N Comlinear CLC532 High-Speed 2:1 Analog Multiplexer General Description Features The CLC532 is a high-speed 2:1 multiplexer with active input and output stages. The CLC532 also employs a closed-loop design which dramatically improves accuracy. This monolithic device is constructed using an advanced high-performance bipolar process. ■ ■ ■ ■ ■ The CLC532 has been specifically designed to provide settling times of 17ns to 0.01%. This, coupled with the adjustable noisebandwidth, makes the CLC532 an ideal choice for infrared and CCD imaging systems. Channel-to-channel isolation is better than 80dB @ 10MHz. Low distortion (80dBc) and spurious signal levels make the CLC532 a very suitable choice for both I/Q processors and receivers. 12-bit settling (0.01%) - 17ns Low noise - 32µVrms High isolation - 80dB @ 10MHz Low distortion - 80dBc @ 5MHz Adjustable bandwidth - 190MHz (max) Applications ■ ■ ■ ■ ■ Infrared system multiplexing CCD sensor signals Radar I/Q switching High definition video HDTV Test and calibration Comlinear CLC532 High-Speed 2:1 Analog Multiplexer August 1996 The CLC532 is offered over both the industrial and military temperature ranges. The Industrial versions, CLC532AJP\AJE\AID, are specified from -40°C to +85°C and are packaged in 14-pin plastic DIP's, 14-pin SOIC's and 14-pin Side-Brazed packages. The extended temperature versions, CLC532A8B/A8D/A8L-2, are specified from -55°C to +125°C and are packaged in a 14-pin hermetic DIP and 20-terminal LCC packages. (Contact factory for LCC and CERDIP availability.) Ordering Information ... -40oC -40oC -40oC -55oC -55oC +85oC +85oC +85oC +125oC +125oC 14-pin plastic DIP 14-pin plastic SOIC dice dice, MIL-STD-833 14-pin CERDIP; MIL-STD-883 14-pin Side-Brazed; CLC532A8D -55oC to +125oC MIL-STD-883 CLC532A8L-2A -55oC to +125oC 20-terminal LCC; MIL-STD-883 Contact factory for other packages and DESC SMD number. CCOMP1 2 INA 1 RIN 12 CLC532 CHANNEL B 4 INB 3 10 11 6 DREF VOUT 8 7 6 5 4 9 SELECT 10 RL 7 CCOMP2 RIN DREF GND CHANNEL A NC 20-Terminal LCC INB Typical Application NC to to to to to DGND CLC532AJP CLC532AJE CLC532ALC CLC532AMC CLC532A8B NC 11 TOP VIEW VEE 12 13 VEE COMP1 NC OUTPUT Printed in the U.S.A. NC 1996 National Semiconductor Corporation 1 14 +VCC 3 INA INA 2 13 +VCC 2 GND 1 NC GND 3 12 COMP1 INB 4 11 OUTPUT DGND 5 10 COMP2 DREF 6 9 VEE SELECT 7 8 VEE cc COMP2 SELECT OUTPUT 1 Channel A 0 Channel B GND INDEX CORNER 20 +Vcc 19 +V 14 15 16 17 18 CHANNEL SELECT Pinout DIP & SOIC http://www.national.com Electrical Characteristics (++V Ω; RL=500Ω Ω; CCOMP=10pF; ECL Mode, pin 6 = NC) =+ +5.0V; -VEE=-5.2V; RIN=50Ω CC PARAMETER1 Case Temperature Case Temperature FREQUENCY DOMAIN PERFORMANCE ✝ -3dB bandwidth -3dB bandwidth ✝ gain flatness peaking rolloff linear phase deviation differential gain differential phase crosstalk rejection TIME DOMAIN PERFORMANCE rise and fall time settling time 2V step; from 50% VOUT overshoot slew rate SWITCH PERFORMANCE channel to channel switching time (2V step at output) switching transient MAX/MIN RATINGS2 -55°C +25°C +125°C -40°C +25°C +85°C CONDITIONS CLC532A8B/A8D/A8L-2A CLC532AJP/AJE/AIB/AID TYP +25°C +25°C UNITS SYMBOL VOUT<0.1Vpp VOUT=2Vpp VOUT<0.1Vpp 0.1MHz to 200MHz 0.1MHz to 100MHz dc to 100MHz CCOMP = 5pF; RL=150Ω CCOMP = 5pF; RL=150Ω 2Vpp, 10MHz 2Vpp, 20MHz 2Vpp, 30MHz 190 45 140 35 140 35 110 30 MHz MHz SSBW LSBW 0.2 1.0 2.0 0.05 0.01 80 74 68 0.7 1.8 0.7 1.8 0.8 2.6 75 69 63 75 69 63 74 68 62 dB dB deg % deg dB dB dB GFP GFR LPD DG DP CT10 CT20 CT30 ns ns ns ns ns % V/µs TRS TRL TS14 TSP TSS OS SR 0.5V step 2V step ±0.0025% ±0.01% ±0.1% 2.0V step 2.7 10 35 17 13 2 160 3.3 12.5 3.3 12.5 3.8 14.5 24 18 5 130 24 18 5 130 27 21 6 110 50% SELECT to 10%VOUT 50% SELECT to 90%VOUT 