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| a FEATURES Supports DOCSIS Standard for Reverse Path Transmission Gain Programmable in 0.75 dB Steps Over a 53.5 dB Range Low Distortion at 60 dBmV Output -56 dBc SFDR at 21 MHz -55 dBc SFDR at 42 MHz Output Noise Level -48 dBmV in 160 kHz Maintains 75 Output Impedance Power-Up and Power-Down Condition Upper Bandwidth: 100 MHz (Full Gain Range) 5 V Supply Operation Supports SPI Interfaces APPLICATIONS Gain-Programmable Line Driver HFC High-Speed Data Modems Interactive Set-Top Boxes PC Plug-in Modems General-Purpose Digitally Controlled Variable Gain Block VIN+ 5 V CATV Line Driver Fine Step Output Power Control AD8323 FUNCTIONAL BLOCK DIAGRAM VCC (7 PINS) BYP R1 AD8323 VOUT+ BUFFER ATTENUATION CORE VIN- DIFF OR SINGLE INPUT AMP POWER AMP VOUT- ZOUT DIFF = 75 8 R2 ZIN (SINGLE) = 800 ZIN (DIFF) = 1.6k DECODE 8 DATA LATCH 8 SHIFT REGISTER POWER-DOWN LOGIC DATEN DATA CLK GND (11 PINS) PD SLEEP GENERAL DESCRIPTION DISTORTION - dBc The AD8323 is a low-cost, digitally controlled, variable gain amplifier optimized for coaxial line driving applications such as cable modems that are designed to the MCNS-DOCSIS upstream standard. An 8-bit serial word determines the desired output gain over a 53.5 dB range resulting in gain changes of 0.7526 dB/LSB. The AD8323 comprises a digitally controlled variable attenuator of 0 dB to -53.5 dB, which is preceded by a low noise, fixed gain buffer and is followed by a low distortion high power amplifier. The AD8323 accepts a differential or single-ended input signal. The output is specified for driving a 75 load, such as coaxial cable. Distortion performance of -56 dBc is achieved with an output level up to 60 dBmV at 21 MHz bandwidth. A key performance and cost advantage of the AD8323 results from the ability to maintain a constant 75 output impedance during power-up and power-down conditions. This eliminates the need for external 75 termination, resulting in twice the effective output voltage when compared to a standard operational amplifier. In addition, this device has a sleep mode function that reduces the quiescent current to 4 mA. The AD8323 is packaged in a low-cost 28-lead TSSOP, operates from a single 5 V supply, and has an operational temperature range of -40C to +85C. -50 FO = 42MHz PO = 60dBmV @ MAX GAIN -55 -60 HD3 -65 HD2 -70 -75 0 8 16 24 32 40 48 56 GAIN CONTROL - DEC Code 64 72 Figure 1. Harmonic Distortion vs. Gain Control REV. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2000 AD8323-SPECIFICATIONS transformer with an insertion loss of 0.5 dB @ 10 MHz unless otherwise noted.) 1 (TA = 25 C, VS = 5 V, RL = RIN = 75 , VIN = 116 mV p-p, VOUT measured through a 1:1 Min Typ 116 13.8 800 1600 2 52.5 26.5 -27 53.5 27.5 -26 0.7526 100 1.3 0 -34 -48 -68 18.5 75 20% -77 -71 -64 -56 -55 -53 0.3 60 30 -30 300 40 3 30 4.75 123 30 2 -40 5 133 35 4 5.25 140 40 7 +85 54.5 28.5 -25 Max Unit mV p-p dB pF dB dB dB dB/LSB MHz dB dB dBmV in 160 kHz dBmV in 160 kHz dBmV in 160 kHz dBm dBc dBc dBc dBc dBc dBc dB ns ns dBc ns ns mV p-p mV p-p V mA mA mA C Parameter INPUT CHARACTERISTICS Specified AC Voltage Noise Figure Input Resistance Input Capacitance GAIN CONTROL INTERFACE Gain Range Maximum Gain Minimum Gain Gain Scaling Factor OUTPUT CHARACTERISTICS Bandwidth (-3 dB) Bandwidth Roll-Off Bandwidth Peaking Output Noise Spectral Density Conditions Output = 60 dBmV, Max Gain Max Gain, f = 10 MHz Single-Ended Input Differential Input Gain Code = 71 Dec Gain Code = 0 Dec All Gain Codes f = 65 MHz f = 65 MHz Max Gain, f = 10 MHz Min Gain, f = 10 MHz Power-Down Mode, f = 10 MHz 1 dB Compression Point Differential Output Impedance OVERALL PERFORMANCE Second Order Harmonic Distortion Max Gain, f = 10 MHz Power-Up and Power-Down f = 21 MHz, POUT = 60 dBmV @ Max Gain f = 42 MHz, POUT = 60 dBmV @ Max Gain f = 65 MHz, POUT = 60 dBmV @ Max Gain f = 21 MHz, POUT = 60 dBmV @ Max Gain f = 42 MHz, POUT = 60 dBmV @ Max Gain f = 65 MHz, POUT = 60 dBmV @ Max Gain f = 10 MHz, Code to Code Min to Max Gain Max Gain, VIN = 0 V to 116 mV p-p Max Gain, PD = 0, f = 42 MHz Max Gain, VIN = 0 Max Gain, VIN = 0 Equivalent Output = 31 dBmV Equivalent Output = 60 dBmV Third Order Harmonic Distortion Gain Linearity Error Output Settling to 1 mV Due to Gain Change Due to Input Step Change Signal Feedthrough POWER CONTROL Power-Up Settling Time to 1 mV Power-Down Settling Time to 1 mV Between Burst Transients2 POWER SUPPLY Operating Range Quiescent Current Power-Up Mode Power-Down Mode Sleep Mode OPERATING TEMPERATURE RANGE NOTES 1 TOKO 617DB-A0070 used for above specifications. MACOM ETC-1-IT-15 can be substituted. 