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FEATURES AD7398--12-Bit Resolution AD7399--10-Bit Resolution Programmable Power Shutdown Single (3 V to 5 V) or Dual ( 5 V) Supply Operation 3-Wire Serial SPI-Compatible Interface Internal Power ON Reset Double Buffered Registers for Simultaneous Multichannel DAC Update Four Separate Rail-to-Rail Reference Inputs Thin Profile TSSOP-16 Package Available Low Tempco 1.5 ppm/ C APPLICATIONS Automotive Output Voltage Span Portable Communications Digitally Controlled Calibration PC Peripherals GENERAL DESCRIPTION
VDD INPUT REG A SERIAL REGISTER CS INPUT REG B
Quad, Serial-Input 12-Bit/10-Bit DACs AD7398/AD7399
FUNCTIONAL BLOCK DIAGRAM
VREFB VREFA
DAC A REGISTER
DAC A
VOUTA
DAC B REGISTER
DAC B
VOUTB
SDI INPUT REG C DAC C REGISTER
CLK
DAC C
VOUTC
12/10
INPUT REG D
DAC D REGISTER
DAC D
VOUTD
The AD7398/AD7399 family of quad, 12-bit/10-bit, voltageoutput digital-to-analog converters is designed to operate from a single 3 V to 5 V or a dual 5 V supply. Built with Analog's robust CBCMOS process, this monolithic DAC offers the user low cost, and ease-of-use in single or dual-supply systems. The applied external reference VREF determines the full-scale output voltage. Valid VREF values include VSS < VREF < VDD that result in a wide selection of full-scale outputs. For multiplying applications ac inputs can be as large as 5 VP. A doubled-buffered serial-data interface offers high-speed, 3-wire, SPI and microcontroller-compatible inputs using serialdata-in (SDI), clock (CLK), and a chip-select (CS). A common level-sensitive load-DAC strobe (LDAC) input allows simultaneous update of all DAC outputs from previously loaded Input Registers. Additionally, an internal power ON reset forces the output voltage to zero at system turn ON. An external asynchronous reset (RS) also forces all registers to the zero code state. A programmable power-shutdown feature reduces power dissipation on unused DACs. Both parts are offered in the same pinout to enable users to select the appropriate resolution for their application without redesigning the layout. For 8-bit resolution applications see the pin compatible AD7304 product. The AD7398/AD7399 is specified over the extended industrial (-40C to +125C) temperature range. Parts are available in wide body SOIC-16 and ultracompact thin 1.1 mm TSSOP16 packages.
POWER ON RESET
VSS
RS
LDAC VREFC VREFD
GND
0.50 0.40 0.30 0.20
DNL - LSB
VDD = +5V VSS = -5V VREF = +2.5V TA = 25 C
0.10 0 -0.10 -0.20 -0.30 -0.40 -0.50 0 512 1024 1536 2560 2048 CODE - Decimal 3072 3584 4096
Figure 1. AD7398 DNL vs. Code (TA = 25C)
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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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2000
AD7398/AD7399-SPECIFICATIONS V, V (@ V = 5
DD
AD7398 12-BIT VOLTAGE OUTPUT DAC < +125 C, unless otherwise noted.)
Parameter
STATIC PERFORMANCE Resolution1 Relative Accuracy2 Differential Nonlinearity2 Zero-Scale Error Full-Scale Voltage Error Full-Scale Tempco3 REFERENCE INPUT VREFIN Range4 Input Resistance5 Input Capacitance3 ANALOG OUTPUT Output Current Capacitive Load3 LOGIC INPUTS Logic Input Low Voltage Logic Input High Voltage Input Leakage Current Input Capacitance3 INTERFACE TIMING 3, 7 Clock Frequency Clock Width High Clock Width Low CS to Clock Set Up Clock to CS Hold Load DAC Pulsewidth Data Setup Data Hold Load Setup to CS Load Hold to CS AC CHARACTERISTICS Output Slew Rate Settling Time8 Shutdown Recovery DAC Glitch Digital Feedthrough Feedthrough SUPPLY CHARACTERISTICS Shutdown Supply Current Positive Supply Current Negative Supply Current Power Dissipation Power Supply Sensitivity Symbol N INL DNL VZSE VFSE TCVFS VREF RREF CREF IOUT CL VIL VIH IIL CIL fCLK tCH tCL tCSS tCSH tLDAC tDS tDH tLDS tLDH SR tS tSDR Q QDF VOUT/VREF Data = 000H to FFFH to 000H To 0.1% of Full Scale Code 7FFH to 800H to 7FFH VREF = 1.5 VDC + 1 V p-p, Data = 000H, f = 100 kHz No Load VIL = 0 V, No Load VIL = 0 V, No Load VIL = 0 V, No Load VDD = 5% Condition 12 1.5 1 7 2.5 1.5 0/VDD 35 5 5 200
SS
= 0 V; or VDD = +5 V, VSS = -5 V, VREF = +2.5 V, -40 C < TA
3 V-5 V 10% 5V 12 1.5 1 2.5 2.5 1.5 VSS/VDD 35 5 5 400 10% Unit Bits LSB max LSB max mV max mV max ppm/C typ V min/max k typ6 pF typ mA typ pF max V max V max V min V min A max pF max MHz max ns min ns min ns min ns min ns min ns min ns min ns min ns min V/s typ s typ s typ nVs typ nVs typ dB typ
Monotonic Data = 000H Data = FFFH
Data = 555H, Worst-Case
Data = 800H, VOUT = 4 LSB No Oscillation VDD = 3 V VDD = 5 V CLK Only
0.5 0.8 80% VDD 2.1-2.4 1 10 11 45 45 10 20 45 15 10 0 20 2 6 6 150 15 -63
0.8 4.0 2.4 1 10 16.6 30 30 5 15 30 10 5 0 15 2 6 6 150 15 -63
IDD_SD IDD ISS PDISS PSS
30/60 1.5/2.5 1.5/2.5 5 0.006
30/60 1.6/2.7 1.6/2.7 16 0.006
A typ/max mA typ/max mA typ/max mW typ %/% max
NOTES 1 One LSB = VREF/4096 V for the 12-bit AD7398. 2 The first eight codes (000 H, 007H) are excluded from the linearity error measurement in single supply operation. 3 These parameters are guaranteed by design and not subject to production testing. 4 When VREF is connected to either the V DD or the VSS power supply the corresponding V OUT voltage will program between ground and the supply voltage minus the offset voltage of the output buffer, which is the same as the V ZSE error specification. See additional discussion in the Operation section of the data sheet. 5 Input resistance is code-dependent. 6 Typicals represent average readings measured at 25C. 7 All input control signals are specified with t R = tF = 2 ns (10% to 90% of 3 V) and timed from a voltage level of 1.5 V. 8 The settling time specification does not apply for negative going transitions within the last 3 LSBs of ground. Specifications subject to change without notice.
