8-Bit DAC0808 D/A Converter
May 1999
DAC0808 8-Bit D/A Converter
General Description
The DAC0808 is an 8-bit monolithic digital-to-analog converter (DAC) featuring a full scale output current settling time of 150 ns while dissipating only 33 mW with 5V supplies. No reference current (IREF) trimming is required for most applications since the full scale output current is typically 1 LSB of 255 IREF/256. Relative accuracies of better than 0.19% assure 8-bit monotonicity and linearity while zero level output current of less than 4 A provides 8-bit zero accuracy for IREF2 mA. The power supply currents of the DAC0808 is independent of bit codes, and exhibits essentially constant device characteristics over the entire supply voltage range. The DAC0808 will interface directly with popular TTL, DTL or CMOS logic levels, and is a direct replacement for the MC1508/MC1408. For higher speed applications, see DAC0800 data sheet.
Features
Relative accuracy: 0.19% error maximum Full scale current match: 1 LSB typ Fast settling time: 150 ns typ Noninverting digital inputs are TTL and CMOS compatible n High speed multiplying input slew rate: 8 mA/s n Power supply voltage range: 4.5V to 18V n Low power consumption: 33 mW @ 5V n n n n
Block and Connection Diagrams
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Dual-In-Line Package
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Top View Order Number DAC0808 See NS Package M16A or N16A
1999 National Semiconductor Corporation
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Block and Connection Diagrams
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Small-Outline Package
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Ordering Information
ACCURACY OPERATING TEMPERATURE RANGE 8-bit 0CTA+75C N PACKAGE (N16A) (Note 1) DAC0808LCN MC1408P8 SO PACKAGE (M16A) DAC0808LCM
Note 1: Devices may be ordered by using either order number.
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Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Power Supply Voltage VCC VEE Digital Input Voltage, V5V12 Applied Output Voltage, VO Reference Current, I14 Reference Amplifier Inputs, V14, V15 Power Dissipation (Note 4) ESD Susceptibility (Note 5) +18 VDC 18 VDC to +18 VDC to +18 VDC 5 mA VCC, VEE 1000 mW TBD
Storage Temperature Range Lead Temp. (Soldering, 10 seconds) Dual-In-Line Package (Plastic) Dual-In-Line Package (Ceramic) Surface Mount Package Vapor Phase (60 seconds) Infrared (15 seconds)
65C to +150C 260C 300C 215C 220C
10 VDC 11 VDC
Operating Ratings
Temperature Range DAC0808 TMIN TA TMAX 0 TA +75C
Electrical Characteristics
(VCC = 5V, VEE = 15 VDC, VREF/R14 = 2 mA, and all digital inputs at high logic level unless otherwise noted.) Symbol Er Parameter Relative Accuracy (Error Relative to Full Scale IO) DAC0808LC (LM1408-8) Settling Time to Within 12 LSB (Includes tPLH) tPLH, tPHL TCIO MSB VIH VIL MSB Propagation Delay Time Output Full Scale Current Drift Digital Input Logic Levels High Level, Logic 1 Low Level, Logic 0 Digital Input Current High Level Low Level I15 Reference Input Bias Current Output Current Range (Figure 3) VIH = 5V VIL = 0.8V (Figure 3) (Figure 3) VEE = 5V VEE = 15V, TA = 25C VREF = 2.000V, R14 = 1000, (Figure 3) Output Current, All Bits Low Output Voltage Compliance (Note 3) VEE = 5V, IREF = 1 mA VEE Below 10V SRIREF Reference Current Slew Rate Output Current Power Supply Sensitivity Power Supply Current (All Bits Low) ICC IEE Power Supply Voltage Range VCC VEE Power Dissipation TA = 25C, (Figure 3) 4.5 4.5 5.0 15 5.5 16.5 VDC VDC 2.3 4.3 22 13 mA mA (Figure 3) (Figure 6) 5V VEE 16.5V 4 8 0.05 2.7 (Figure 3) Er 0.19%, TA = 25C 0.55, +0.4 5.0, +0.4 VDC VDC mA/s A/V 1.9 1.99 0 2.1 4 mA A 0 0 0 0.003 1 2.0 2.0 (Figure 3) 2 0.8 0.040 0.8 3 2.1 4.2 VDC VDC mA mA A mA mA TA = 25C (Note 7), (Figure 5) TA = 25C, (Figure 5) 150 30 100 Conditions (Figure 4) Min Typ Max Units %
