Am1508/1408 * SSS1508A/1408A 8-Bit Multiplying D/A Converter Distinctive Characteristics Improved direct replacement for MC1508/1408 +0.19% nonlinearity guaranteed over temperature range Improved settling time (SSS1508A/1408A) 250ns, typ. Improved power consumption (SSS1508A/1408A) 157mW, typ. Compatible with TTL, CMOS logic Output voltage swing: +0.5V to 5.0V e e e @ High speed multiplying input: 4.0mA/xzs FUNCTIONAL DESCRIPTION The SSS1508A/1408A, Am1508/1408 are 8-bit monolithic multiplying Digital-to-Analog Converters consisting of a reference current amplifier, an R-2R ladder, and eight high speed current switches. For many applications, only a refer- ence resistor and reference voltage need be added. Improve- ments in design and processing techniques provide faster settling times combined with lower power consumption while retaining direct interchangeability with MC1508/1408 devices. The R-2R ladder divides the reference current into eight binarily-related components which are fed to the switches. A remainder current equal to the least significant bit is always shunted to ground, therefore the fiaximum output current is 255/256 of the reference amplifier input current. For example, a full scale output current of 1.992mA would result from a reference input current of 2.0mA. The SSS1508A/1408A, Am1508/1408 is useful in a wide variety of applications, including waveform synthesizers, digitally programmable gain and attenuation blocks, CRT character generation, audio digitizing and decoding, stepping motor drives, programmable power supplies and in building Tracking and Successive Approximation Analog-to-Digital Converters. BLOCK DIAGRAM METALLIZATION AND PAD LAYOUT RANGE MSB OAD Ay Ag Ag 4% Ay 138 CONTROL i * t i t i ft f I 8 GROUND COMP RANGE Jo CONTROL _- vo o_ CURRENT SWITCHES -o Vaert-) Titty fy | Vrer(+) GND R 2R LADDER BIAS CIRCUIT --O | OUT + Ebes A . Veer 0 | l vc ra Lse oS Aa Yager (-! REFERENCE nen current | COMPENSATION Ae ay CURRENT AMP SOURCE PAIR Ay Ag - T. My 8 9 As - 038198-1 DIE SIZE: 0.068 X 0,088" 039198-2 ORDERING INFORMATION* CONNECTION DIAGRAM Part Package Temperature Order Top View Number Type Range Number D- 16-1 Hermetic DIP. Oto +70C. = AM1408L8 P-16-1 Hermetic DIP Oto +70C AM1408L7 Hermetic DIP Oto +70C AM1408L6 contnce C+ compensation Hermetic DIP Oto+70C SSS1408A-8Q nn Ls veer Am1408 Hermetic DIP Oto +70C = SSS1408A-70 sno Spo rer Hermetic DIP Oto +70C SSS1408A-60 v- (3 1417] Vrer Plastic DIP Oto +70C AM1408N8 oe Plastic DIP Oto +70C + AM1408N7 oC} + af Plastic DIP Oto +70C AM1408N6 MsB A,[_] 5 12,7] 4g tse Dice Oto +70C LD1408 Ao(]6 uf] Az Hermetic DIP ~56 to +126C + AM1508L3 a Am1508 Hermetic DIP = 58 to +125C + SSS1508A-8Q oll? oT 46 Dice ~5 to +128C 101508 Ag ft ag *Also available with burn-in processing. To order, add suffix B to the part number. Note: Pin 1 is marked for orientation. 039198-3 3-7 03919B-ANA Standard supply voltage: +5.0V and 5.0V to 15VAm1508/1408 - SSS1508A/1408A MAXIMUM RATINGS (Above which the useful life may be impaired) (Ta = +25C unless otherwise noted) Power Supply Voltage Power Dissipation (Package Limitation), Pp vet +5.5Vde Ceramic Package 1000mw V- 16.5Vde Derate above Ta = +25C 6.7mW/C Digital Input Voltage, V5~V12 +5.5, OVdce Operating Temperature Range, TA Applied Output Voltage, Vo +0.5, 5.2Vde SSS1508A-8, Am1508 55C to +125C Reference Current, 144 5.0mA SSS1408A Series, Am1408 Series 0'C to +75C Reference Amplifier Inputs, V14, V15 Vec. VEE Vde Storage Temperature, Tstg 65C to +150C ELECTRICAL CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (V+ = 5.0V,V- = -15V, = = 2.0mA, SSS1508A-B/Am1508L8: Ta = 55 to +125C, SSS1408A/Am 1408 Series: Ta = 0 to +75C unless otherwise noted. All digital inputs at high logic level.) : Parameters Description Test Conditions Min. Typ. Max. Units Relative Accuracy $SS$1508A-8, SSS1408A-8, Am1508L8, Am1408L8 +0.19 Er SSS 140BA-7, Am1408L7 0.39 % IFS $SS1408A-6, Am1408L6 +0.78 Settling Time to within 1/2 LSB (includes tp; 4) ts SSS1508A/1408A Ta = +25C 250 as Am1508/1408 300 