Philips Semiconductors Linear Products Product specification 8-bit multiplying D/A converter MC1508-8/1408-8 DESCRIPTION PIN CONFIGURATIONS The MC1508/MC1408 series of 8-bit monolithic digital-to-analog converters provide high-speed performance with low cost. They are designed for use where the output current is a linear product of an 8-bit digital word and an analog reference voltage F, N Packages NC 1 16 COMPEN GND 2 15 VREF(–) VEE 3 14 V REF(+) IO 4 13 V CC MSB A1 5 12 A 8 A2 6 11 A7 A3 7 10 A6 A4 8 9 A5 FEATURES • Fast settling time — 70ns (typ) • Relative accuracy ±0.19% (max error) • Non-inverting digital inputs are TTL and CMOS compatible • High-speed multiplying rate 4.0mA/µs (input slew) • Output voltage swing +0.5V to –5.0V • Standard supply voltages +5.0V and –5.0V to –15V • Military qualifications pending LSB D Package1 V+ 1 16 A8 2 15 A7 VREF(–) 3 14 A6 COMPEN 4 13 A5 NC 5 12 A4 GND 6 V– 7 IO 8 VREF(+) APPLICATIONS • Tracking A-to-D converters • 2 1/2-digit panel meters and DVMs • Waveform synthesis • Sample-and-Hold • Peak detector • Programmable gain and attenuation • CRT character generation • Audio digitizing and decoding • Programmable power supplies • Analog-digital multiplication • Digital-digital multiplication • Analog-digital division • Digital addition and subtraction • Speech compression and expansion • Stepping motor drive modems • Servo motor and pen drivers LSB 11 A3 TOP VIEW 10 A2 9 A1 MSB NOTE: 1. SO and non-standard pinouts. ORDERING INFORMATION TEMPERATURE RANGE ORDER CODE DWG # 16-Pin Ceramic Dual In-Line Package (CERDIP) DESCRIPTION -55 to +125°C MC1508-8F 0582B 16-Pin Ceramic Dual In-Line Package (CERDIP) 0 to +70°C MC1408-8F 0582B 16-Pin Plastic Dual In-Line Package (DIP) 0 to +70°C MC1408-8N 0406C 16-Pin Small Outline (SO) Package 0 to +70°C MC1408-8D 0005D August 31, 1994 737 853-0935 13721 Philips Semiconductors Linear Products Product specification 8-bit multiplying D/A converter MC1508-8/1408-8 BLOCK DIAGRAM MSB A1 A2 5 A3 6 A4 7 A5 8 9 A6 10 A7 11 LSB A8 12 IO 4 CURRENT SWITCHES BIAS CURRENT R-2R LADDER 2 GND VREF (+) 14 13 REFERENCE CURRENT AMPLIFIER 15 (–) VREF VCC 16 COMPEN VEE 3 NPN CURRENT SOURCE PAIR feedback. The termination amplifier holds the parasitic capacitance of the ladder at a constant voltage during switching, and provides a low impedance termination of equal voltage for all legs of the ladder. CIRCUIT DESCRIPTION The MC1508/MC1408 consists of a reference current amplifier, an R-2R ladder, and 8 high-speed current switches. For many applications, only a reference resistor and reference voltage need be added. The R-2R ladder divides the reference amplifier current into binarily-related components, which are fed to the remainder current which is equal to the least significant bit. This current is shunted to ground, and the maximum output current is 255/256 of the reference amplifier current, or 1.992mA for a 2.0mA reference amplifier current if the NPN current source pair is perfectly matched. The switches are non-inverting in operation; therefore, a high state on the input turns on the specified output current component. The switch uses current steering for high speed, and a termination amplifier consisting of an active load gain stage with unity gain ABSOLUTE MAXIMUM RATINGS RATING UNIT VCC SYMBOL Positive power supply voltage PARAMETER +5.5 V VEE Negative power supply voltage –16.5 V V5 – V12 Digital