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REV. 0
AD7398/AD7399 AD7399 10-BIT VOLTAGE OUTPUT DAC < +125 C, unless otherwise noted.)
Parameter
STATIC PERFORMANCE Resolution1 Relative Accuracy2 Differential Nonlinearity2 Zero-Scale Error Full-Scale Voltage Error Full-Scale Tempco3 REFERENCE INPUT VREFIN Range4 Input Resistance5 Input Capacitance3 ANALOG OUTPUT Output Current Capacitive Load3 LOGIC INPUTS Logic Input Low Voltage Logic Input High Voltage Input Leakage Current Input Capacitance3 INTERFACE TIMING 3, 7 Clock Frequency Clock Width High Clock Width Low CS to Clock Set Up Clock to CS Hold Load DAC Pulsewidth Data Setup Data Hold Load Setup to CS Load Hold to CS AC CHARACTERISTICS Output Slew Rate Settling Time8 Shutdown Recovery DAC Glitch Digital Feedthrough Feedthrough SUPPLY CHARACTERISTICS Shutdown Supply Current Positive Supply Current Negative Supply Current Power Dissipation Power Supply Sensitivity Symbol N INL DNL VZSE VFSE TCVFS VREF RREF CREF IOUT CL VIL VIH IIL CIL fCLK tCH tCL tCSS tCSH tLDAC tDS tDH tLDS tLDH SR tS tSDR Q QDF VOUT/VREF Data = 000H to 3FFH to 000H To 0.1% of Full Scale Code 1FFH to 200H to 1FFH VREF = 1.5 VDC + 1 V p-p, Data = 000H, f = 100 kHz No Load VIL = 0 V, No Load VIL = 0 V, No Load VIL = 0 V, No Load VDD = 5% Condition 10 1 1 7 15 1.5 0/VDD 40 5
(@ VDD = 5 V, VSS = 0 V; or VDD = +5 V, VSS = -5 V, VREF = +2.5 V, -40 C < TA
3 V-5 V 10% 5V 10 1 1 4 15 1.5 VSS/VDD 40 5 5 400 10% Unit Bits LSB max LSB max mV max mV max ppm/C typ V min/max k typ6 pF typ mA typ pF max V max V max V min V min A max pF max MHz max ns min ns min ns min ns min ns min ns min ns min ns min ns min V/s typ s typ s typ nVs typ nVs typ dB typ
Monotonic Data = 000H Data = 3FFH
Data = 155H, Worst-Case
Data = 200H, VOUT = 1 LSB No Oscillation VDD = 3 V VDD = 5 V CLK Only
200 0.5 0.8 80% VDD 2.1-2.4 1 10 11 45 45 10 20 45 15 10 0 20 2 6 6 150 15 -63
0.8 4.0 2.4 1 10 16.6 30 30 5 15 30 10 5 0 15 2 6 6 150 15 -63
IDD_SD IDD ISS PDISS PSS
30/60 1.5/2.5 1.5/2.5 5 0.006
30/60 1.6/2.7 1.6/2.7 16 0.006
A typ/max mA typ/max mA typ/max mW typ %/% max
NOTES 1 One LSB = VREF/1024 V for the 10-bit AD7399. 2 The first two codes (000 H, 001H) are excluded from the linearity error measurement in single supply operation. 3 These parameters are guaranteed by design and not subject to production testing. 4 When VREF is connected to either the V DD or the VSS power supply the corresponding V OUT voltage will program between ground and the supply voltage minus the offset voltage of the output buffer, which is the same as the V ZSE error specification. See additional discussion in the Operation section of the data sheet. 5 Input resistance is code-dependent. 6 Typicals represent average readings measured at 25C. 7 All input control signals are specified with t R = tF = 2 ns (10% to 90% of 3 V) and timed from a voltage level of 1.5 V. 8 The settling time specification does not apply for negative going transitions within the last 3 LSBs of ground. Specifications subject to change without notice.