5 15 30 7 20 7 20 8 23 ns ns mV SWT10 SWT90 ST DISTORTION AND NOISE PERFORMANCE ✝ 2nd harmonic distortion 2Vpp, 5MHz ✝ 3rd harmonic distortion 2Vpp, 5MHz equivalent input noise spot noise voltage >1MHz integrated noise 1MHz to 100MHz spot noise current 80 86 67 68 67 68 67 68 dBc dBc HD2 HD3 3.1 32 3 42 42 46 nV/√Hz µVrms pA/√Hz SNF INV SNC STATIC AND DC PERFORMANCE * analog output offset voltage temperature coefficient analog output offset voltage matching * analog input bias current temperature coefficient analog input bias current matching analog input resistance analog input capacitance * gain accuracy gain matching integral endpoint non-linearity output voltage output current output resistance 1 15 TBD 50 0.3 TBD 200 2 0.998 TBD 0.02 ±3.4 45 1.5 6.5 90 3.5 5.5 20 250 2.0 120 120 0.8 90 3.0 0.988 120 2.5 0.988 120 2.5 0.988 0.05 2.4 20 4.0 0.03 2.8 30 2.5 0.03 2.8 30 2.5 mV µV/°C mV µA µA/°C µA kΩ pF V/V V/V %FS V mA Ω VOS DVIO VOSM IBN DIBN IBNM RIN CIN GA GAM ILIN VO IO RO 14 50 -1.1 -1.5 50 270 -1.1 -1.5 30 110 -1.1 -1.5 30 110 V V µA µA VIH1 VIL1 IIH1 IIL1 14 50 2.0 0.8 50 270 2.0 0.8 30 110 2.0 0.8 30 110 V V µA µA VIH2 VIL2 IIH2 IIL2 30 31 28 30 25 26 60 64 64 mA mA mW dB ICC IEE PD PSRR ±2V ±2V ±1V (full scale) no load dc DIGITAL INPUT PERFORMANCE ECL mode (pin 6 floating) input voltage logic HIGH input voltage logic LOW input current logic HIGH input current logic LOW TTL mode (pin 6 = +5V) input voltage logic HIGH input voltage logic LOW input current logic HIGH input current logic LOW POWER REQUIREMENTS * supply current (+VCC = +5.0V) * supply current (-VEE = -5.2V) nominal power dissipation * power supply rejection ratio no load no load no load 23 24 240 73 Min/max ratings are based on product characterization and simulation. Individual parameters are tested as noted. Outgoing quality levels are determined from tested parameters. http://www.national.com 2 Absolute Maximum Ratings3 Recommended Operating Conditions positive supply voltage (+VCC) negative supply voltage (-VEE) differential voltage between any two GND’s analog input voltage range SELECT input voltage range (TTL mode) SELECT input voltage range (ECL mode) CCOMP range2 thermal data 14-pin plastic 14-pin Cerdip 14-pin Side-Brazed 14-pin SOIC 20-terminal LCC θJC(°C/W) 35 positive supply voltage (+VCC) negative supply voltage (-VEE) differential voltage between any two GND’s analog input voltage range digital input voltage range output short circuit duration (output shorted to GND) junction temperature operating temperature range CLC532AJP/AJE/AIB/AID CLC532A8B/A8D/A8L-2A storage temperature range lead solder duration (+300°C) +5V -5.2V or -5.0V 10mV ±2V 0.0V to +3.0V -2.0V to 0.0V 0pF to 100pF θCA(°C/W) 75 75 75 100 Note 1:Test levels are as follows: * AI, AJ : 100% tested at +25°C, sample at +85°C. ✝ AJ : Sample tested at +25°C. ✝ AI : 100% tested at +25°C. * A8 : 100% tested at +25°C, -55°C, +125°C. ✝ A8 : 100% tested at +25°C, sample at -55°C, +125°C -0.5V to +7.0V +0.5V to -7.0V 200mV -VEE to +VCC -VEE to +VCC Infinite +175°C -40°C to +85°C -55°C to +125°C -65°C to +150°C 10 sec Note 2: The CLC532 does not require external CCOMP capacitors for proper operation. Note 3: Absolute maximum ratings are limiting values, to be applied individually, and beyond which the serviceability of the circuit may be impaired. Functional operability under any of these conditions is not necessarily implied. Exposure to maximum ratings for extended periods may affect device reliability. Switching Transient Timing Diagram System Timing Diagram SETTLING ERROR WINDOW A A SELECT SELECT B B TSx SWT90 SWT10 TRx TRx ST 90% OUTPUT 10% ~ ~ 2ns OUTPUT OS CHANNEL A = +1V CHANNEL B = -1V Channel A = 0V Channel B = 0V ... where