input voltage 0 to VCC V VO Applied output voltage I14 Reference current V14, V15 Reference amplifier inputs PD Maximum power dissipation, TA = 25°C (still-air)1 –5.2 to +18 V 5.0 mA VEE to VCC F package 1190 mW N package 1450 mW D package 1080 mW TSOLD Lead soldering temperature (10 sec) 300 °C TA Operating temperature range 300 °C MC1508 –55 to +125 °C MC1408 0 to +75 °C -65 to +150 °C TSTG Storage temperature range NOTES: 1. Derate above 25°C, at the following rates: F package at 9.5mW/°C; N package at 11.6mW/°C; D package at 8.6mW/°C August 31, 1994 738 Philips Semiconductors Linear Products Product specification 8-bit multiplying D/A converter MC1508-8/1408-8 DC ELECTRICAL CHARACTERISTICS Pin 3 must be 3V more negative than the potential to which R15 is returned. VCC = +5.0VDC, VEE = –15VDC, VREF/R14 = 2.0mA unless otherwise specified. MC1508: TA = –55°C to 125°C. MC1408: TA = 0°C to 75°C, unless otherwise noted. SYMBOL PARAMETER TEST CONDITIONS MC1508-8 Min Typ Er Relative accuracy Error relative to full-scale IO, Figure 3 tS Settling time1 To within 1/2 LSB, includes tPLH, TA = +25°C, Figure 4 70 TA = +25°C, Figure 4 35 tPLH tPHL Propagation delay time Low-to-High High-to-Low TCIO Output full-scale current drift VIH VIL Digital input logic level (MSB) High Low IIH IIL Digital input current (MSB) High Low I15 Reference input bias current IOR Output current range IO Output current IO(min) VO Off-state Output voltage compliance MC1408-8 Max Min ±0.19 2.0 Max ±0.19 70 100 35 –20 Figure 5 Typ % ns 100 –20 0.8 UNIT ns ppm/°C VDC 2.0 0.8 Figure 5 VIH = 5.0V VIL = 0.8V 0 –0.4 0.04 –0.8 0 –0.4 0.04 –0.8 mA Pin 15, Figure 5 –1.0 –5.0 –1.0 –5.0 µA 0 0 2.0 2.0 2.1 4.2 0 0 2.0 2.0 2.1 4.2 mA 1.9 1.99 2.1 1.9 1.99 2.1 mA 0 4.0 0 4.0 µA –0.6 +10 –5.5, +10 –0.55, +0.5 –5.0, +0.5 –0.6 +10 –5.5, +10 –0.55, +0.5 –5.0, +0.5 Figure 5 VEE = –5.0V VEE = –7.0V to –15V Figure 5 VREF = 2.000V, R14 = 1000Ω All bits low Er ≤ 0.19% at TA = +25°C, Figure 5 VEE = –5V VEE below –10V SRIREF Reference current slew rate Figure 6 8.0 PSRR(–) Output current power supply sensitivity IREF = 1mA 0.5 2.7 0.5 2.7 µA/V Power supply current Positive Negative All bits low, Figure 5 +2.5 –6.5 +22 –13 +2.5 –6.5 +22 –13 mA Power supply voltage range Positive Negative TA = +25°C, Figure 5 +5.0 –15 +5.5 –16.5 +5.0 –15 +5.5 –16.5 VDC Power dissipation All bits low, Figure 5 VEE = –5.0VDC VEE = –15.0VDC 34 110 170 305 34 110 170 305 mW ICC IEE VCCR VEER PD NOTES: 1. All bits switched. August 31, 1994 739 +4.5 –4.5 8.0 VDC +4.5 –4.5 mA/µs Philips Semiconductors Linear Products Product specification 8-bit multiplying D/A converter MC1508-8/1408-8 4.5V (or 8V — see above) above the negative supply voltage without significant degradation of accuracy. Philips Semiconductors MC1508/MC1408 can be used in sockets designed for other manufacturers’ MC1508/MC1408 without circuit modification. TYPICAL PERFORMANCE CHARACTERISTICS IO OUTPUT CURRENT (mA) D-to-A TRANSFER CHARACTERISTICS 0 Output Current Range Any time the full-scale current exceeds 2mA, the negative supply must be at least 8V more negative than the output voltage. This is due to the increased internal voltage drops between the negative supply and the outputs with higher reference currents. 