0.19
% ns ns ppm/C
20
IO
Output Current
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Electrical Characteristics
Symbol All Bits Low All Bits High Parameter
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(VCC = 5V, VEE = 15 VDC, VREF/R14 = 2 mA, and all digital inputs at high logic level unless otherwise noted.) Conditions VCC = 5V, VEE = 5V VCC = 5V, VEE = 15V VCC = 15V, VEE = 5V VCC = 15V, VEE = 15V Min Typ 33 106 90 160 Max 170 305 Units mW mW mW mW
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its specified operating conditions. Note 3: Range control is not required. Note 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, JA, and the ambient temperature, TA. The maximum allowable power dissipation at any temperature is PD = (TJMAX TA)/JA or the number given in the Absolute Maixmum Ratings, whichever is lower. For this device, TJMAX = 125C, and the typical junction-to-ambient thermal resistance of the dual-in-line J package when the board mounted is 100C/W. For the dual-in-line N package, this number increases to 175C/W and for the small outline M package this number is 100C/W. Note 5: Human body model, 100 pF discharged through a 1.5 k resistor. Note 6: All current switches are tested to guarantee at least 50% of rated current. Note 7: All bits switched. Note 8: Pin-out numbers for the DAL080X represent the dual-in-line package. The small outline package pinout differs from the dual-in-line package.
Typical Application
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FIGURE 1. +10V Output Digital to Analog Converter (Note 8)
Typical Performance Characteristics
Logic Input Current vs Input Voltage
VCC = 5V, VEE = 15V, TA = 25C, unless otherwise noted Logic Threshold Voltage vs Temperature
Bit Transfer Characteristics
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Typical Performance Characteristics
noted (Continued) Output Current vs Output Voltage (Output Voltage Compliance)
VCC = 5V, VEE = 15V, TA = 25C, unless otherwise
Output Voltage Compliance vs Temperature
Typical Power Supply Current vs Temperature
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Typical Power Supply Current vs VEE
Typical Power Supply Current vs VCC
Reference Input Frequency Response
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Unless otherwise specified: R14 = R15 = 1 k, C = 15 pF, pin 16 to VEE; RL = 50, pin 4 to ground. Curve A: Large Signal Bandwidth Method of Figure 7, VREF = 2 Vp-p offset 1V above ground. Curve B: Small Signal Bandwidth Method of Figure 7, RL = 250, VREF = 50 mVp-p offset 200 mV above ground. Curve C: Large and Small Signal Bandwidth Method of Figure 9 (no op amp, RL = 50), RS = 50, VREF = 2V, VS = 100 mVp-p centered at 0V.
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FIGURE 2. Equivalent Circuit of the DAC0808 Series (Note 8)
Test Circuits
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VI and I1 apply to inputs A1A8. The resistor tied to pin 15 is to temperature compensate the bias current and may not be necessary for all applications.