TSx is TS14 or TSP or TSS, and TRx is TRS ro TSL. Package Dimensions 3 http://www.national.com CLC532 Electrical Characteristics (+25 C unless specified) ° http://www.national.com 4 CLC532 Electrical Characteristics (+25 C unless specified) ° 5 http://www.national.com Applications Information Operation The CLC532 is a 2:1 analog multiplexer with high-impedance buffered inputs, and a low-impedance, low-distortion, output stage. The CLC532 employs a closed-loop design, which dramatically improves accuracy. The channel SELECT control (Figure 1) determines which of the two inputs (INA or INB) is present at the OUTPUT. Beyond the basic multiplexer function, the CLC532 offers compatibility with either TTL or ECL logic families, as well as adjustable bandwidth. CLC532 6 Figure 3: TTL/CMOS Level Channel SELECT Configuration CHANNEL A Compensation The CLC532 incorporates compensation nodes that allow both its bandwidth and its settling time/slew rate to be adjusted. Bandwidth and settling time/slew adjustments are linked, meaning that lowering the bandwidth also lowers slew rate and lengthens settling time. Proper adjustment (compensation) is necessary to optimize system performance. Time Domain applications should generally be optimized for lowest RMS noise at the CLC532 output, while maintaining settling time and slew rates at adequate levels to meet system needs. Frequency Domain applications should generally be optimized for maximally flat frequency response. CCOMP1 13 14 12 11 CLC532 4 INB 3 RIN 10 5 7 8 R2 R1 0.1 µ F CHANNEL B +5V A/B +6.8 µ F RIN DREF 7 +5V R3 CHANNEL SELECT +5V 2 INA 1 TTL CMOS 620 Ω 3.6k Ω 200 Ω 510 Ω 510 Ω 680 Ω R3 R2 R1 9 VOUT 6 RL DREF CCOMP2 DGND Figure 4 below describes the basic relationship between bandwidth and RS for various values of load capacitance, CL, where CCOMP = 10pF. +6.8 µ F CHANNEL SELECT 0.1µF 100 Figure 1: Standard CLC532 Circuit Configuration Digital Interface and Channel SELECT The CLC532 functions with ECL, TTL and CMOS logic families. DREF controls logic compatibility. In normal operation, DREF is left floating, and the channel SELECT responds to ECL level signals, Figure 2. For TTL or CMOS level SELECT inputs (Figure 3), DREF should be tied to +5V (the CLC532 incorporates an internal 2300Ω series isolation resistor for the DREF input). For TTL or CMOS operation, the channel SELECT requires a resistor input network to prevent saturation of the channel select circuitry. Without this input network, channel SELECT logic levels above 3V will cause internal junction saturation and slow switching speeds. 50Ω 50Ω To ECL Gate R2 40 30 Ts 20 30 0.01% 20 10 0.05% 0 1000 100 C L (pF) OUTPUTNOISERMS = (nV)(√1.57*BW-3dB) where... nV = input spot noise voltage; BW-3dB = Bandwidth is from figure 5. 200 180 160 140 120 100 80 60 40 20 0 81Ω 130 Ω -5.2V Figure 2: ECL Level Channel SELECT Configuration http://www.national.com 50 40 Figure 5 shows the resulting changes in bandwidth and slew rate for increasing values of CCOMP . The RMS noise at the CLC532 output can be approximated as: To SELECT -2V 60 50 Figure 4: Settling Time and RS vs. CL DREF (NC) R1 70 60 1 Thevinen Equivalent Output Termination A/B 80 2V Output Step Rs 70 90 1kΩ Slew Rate -3dB Bandwidth 1 10 Ccomp (pF) 200 180 160 140 120 100 80 60 40 20 Slew Rate (V/µs) ECL GATE CL 0 6 CHANNEL SELECT 80 10 CLC532 7 SELECT Rs Recommended R s (Ω ) S e t t l i n g t i m e , Ts ( n s ) -5.2V 100 90 100 Figure 5: CCOMP for Maximally Flat Frequency Response 6 Use of "small" value input termination resistors will also improve channel-to-channel isolation. However, extremely low values (<25Ω) tend to stress the driving source's ability to provide a high-quality input signal to the CLC532. Higher values tend to aggravate any layout dependent crosstalk. 