see Table 1) followed by the 4-bit DAC address A3-A0, (see Table 2) and finally the 16/14/12-bit data word. The data word comprises the 16- 14- 12- bit input code followed by 4, 6 or 8 don't care bits, the AD5668, AD5648 and AD5628 respectively. See figure 24, 25, 26. These data bits are transferred to the DAC register on the 32nd falling edge of SCLK.
DB0 (LSB) X X X X C3 C2 C1 C0 A3 A2 A1 A0 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X
COMMAND BITS
ADDRESS BITS
Figure 24 AD5668. Input Register Contents
DB0 (LSB) X X X X C3 C2 C1 C0 A3 A2 A1 A0 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X
COMMAND BITS
ADDRESS BITS
Figure 25. AD5648. Input Register Contents
DB0 (LSB) X X X X C3 C2 C1 C0 A3 A2 A1 A0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X X X
COMMAND BITS
ADDRESS BITS
Figure 26. AD5628 Input Register Contents
Rev. PrA| Page 17 of 24
AD5628/AD5648/AD5668
Command C3 0 0 0 0 0 0 0 0 1 1 * 1 C2 0 0 0 0 1 1 1 1 0 0 * 1 C1 0 0 1 1 0 0 1 1 0 0 * 1 C0 0 1 0 1 0 1 0 1 0 1 * 1 Write to Input Register n Update DAC Register n Write to Input Register n, Update All Write to and Update DAC channel n Power Down DAC (Power-up) Load Clear Code Register Load LDAC Register (LDAC overwrite) Reset (Power-on-Reset) REF Setup Register Reserved Reserved Reserved A3 0 0 0 0 0 0 0 0 1 A2 0 0 0 0 1 1 1 1 1
Preliminary Technical Data
ADDRESS (n) A1 0 0 1 1 0 0 1 1 1 A0 0 1 0 1 0 1 0 1 1 DAC A DAC B DAC C DAC D DAC E DAC F DAC G DAC H All DACs
Table 1. Command Definition
Table2. Address Command
SYNC Interrupt In a normal write sequence, the SYNC line is kept low for 32 falling edges of SCLK and the DAC is updated on the 32nd falling edge and rising edge of SYNC . However, if SYNC is brought high before the 32nd falling edge this acts as an interrupt to the write sequence. The shift register is reset and the write sequence is seen as invalid. Neither an update of the DAC register contents or a change in the operating mode occurs--see Figure 27.
SCLK
SYNC
DIN
DB31
DB0
DB31
DB0
INVALID WRITE SEQUENCE: SYNC HIGH BEFORE 32ND FALLING EDGE
VALID WRITE SEQUENCE, OUTPUT UPDATES ON THE 32ND FALLING EDGE
Figure 27. SYNC Interrupt Facility
Rev.PrA | Page 18 of 24
Preliminary Technical Data
AD5628/AD5648/AD5668
Reference Setup -External to Internal The on-board reference is turned off at power-up by default. This allows the use of an external reference. The AD5628/48/68 have an onchip reference with an internal gain of two. The AD56x8-1 has a 1.25V 10ppm/C max reference and the AD56x8-2,-3 have a 2.5V 10ppm/C max reference. The on-board reference can be turned on/off through a software executable REF Setup function, see Table 3. Command 1000 is reserved for this REF Setup function, see Table 1. The reference mode is software-programmable by setting a bit (DB0) in the REF Setup register. Table 4 shows how the state of the bits corresponds to the mode of operation of the device. REF Setup Register (DB0) 0 1 Action Ref Off (Default) Ref On
Table 3. Reference Set-up Register
MSB
LSB
DB31 - DB28
DB27
DB26
DB25
DB24
DB23
DB22
DB21
DB20
DB1DB19
DB0
x Don't Cares
1
0
0
0
x
x
x
x
x Don't Cares
1/0 REF Setup Register
COMMAND BITS (C3-C0)
ADDRESS BITS (A3 - A0)
Table 4 32-Bit Input Shift Register Contents for Reference Setup Function
Power-On-Reset The AD5628/AD5648/AD5668 family contains a power-on-reset circuit that controls the output voltage during power-up. The AD5628/AD5648/AD5668x-1/2 DAC output powers up to zero volts and the AD5668-3 DAC output powers up to midscale. The output remains there until a valid write sequence is made to the DAC. This is useful in applications where it is important to know the state of the output of the DAC while it is in the process of powering up. There is also a software executable Reset function that will reset the DAC to the Power-on -Reset code. Command 0111 is reserved for this Reset function, see Table 1.
