LMH6514 600 MHz, Digital Controlled, Variable Gain Amplifier General Description Features The LMH6514 is a high performance, digitally controlled variable gain amplifier (DVGA). It combines precision gain control with a low noise, ultra-linear, differential amplifier. Typically, the LMH6514 drives a high performance ADC in a broad range of mixed signal and digital communication applications such as mobile radio and cellular base stations where automatic gain control (AGC) is required to increase system dynamic range. When used in conjunction with a high speed ADC, system dynamic range can be extended by up to 42 dB. The LMH6514 has a differential input and output allowing large signal swings on a single 5V supply. It is designed to accept signals from RF elements and maintain a terminated impedance environment. The input impedance is 200Ω resistive. The output impedance is either 200Ω or 400Ω and is user selectable. A unique internal architecture allows use with both single ended and differential input signals. Input signals to the LMH6514 are scaled by a highly linear, digitally controlled attenuator with seven accurate 6 dB steps. The attenuator output provides the input signal for a high gain, ultra linear differential transconductor. The transconductor differential output current can be converted into a voltage by using the on-chip 200Ω or 400Ω loads. The transconductance gain is 0.1 Amp/Volt resulting in a maximum voltage gain of +32 dB when driving a 200Ω load, or 38 dB when driving the 400Ω load. On chip digital latches are provided for local storage of the gain setting. The gain step settling time is 5 ns and care has been taken to reduce the sensitivity of bandwidth and phase to gain setting. The LMH6514 operates over the industrial temperature range of −40°C to +85°C. The LMH6514 is available in a 16-Pin, thermally enhanced, LLP package. ■ ■ ■ ■ ■ ■ ■ ■ Adjustable gain with a 42 dB range Precise 6.02 dB gain steps Parallel 3 bit gain control On chip register gain setting Fully differential signal path Single ended to differential capable 200Ω input impedance Small footprint (4 mm x 4 mm) LLP package Key Specifications ■ ■ ■ ■ ■ ■ ■ 600 MHz bandwidth at 100Ω load 39 dBm OIP3 at 75 MHz, 200Ω load 26 dB to 38 dB maximum gain Selectable output impedance of 200Ω or 400Ω. 8.3 dB noise figure 5 ns gain step switching time 100 mA supply current Applications ■ ■ ■ ■ ■ ■ Cellular base stations IF sampling receivers Instrumentation Modems Imaging Differential line receiver Typical Application 30042901 LMH™ is a trademark of National Semiconductor Corporation. © 2008 National Semiconductor Corporation 300429 www.national.com LMH6514 600 MHz, Digital Controlled, Variable Gain Amplifier January 24, 2008 LMH6514 Storage Temperature Range Soldering Information Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Human Body Model Machine Model Positive Supply Voltage (Pin 3) Output Voltage (Pin 14,15) Differential Voltage between Any Two Grounds Analog Input Voltage Range Digital Input Voltage Range Output Short Circuit Duration (one pin to ground) Junction Temperature Infrared or Convection (20 sec) Wave Soldering (10 sec) Operating Ratings 2 kV 150V −0.6V to 5.5V −0.6V to 6.8V <200 mV −0.6V to VCC −0.6V to 3.6V Infinite +150°C 5V Electrical Characteristics −65°C to +150°C 235°C 260°C (Note 1) Supply Voltage (Pin 3) Output Voltage Range (Pin 14, 15) Differential Voltage Between Any Two Grounds Analog Input Voltage Range, AC Coupled Temperature Range (Note 3) 4V to 5.25V 1.4V to 6.4V ±1.4V −40°C to +85°C Package Thermal Resistance (θJA) 16-Pin LLP 47°C/W <10 mV (Note 4) The following specifications apply for single supply with VCC = 5V, Maximum Gain , RL = 100Ω (200Ω external || 200Ω internal), VOUT = 2 VPP, fin = 150 MHz. Boldface limits apply at temperature extremes. Symbol Parameter Conditions Min (Note 6) Typ (Note 5) Max (Note 6) Units Dynamic Performance SSBW −3 dB Bandwidth Average of all Gain Settings 600 f = 75 MHz, V OUT = 2 VPP −70 f = 150 MHz, V OUT = 2 VPP −66 f = 250 MHz, V OUT = 2 VPP −60 f = 450 MHz, V OUT = 2 VPP −52 Output Third Order Intercept