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-3-
AD7398/AD7399
ABSOLUTE MAXIMUM RATINGS*
VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 V, +7 V VSS to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3 V, -7 V VREF to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VSS, VDD Logic Inputs to GND . . . . . . . . . . . . . . . . . . . . -0.3 V, +8 V VOUT to GND . . . . . . . . . . . . . . . . . VSS - 0.3 V, VDD + 0.3 V IOUT Short Circuit to GND . . . . . . . . . . . . . . . . . . . . . 50 mA Thermal Resistance JA 16-Lead SOIC Package (R-16) . . . . . . . . . . . . . . 158C/W 16-Lead Thin Shrink Surface Mount (RU-16) . . . 180C/W Maximum Junction Temperature (TJ Max) . . . . . . . . 150C Package Power Dissipation . . . . . . . . . . . . . (TJ Max-TA)/JA
Operating Temperature Range . . . . . . . . . . -40C to +125C Storage Temperature Range . . . . . . . . . . . . -65C to +150C Lead Temperature R-16 (Vapor Phase, 60 secs) . . . . . . . . . . . . . . . . . . 215C RU-16 (Infrared, 15 secs) . . . . . . . . . . . . . . . . . . . . 224C
*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 sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ORDERING GUIDE
Model AD7398BR AD7398BR-REEL7 AD7398BRU-REEL7 AD7399BR AD7399BR-REEL7 AD7399BRU-REEL7
Resolution (Bits) 12 12 12 10 10 10
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package Description SOL-16 SOL-16 TSSOP-16 SOL-16 SOL-16 TSSOP-16
Package Option R-16 R-16 RU-16 R-16 R-16 RU-16
Container Quantity 48 1,000 1,000 48 1,000 1,000
The AD7398 contains 3254 transistors. The die size measures 108 mil x 144 millimeters.
SDI
SA
SD
A1
A0
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
CLK
IN REG LD tDS tDH tCH tCL tCSH
CS
tCSS
LDAC tLDS
tLDH tLDAC
Figure 2. AD7398 Timing Diagram (AD7399 with SDI = 14 Bits Only)
CLK tCH LDAC tLDS tCL tLDH tLDAC CS tCSS tCSH tCSS 1/fCLK tLDS
Figure 3. Continuous Clock Timing Diagram
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 the AD7398/AD7399 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.
WARNING!
ESD SENSITIVE DEVICE
-4-
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AD7398/AD7399
PIN CONFIGURATION
VOUTB 1 VOUTA 2 VSS 3 VREFA 4
16 VOUTC 15 VOUTD
AD7398/ AD7399
14 VDD
13 VREFC TOP VIEW VREFB 5 (Not to Scale) 12 VREFD GND 6 LDAC 7 RS 8 11 SDI 10 CLK 9 CS
PIN FUNCTION DESCRIPTIONS
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Mnemonic VOUTB VOUTA VSS VREFA VREFB GND LDAC RS CS CLK SDI VREFD VREFC VDD VOUTD VOUTC
Function DAC B Voltage Output. DAC A Voltage Output. Negative Power Supply Input. Specified range of operation 0 V to -5.5 V. DAC A Reference Voltage Input Terminal. Establishes DAC A full-scale output voltage. Pin can be tied to VDD or VSS pin. DAC B Reference Voltage Input Terminal. Establishes DAC B full-scale output voltage. Pin can be tied to VDD or VSS pin. Ground Pin. Load DAC Register Strobe, Level Sensitive Active Low. Transfers all Input Register data to DAC registers. Asynchronous active low input. See Control Logic Truth Table for operation. Resets Input and DAC Registers to All Zero Codes. Shift Register contents unchanged. Chip Select, Active Low Input. Disables shift register loading when high. Transfers Serial Register Data to the Input Register when CS returns High. Does not effect LDAC operation. Schmitt Triggered Clock Input, Positive Edge Clocks Data into Shift Register. Serial Data Input. Input data loads directly into the shift register. DAC D Reference Voltage Input Terminal. Establishes DAC D full-scale output voltage. Pin can be tied to VDD or VSS pin. DAC C Reference Voltage Input Terminal. Establishes DAC C full-scale output voltage. Pin can be tied to VDD or VSS pin. Positive Power Supply Input. Specified range of operation 3 V to 5 V 10%. DAC D Voltage Output. DAC C Voltage Output.
REV. 0
-5-
AD7398/AD7399
Table I. Control Logic Truth Table
CS H L L L
+
CLK X L
+
LDAC H H H H H L
+
Serial Shift Register Function No Effect No Effect Shift-Register-Data Advanced One Bit No Effect No Effect No Effect No Effect
Input Register Function No Effect No Effect Latched Latched Updated with SR Contents Latched Latched
DAC Register No Effect No Effect Latched Latched Latched Transparent Latched
H H
H L/H X X
NOTES 1. + Positive logic transition; - Negative logic transition; X Don't Care; SR shift register. 2. At power ON, both the Input Register and the DAC Register are loaded with all zeros. 3. During Power Shutdown, reprogramming of any internal registers can take place, but the output amplifiers will not produce the new values until the part is taken out of Shutdown mode. 4. LDAC input is a level-sensitive input that controls the four DAC registers.
Table II. AD7398 Serial Input Register Data Format, Data Is Loaded in the MSB-First Format
MSB Bit Position B15 AD7398 SA B14 SD B13 A1 B12 A0 B11 D11 B10 D10 B9 D9 B8 D8 B7 D7 B6 D6 B5 D5 B4 D4 B3 D3 B2 D2 B1 D1 LSB B0 D0
NOTE Bit positions B14 and B15 are power shutdown control Bits SD and SA. If SA is set to Logic 1, all DACs are placed in the power shutdown mode. If SD is set to Logic 1, the address decoded by Bits B12 and B13 (A0 and A1) determine the DAC channel that will be placed in the power shutdown state.