Power-Down Modes The AD5628/AD5648/AD5668 contains four separate modes of operation. Command 0100 is reserved for the Power-Down function, see Table 1. These modes are software-programmable by setting two bits (DB9 and DB8) in the control register. Table 5 shows how the state of the bits corresponds to the mode of operation of the device. Any or all DACs, (DacH to DacA) may be powered down to the selected mode by setting the corresponding 8 bits (DB7 to DB0) to a "1". See Table 6 for contents of the Input Shift Register during power down/up operation. When both bits are set to 0, the part works normally with its normal power consumption of 250 A at 5 V. However, for the three powerRev. PrA| Page 19 of 24
AD5628/AD5648/AD5668
Preliminary Technical Data
down modes, the supply current falls to 200 nA at 5 V (50 nA at 3 V). Not only does the supply current fall but the output stage is also internally switched from the output of the amplifier to a resistor network of known values. This has the advantage that the output impedance of the part is known while the part is in power-down mode. There are three different options. The output is connected internally to GND through a 1 k resistor, a 100 k resistor or it is left open-circuited (Tri-State). The output stage is illustrated in figure 24. The bias generator of selected DAC(s), the output amplifier, the resistor string and other associated linear circuitry are all shut down when the power-down mode is activated. However, the contents of the DAC register are unaffected when in power-down. The time to exit power-down is typically (2.5 s for VDD = 5 V and 5 s for VDD = 3 V). See Figure 20 for a plot. Any combination of DACs can be powered up by setting PD1 and PD0 to "0" (normal operation). Output powers-up to value in input register (/LDAC Low) or to value in DAC register before Power-Down (/LDAC High).
DB9 0 0 1 1 DB8 0 1 0 1 Operating Mode Normal Operation Power Down Modes 1 k to GND 100 k to GND Tri State
Table 5. Modes of Operation for the AD5628/AD5648/AD5668
MSB
LSB
DB31 - DB28 x
DB27
DB26
DB25
DB24
DB23
DB22
DB21
DB20
DB10-- DB19 x
DB9
DB8
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
1
0
0
x
x
x
x
PD1
PD0
DacH
DacG
DacF
DacE
DacD
DacC
DacB
DacA
Don't Cares
COMMAND BITS (C2-C0)
ADDRESS BITS (A3 - A0) Don't cares
Don't Cares
Power Down Mode
Power Down/Up Channel Selection - Set Bit to a "1" to select
Table 6. 32-Bit Input Shift Register Contents for Power Down/Up Function
Rev.PrA | Page 20 of 24
Preliminary Technical Data
Clear Code Register
AD5628/AD5648/AD5668
The AD5628/AD5648/AD5668 gives the option of clearing any one or all DAC channels to 0, midscale or fullscale code. Command 0101 is reserved for the Clear Code function. See Table1. These clear code values are software-programmable by setting two bits (DB1 and DB0) in the control register. Table shows how the state of the bits corresponds to the clear code values of the device. Upon execution of the hardware /CLR pin (active LOW), the DAC output is cleared to the clear code register value (default setting is zero). See Table 8 for contents of the Input Shift Register during the Clear Code Register operation. The part will exit Clear code mode on the 32nd falling edge of the next write to the part.
Clear Code Register CR1 0 0 1 1 CR0 0 1 0 1 Clears to code 0000h 8000h FFFFh No operation
Table 7. Clear Code Register
MSB
LSB
DB31 - DB28
DB27
DB26
DB25
DB24
DB23
DB22
DB21
DB20
DB2DB19
DB1
DB0
X Don't Cares
0
1
0
1
1/0
1/0
1/0
1/0
x Don't Cares
1/0
1/0
COMMAND BITS (C2-C0)
ADDRESS BITS (A3 - A0)
Clear Code Register (CR1CR0)
Table 8. 32-Bit Input Shift Register Contents Clear Code Function
LDAC Function The outputs of all DACs may be updated simultaneously using the hardware /LDAC pin. Synchronous LDAC: The DAC registers are updated after new data is read in on the falling edge of the 32nd SCLK pulse. LDAC can be permanently low or pulsed as in Figure 1. Asynchronous LDAC: The outputs are not updated at the same time that the input registers are written to. When LDAC goes low, the DAC registers are updated with the contents of the input register. The outputs of all DACs may be updated simultaneously using the /LDAC function, with the added functionality of selecting through software any number of DAC channels to synchronize. Writing to the DAC using command 0110, the hardware /LDAC pin can be overwritten by setting the bits of the 8-bit /LDAC register (DB7-DB0) . SeeTable 9 for the /LDAC mode of operation. The default for each channel is "0" ie /LDAC pin works normally. Setting the bits to a "1" means the DAC channel will be updated regardless of the state of the /LDAC pin. This gives the added benefit of allowing any combination of channels to be synchronously updated. See Table 10 for contents of the Input Shift Register during the /LDAC overwrite mode of operation.
