Am1508/1408 * SSS1508A/1408A 8-Bit Multiplying D/A Converter Distinctive Characteristics Improved direct replacement for MC 1508/1408 +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 High speed multiplying input: 4.0mA/ys FUNCTIONAL DESCRIPTION The SSS1508A4/1408A, 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 maximum 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 AANGE MSB OO Ag Ag Ag Ag Ag Ay LsB CONTROL I i I 1 i { 1 it *s GROUND COMP RANGE 'o CONTRGL a vo Oo CURRENT SWITCHES to Vaer(-) [TT Tit ttf Veer(+) GND R.2R LADDER BIAS CIRCUIT r-_o I OUT vt MSB Veer J v A LsB oY+ -_o Ag Vrer i) REFERENCE NPN CURRENT | COMPENSATION Ag Ay CURRENT AMP SOURCE PAIA Ag Ag t Ag As . 039188-1 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 conangt I=] compensation Hermetic DIP 0to+70C + SSS1408A-8Q ono me bs vnce Am1408 Hermetic DIP Oto +70C + SSS1408A-70 TET SREF m Hermetic DIP Oto +70C + SSS1408A-6Q vs raf Vacet Plastic DIP Oto +70C AM1408N8 . Plastic DIP O10 +70C = AM1408N7 oC 4 Pv Plastic DIP 0 to +70C AM1408N6 mse a, (| 5 12] Ag LSB i 70 1408 Dice 0 to +70C LD ards nha Hermetic DIP 5to +125C + AM1508LB A a Am1508 Hermetic DIP 55 to +125C SSS150BA-8Q sO}? vol] 5 Dice 85 to +125C LD1508 2g ee ng *Also available with burn-in processing. To order, add suffix B to the part number. Note: Pin 1 is marked for orientation. 03919B-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 Vt +6.5Vdce Ceramic Package 1000m\V v- 16.5Vdc Derate above Ta = +25C 6.7mW/C Digital Input Voltage, V5--V12 +5.5, OVde Operating Temperature Range, Ta Applied Output Voltage, Vo +0.5, 5.2Vdc SSS1508A-8, Am1508 55C to +125C Reference Current, 144 5.0mA SSS1408A Series, Am 1408 Series 0C ta +75C Reference Amplifier Inputs, V14, V15 Vcc. VEE Vde Storage Temperature, Tstg 65C to +150C ELECTRICAL CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE Vret Rig otherwise noted. All digital inputs at high logic level.) (V+ = 5.0V, V- = 15V, = 2.0mA, SSS1508A-8/Am1508L8: Ta = 55 to +125C, SSS1408A/Am1408 Series: Ta = 0 to +75C unless Parameters Description Test Conditions Min. Typ. Max. Units Relative Accuracy $SS1508A-8, SSS1408A-8, Am1508L8, Am1408L8 0.19 ER SSS 1408A-7, Am1408L7 +0.39 % IFS SSS1408A-6, Am1408L6 +0.78 Settling Time to within 1/2 LSB (includes tp_}) 8SS1508A/1408A 250 ts Ta =+25C ns 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) Vv High Level, Logic 1 2.0 IH igh Level, oie Vde Vit Low Level, Logic 0 0.8 | High Level, VjH = 5.0V 0 0.04 IH Digital t{nput Current (MSB) tah Seve. NIH mA Ne Low Level, Vj = 0.8V 0.002 -0.8 Reference tnput Bias Current (Pin 15) SSS 1508A/1408A 1.0 3.0 his BA Am1508/1408 1.0 5.0 : V- = -5.0V 0 2.0 2.1 Output Current Range mA 'o V= = -7.0V to -15V 0 2.0 42 lo Output Current Vref = 2.000V,Ry4= 10002 | 19 | 1.99 24 mA 10 (min.) Output Current (All Bits Low) 0 4.0 BA Output Voltage Compliance V- = -5V 0.6,+0.5 Vo 3 Vde {E, < 0.19% at Ta = +25C) V- below -10V 5.0, +0.5 SRl ret Reference Current Slew Rate 4.0 mA/us PSSIg Output Current Power Supply Sensitivity O5 2.7 BAIV Power Supply Current I+ 25 14 SSS1508A/1408A i 64 13 2.5 22 ma * Am1508/1408 : I- -64 13 ave 5 45 5.0 5.5 Power Supply Voltage Range Ta = +26C Vde av 45 -15 16.5 Power Dissipation All Bits Low V- = -5.0Vdc 34 136 Vo = -15Vd 1 265 SSS1508A/1408A 08 All Bits