Point f = 75 MHz, V OUT = 2 VPP, Tone Spacing = 0.5 MHz 35 MHz Noise and Distortion Third Order Intermodulation Products OIP3 P1 dB Output Level for 1 dB Gain Compression f = 150 MHz, V OUT = 2 VPP, Tone Spacing = 2 MHz 33 f = 250 MHz, V OUT = 2 VPP, Tone Spacing = 2 MHz 31 f = 75 MHz, RL= 200Ω, V OUT = 2 VPP Tone Spacing = 0.5 MHz 39 f = 150 MHz, RL = 200Ω, V OUT = 2 VPP, Tone Spacing = 2 MHz 37 f = 250 MHz, RL = 200Ω, V OUT = 2 VPP, Tone Spacing = 2 MHz 34 f = 75 MHz, R L = 200Ω 16.7 f = 250 MHz, R L = 200Ω 14.7 f = 75 MHz 14.5 f = 450 MHz 13.2 dBc dBm dBm VNI Input Noise Voltage Maximum Gain, f = 40 MHz 1.8 nV/ VNO Output Noise Voltage Maximum Gain, f = 40 MHz 36 nV/ NF Noise Figure Maximum Gain 8.3 dB Analog I/O Differential Input Resistance 165 158 188 220 230 Ω Input Common Mode Resistance 825 785 955 1120 1160 Ω www.national.com 2 Parameter Differential Output Resistance Conditions Min (Note 6) Low Gain Option Typ (Note 5) Max (Note 6) Units 186 High Gain Option 330 325 370 420 425 Ω Internal Load Resistors Between Pins 13, 14 and Pins 15, 16 165 158 187 215 225 Ω Input Signal Level (AC Coupled) Max Gain, VO = 2 VPP, RL = 1 kΩ 63 Maximum Differential Input Signal AC Coupled Input Common Mode Voltage Self Biased Input Common Mode Voltage Range Driven Externally Minimum Input Voltage Maximum Input Voltage mVPP 5.6 1.3 1.1 1.4 VPP 1.5 1.7 V 0.9 to 2.0 V DC 0 V DC 3.3 V Maximum Differential Output Voltage Swing VCC = 5V, Output Common Mode = 5V 5.5 VPP VOS Output Offset Voltage All Gain Settings −21 mV CMRR Common Mode Rejection Ratio Maximum Gain 81 dB PSRR Power Supply Rejection Ratio Maximum Gain 63 61 81 29.3 28.7 30 30.3 30.9 dB −12.75 −13.15 −12 −11.85 −11.45 dB dB Gain Parameters Maximum Gain DC, Internal RL = 186Ω, External RL = 1280Ω Minimum Gain DC, Internal RL = 186Ω, External RL = 1280Ω Gain Step Size DC 6.02 Gain Step Error DC 0.02 f = 150 MHz 0.07 Cumulative Gain Step Error DC, Gain Step 7 to Gain Step 0 −0.35 −0.50 Gain Step Switching Time 0.02 dB dB 0.30 0.45 5 dB ns Digital Inputs/Timing Logic Compatibility CMOS Logic 3.3 V VIL Logic Input Low Voltage 0.8 VIH Logic Input High Voltage V IIH Logic Input High Input Current TSU Setup Time 3 ns THOLD Hold Time 3 ns TPW Minimum Latch Pulse Width 10 ns 2.0 Digital Input Voltage = 3.3V V 33 μA 40 Power Requirements ICC Total Supply Current VOUT = 0V Differential, VOUT Common Mode = 5V 107 124 134 mA Amplifier Supply Current Pin 3 Only 56 66 74 mA Output Stage Bias Currents Pins 13, 14 and Pins 15, 16; VOUT Common Mode = 5 V 51 58 60 mA 3 www.national.com LMH6514 Symbol LMH6514 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications, see the Electrical Characteristics tables. Note 2: Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC) Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC). Note 3: The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) – TA)/ θJA. All numbers apply for packages soldered directly onto a PC Board. Note 4: Electrical Table values apply only for factory testing conditions at the temperature indicated. No guarantee of parametric performance is indicated in the electrical tables under conditions different than those tested Note 5: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material. Note 6: Limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. Note 7: Negative input current implies current flowing out of the device. Note 8: Drift determined by dividing the change in parameter at temperature extremes by the total temperature change. Connection Diagram 16-Pin LLP 30042904 Top View Gain Control Pins Pin Number Pin Name Gain Step Size 11 GAIN_0 6.02 dB 10 GAIN_1 12.04 dB 9 GAIN_2 24.08 dB Ordering Information Package 16-Pin LLP www.national.com Part Number LMH6514SQ LMH6514SQX Package Marking L6514SQ 4 Transport Media 1k Units Tape and Reel 4.5k Units Tape and Reel NSC Drawing SQA16A LMH6514 Pin Descriptions Pin Number Symbol Description 6 IN+ Non-inverting analog input. Internally biased to 1.4V. Input voltage should not exceed VCC or go below GND by more than 0.5V. 7 IN− Inverting analog input. Internally biased to 1.4V. Input voltage should not exceed VCC or go below GND by more than 0.5V. If using amplifier single ended this input should be capacitively coupled to ground. 