Table III. AD7399 Serial Input Register Data Format, Data Is Loaded in the MSB-First Format
MSB Bit Position B13 AD7399 SA B12 SD B11 A1 B10 A0 B9 D9 B8 D8 B7 D7 B6 D6 B5 D5 B4 D4 B3 D3 B2 D2 B1 D1 LSB B0 D0
NOTE Bit positions B12 and B13 are power shutdown control Bits SD and SA. If SA is set to Logic 1, all DACs are placed in the power shutdown mode. If SD is set to Logic 1, the address decoded by Bits B10 and B11 (A0 and A1) determine the DAC channel that will be placed in the power shutdown state.
Table IV. AD7398/AD7399 Address Decode Control
SA 1 0 0 0 0 0 0 0 0
SD X 1 1 1 1 0 0 0 0
A1 X 0 0 1 1 0 0 1 1
A0 X 0 1 0 1 0 1 0 1
DAC Channel Affected All DACs Shutdown DAC A Shutdown DAC B Shutdown DAC C Shutdown DAC D Shutdown DAC A Input Register Decoded DAC B Input Register Decoded DAC C Input Register Decoded DAC D Input Register Decoded
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AD7398/AD7399
TERMINOLOGY Relative Accuracy, INL
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 versus code plot can be seen in TPC 1.
Differential Nonlinearity, DNL
state. It is normally specified as the area of the glitch in nV-s and is measured when the digital input code is changed by 1 LSB at the major carry transition (midscale transition). A plot of the glitch impulse is shown in TPC 10.
Digital Feedthrough, Q DF
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. TPC 3 illustrates a typical DNL versus code plot.
Zero-Scale Error, V ZSE
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. CS is held high, while the CLK and SDI signals are toggled. It is specified in nV-s and is measured with a full-scale code change on the data bus, i.e., from all 0s to all 1s and vice versa. A typical plot of digital feedthrough is shown in TPC 11.
Power Supply Sensitivity, PSS
Zero-scale error is a measure of the output voltage error from zero voltage when zero code is loaded to the DAC register.
Full-Scale Error, VFSE
Full-scale error is a measure of the output voltage error from fullscale voltage when full-scale code is loaded to the DAC register.
Full-Scale Temperature Coefficient, TC VFS
This specification indicates how the output of the DAC is affected by changes in the power supply voltage. Power supply sensitivity is quoted in terms of % change in output per % change in VDD for full-scale output of the DAC. VDD is varied by 10%.
Reference Feedthrough, V OUT/VREF
This is a measure of the change in full-scale error with a change in temperature. It is expressed in ppm/C or mV/C.
DAC Glitch Impulse, Q
Digital-to-analog glitch impulse is the impulse injected into the analog output when the input code in the DAC register changes
This is a measure of the feedthrough from the VREF input to the DAC output when the DAC is loaded with all 0s. A 100 kHz, 1 V p-p is applied to VREF. Reference feedthrough is expressed in dB or mV p-p.
REV. 0
-7-
AD7398/AD7399-Typical Performance Characteristics
1.50 1.25 1.00 0.75
INL - LSB
0.50
AD7398 VDD = +5V VSS = -5V VREF = +2.5V TA = 25 C
DNL - LSB
0.40 0.30 0.20 0.10 0 -0.10 -0.20 -0.30 -0.40
AD7398 VDD = +5V VSS = -5V VREF = +2.5V TA = 25 C
0.50 0.25 0 -0.25 -0.50 -0.75 -1.00 0 512 1024 2560 1536 2048 CODE - Decimal 3072 3584 4096
-0.50
0
512
1024
2560 1536 2048 CODE - Decimal
3072
3584
4096
TPC 1. AD7398 INL vs. Code (TA = 25C)
TPC 3. AD7398 DNL vs. Code (TA = 25C)
0.50
INL - LSB
0.50
DNL - LSB
0.25 0 -0.25 -0.50 0 TA = 25 C VDD = +5V VSS = -5V VREF = +2.5V 128 256 384 512 640 CODE - Decimal 768
DAC-D
0.25 0 -0.25 -0.50 0
TA = 25 C, VDD = +5V VSS = -5V, VREF = +2.5V
DAC-D
896
1024
128
256
384 512 640 CODE - Decimal
768
896
1024
0.50
INL - LSB
0.25 0 -0.25 -0.50 0 TA = 25 C VDD = +5V VSS = -5V VREF = +2.5V 128 256 384 512 640 CODE - Decimal 768
DNL - LSB
DAC-C
0.50 TA = 25 C, VDD = +5V 0.25 VSS = -5V, VREF = +2.5V 0 -0.25 -0.50 0 128 256 384 512 640 CODE - Decimal 768
DAC-C
896
1024
896
1024
0.50
DNL - LSB
0.50
INL - LSB
0.25 0 -0.25 -0.50 0
TA = 25 C, VDD = +5V VSS = -5V, VREF = +2.5V
DAC-B
0.25 0 -0.25 -0.50 0
TA = 25 C, VDD = +5V VSS = -5V, VREF = +2.5V
DAC-B
128
256
384 512 640 CODE - Decimal
768
896
1024
128
256
384 512 640 CODE - Decimal
768
896
1024
0.50
DNL - LSB
0.50
INL - LSB
0.25 0 -0.25 -0.50 0 TA = 25 C, VDD = +5V VSS = -5V, VREF = +2.5V 128 256 384 512 640 CODE - Decimal 768