75Ω to 50Ω is a reasonable target, but the lower the better. Power Supplies and Grounding Proper power supply bypassing and grounding is essential to the CLC532’s operation. A 0.1µF to 0.01mF ceramic chip capacitor should be located as close as possible to the individual power supply pins. Larger +6.8µF tantalum capacitors should be used within a few inches of the CLC532. The ground connections for these larger by-pass capacitors should be very symmetrically located relative the CLC532 output load ground connection. Harmonic distortion can be heavily influenced by non-symmetric decoupling capacitor grounding. The smaller chip capacitors located directly at the power supply pins are not particularly susceptible to this effect. Combining Two Signals in ADC Applications The CLC532 is applicable in a wide range of circuits and applications. A classic example of this flexibility is combining two or more signals for digitization by an analog-to-digital converter (ADC). A clear understanding of both the multiplexer and the ADC's operation is needed to optimize this configuration. Separation of analog and digital ground planes is not recommended. In most cases, a single low-impedance ground plane will provide the best performance. In those special cases requiring separate ground planes, the following table indicates the signal and supply ground connections. Pin 1,3 5 To obtain the best performance from the combination, the output of the CLC532 must be an accurate representation of the selected input during the ADC conversion cycle. The time at which the ADC samples the input varies with the type of ADC that is being used. Functions Ground Return Shield /Supply Returns Supplies and Inputs DREF Ground DREF Currents Only Subranging ADCs usually have a Track-and-Hold (T/H) at their input. For a successful combination of the multiplexer and the ADC, the multiplexer timing and the T/H timing must be compatible. When the ADC is given a convert command, the T/H transitions from Track mode to Hold mode. The delay between the convert command and this transition is usually specified as Aperture Delay or as Sampling Time Offset. Input Shielding The CLC532 has been designed for use in high-speed widedynamic range systems. Guard-ring traces and the use of the ground pins separating the analog inputs are recommended to maintain high isolation (Figure 6). Likely sources of noise and interference that may couple onto the inputs, are the logic signals and power supplies to the CLC532. Other types of clock and signal traces should not be overlooked, however. Channel A Connector To maximize the time that the multiplexer output has to settle, and that the T/H has to acquire the signal, the multiplexer should begin its transition from one input to the other immediately after the T/H transition into HOLD mode. Unfortunately it is during the initial portion of the HOLD period that a subranging ADC performs analog processing of the sampled signal. High slew rate transitions on the input during this time may have a detrimental effect on the conversion accuracy. Pin 1 Chip Resistors To minimize the effects of high input slew rates, two strategies that can employed. Strategy one applies when the sample rate of the system is below the rated speed of the ADC. Here the CLC532 SELECT timing is delayed until after the multiplexer transition takes place, and after the A/D has completed one conversion cycle and is waiting for the next convert command. As an example, if a CLC935 (15MSPS) ADC is being used at 10MSPS, the conversion takes place in the first 67ns after the CONVERT command. The next 33ns are spent waiting for the next CONVERT command, and would