15 OUT− Open collector inverting output. This pin is an output that also requires a power source. This pin should be connected to 5V through either an RF choke or an appropriately sized inductor that can form part of a filter. See application section for details. 14 OUT+ Open collector non-inverting output. This pin is an output that also requires a power source. This pin should be connected to 5V through either an RF choke or an appropriately sized inductor that can form part of a filter. See application section for details. 16 LOAD− Internal 200Ω resistor connection to pin 15. This pin can be left floating for higher gain or shorted to pin 13 for lower gain and lower effective output impedance. See application section for details. 13 LOAD+ Internal 200Ω resistor connection to pin 14. This pin can be left floating for higher gain or shorted to pin 16 for lower gain and lower effective output impedance. See application section for details. 3 VCC 5V power supply pin. Use ceramic, low ESR bypass capacitors. This pin powers everything except the output stage. 5,8 GND Ground pins. Connect to low impedance ground plane. All pin voltages are specified with respect to the voltage on these pins. The exposed thermal pad is also a ground connection. 11,10,9 GAIN_0 to GAIN_2 Gain setting pins. See above table for gain step sizes for each pin. These pins are 3.3V CMOS logic compatible. 5V inputs may cause damage. 2 LATCH This pin controls the function of the gain setting pins mentioned above. With LATCH in the logic HIGH state the gain is fixed and will not change. With the LATCH in the logic LOW state the gain is set by the state of the gain control pins. Any changes in gain made with the LATCH pin in the LOW state will take effect immediately. This pin is 3.3V CMOS logic compatible. 5V inputs may cause damage. 1,4,12 NC These pins are not connected. They can be grounded or left floating. Analog I/O Power Digital Inputs 5 www.national.com LMH6514 Typical Performance Characteristics VCC = 5V Frequency Response All Gain Settings Frequency Response over Temperature, Maximum Gain 30042922 30042949 Frequency Response over Temperature, Minimum Gain OIP3 High Gain Mode 30042943 30042950 OIP3 Low Gain Mode OIP3 Over Temperature 30042942 www.national.com 30042926 6 LMH6514 IMD3 Low Gain Mode IMD3 High Gain Mode 30042940 30042941 HD2 vs. Frequency HD3 vs. Frequency 30042936 30042939 HD2 vs. Frequency HD3 vs. Frequency 30042938 30042937 7 www.national.com LMH6514 Noise Figure for All Gain Settings Noise Figure vs. Frequency 30042914 30042917 Differential Output Noise Maximum Gain vs. Supply Voltage 30042918 30042927 Gain vs. External Load Maximum Gain over Temperature 30042912 www.national.com 30042944 8 LMH6514 Worst Case Gain Step Error vs Frequency Gain Steps over Temperature 30042961 30042945 Worst Case Gain Step Error over Temperature Input Impedance (S11) at Maximum Gain 30042951 30042964 Input Impedance (S11) at Minimum Gain Output Impedance (S22) at Maximum Gain Low Gain Mode 30042966 30042965 9 www.national.com LMH6514 Output Impedance (S22) at Maximum Gain High Gain Mode Digital Crosstalk 30042947 30042967 Digital Crosstalk Digital Pin to Output Isolation 30042948 30042919 Minimum Gain to Maximum Gain Switching Using Latch Pin Maximum Gain to Minimum Gain Switching Using Latch Pin 30042930 www.national.com 30042935 10 LMH6514 24 dB Gain Step 24 dB Gain Step 30042932 30042929 12 dB Gain Step 12 dB Gain Step 30042928 30042931 6 dB Gain Step 6 dB Gain Step 30042934 30042933 11 www.national.com LMH6514 Power On Timing, Maximum Gain Power On Timing, Minimum Gain 30042953 30042954 Power Off Timing, Maximum Gain Power Off Timing, Minimum Gain 30042956 www.national.com 30042955 12 LMH6514 Application Information The LMH6514 is a fully differential amplifier optimized for signal path applications up to 400 MHz. The LMH6514 has a 200Ω input. The absolute gain is load dependent, however the gain steps are always 6 dB. The LMH6514 output stage is a class A amplifier. This class A operation results in excellent distortion and linearity characteristics. This makes the LMH6514 ideal for voltage amplification and an ideal ADC driver where high linearity is necessary. 