DAC-A
0.25 0 -0.25 -0.50 0
TA = 25 C, VDD = +5V VSS = -5V, VREF = +2.5V
DAC-A
896
1024
128
256
384
512
640
768
896
1024
CODE - Decimal
TPC 2. AD7399 INL vs. Code (TA = 25C)
TPC 4. AD7399 DNL vs. Code (TA = 25C)
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REV. 0
AD7398/AD7399
1.00 0.75 DNL 0.50
INL, DNL, FSE - LSB
10.0
AD7398 TA = 25 C VDD = +5V VSS = -5V
8.0 6.0 4.0
SINKING CURRENT INTO VOUT VDD = +3V, VSS = 0V VDD = +5V, VSS = -5V
AD7398/AD7399 TA = 25 C
INL 0 FSE -0.25 -0.50
VOUT - mV
0.25
2.0 0 -2.0 -4.0 -6.0 SOURCING CURRENT FROM VOUT VDD = +5V, VSS = -5V VDD = +5V, VSS = 0V VDD = +3V, VSS = 0V -15 -10 -5 0 5 10 15 SOURCE OR SINK CURRENT FROM VOUT - mA 20 VDD = +5V, VSS = 0V
-0.75 -1.00 -5
-8.0
-4
-3
-2 -1 0 1 2 REFERENCE VOLTAGE - Volts
3
4
5
-10.0 -20
TPC 5. AD7398 INL, DNL, FSE vs. Reference Voltage
TPC 8. VOUT vs. Load Current
100.00 90.00 AD7398 TA = 25 C VDD = +5V VSS = -5V VREF = +2.5V
25 AD7398 SAMPLE SIZE = 125 -40 C TO +125 C 20
REFERENCE INPUT CURRENT - A
80.00 70.00 60.00 50.00 40.00 30.00 20.00 10.00 0 0
COUNTS
512 3072 4096
15
10
5
1024
1536 2048 2560 CODE - Decimal
3584
0 0.4
0.6
0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 FULL SCALE ERROR TEMPCO - ppm/ C
2.4
2.6
TPC 6. AD7398 Reference Input Current vs. Code
TPC 9. AD7398 Full-Scale Error Tempco
1000 AD7398 VDD = +5V VSS = -5V TA = 25 C
100 90
REFERENCE INPUT RESISTANCE - k
100
CS (5V/DIV)
10 0%
VOUT (0.2V/DIV)
TIME - 2 s/DIV
10 0 512 1024 1536 2048 2560 CODE - Decimal 3072 3584 4096
TPC 7. AD7398 Reference Input Resistance vs. Code
TPC 10. AD7398 Midscale Glitch
REV. 0
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AD7398/AD7399
FFFH 800H 400H 200H 100H 080H 040H 020H 010H 008H 004H 002H 001H 0 -12 -24
100 90
VOUT (50mV/DIV)
-48 -60 -72 -84
10 0%
CLOCK (5V/DIV)
000H VDD = +5V VSS = -5V VREF = 100mV rms TA = 25 C 1k 10k FREQUENCY - Hz 100k
-96 -108 1M
TIME - 100ns/DIV
100
TPC 11. AD7398 Digital Feedthrough
TPC 14. AD7398 Multiplying Gain vs. Frequency
VDD = 5V, VSS = -5V, VREF = 5V
5 TA = 25 C 1. VDD = +5V, VSS = -5V, CODE = 000H, FFFH 2. VDD = +5V, VSS = -5V, CODE = 555H 3. VDD = +5V, VSS = 0V, CODE = 000H, FFFH 4. VDD = +5V, VSS = 0V, CODE = 555H 5. VDD = +3V, VSS = 0V, CODE = 000H, FFFH 6. VDD = +3V, VSS = 0V, CODE = 555H 2 4
4
SUPPLY CURRENT - mA
100 90
VOUT (2V/DIV)
3
1 6 2 5 1 3
10 0%
CS (5V/DIV)
TIME - 5 s/DIV
0 1.E+03 1.E+04 1.E+06 1.E+05 CLOCK FREQUENCY - Hz 1.E+07 1.E+08
TPC 12. AD7398 Large Signal Settling Time
TPC 15. AD7398 Supply Current vs. Clock Frequency
VDD = 5V, VSS = -5V, VREF = 5V
2.0 AD7398 TA = 25 C VREF = 2.5V 1.75 3V 5V DUAL SUPPLIES
100 90
VOUT (2V/DIV)
POWER SUPPLY CURRENT - mA
1.5
SINGLE SUPPLY
10 0%
CS (5V/DIV)
1.25
TIME - 2 s/DIV
1.0
2
4 3 5 POWER SUPPLY VOLTAGE - V
6
TPC 13. AD7398 Shutdown Recovery
TPC 16. AD7398 Supply Current vs. Supply Voltage
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ATTENUATION - dB
-36
AD7398/AD7399
3.0 NOMINAL CHANGE IN VOLTAGE - mV AD7398/AD7399 VDD = +5V VSS = -5V 1.0 AD7398 SAMPLE SIZE = 135 VREF = 2.5V 0.75 2.5 SUPPLY CURRENT - mA
2.0
1.5
0.5
CODE = FFFH
1.0
0.25 CODE = 000H
0.5
0 -50
0
50 TEMPERATURE - C
100
150
0 0 100 200 400 300 HOURS OF OPERATION AT 150 C 500 600
TPC 17. Supply Current vs. Temperature
TPC 19. AD7398 Long-Term Drift
36 AD7398/AD7399 VDD = +5V VSS = -5V
SHUTDOWN CURRENT - A
35
34
33
32
31 -60
-40
-20
0
20 40 60 80 TEMPERATURE - C
100
120
140
TPC 18. Shutdown Current vs. Temperature
REV. 0
-11-
AD7398/AD7399
VDD VREF A B C D
AD7398/AD7399
CS CLK 4 SDI INPUT REGISTER DAC REGISTER DAC B VOUTB ADDRESS DECODE INPUT REGISTER DAC REGISTER DAC A VOUTA
SERIAL REGISTER INPUT REGISTER DAC REGISTER DAC C VOUTC
12/10 INPUT REGISTER POWER ON RESET RS GND LDAC VSS DAC REGISTER
DAC D
VOUTD
Figure 4. Simplified Block Diagram
CIRCUIT OPERATION
The AD7398 and AD7399 contain four, 12-bit and 10-bit, voltage-output, digital-to-analog converters respectively. Each DAC has its own independent multiplying reference input. Both AD7398/AD7399 use 3-wire SPI-compatible serial data interface, with an asynchronous RS pin for zero-scale reset. In addition, a LDAC strobe enables four channel simultaneous updates for hardware synchronized output voltage changes.