tPLH. TPHL. Propagation Delay Time Ta = +25C 30 100 ns TClo Output Full Scale Current Drift +20 PPM/C Digital Input Logic Levels {MSB) Vin High Level, Logic "1" 2.0 Vide ViL Low Level, Lagic 0 08 MH Digital Input Current (MSB) High Level, Vin = 8.0V 8 0.04 mA Ne Low Level, Vi, = 0.8V ~0.002 -0.8 Reference Input Bias Current (Pin 15) SSS1508A/1408A 1.0 -3.0 "15 BA Am1508/1408 -1.0 5.0 Alo Output Current Range > = a Ta 5 _ ~ mA fo Output Current Vref = 2.000V, R14 = 10008 | 1.9 1.99 21 mA 10 (min.) Output Current {All Bits Low} 0 4.0 uA Output Voltage Compliance V- = -5V 0.6, +0.5 Vo 5 Vde (E, < 0.19% at Ta = +25C) V- below 10V 5.0, +0.5 SRlret Reference Current Slew Rate 4.0 mAlus PSSI9g Output Current Power Supply Sensitivity 0.5 2.7 HAIV Power Supply Current a 28 14 SSS1508A/1408A i- 6.4 13 mA I" Am1508/1408 25 22 I- 64 13 ave Power Supply Voltage Range Ta = +28C 45 5.0 5.6 Vde Ave 4.5 ~15 ~16.5 Power Dissipation All Bits Low V- = -5.0Vde 34 136 $881508A/1408A Vo = ~18Vde 108 268 All Bits High V- = -5.0Vde 34 Py V> = -15Vde 108 mw Ali Bits Low V- = .0Vde 34 170 Am1508/1408 Vo = -15Vde 108 305 Ail Bits High V7 = -5.0Vde 34 V~ = -15Vde 108 3-8Am1508/1408 + SSS1508A/1408A TYPICAL APPLICATIONS USE WITH CURRENT-TO-VOLTAGE CONVERTING OP AMP ve ? 1 MSB 3 RELATIVE ACCURACY TEST CIRCUIT ze" QTO+l0v . CONVERTER AY oJ 14 Vaer {20.01% 6 A Ag ERROR MAX) 2 O- 15 Aig Vage = 2.0Vde A 7 REF 304 Am1508 pa Rigs Rig? 10k A A, Am1408 Bag Aig Art Aig soe a oF SSS1508A = Ro = 5.0ke 5 O- SSS 14084 Ag oS SERIES arc 12 ABO Vo bo LsB 16 a HOV = 1%) 15 pF vo THEORETICAL Vo VREF E Ag Ag Ag Ag Ag Az =| b] + tt ttt et 2 4 8 16 32 64 126 256 gait COUNTER ADJUST VREF. R14 OR Ro SO THAT Vo WITH ALL DIGITAL INPUTS AT HIGH LEVEL IS EQUAL TO 9.961 VOLTS 2Vv 11 =4 1 4 1 1 1 Vo = (5k)]-+ +- 4+ + + t+ 1k 2 4 8 16 32 64 126 256 255 = 10V||= 9.961V 256 039198-5 USE WITH NEGATIVE Var 039198-4 USE WITH POSITIVE Vrer te yt . te Ria Fag 3 Aya * Pag Ao2 JL Ao 6 14 1 42 0 vs Ais O Wl VaeF 420-7 30-7 m1508 pi | 43 O- m1508 A, Am1408 4 Am1408 40f dco? $85 15088 2} 4 io $8$15084 5O SSS 14084 ? > sO 8851408 4g 04 SERIES 4540-24 SERIES A uv =~ | A 11 7 ona e] LF 70-7 BOS Ag O44 c 7 iSEE TEXT FOR ; {SEE TEXT FOR VALUES OF CI VALUES OF C} vo vo = 039158-6 039198-7 TRANSIENT RESPONSE AND SETTLING TIME TEST CIRCUIT + our 69 3 ye Oar 14 1.0k2 rd WA = 15 = Am 1508 7; ions \ Am1408 < $SS1508A 2 t sie $851408A => eg FOR SETTLING TIME SERIES + _ MEASUREMENT 16 (ALL BITS SWITCHED LOW TO HIGH) 15pF + Co <25pF 3 vo = 039198-8 3-9Am1508/1408 - SSS1508A/1408A GENERAL INFORMATION AND APPLICATION NOTES REFERENCE AMPLIFIER DRIVE AND COMPENSATION The reference amplifier provides a voltage at pin 14 for con- verting the reference voltage to a current and a turn-around circuit or current mirror for feeding the ladder. The reference amplifier input current, I1q must always flow into pin 14 re- gardless of the setup method or reference voltage polarity. : Connections for a positive voltage are shown on the previous page. The reference voltage source supplies the full current 114. For bipolar reference signals, as in the multiplying mode, Ris 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 in- creases in Ryq4 to maintain proper phase margin; for Ry4 val- ues of 1.0, 2.5 and 5.0 kilohms, minumum capacitor values are 15, 37, and 75pF. The capacitor may be tied to either V- or ground, but using V increases negative supply rejection. A negative reference voltage may be used if R14 is grounded and the reference voltage is applied to Ris as shown. A high input impedance is the main advantage of this method. Com- pensation involves a capacitor to V~ on pin 16, using the val- ues of the previous paragraph. The negative reference voltage must be at least 4.0 volts above the V- supply. Bipolar input signals may be handled by connecting Ry4 to a positive refer- ence 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 5.0V logic supply is not recom- mended as a reference voltage. If a well regulated 5.0V supply which drives logic is to be used as the reference, R14 should be