be an ideal place to switch the multiplexer from one channel to the next. Channel B Connector Figure 6: Alternate Layout Using Guard Ring The general rule in maintaining isolation has two facets, minimize the primary return ground current path impedances back to the respective signal sources, while maximizing the impedance associated with common or secondary ground current return paths. Success or failure to optimize input signal isolation can be measured directly as the isolation between the input channels with the CLC532 removed from circuit. The channel-to-channel isolation of the CLC532 can never be better than the isolation level present at its inputs. 50 45 Ccomp (pF) 40 Special attention must be paid to input termination resistors. Minimizing the return current path that is common to both of the input termination resistors is essential. In the event that a ground return current from one input termination resistor is able to find a secondary path back to its signal source (which also happens to be common with either the primary or secondary return path for the second input termination resistor), a small voltage can appear across the second input termination resistor. The small voltage seen across the second input termination resistor will be highly correlated with the signal generating the initial return currents. This situation will severely degrade channel-to-channel isolation at the input of the CLC532, even if the CLC532 were removed from circuit. Poor isolation at the input will be transmitted directly to the output. 35 30 25 20 15 10 5 10 11 12 13 14 15 16 17 Sample Rate (MSPS) 18 19 20 Figure 7: Recommended CCOMP vs. ADC Sample Rate The second optimization strategy involves lowering the slew rate at the input of the ADC so that fewer high frequency components are available to feed through to the hold capacitor during HOLD 7 http://www.national.com mode. The CLC532 output signal can be slew limited by using its compensation capacitors. This approach also has the advantage of limiting the excess noise passed through the CLC532 and on to the ADC. Figure 7 shows the recommended CCOMP values as a function of ADC Sample rate. Since the optimal values will change from one ADC to the next, this graph should be used as a starting point for CCOMP selection. Both CCOMP capacitors should be the same value to maintain output symmetry. +1 INA RECTIFIER INPUT RL INB -1 Flash ADCs are similar to subranging ADCs in that the sampling period is very brief. The primary difference is that the acquisition time of a flash converter is much shorter than that of a subranging ADC. With a flash ADC, the transition of the CLC532 output should be after the sampling instant ("Aperture Delay" after the CONVERT command). It is only during this period that a flash converter is susceptible to interference from a rapidly changing analog input signal. VOUT CLC532 10114 +20 50Ω 0.1µF VBB 50Ω 50Ω 50Ω -2V Gain Selection for an ADC In many applications, such as RADAR, the dynamic range requirements may exceed the accuracy requirements. Since wide dynamic range ADCs are also typically highly accurate ADCs, this often leads the designer into selecting an ADC which is a technical overkill and a budget buster. By using the CLC532 as a selectable-gain stage, a less expensive ADC can be used. As an example, if an application calls for 80dB of dynamic Range and 0.05% accuracy, rather than using a 14-bit converter, a 12bit converter combined with the circuit in figure 8 will meet the same objective. The CLC532 is used to select between the analog input signal and a version of the input signal attenuated by 12dB. This circuit affords 14-bit dynamic range, 12-bit accuracy and 12-bit ease of implementation. Zero