D/A Converter Section
VDD
The nominal DAC output voltage is determined by the externally applied VREF and the digital data (D) as: VOUT = VREF x VOUT = VREF x D 4096 D 1024 (For AD7398) (1)
(For AD7399)
(2)
Where D is the 12-bit or 10-bit decimal equivalent of the data word. VREF is the externally applied reference voltage. In order to maintain good analog performance, bypass power supplies with 0.01 F ceramic capacitors (mount them close to the supply pins) and 1 F-10 F Tantalum capacitors in parallel. In additions, clean power supplies with low ripple voltage capability should be used. Switching power supplies may be used for this application but beware of its higher ripple voltage and PSS frequency-dependent characteristics. It is also best to supply the AD7398/AD7399's power from the system's analog supply voltages. (Don't use the digital 5 V supply). The reference input resistance is code dependent exhibiting worst case 35 k for AD7398 when the DAC is loaded with alternating codes 010101010101. Similarly, the reference input resistance is 40 k for AD7399 when the DAC is loaded with 0101010101.
OPERATION WITH V REF EQUAL TO THE SUPPLY
AD7398/AD7399
VREF VOUTA
R
R
GND
VSS
Figure 5. Simplified DAC Channel
DAC OPERATION
The internal R-2R ladder of the AD7398 and AD7399 operate in the voltage switching mode maintaining an output voltage that is the same polarity as the input reference voltage. A proprietary scaling technique is used to attenuate the input reference voltage in the DAC. The output buffer amplifies the internal DAC output to achieve a VREF to VOUT gain of unity.
The AD7398/AD7399 is designed to approach the full output voltage swing from ground to VDD or VSS. The maximum output swing is achieved when the corresponding VREF input pin is tied to the same power supply. This power supply should be low noise and low ripple, preferably operated by a suitable reference voltage source such as ADR292 and REF02. The output swing
-12-
REV. 0
AD7398/AD7399
is limited by the internal buffer offset voltage and the output drive current capability of the output stage. One should at least budget the VZSE offset voltage as the closest the output voltage can get to either supply voltage under a no load condition. Under a loaded output, degrade the headroom by a factor of 2 mV per 1 mA of load current. Also note that the internal op amp has an offset voltage so that the first eight codes of AD7398 may not respond at either the supply voltage or at ground until the internal DAC voltage exceeds the output buffers offset voltage. Similarly, the first two codes of AD7399 should not be used.
POWER SUPPLY SEQUENCING
serial data is in 8-bit bytes, two right-justified data bytes can be written to the AD7398 and AD7399. Keeping the CS line low between the first and second bytes transfer will result in a successful serial register update. Once the data is properly aligned in the shift register, the positive edge of the CS initiates the transfer of new data to the target DAC register, determined by the decoding of address Bits A1 and A0. For the AD7398, Tables I, II, IV, and Figures 2 and 3 define the characteristics of the software serial interface. For the AD7399, Tables I, III, IV, and Figure 3 (with 14-bits exception) define the characteristics of the software serial interface. Figures 6 and 7 show the equivalent logic interface for the key digital control pins for AD7398 and AD7399. An asynchronous RS provides hardware control reset to zerocode state over the preset function and DAC Register loading. If this function is not needed, the RS pin can be tied to logic high.
TO INPUT REGISTER A B C D
VDD/VSS of AD7398/AD7399 should be powered from the system analog supplies. In addition, VIN of the external reference should also be coming from the same supply. Such practice will avoid a possible latch-up when the reference is powered on prior to VDD/VSS, or powered off subsequent to VDD/VSS. If VDD/VSS and VREF are separate power sources, then ensure VDD/VSS is powered on before VREF and powered off after VREF. In addition, VREF pins of the unused DACs should also be connected to GND or some power sources to ensure similar power-up/-down sequence.
PROGRAMMABLE POWER SHUTDOWN
CS
ADDRESS DECODER
The two MSBs of the serial input register, SA and SD, are used to program various shutdown modes. If SA is set to Logic 1, all DACs will be in shutdown mode. If SA = 0 and SD = 1, a corresponding DAC will be shut down addressed by Bits A0 and A1, See Tables II-IV.