1.0 2.0 (00000000) INPUT DIGITAL WORD (11111111) Accuracy Absolute accuracy is the measure of each output current level with respect to its intended value, and is dependent upon relative accuracy, full-scale accuracy and full-scale current drift. Relative accuracy is the measure of each output current level as a fraction of the full-scale current after zero-scale current has been nulled out. The relative accuracy of the MC1508/MC1408 is essentially constant over the operating temperature range because of the excellent temperature tracking of the monolithic resistor ladder. The reference current may drift with temperature, causing a change in the absolute accuracy of output current; however, the MC1508/MC1408 has a very low full-scale current drift over the operating temperature range. FUNCTIONAL DESCRIPTION Reference Amplifier Drive and Compensation The reference amplifier input current must always flow into Pin 14. regardless of the setup method or reference supply voltage polarity. Connections for a positive reference voltage are shown in Figure 1. The reference voltage source supplies the full reference current. For bipolar reference signals, as in the multiplying mode, R15 can be tied to a negative voltage corresponding to the minimum input level. R15 may be eliminated and Pin 15 grounded, with only a small sacrifice in accuracy and temperature drift. The MC1508/MC1408 series is guaranteed accurate to within ±1/2LSB at +25°C at a full-scale output current of 1.99mA. The relative accuracy test circuit is shown in Figure 3. The 12-bit converter is calibrated to a full-scale output current of 1.99219mA; then the MC1508/MC1408’s 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 the oscilloscope, detected by comparators, or stored in a peak detector. The compensation capacitor value must be increased with increasing values of R14 to maintain proper phase margin. For R14 values of 1.0, 2.5, and 5.0kΩ, minimum capacitor values are 15, 37, and 75pF. The capacitor may be tied to either VEE or ground, but using VEE increases negative supply rejection. (Fluctuations in the negative supply have more effect on accuracy than do any changes in the positive supply.) A negative reference voltage may be used if R14 is grounded and the reference voltage is applied to R15, as shown in Figure 2. A high input impedance is the main advantage of this method. The negative reference voltage must be at least 3.0V 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. Two 8-bit D-to-A converters may not be used to construct a 16-bit accurate D-to-A converter. 16-bit accuracy implies a total of ±1/2 part in 65,536, or ±0.00076%, which is much more accurate than the ±0.19% specification of the MC1508/MC1408. Monotonicity A monotonic converter is one which always provides an analog output greater than or equal to the preceding value for a corresponding increment in the digital input code. The MC1508/MC1408 is monotonic for all values of reference current above 0.5mA. The recommended range for operation is a DC reference current between 0.5mA and 4.0mA. Capacitive bypass to ground is recommended when a DC reference voltage is used. The 5.0V logic supply is not recommended as a reference voltage, but if a well regulated 5.0V supply which drives logic is to be used as the reference, R14 should be formed of two series resistors and the junction of the two resistors bypassed with 0.1µF to ground. For reference voltages greater than 5.0V, a clamp diode is recommended between Pin 14 and ground. Settling Time The worst case switching condition occurs when all bits are switched on, which corresponds to a low-to-high transition for all input bits. This time is typically 70ns for settling to within 1/2LSB for 8-bit accuracy. This time applies when RL < 500Ω and CO < 25pF. The slowest single switch is the least significant bit, which typically turns on and settles in 65ns. In applications where the D-to-A converter functions in a positive going ramp mode, the worst-case condition does not occur and settling times less than 70ns may be realized. 