AD509

ANALOGDEVICES fAX-ON-DEHAND HOTLINE - Page 12 .' LIllI DEVICES FEATURES Fat Settting Time ~O.1'" in 5OOns mex 0.01% in 2.5ps max High Slew Rate: 100V/1lS min' Low 10': 25nA max Guaranteed VOl Drift: 3OIlVrC mex High CMRR: BOdB min Orive.5OOpF Low Price r. ANALOG HighSpeed, FastSettling UpAmp Ie . PIN CONFIGURATION TO-99 FREQUENCY COMPENSATION AD509 I OBS APPLICATIONS 01 A and AID Converlion Wideband Amplifi8n MultiplexeR Pul. AmplifieR INVERTING 2 INPUT r PRODUCT DESCRIPTION The ADS09j, ADS09K and ADS09S are monolithic operational amplifiers specifically designed for applications requiring fast settling times to high accuracy. Other comparable dynamic parameters include a small signal bandwidth of 2OMHz, slew rate of lOOV/JlS min and a full power response of 150kHz min. The devices are internally compensated for all closed loop gains greater than 3, and are compensated with a single capacitor for lower gains. The input characteristics of the AD.509 are consistent with 0.01 % accuracy over limited temperature ranges; offset current is 2SnA max, offset voltage is 8mV max, nullable to' zero, and offset voltage drift is limited to 30p.V/'C max. PSRR and CMRR are typically 90dB. The ADS09 is designed for use with high speed D/A or AID conveners where the minimum conversion time is limited by the amplifier setding time. If 0.01 % accuracy of conversion is required. a conversion cannot be made in a shoner period than the time required for the amplifier to settle to within 0.01 % of its final value, All devices are supplied in the TO-99 package. The ADS09j and ADS09K are specified for 0 to +70oC temperatUte range; the ADS09S for operation from -SSoC to +12SoC. OLE ~ 2.. v- V+ T !. TOPVIEW PRODUCT HIGHLIGHTS 1. The ADS09 is internally compensated for all closed loop gains above 3. and compensated with a single capacitor for lower gains thus eliminating the c:laborate stabilizing techniques required by other high speed IC op amps. 2. The ADSO9 will drive capaciti~ loads of SOOpF without deterioration in settling time. Larger capacitive loads can be driven by tailoring the compensation to minimize settling time. 3. Common Mode Rejection, Gain and Noise are compatible with a 0.01 % accuracy device. 4. The ADSO9K and ADSO9S are 100% tested for minimum slew rate and guaranteed to settle to 0.01% of its final value in less than 2.Slls. TE -1- ANALOGDEVICES fAX-ON-DEMAND HOTLINE - Page 13 ,. AD509-SPECIFICATIONS andVs= %15Vdeunless (@ %25°& Model OPEN LOOP GAIN Vo = :t10V,RL2:2kO TmiDtoT...,RL '" 2kO OUTPUT CHARACTERISTICS Voltage@RL = 2k.O,T....D[oTFREQUENCY RESPONSE Unity teed, SpecifJCaDoaSshown ill boldface are tared on all 'prodUCtion units at fmal dectric:aI tat. Results from t~ tests are used to calculate outgoing quality Ie¥$. ORDERING GUIDE Model AD509JH , AD509KH AD509SH Temperature Range DoCto +70°C DoCto + 70°C -55"C to +12S"C Package Option* H-o8A H-o8A H-o8A "H-O8A = TO-99 Style Metal Can. For outline information see Package Information section. -2- ANALOGDEVICES fAX-ON-DEMAND HOTLINE - Page 1~ " Applying AD509 the APPLYING THE ADS09 MEASURING SETTLING TIME. Settling time is defined as that period required for an amplifier output to swing from 0 volts to full scale, usually 10 voltS, and to settle to within a specified percentage of tbe final output voltage. For high accuracy systems, the accuracy requirement is normally specified as either 0.1'.16(lo-bit accuracy) or 0.01'.16(12-bit accuracy) of the 10 volt output level. The settling time perioo is comprised of an initial propagation delay, an additional time for the amplifier to slew to the vicinity of 10 volts, and a final time period to'recover from internal saturation and other effects, and settle within the specified error band. Because settling time depends on both .linear and nonlinear factors, there is no simple approach to predicting itS final value to different levels of accuracy, ]n particular, extremely high slew rates do not assure a rapid scnling time, since this is only one of many factors affecting settling time. In most high speed. amplifiers, after the amplifier has slewed to the vicinity of tbe final output voltage, it must recover from internal saturation and then allow any overshoot and ringing to damp out. These definitions are illustrated in Figure 1. EIN) of a typical display. The resultant waveform of (Eo ADS09 is shown in Figure 3. Note that the waveform crosses the 1mV point representing 0.01 % ac~uracy in approximately l.S/JS. The top trace represents the output signal; the bottom trace represents the error signal. - OUTPUT I II i .0 . ,.. ERROR SIGNAL -- t ....1--r11m' T n. OBS E::~~{r!