30042962 FIGURE 2. Output Voltage with Respect to the Output Common Mode In order to help with system design National Semiconductor offers the ADC14V155KDRB High IF Receiver reference design board. This board combines the LMH6514 DVGA with the ADC14V155 ADC and provides a ready made solution for many IF receiver applications. Using an IF frequency of 169 MHz it achieves a small signal SNR of 72 dBFS and an SFDR of greater than 90 dBFS. Large signal measurements show an SNR of 68 dBFS and an SFDR of 77 dBFS. The High IF Receiver board also features the LMK03000 low-jitter precision clock conditioner. 30042903 FIGURE 1. LMH6514 Typical Application The LMH6514 output common mode should be set carefully. Using inductors to set the output common mode is one preferred method and will give maximum output swing. AC coupling of the output is recommended. The inductors mentioned above will shift the idling output common mode to the positive supply. Also, with the inductors, the output voltage can exceed the supply voltage. Other options for setting the output common mode require supply voltages above 5V. If using a supply higher than 5V care should be taken to make sure the output common mode does not exceed the 5.25V supply rating. It is also important to note the maximum voltage limits for the OUT+ and OUT− pins, which is 6.4V. When using inductors these pins will experience voltage swings beyond the supply voltage. With a 5V output common mode operating point this makes the effective maximum swing 5.6 VPP differential. System calibration and automatic gain control algorithms should be tailored to avoid exceeding this limit. Figure 2 shows how output voltage and output common mode add together and approach the maximum output voltage. 30042911 FIGURE 3. LMH6514 Block Diagram INPUT CHARACTERISTICS The LMH6514 input impedance is set by internal resistors to a nominal 200Ω. Process variations will result in a range of values as shown in the 5V Electrical Characteristics table. At higher frequencies parasitics will start to impact the impedance. This characteristic will also depend on board layout and should be verified on the customer’s system board. At maximum gain the digital attenuator is set to 0 dB and the input signal will be much smaller than the output. At minimum gain the output is 4 dB or more smaller than the input. In this configuration the input signal size may limit the amplifier output amplitude, depending on the output configuration and the desired output signal voltage. The input signal cannot swing more than 0.5V below the negative supply voltage (normally 0V) nor should it exceed the positive supply voltage. The input signal will clip and cause severe distortion if it is too large. Because the input stage self biases to approximately 1.4V the lower supply voltage will impose the limit for input voltage 13 www.national.com LMH6514 swing. To drive larger input signals the input common mode can be forced higher than 1.4V to allow for more swing. An input common mode of 2.0V will allow an 8 VPP maximum input signal. The trade off for input signal swing is that as the input common mode is shifted away from the 1.4V internal bias point the distortion performance will suffer slightly. 30042969 30042907 FIGURE 6. Differential 200Ω LC Conversion Circuit FIGURE 4. Single Ended Input (Note capacitor on grounded input) In Figure 6 the input source resistance is 200Ω differential. Here the desired input impedance is higher than the amplifier input impedance, and is differential as well. The amplifier impedance of (150–j0)Ω is increased to (202–j0.5)Ω. For an easy way to calculate the L and C circuit values there are several options for online tools or down-loadable programs. The following tool might be helpful. http://www.circuitsage.com/matching/matcher2.html Excel can also be used for simple circuits; however, the “Analysis ToolPak” add-in must be