WORST CASE ACCURACY
EN CLK SDI
SHIFT REGISTER
Figure 6. Equivalent Logic Interface
POWER-ON RESET
Assuming a perfect reference, the worst-case output voltage may be calculated from the following equation. VOUT = where D = Decimal Code Loaded to DAC Ranges 0 D 2N-1 N = Number of Bits VREF = Applied Reference Voltage VFSE = Full-Scale Error in Volts VZSE = Zero-Scale Error in Volts INL = Integral Nonlinearity in Volts INL is 0 at Full Scale or Zero Scale
SERIAL DATA INTERFACE
D x (VREF + VFSE ) + VZSE + INL 2N
(3)
When the VDD power supply is turned ON, an internal reset strobe forces all the Input and DAC registers to the zero-code state. The VDD power supply should have a smooth positive ramp without drooping in order to have consistent results, especially in the region of VDD = 1.5 V to 2.2 V. The VSS supply has no effect on the power-on reset performance. The DAC register data will stay at zero until a valid serial register data load takes place.
ESD Protection Circuits
All logic input pins contain back-biased ESD protection Zeners connected to ground (GND) and VDD as shown in Figure 7.
VDD DIGITAL INPUTS 5k GND
The AD7398/AD7399 uses a 3-wire (CS, SDI, CLK) SPIcompatible serial data interface. Serial data of the AD7398 and AD7399 is clocked into the serial input register in a 16-bit and 14-bit data-word format respectively. MSB bits are loaded first. Table II defines the 16 data-word bits for AD7398. Table III defines the 14 data-word bits for the AD7399. Data is placed on the SDI pin, and clocked into the register on the positive clock edge of CLK subject to the data setup and data hold time requirements specified in the Interface Timing specifications. Data can only be clocked in while the CS chip select pin is active low. For the AD7398, only the last 16 bits which are clocked into the serial register, will be interrogated when the CS pin returns to the logic high state, extra data bits are ignored. For the AD7399, only the last 14 bits, which are clocked into the serial register, will be interrogated when the CS pin returns to the logic high state. Since most microcontrollers' output REV. 0
Figure 7. Equivalent ESD Protection Circuits
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the AD7398/AD7399 is via a serial bus that uses standard protocol compatible with DSP processors and microcontrollers. The communications channel requires a 3-wire interface consisting of a clock signal, a data signal and a synchronization signal. The AD7398/AD7399 requires a 16-bit/14-bit data word with data valid on the rising edge of CLK. The DAC update may be done automatically when all the data is clocked in, or it may be done under control of LDAC.
-13-
AD7398/AD7399
ADSP-2101/ADSP-2103 to AD7398/AD7399 Interface 80C51/80L51 to AD7398/AD7399 Interface
Figure 8 shows a serial interface between the AD7398/AD7399 and the ADSP-2101/ADSP-2103. The ADSP-2101/ADSP-2103 is set to operate in the SPORT (Serial Port) transmit alternate framing mode. The ADSP-2101/ADSP-2103 is programmed through the SPORT control register and should be configured as follows: Internal Clock Operation, Active Low Framing, 16-Bit-Word Length. For the AD7398, transmission is initiated by writing a word to the Tx register after the SPORT has been enabled. For the AD7399, the first two bits are don't care as the AD7399 will keep the last 14 bits. Similarly, transmission is initiated by writing a word to the Tx register after the SPORT has been enabled. Because of the edge-triggered difference, an inverter is required at the SCLKs between the DSP and the DAC.
FO ADSP-2101/ TFS ADSP-2103* DT SCLK LDAC CS SDI CLK
A serial interface between the AD7398/AD7399 and the 80C51/ 80L51 microcontroller is shown in Figure 11. TxD of the microcontroller drives the CLK of the AD7398/AD7399, while RxD drives the serial data line of the DAC. P3.3 is a bit programmable pin on the serial port which is used to drive CS.
P3.4 80C51/ 80L51* P3.3 RXD TXD LDAC CS SDI CLK
AD7398/ AD7399
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 11. 80C51/80L51 to AD7398/AD7399 Interface
AD7398/ AD7399
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 8. ADSP-2101/ADSP-2103 to AD7398/AD7399 Interface
68HC11 to AD7398/AD7399 Interface
Note that the 80C51/80L51 provides the LSB first, while the AD7398/AD7399 expect the MSB of the 16-bit/14-bit word first. Care should be taken to ensure the transmit routine takes this into account. It can usually be done through software by shifting out and accumulating the bits in the correct order before inputting to the DAC. In addition, 80C51 outputs two byte words/16 bits data, thus for AD7399, the first two bits, after rearrangement, should be Don't Care as they will be dropped from the AD7399's 14-bit word. When data is to be transmitted to the DAC, P3.3 is taken low. Data on RxD is valid on the falling edge of TxD, so the clock must be inverted as the DAC clocks data into the input shift register on the rising edge of the serial clock. The 80C51/80L51 transmits its data in 8-bit bytes with only eight falling clock edges occurring in the transmit cycle. As AD7399 requires a 14-bit word, P3.3 (or any one of the other programmable bits) is the CS input signal to the DAC, so P3.3 should be brought low at the beginning of the 16-bit write cycle 2 x 8 bit words, and held low until the 16-bit 2 x 8 cycle is completed. After that, P3.3 is brought high again and the new data loads to the DAC. Again, the first two bits, after rearranging, should be don't care. LDAC on the AD7398/AD7399 may also be controlled by the 80C51/ 80L51 serial port output by using another bit-programmable pin, P3.4.