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 at Pin 4 must always be at least 4.5V more positive than the voltage of the negative supply (Pin 3) when the reference current is 2mA or less, and at least 8V more positive than the negative supply when the reference current is between 2mA and 4mA. This is necessary to avoid saturation of the output transistors, which would cause serious degradation of accuracy. Extra care must be taken in board layout since this usually is the dominant factor in satisfactory test results when measuring settling time. Short leads, 100µF supply bypassing for low frequencies, minimum scope lead length, good ground planes, and avoidance of ground loops are all mandatory. Philips Semiconductors MC1508/MC1408 does not need a range control because the design extends the compliance range down to August 31, 1994 740 Philips Semiconductors Linear Products Product specification 8-bit multiplying D/A converter MC1508-8/1408-8 VCC VCC R14 = R15 13 A1 A2 A3 A4 5 6 14 7 15 8 1 9 A5 A6 A7 A8 MC1508 MC1408 (+)VREF A2 A3 R15 A4 2 10 4 11 16 6 14 7 15 8 1 9 A6 IO A7 SEE TEXT FOR VALUES OF C. A8 C 3 5 A5 RL 12 R14 = R15 13 A1 R14 MC1508 MC1408 R14 (–)VREF R15 2 RL 4 10 11 IO 16 12 SEE TEXT FOR VALUES OF C. C 3 VEE VEE Figure 2. Negative VREF Figure 1. Positive VREF MSB A1 A2 12-BIT A3 D-TO-A A4 CONVERTER (±0.02% A5 A6 ERROR MAX) A7 A8A9 A10 A11 A12 0 TO +10V OUTPUT 5k LSB 50k 0.1µF VREF = 2V – + 100 950 R14 8-BIT COUNTER 4 MC1508 MC1408 15 16 1k NE530 13 MSB 14 5 6 7 8 9 10 11 12 LSB VCC 3 2 1 C VEE Figure 3. Relative Accuracy August 31, 1994 741 ERROR (1V = 1%) Philips Semiconductors Linear Products Product specification 8-bit multiplying D/A converter MC1508-8/1408-8 VCC 0.1µF 13 eIN 6 14 7 8 9 10 11 15 1 2 MC1508 MC1408 1.0k RL 12 1.4V 0.4V tPHL = tPLH = 10ns FOR TURN OFF MEASUREMENT RL = 500Ω SETTLING TIME FOR SETTLING TIME MEASUREMENT (ALL BITS eO SWITCHED LOW TO HIGH) 0 tS = 70ns TYPICAL TO ±1/2LSB 15pF 3 USE RL to GND 1.0V 0.1µF 1.0k 51 eIN R14 4 16 0.1µF 2.4V +2VDC 5 CO ≤ 25pF 0 TRANSIENT RESPONSE –100 mV VEE RL = 50Ω PIN 4 TO GND tPLH tPHL Figure 4. Transient Response and Settling Time VCC TYPICAL VALUES R14 = R15 = 1k VREF = +2.0V C = 15pF ICC 13 DIGITAL INPUTS A1 A2 A3 A4 A5 A6 A7 A8 (+) VI 5 14 6 7 8 9 15 1 2 MC1508 MC1408 I14 VI AND II APPLY TO INPUTS A1 THROUGH A8 R14 VREF(+) THE RESISTOR TIED TO PIN 15 IS TO TEMPERATURE COMPENSATE THE BIAS CURRENT AND MAY NOT BE NECESSARY FOR ALL APPLICATIONS I15 R15 I 10 11 4 12 16 VO OUTPUT O A1 K 2 where K IO 3 IEE A2 4 A3 8 A4 16 A5 32 A6 64 V REF RL II R 14 and AN = “1” IF AN IS AT HIGH LEVEL AN = “0” IF AN IS AT LOW LEVEL VEE (SEE TEXT FOR VALUES OF C.) Figure 5. Notation Definitions VCC 13 5 6 7 8 9 10 11 MC1508 MC1408 14 15 1 2 1k VREF 1k 4 16 12 3 dI dt SCOPE 15pF RL = 50 I dV R L dt 10% 90% SLEWING TIME VEE Figure 6. Reference Current Slew Rate Measurement August 31, 1994 742 0 2.0mA A8 A7 128 256