installed to calculate complex numbers. At the frequencies where the LMH6514 is the most useful the input impedance is not 200 Ω and it may not be purely resistive. For many AC coupled applications the impedance can be easily changed using LC circuits to transform the actual impedance to the desired impedance. OUTPUT CHARACTERISTICS The LMH6514 has the option of two different output configurations. The LMH6514 is an open collector topology. As shown in Figure 11 each output has an on chip 200Ω pull up resistor. In addition there is an internal 400Ω resistor between the two outputs. This results in a 200Ω or a 400Ω differential load in parallel with the external load. The 400Ω option is the high gain option and the 200Ω provides for less gain. The 200Ω configuration is recommended unless more gain is required. The output common mode of the LMH6514 must be set by external components. Most applications will benefit from the use of inductors on the output stage. In particular, the 400Ω option as shown in Figure 12 will require inductors in order to be able to develop an output voltage. The 200Ω option as shown in Figure 13 or Figure 14 will also require inductors since the voltage drop due to the on chip 200Ω resistors will saturate the output transistors. It is also possible to use resistors and high voltage power supplies to set the output common mode. This operation is not recommended, unless it is necessary to DC couple the output. If DC coupling is required the input common mode and output common mode voltages must be taken into account. Maximum bandwidth with the LMH6514 is achieved by using the low gain, low impedance output option and using a low load resistance. With an effective load of 67Ω a bandwidth of nearly a 1 GHz can be realized. As the effective resistance on the output stage goes up the capacitance of the board traces and amplifier output stage limit bandwidth in a roughly linear fashion. At an output impedance of 100Ω the bandwidth is down to 600 MHz, and at 200Ω the bandwidth is 260 MHz. 30042968 FIGURE 5. Single Ended Input with LC Matching As shown in Figure 5 a single ended 50Ω source is matched to the LMH6514 input at 100 MHz. The loss in this circuit is related to the parasitic resistance in the inductor and capacitor and the bandwidth is related to the loaded Q of the circuit. Since the Q, at 1.4 is quite low, the bandwidth is very wide. (59 MHz 0.3 dB bandwidth). The input match of this circuit is quite good. It converts the ZAMP of the amplifier, which is (150 +j0)Ω to (50+j1)Ω. The benefit of LC matching circuits over a transformer is the ability to match ratios that are not commonly found on transformers and also the ability to neutralize reactance to present a purely resistive load to the voltage source. www.national.com 14 LMH6514 For this reason driving very high impedance loads is not recommended. Although bandwidth goes down with higher values of load resistance, the distortion performance improves and gain increases. The LMH6514 has a common emitter Class A output stage and minimizing the amount of current swing in the output devices improves distortion substantially. The LMH6514 output stage is powered through the collectors of the output transistors. Power for the output stage is fed through inductors and the reactance of the inductors allows the output voltage to develop. In Figure 1 the inductors are shown with a value of 44.4 nH. The value of the inductors used will be different for different applications. In Figure 1 the inductors have been chosen to resonate with the ADC and the load capacitor to provide a weak band pass filter effect. For broad band applications higher value inductors will allow for better low frequency operation. However, large valued inductors will reduce high frequency performance, particularly inductors of small physical sizes like 0603 or smaller. Larger inductors will tend to perform better than smaller ones of the same value even for narrow band applications. This is because the larger inductors will have a lower DC resistance and less inter-winding capacitance and hence a higher Q and a higher self resonance frequency. The self resonance frequency should be higher than any desired signal content by at least a factor of 2. Another consideration is that the power inductors and the filter inductors need to be placed on the circuit board such that their magnetic fields do not cause coupling. Mutual coupling of inductors can compromise filter characteristics and lead to unwanted distortion products. 