High V- = -5.0Vde 34 Py Vo = =15Vde 108 mw All Bits Low V- = -5.0Vde 34 170 V- = -15Vd 305 Am1508/1408 Bvae 108 All Bits High V- = -.0Vde 34 Vo = -15Vde 108Am1508/1408 - SSS1508A/1408A TYPICAL APPLICATIONS USE WITH CURRENT-TO-VOLTAGE CONVERTING OP AMP yt 13 oTO +10 MSB Ay O VRE RELATIVE ACCURACY TEST CIRCUIT SB Ay Ag Ag 12.61T DIA CONVERTER Ay 5 (20.01% Aygo Ag ERROR MAX} X 7 tS Ris Vaer 7 2.0Vde Ay 30-4 Am1508 oO Rig = By = 1.02 A Ay o_4] Am1408 : Shy Ang Art Ane 50k 9 SSS15088 = Ro sono = As 881408 u Ago_+ SERIES Vaer 2.0V 16 3 COV = 1%) 15 pF vw THEORETICAL Vg VREF Ar Az Aa Aa As Ag AZ Ag 2 4 8 16 32 64 126 266 8-BIT COUNTER ADJUST VREE. R14 OR Rg SO THAT Vg WITH ALL DIGITAL INPUTS AT HIGH LEVEL IS EQUAL TO 9.961 VOLTS 7114 4 +4 1 2Vv 1 4 Vo =(BkJ- + ~+-+ + $+ + 2 4 8 16 32 64 126 256 255 = 10V||= 9.961V 256 03919B-4 039198-5 USE WITH POSITIVE Vrer USE WITH NEGATIVE Vper fe Ts 13 Rig Rag 13 Ria = yg 5 ayo a {| JL ao A, 04 z O (+ Vpee Ao 4 7 15 15 z . A A, 30-4 Am1508 Po 3 O Am1508 8 1 a Ayo 4 Am1408 Ago Am1408 A 9 S8S1508A 2 i 8 SSS1508A sO 58814084 7 = = 5 OS $85 14084 4504 SERIES Ag ol SERIES A190 0 ~TF A mW 7 12 16 LY 70 12 16 'o LE AgOS Ag OJ c c R ; (SEE TEXT FOR 3 (SEE TEXT FOR t VALUES OF C} VALUES OF C) vO vo = 03919B-7 03919B-6 TRANSIENT RESPONSE AND SETTLING TIME TEST CIRCUIT + Ole Ov I 13 +2.0Vae 5 Ot uF g FL 7 ~ r Am1508 see1508A 10ka 9 SS51408A eo FOR SETTLING TIME 10 SERIES MEASUREMENT 4 (ALL BITS SWITCHED LOW TO HIGH} en ( I 12 51D 18pF Co <25pF | vw = 039198-8Am1508/1408 + 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, |44 must always flow into pin 14 re- gardiess of the setup method or reference voltage polarity. Connections far a positive voltage are shown on the previous page. The reference voitage source supplies the full current l44. For bipolar reference signals, as in the multiplying mode, Ri5 can be tied to a negative voltage corresponding ta the minimum input level. it is possible to eliminate Ry5 with only a small sacrifice in accuracy and temperature drift. The compensation capacitor vaiue must be increased with in- creases in R14 to maintain proper phase margin; for R44 val- ues of 1.0, 2.5 and 5.0 kila&hms, 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 R45 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 R44 to a positive refer- ence voltage equal ta 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 0.1,.F 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 Ry 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 fevel as a fraction of the full seale 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 (8.0,A) which is the ladder remainder shunted to ground. The input current to pin 14 has a guaranteed value of between 1.9 and 2.1mA, 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 scate cur- rent is trimmed to the same value with Ry4 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 164A to 4.0mA, the additional error contributions are less than 1.6yA. 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 SSS1508A-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 ail 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 R_ <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, 100,F supply bypassing for low fre- quencies, and minimum scope lead length are all mandatory. 3-10