~~~!~~~:~=:===~--,-Eo - AE DEAO TIME Figure 3. Settling Time of AD509 OLE OIJTP\IT I SETTLING TIME VS. Rf AND Ri. Settling time of an amplifier is a function of the feedback and input resistors, since they interact with the input capacitance of the amplifier. When operating in the non-inverting mode, the source impedance should be kept relatively low; e.g., Sill; in order to insure optimum performance. The small feedback capacitor (SpF) is used in the settling time test circuit in parallel with tbe feedback resistor to reduce ringing. This capacitor partially cancels the pole formed in the loop gain response as a result of the feedback and input resistors, and the input capacitance. SETTLING TIME VS. CAPACIT]VE LOAD. The ADS09 will drive capacitive loads of SOOpF without appreciable deterioration in settling time. Larger capacitive loads can be dtiven by tailoring the compensation to minimize settling time, Figure 4 shows the settling time of a typical ADS09, compensated for unity gain witb a 1SpF capacitOr, with a SOOpF capacitive load on the output. Note that settling time to 0.01 % is still under 2.01-15. j SLEWING IRECOIIERYLINEAR SETTLING I ~ TE , m t -SETTLING TIME To1:..:lE-1 OR .:!:~: x100% Figure 1. Settling Time The AD509K and AD509S are guaranteed to settle to 0.1% in SOOnsand 0.01" in 2.S/JS when tested as shown in Figure 2. There is no appreciable degradation in settling time when the capacitive load is increa.scd to 500pF, as discussed below. The settling time is computed by summing the output and the input into a differential amplifier, which then drives a scope I 1/ i, i- no - ERROR SIGNAL f1$ Figure 4. AD509 with 500pF Capacitive Load 5f>f DECOUI'lING CAPACITORS OMITTED fOR CLARITY SCOI'£ fin Figure 2. AD509 Settling Time Test Circuit -3- SUGGESTIONS FOR MINIMIZING SETTL]NG TIME. The ADS09 has been designed to settle to 0.01 % accuracy in 1 to 2.S/JS. However, this amplifier is only a building block in a circuit that also has a feedback network, input and output connections, power supply connections, and a number of external componentS. What has been painsta.kingly gained in amplifier design can be lost without careful circuit design, Some of the elements of a good high speed design are.......... CONNECTIONS. It is essential that care be taken in the. signal and power ground circuits to avoid inducing or generating extraneous voltages in the ground signal paths. ANALOGDEVICES fAX-ON-DEMAND HOTLINE - Page 15 " AD509 The O.lIlF cetatnic power supply bypass capacitors are considerably more important for the AD509 than for low frequency general purpose amplifiers. Their main purpose is to convert the distributed high frequency ground to a 'lumped singJe point (the V+ point). The V+ to V- O.lIlF capacitor equalizes the supply grounds while the O.lIlF capacitor from V+ to signal ground should be returned to signal common. The signal common, which is bypassed to pin 7, is defined as that point at which the input signal source, tltc feedback network, and tbe retUrn side of the load are joined to the power common, Note that the diagram shows each individual capacitor directly connected to the appropriate terminal (pin 7 [V+). [n addition, it is suggested that all connections be sbort and direct, and as physically dose to the case as possible, so that the length of any conducting path shared by external components will be minimized. . COMPONENTS. Resistors are preferably metal fIlm types. because they have less capacitance and stray inductance than wire wound types, and are available with excellent accuracies and temperatUre coefficients. Diodes are hot carrier types for the very fastest-settling applications, but lN914 types are suitable for more routine uses. Capacitors in critical locations are polystyrene, teflon, or polycarbonate to minimize dielectric absorption. CIRCUIT. For the fastest settling times, keep leads short, orient components to minimize stray capacitance, keep circuit impedance levels as low as consistent with the output capabilities of the amplifier and the signal source, reduce all extemalload capacitances to the absolute minimum. Don't overlook sockets or printed circuit board mounting as possible sources of dielectric absorption. Avoid pole-zero mismatches in any feedback networks used with the amplifier. Minimize noise pickup, OBS INVERTING INPUT TO SIGNAL COMMON POINT OUTPUT _INVERTING INPUT O.,..F CEIlAMIe OISe Figunt 5. Configuration for Unity Gain Applications DYNAMIC RESPONSE OF ADS09 120 ,100 8' ..! 10 ~:i ~ ... z'" 80