Crossing Treshold Detector Figure 9: Low Distortion Full Wave Rectifier Use of the CLC532 as a Mixer. A double balanced mixer, such as is shown in figure 10, operates by multiplying the RF input by the LO input. This is done by using the LO to select one of two paths through a diode bridge depending upon the LO sign. The result is an output where IF=RF when LO>0 and IF=-RF if LO<0. This same result can be obtained with the circuit shown in figure 11. The CLC532 based circuit uses a digital LO making system design easier in those cases where the LO is digitally derived. One advantage of the CLC532 based approach is excellent isolation between all three ports. Also see the RF design awards article by Thomas Hack in the January 1993 issue of RF Design. +5V +6.8µ F LO INPUT 0.1µ F To 0Ω Input Source 50 Ω R7 2 INA 1 10pF 13 14 12 200 Ω R6 66.6 Ω R INB To 50 Ω Source 11 48.7 Ω CLC532 4 IN 3 B RF INPUT 10 5 7 8 9 6 To 50 Ω Load IF OUTPUT R OUT Figure 10: Typical Double-Balanced Mixer DREF 10pF DGND 50 Ω MINI-CIRCUITS T4-1T +6.8 µ F Gain SELECT RF INPUT 0.1µF INA IF OUTPUT 200Ω -5.2V INB Figure 8: Selectable Gain Stage Improves ADC Dynamic Range RL DIGITAL LO INPUT Full Wave Rectifier Circuit The use of a diode rectifier provides significant distortion for signals that are small compared to the forward bias voltage. Accordingly, when low distortion performance is needed, standard diode based circuits do not work well. The CLC532 can be configured to provide a very low distortion full wave rectifier. The circuit in figure 9 is used to select between an analog input signal and an inverted version of the input signal. The resulting output exhibits very little distortion for small scale signals up to several hundred kilohertz. http://www.national.com CLC532 Figure 11: High-Isolation Mixer Implementation Evaluation Board An evaluation board (part number 730028) for the CLC532 is available. This board can be used for fast, trouble-free, evaluation and characterization of the CLC532. Additionally, this board serves as a template for layout and fabrication information. The CLC532 evaluation board data sheet is available from Comlinear. 8 This page intentionally left blank. 9 http://www.national.com This page intentionally left blank. 10 http://www.national.com This page intentionally left blank. 11 http://www.national.com Comlinear CLC532 High-Speed 2:1 Analog Multiplexer Customer Design Applications Support National Semiconductor is committed to design excellence. For sales, literature and technical support, call the National Semiconductor Customer Response Group at 1-800-272-9959 or fax 1-800-737-7018. Life Support Policy National’s products are not authorized for use as critical components in life support devices or systems without the express written approval of the president of National Semiconductor Corporation. As used herein: 1. Life support devices or systems are devices or systems which, a) are intended for surgical implant into the body, or b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. N National Semiconductor Corporation National Semiconductor Europe National Semiconductor Hong Kong Ltd. National Semiconductor Japan Ltd. 1111 West Bardin Road Arlington, TX 76017 Tel: 1(800) 272-9959 Fax: 1(800) 737-7018 Fax: (+49) 0-180-530 85 86 E-mail: europe.support.nsc.com Deutsch Tel: (+49) 0-180-530 85 85 English Tel: (+49) 0-180-532 78 32 Francais Tel: (+49) 0-180-532 93 58 Italiano Tel: (+49) 0-180-534 16 80 13th Floor, Straight Block Ocean Centre, 5 Canton Road Tsimshatsui, Kowloon Hong Kong Tel: (852) 2737-1600 Fax: (852) 2736-9960 Tel: 81-043-299-2309 Fax: 81-043-299-2408 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. http://www.national.com 12 Lit #150532-002