and AN = 1 if AN is at high level AN = 0 if AN is at low level
FIGURE 3. Notation Definitions Test Circuit (Note 8)
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FIGURE 4. Relative Accuracy Test Circuit (Note 8)
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Test Circuits
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FIGURE 5. Transient Response and Settling Time (Note 8)
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FIGURE 6. Reference Current Slew Rate Measurement (Note 8)
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FIGURE 7. Positive VREF (Note 8)
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Test Circuits
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FIGURE 8. Negative VREF (Note 8)
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FIGURE 9. Programmable Gain Amplifier or Digital Attenuator Circuit (Note 8)
Application Hints
REFERENCE AMPLIFIER DRIVE AND COMPENSATION The reference amplifier provides a voltage at pin 14 for converting the reference voltage to a current, and a turn-around circuit or current mirror for feeding the ladder. The reference amplifier input currrent, I14, must always flow into pin 14, regardless of the set-up method or voltage reference polarity. Connections for a positive voltage are shown in Figure 7. The reference voltage source supplies the full current I14. For bipolar reference signals, as in the multiplying mode,
R15 can be tied to a negative voltage corresponding to the minimum input level. It is possible to eliminate R15 with only a small sacrifice in accuracy and temperature drift. The compensation capacitor value must be increased with increases in R14 to maintain proper phase margin; for R14 values of 1, 2.5 and 5 k, minimum capacitor values are 15, 37 and 75 pF. The capacitor may be tied to either VEE or ground, but using VEE increases negative supply rejection. A negative reference voltage may be used if R14 is grounded and the reference voltage is applied to R15 as shown in Figure 8. A high input impedance is the main advantage of this method. Compensation involves a capacitor
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Application Hints
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to VEE on pin 16, using the values of the previous paragraph. The negative reference voltage must be at least 4V above the VEE supply. Bipolar input signals may be handled by connecting R14 to a positive reference voltage equal to the peak positive input level at pin 15. When a DC reference voltage is used, capacitive bypass to ground is recommended. The 5V logic supply is not recommended as a reference voltage. If a well regulated 5V supply which drives logic is to be used as the reference, R14 should be decoupled by connecting it to 5V through another resistor and bypassing the junction of the 2 resistors with 0.1 F to ground. For reference voltages greater than 5V, a clamp diode is recommended between pin 14 and ground. If pin 14 is driven by a high impedance such as a transistor current source, none of the above compensation methods apply and the amplifier must be heavily compensated, decreasing the overall bandwidth. OUTPUT VOLTAGE RANGE The voltage on pin 4 is restricted to a range of 0.55 to 0.4V when VEE = 5V due to the current switching methods employed in the DAC0808. The negative output voltage compliance of the DAC0808 is extended to 5V where the negative supply voltage is more negative than 10V. Using a full-scale current of 1.992 mA and load resistor of 2.5 k between pin 4 and ground will yield a voltage output of 256 levels between 0 and 4.980V. Floating pin 1 does not affect the converter speed or power dissipation. However, the value of the load resistor determines the switching time due to increased voltage swing. Values of RL up to 500 do not significantly affect performance, but a 2.5 k load increases worst-case settling time to 1.2 s (when all bits are switched ON). Refer to the subsequent text section on Settling Time for more details on output loading. OUTPUT CURRENT RANGE The output current maximum rating of 4.2 mA may be used only for negative supply voltages more negative than 8V, due to the increased voltage drop across the resistors in the reference current amplifier. ACCURACY Absolute accuracy is the measure of each output current level with respect to its intended value, and is dependent upon relative accuracy and full-scale current drift. Relative accuracy is the measure of each output current level as a fraction of the full-scale current. The relative accuracy of the DAC0808 is essentially constant with temperature due to the excellent temperature tracking of the monolithic resistor lad-
der. The reference current may drift with temperature, causing a change in the absolute accuracy of output current. However, the DAC0808 has a very low full-scale current drift with temperature. The DAC0808 series is guaranteed accurate to within 12 LSB at a full-scale output current of 1.992 mA. This corresponds to a reference amplifier output current drive to the ladder network of 2 mA, with the loss of 1 LSB (8 A) which is the ladder remainder shunted to ground. The input current to pin 14 has a guaranteed value of between 1.9 and 2.1 mA, allowing some mismatch in the NPN current source pair. The accuracy test circuit is shown in Figure 4. The 12-bit converter is calibrated for a full-scale output current of 1.992 mA. This is an optional step since the DAC0808 accuracy is essentially the same between 1.5 and 2.5 mA. Then the DAC0808 circuits full-scale current is trimmed to the same value with R14 so that a zero value appears at the error amplifier output. The counter is activated and the error band may be displayed on an oscilloscope, detected by comparators, or stored in a peak detector. Two 8-bit D-to-A converters may not be used to construct a 16-bit accuracy D-to-A converter. 16-bit accuracy implies a total error of 12 of one part in 65,536 or 0.00076%, which is much more accurate than the ...