30042906 FIGURE 8. Gain vs. External Load DIGITAL CONTROL The LMH6514 has eight gain settings covering a range of 42 dB. To avoid undesirable signal transients the LMH6514 should be powered on at the minimum gain state (all logic input pins at 0V). The LMH6514 has a 3-bit gain control bus as well as a Latch pin. When the Latch pin is low, data from the gain control pins is immediately sent to the gain circuit (i.e. gain is changed immediately). When the Latch pin transitions high the current gain state is held and subsequent changes to the gain set pins are ignored. To minimize gain change glitches multiple gain control pins should not change while the latch pin is low. In order to achieve the very fast gain step switching time of 5 ns the internal gain change circuit is very fast. Gain glitches could result from timing skew between the gain set bits. This is especially the case when a small gain change requires a change in state of three or more gain control pins. If continuous gain control is desired the Latch pin can be tied to ground. This state is called transparent mode and the gain pins are always active. In this state the timing of the gain pin logic transitions should be planned carefully to avoid undesirable transients. The LMH6514 was designed to interface with 3.3V CMOS logic circuits. If operation with 5V logic is required a simple voltage divider at each logic pin will allow for this. To properly terminate 100Ω transmission lines a divider with a 66.5Ω resistor to ground and a 33.2Ω series resistor will properly terminate the line as well as give the 3.3V logic levels. Care should be taken not to exceed the 3.6V absolute maximum voltage rating of the logic pins. 30042915 EXPOSED PAD LLP PACKAGE The LMH6514 is packaged in a thermally enhanced package. The exposed pad is connected to the GND pins. It is recommended, but not necessary, that the exposed pad be connected to the supply ground plane. In any case, the thermal dissipation of the device is largely dependent on the attachment of this pad. The exposed pad should be attached to as much copper on the circuit board as possible, preferably external copper. However, it is also very important to maintain good high speed layout practices when designing a system board. Please refer to the LMH6514 evaluation board for suggested layout techniques. Package information is available on the National web site. http://www.national.com/packaging/folders/sqa16a.html FIGURE 7. Bandwidth Changes Due to Different Inductor Values 15 www.national.com LMH6514 Filter Component Values INTERFACING TO ADC The LMH6514 was designed to be used with high speed ADCs such as the ADC14155. As shown in the Typical Application on page 1, AC coupling provides the best flexibility especially for IF sub-sampling applications. Any resistive networks on the output will also cause a gain loss because the output signal is developed across the output resistors. The chart Maximum Gain vs. External Load shows the change in gain when an external load is added. The inputs of the LMH6514 will self bias to the optimum voltage for normal operation. The internal bias voltage for the inputs is approximately 1.4V. In most applications the LMH6514 input will need to be AC coupled. The output common mode voltage is not self biasing, it needs to be pulled up to the positive supply rail with external inductors as shown in Figure 1. This gives the LMH6514 the capability for large signal swings with very low distortion on a single 5V supply. The internal load resistors provide the LMH6514 with very consistent gain. A unique internal architecture allows the LMH6514 to be driven by either a differential or single ended source. If driving the LMH6514 