Rev. PrA| Page 21 of 24
AD5628/AD5648/AD5668
Preliminary Technical Data
Load DAC OVERWRITE /LDACBITS (DB7DB0) 0 1 /LDAC PIN 1/0 x - Don't Care /LDAC Operation Determined by /LDAC pin DAC channels will update, overwriting the /LDAC pin
Table 9. LDAC Overwrite Definition
MSB
LSB
DB31 - DB28 x
DB27
DB2 6
1
DB2 5
1
DB2 4
0
DB2 3
x
DB2 2
x
DB2 1
x
DB2 0
x
DB8 - DB19
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
x
DacH
DacG
DacF
DacE
DacD
DacC
DacB
DacA
Don't Cares
COMMAND BITS (C2-C0)
ADDRESS BITS (A3 - A0) Don't cares
Don't Cares
Setting /LDAC bit to "1" overwrites /LDAC pin
Table 10. 32-Bit Input Shift Register Contents for /LDAC Overwrite Function Effective Series Inductance (ESI), e.g., common ceramic types of capacitors. This 0.1 F capacitor provides a low impedance path to ground for high frequencies caused by transient currents due to internal logic switching. The power supply line itself should have as large a trace as possible to provide a low impedance path and reduce glitch effects on the supply line. Clocks and other fast switching digital signals should be shielded from other parts of the board by digital ground. Avoid crossover of digital and analog signals if possible. When traces cross on opposite sides of the board, ensure that they run at right angles to each other to reduce feedthrough effects through the board. The best board layout technique is the microstrip technique where the component side of the board is dedicated to the ground plane only and the signal traces are placed on the solder side. However, this is not always possible with a two-layer board.
Power Supply Bypassing and Grounding When accuracy is important in a circuit it is helpful to carefully consider the power supply and ground return layout on the board. The printed circuit board containing the AD5628/AD5648/AD5668 should have separate analog and digital sections, each having its own area of the board. If the AD5628/AD5648/AD5668 is in a system where other devices require an AGND to DGND connection, the connection should be made at one point only. This ground point should be as close as possible to the AD5628/AD5648/AD5668. The power supply to the AD5628/AD5648/AD5668 should be bypassed with 10 F and 0.1 F capacitors. The capacitors should be physically as close as possible to the device with the 0.1 F capacitor ideally right up against the device. The 10 F capacitors are the tantalum bead type. It is important that the 0.1 F capacitor has low Effective Series Resistance (ESR) and
Rev.PrA | Page 22 of 24
Preliminary Technical Data OUTLINE DIMENSIONS
0.201 (5.10) 0.193 (4.90)
14 8
AD5628/AD5648/AD5668
0.177 (4.50) 0.169 (4.30)
1
7
PIN 1 0.006 (0.15) 0.002 (0.05) 0.0118 (0.30) 0.0075 (0.19) 0.0433 (1.10) MAX 0.0256 (0.65) BSC 0.0079 (0.20) 0.0035 (0.090)
0.256 (6.50) 0.246 (6.25)
SEATING PLANE
8 0
0.028 (0.70) 0.020 (0.50)
Figure 28. 14-Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters
0.201 (5.10) 0.193 (4.90)
16
9
0.177 (4.50)
0.169 (4.30)
0.256 (6.50)
8
1
0.006 (0.15) 0.002 (0.05)
PIN 1 0.0433 (1.10) MAX 0.0256 (0.65) BSC 0.0118 (0.30) 0.0075 (0.19) 0.0079 (0.20) 0.0035 (0.090)
0.246 (6.25)
SEATING PLANE
8 0
0.028 (0.70) 0.020 (0.50)
Figure 29. 16-Thin Shrink Small Outline Package [TSSOP] (RU-16) Dimensions shown in millimeters
ORDERING GUIDE
Model AD5628BRUZ-1 AD5628BRUZ-2 AD5628ARUZ-2 AD5648BRUZ-1 AD5648BRUZ-2 AD5648ARUZ-2 AD5668BRUZ-1 Bit 12 12 12 14 14 14 16 Power-On-Reset Zero Zero Zero Zero Zero Zero Zero Internal Reference 1.25V 2.5V 2.5V 1.25V 2.5V 2.5V 1.25V Package Option1 RU-14 RU-16 RU-16 RU-14 RU-16 RU-16 RU-14
Rev. PrA| Page 23 of 24
AD5628/AD5648/AD5668
AD5668BRUZ-2 AD5668BRUZ-3 AD5668ARUZ-2 AD5668ARUZ-3 16 16 16 16 Zero Midscale Zero Midscale
Preliminary Technical Data
2.5V 2.5V 2.5V 2.5V RU-16 RU-16 RU-16 RU-16
1 Thin Shrink Small Outline Package (TSSOP)
(c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective companies. PR05302-0-12/04(PrA) Printed in the U.S.A.
Rev.PrA | Page 24 of 24

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