Figure 9 shows a serial interface between the AD7398/AD7399 and the 68HC11 microcontroller. SCK of the 68HC11 drives the CLK of the DAC, while the MOSI output drives the serial data lines SDI. CS signal is driven from one of the port lines. The 68HC11 is configured for master mode; MSTR = 1, CPOL = 0, and CPHA = 0. Data appearing on the MOSI output is valid on the rising edge of SCK.
PC6 PC7 68HC11/ 68L11* MOS1 SCK LDAC CS SDI CLK
AD7398/ AD7399
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 9. 68HC11/68L11 to AD7398/AD7399 Interface
MICROWIRE to AD7398/AD7399 Interface
Figure 10 shows an interface between the AD7398/AD7399 and any MICROWIRE-compatible device. Serial data is shifted out on the falling edge of the serial clock and into the AD7398/ AD7399 on the rising edge of the serial clock. No glue logic is required as the DAC clocks data into the input shift register on the rising edge.
CS MICROWIRE* SO SCK CS SDI CLK
AD7398/ AD7399
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 10. MICROWIRE to AD7398/AD7399 Interface
-14-
REV. 0
AD7398/AD7399
APPLICATIONS
STAIRCASE WINDOWS COMPARATOR
VREF VOUTB VOUTA VOUTD VOUTC GND WINDOW 3 WINDOW 1 WINDOW 2
Many applications need to determine whether voltage levels are within predetermined limits. Some requirements are for nonoverlapping windows and others for overlapping windows. Both circuit configurations are shown in Figures 12 and 13 respectively.
VTEST V+ AD8564 VREF VDD V+ 10k WINDOW 2 10k WINDOW 1
Figure 15. Overlapping Windows Range
VREFA
VOUTA
The nonoverlapping circuit employs one AD7398/AD7399 and ten comparators to achieve five voltage windows. These windows range between VREF and analog ground as shown in Figure 13. Similarly, the overlapping circuit employs six comparators to achieve three overlapping windows, Figure 15.
PROGRAMMABLE DAC REFERENCE VOLTAGE
AD7398/ AD7399
AD8564 VREFB VOUTB V+ 10k WINDOW 3
With AD7398/AD7399's flexibility, one of the internal DACs can be used to control a common programmable VREFX for the rest of the DACs. The circuit configuration is shown in Figure 16. The relationship of VREFX to VREF is dependent upon the digital code and the ratio of R1 and R2, and is given by: R2 D R2 VREFX = VREF x 1 + - VREFX x N x R1 2 R1 (5)
VREFC
VOUTC
V+ 10k WINDOW 4
1/2 AD8564 VREFD GND VOUTD
V+ 10k WINDOW 5
VREFX
Figure 12. Nonoverlapping Windows Comparator
VREF WINDOW 1 VOUTA VOUTB VOUTC WINDOW 4 VOUTD GND WINDOW 5 WINDOW 2 WINDOW 3
R2 VREF x 1 + R1 = D R2 1 + N x 2 R1
(6)
Where D = Decimal Equivalent of Input Code N = Number of Bits VREF = Applied External Reference VREFX = Reference Voltage for DAC A to D
Table V. VREFX vs. R1 and R2
R1, R2
Figure 13. Nonoverlapping Windows Range
VTEST V+ AD8564 VREF VDD VREFA VREFB VOUTA VOUTB V+ 10k WINDOW 2 10k WINDOW 1
Digital Code 0000 1000 1111 0000 1000 1111 0000 0000 1111 0000 0000 1111 0000 0000 1111 0000 0000 1111
VREFX 2 VREF 1.3 VREF VREF 4 VREF 1.6 VREF VREF
R1 = R2 R1 = R2 R1 = R2 R1 = 3R2 R1 = 3R2 R1 = 3R2
AD7398/ AD7399
VREFC VOUTC 1/2 AD8564 VREFD VOUTD GND
The accuracy of VREFX will be affected by the quality of R1 and R2 and therefore, tight tolerance low tempco thin film resistors should be used.
V+ 10k WINDOW 3
Figure 14. Overlapping Windows Comparator
REV. 0
-15-
AD7398/AD7399
R2 0.1% VREFA DAC A VOUTA R1 0.1% VIN VREF
VREFB DAC B
VOUTB
VREFC DAC C
VOUTC
TO OTHER COMPONENTS
VREFD DAC D
VOUTD
AD7398/AD7399
Figure 16. Programmable DAC Reference
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
16-Lead Wide SOIC (R-16)
0.4133 (10.50) 0.3977 (10.00)
16-Lead TSSOP (RU-16)
0.201 (5.10) 0.193 (4.90)
16
9
16
9
0.2992 (7.60) 0.2914 (7.40)
1 8
0.177 (4.50) 0.169 (4.30) 0.256 (6.50) 0.246 (6.25)
1 8
0.4193 (10.65) 0.3937 (10.00)
PIN 1
0.050 (1.27) BSC
0.1043 (2.65) 0.0926 (2.35)
PIN 1
0.0291 (0.74) 0.0098 (0.25) 45
0.006 (0.15) 0.002 (0.05)
0.0433 (1.10) MAX
-16-
REV. 0
PRINTED IN U.S.A.
0.0118 (0.30) 0.0040 (0.10)
8 0.0192 (0.49) SEATING 0 0.0125 (0.32) 0.0138 (0.35) PLANE 0.0091 (0.23)
0.0500 (1.27) 0.0157 (0.40)
SEATING PLANE
0.0256 (0.65) 0.0118 (0.30) BSC 0.0075 (0.19)
0.0079 (0.20) 0.0035 (0.090)
8 0
0.028 (0.70) 0.020 (0.50)
C02179-4.5-10/00 (rev. 0)
ADR293

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