single ended the unused input should be terminated to ground with a 0.01 µF capacitor. Directly shorting the unused input to ground will disrupt the internal bias circuitry and will result in poor performance. Filter Component Values Fc 75 MHz 140 MHz BW 40 MHz 20 MHz 25 MHz Narrow Band Components L1, L2 10 µH 10 µH 170 MHz 10 µH 250 MHz 10 µH L3, L4 390 nH 39 0nH 560 nH — C1, C2 10 pF 3 pF 1.4 pF 47 pF C3 22 pF 41 pF 32 pF 11 pF L5 220 nH 27 nH 30 nH 22 nH R1, R2 100 100 499 200 30042913 FIGURE 10. Sample Filter POWER SUPPLIES As shown in Figure 11, the LMH6514 has a number of options for power supply connections on the output pins. Pin 3 (VCC) is always connected. The output stage can be connected as shown in Figure 12, Figure 13, and Figure 14. The supply voltage range for VCC is 4V to 5.25V. A 5V supply provides the best performance while lower supplies will result in less power consumption. Power supply regulation of 2.5% or better is advised. Of special note is that the digital circuits are powered from an internal supply voltage of 3.3V. The logic pins should not be driven above the absolute maximum value of 3.6V. See the Digital Control section for details. 30042906 FIGURE 9. Bandpass Filter Center Frequency is 140 MHz with a 20 MHz Bandwidth Designed for 200Ω Impedance ADC Noise Filter Below is a filter schematic and a table of values for some common IF frequencies. The filter shown below offers a good compromise between bandwidth, noise rejection and cost. This filter topology is the same as is used on the ADC14V155KDRB High IF Receiver reference design board. This filter topology works best with the 12 and 14 bit subsampling analog to digital converters shown in the Compatible High Speed Analog to Digital Converters table. www.national.com 16 LMH6514 30042902 30042909 FIGURE 11. Internal Load Resistors FIGURE 13. Using Low Gain Mode (200Ω Load) 30042908 30042910 FIGURE 14. Alternate Connection for Low Gain Mode (200Ω Load) FIGURE 12. Using High Gain Mode (400Ω Load) 17 www.national.com LMH6514 Compatible High Speed Analog to Digital Converters Product Number Max Sampling Rate (MSPS) Resolution Channels ADC12L063 62 12 SINGLE ADC12DL065 65 12 DUAL ADC12L066 66 12 SINGLE ADC12DL066 66 12 DUAL CLC5957 70 12 SINGLE ADC12L080 80 12 SINGLE ADC12DL080 80 12 DUAL ADC12C080 80 12 SINGLE ADC12C105 105 12 SINGLE ADC12C170 170 12 SINGLE ADC12V170 170 12 SINGLE ADC14C080 80 14 SINGLE ADC14C105 105 14 SINGLE ADC14DS105 105 14 DUAL ADC14155 155 14 SINGLE ADC14V155 155 14 SINGLE ADC08D500 500 8 DUAL ADC08500 500 8 SINGLE ADC08D1000 1000 8 DUAL ADC081000 1000 8 SINGLE ADC08D1500 1500 8 DUAL ADC081500 1500 8 SINGLE ADC08(B)3000 3000 8 SINGLE ADC08L060 60 8 SINGLE ADC08060 60 8 SINGLE ADC10DL065 65 10 DUAL ADC10065 65 10 SINGLE ADC10080 80 10 SINGLE ADC08100 100 8 SINGLE ADCS9888 170 8 SINGLE ADC08(B)200 200 8 SINGLE ADC11C125 125 11 SINGLE ADC11C170 170 11 SINGLE www.national.com 18 LMH6514 Physical Dimensions inches (millimeters) unless otherwise noted 16-Pin Package NS Package Number SQA16A 19 www.national.com LMH6514 600 MHz, Digital Controlled, Variable Gain Amplifier Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH www.national.com/webench Audio www.national.com/audio Analog University www.national.com/AU Clock Conditioners www.national.com/timing App Notes www.national.com/appnotes Data Converters www.national.com/adc Distributors www.national.com/contacts Displays www.national.com/displays Green Compliance www.national.com/quality/green Ethernet www.national.com/ethernet Packaging www.national.com/packaging Interface www.national.com/interface Quality and Reliability www.national.com/quality LVDS www.national.com/lvds Reference Designs www.national.com/refdesigns Power Management www.national.com/power Feedback www.national.com/feedback Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www.national.com/led PowerWise www.national.com/powerwise Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors Wireless (PLL/VCO) www.national.com/wireless THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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