decoupled by connecting it to +5.0V through another resis- tor and bypassing the junction of the two resistors with 0.1uF to ground. For reference voltages greater than 5.0V, 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, de- creasing the overall bandwidth. OUTPUT VOLTAGE RANGE The voltage on pin 4 is restricted to a range of 0.6 to +0.5 volts when V- = 5.0V due to the current switching methods employed in the SSS1508A-8, Am1508. The negative output voltage compliance of the SSS1508A-8, Am1508 is extended to 5.0V where the negative supply volt- age is more negative than 10 volts. Using a full scale current of 1.992mA and load resistor of 2.5 kilohms between pin 4 and ground will yield a voltage output of 256 levels between 0 and ~4.980 volts. Floating pin 1 does not affect the converter speed or power dissipation. However, the value of the load re- sistor determines the switching time due to increased voltage swing. Values of RL up to 500 ohms do not significantly affect performance but a 2.5-kilohm load increases worst case settling time to 1.2us (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 4.2mA may be used only for negative supply voltages more negative than 12.0 volts, 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 rela- tive 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 SSS1508A-8, Am1508 is essentially constant with temperature due to the ex- cellent 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 SSS1508A-8 has a very low full scale current drift with temperature. The SSS1508A-8/Am1508 Series is guaranteed accurate to within + 1/2 LSB at a full scale output current of 1.992mA. This corresponds to a reference amplifier output current drive to the ladder network of 2.0mA, with the loss of one LSB (8.0A) which is the ladder remainder shunted to ground. The input current to pin 14 has a guaranteed value of between 1.9 and 2.1mA, allowing some mismatch in the NPN current source pair. The accuracy test circuit is shown on page 3. The 12-bit converter is calibrated for a full scale output current of 1.992mA. This is an optional step since the SSS1508A-8, Am1508 accuracy is essentially the same between 1.5 and 2.5mA. Then the SSS1508A-8, Am1508 circuits full scale cur- rent is trimmed to the same value with R44 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, de- tected 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 +1/2 of one part in 65,536 or +0.00076%, which is much more accurate than the +0.19% specification provided by the SSS1508A-8, Am1508. MULTIPLYING ACCURACY The SSS1508A-8, Am1508 may be used in the multiplying mode with eight-bit accuracy when the reference current is varied over a range of 256:1. If the reference current in the multiplying mode ranges from 16yA to 4.0mA, the additional error contributions are less than 1.6uA. This is well within eight-bit accuracy when referred to full scale. A monotonic converter is one which supplies an increase in current for each increment in the binary word. Typically, the $SS1508A-8, Am1508 is monotonic for all values of reference current above 0.5mA. The recommended range for operation with a DC reference current is 0.5 to 4.0mA. SETTLING TIME The worst case switching condition occurs when all bits are switched on, which corresponds to a LOW-to-HIGH transition for all bits. This time is typically 250ns for settling to within + 1/2 LSB, for 8-bit accuracy, and 200ns to 1/2 LSB for 7 and 6-bit accuracy. The turn off is typically under 100ns. These times apply when Ry, <500 ohms and Co <25pF. The slowest single switch is the least significant bit. In applica- tions where the D-to-A converter functions in a positive-going ramp mode, the worst case switching condition does not occur, and a settling time of less than 250ns may be realized. Extra care must be taken in board layout since this is usually the dominant factor in satisfactory test results when measuring settling time. Short leads, 100uF supply bypassing for low fre- quencies, and minimum scope lead length are all mandatory. 3-10