2 Between Burst Transients measured at the output of a 42 MHz diplexer. Specifications subject to change without notice. -2- REV. 0 AD8323 LOGIC INPUTS (TTL/CMOS Compatible Logic) (DATEN, CLK, SDATA, PD, SLEEP, V Parameter Logic "1" Voltage Logic "0" Voltage Logic "1" Current (VINH = 5 V) CLK, SDATA, DATEN Logic "0" Current (VINL = 0 V) CLK, SDATA, DATEN Logic "1" Current (VINH = 5 V) PD Logic "0" Current (VINL = 0 V) PD Logic "1" Current (VINH = 5 V) SLEEP Logic "0" Current (VINL = 0 V) SLEEP Min 2.1 0 0 -600 50 -250 50 -250 Typ CC = 5 V: Full Temperature Range) Max 5.0 0.8 20 -100 190 -30 190 -30 Unit V V nA nA A A A A TIMING REQUIREMENTS Parameter (Full Temperature Range, VCC = 5 V, TR = TF = 4 ns, fCLK = 8 MHz unless otherwise noted.) Min 16.0 32.0 5.0 15.0 5.0 3.0 10 Typ Max Unit ns ns ns ns ns ns ns Clock Pulsewidth (TWH) Clock Period (TC) Setup Time SDATA vs. Clock (TDS) Setup Time DATEN vs. Clock (TES) Hold Time SDATA vs. Clock (TDH) Hold Time DATEN vs. Clock (TEH) Input Rise and Fall Times, SDATA, DATEN, Clock (TR, TF) TDS SDATA VALID DATA WORD G1 MSB. . . .LSB VALID DATA WORD G2 TC TWH CLK TES DATEN TEH 8 CLOCK CYCLES GAIN TRANSFER (G1) TOFF PD TGS GAIN TRANSFER (G2) TON ANALOG OUTPUT SIGNAL AMPLITUDE (p-p) PEDESTAL Figure 2. Serial Interface Timing VALID DATA BIT SDATA MSB MSB-1 MSB-2 TDS TDH CLK Figure 3. SDATA Timing REV. 0 -3- AD8323 ABSOLUTE MAXIMUM RATINGS* PIN CONFIGURATION DATEN SDATA CLK GND VCC PD SLEEP GND VCC 1 2 3 4 5 6 7 8 9 28 27 26 25 24 Supply Voltage +VS Pins 5, 9, 10, 19, 20, 23, 27 . . . . . . . . . . . . . . . . . . . . . . 6 V Input Voltages Pins 25, 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 V Pins 1, 2, 3, 6, 7 . . . . . . . . . . . . . . . . . . . . . -0.8 V to +5.5 V Internal Power Dissipation TSSOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.9 W Operating Temperature Range . . . . . . . . . . . -40C to +85C Storage Temperature Range . . . . . . . . . . . . -65C to +150C Lead Temperature, Soldering 60 seconds . . . . . . . . . . . 300C *Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. GND VCC VIN- VIN+ GND VCC AD8323 23 22 GND TOP VIEW (Not to Scale) 21 BYP 20 19 18 17 16 15 VCC VCC GND GND GND OUT+ VCC 10 GND 11 GND 12 GND 13 OUT- 14 ORDERING GUIDE Model AD8323ARU AD8323ARU-REEL AD8323-EVAL Temperature Range -40C to +85C -40C to +85C Package Description 28-Lead TSSOP 28-Lead TSSOP Evaluation Board JA Package Option RU-28 RU-28 67.7C/W* 67.7C/W* *Thermal Resistance measured on SEMI standard 4-layer board. CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD8323 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. PIN FUNCTION DESCRIPTIONS WARNING! ESD SENSITIVE DEVICE Pin No. 1 Mnemonic DATEN Description Data Enable Low Input. This port controls the 8-bit parallel data latch and shift register. A Logic 0-to-1 transition transfers the latched data to the attenuator core (updates the gain) and simultaneously inhibits serial data transfer into the register. A 1-to-0 transition inhibits the data latch (holds the previous gain state) and simultaneously enables the register for serial data load. Serial Data Input. This digital input allows for an 8-bit serial (gain) word to be loaded into the internal register with the MSB (Most Significant Bit) first. Clock Input. The clock port controls the serial attenuator data transfer rate to the 8-bit masterslave register. A Logic 0-to-1 transition latches the data bit and a 1-to-0 transfers the data bit to the slave. This requires the input serial data word to be valid at or before this clock transition. Common External Ground Reference. 2 3 SDATA CLK 4, 8, 11,12, 13, 16, 17, 18, 22, 24, 28 5, 9, 10, 19, 20, 23, 27 6 7 14 15 21 25 26 GND VCC PD SLEEP OUT- OUT+ BYP VIN+ VIN- Common Positive External Supply Voltage. A 0.1 F capacitor must decouple each pin. Logic "0" powers down the part. Logic "1" powers up the part. Low Power Sleep Mode. In the Sleep mode, the AD8323's supply current is reduced to 4 mA. A Logic "0" powers down the part (High ZOUT State) and a Logic "1" powers up the part. Negative Output Signal. Positive Output Signal. Internal Bypass. This pin must be externally ac-coupled (0.1 F cap). Noninverting Input. DC-biased to approximately VCC/2. For single-ended inverting operation, use a 0.1 F decoupling capacitor and a 39.2 resistor between VIN+ and ground. Inverting Input. DC-biased to approximately VCC/2. Should be ac-coupled with a 0.1 F capacitor. -4- REV. 0 Typical Performance Characteristics- AD8323 34 1:1 IN 31 VIN- VIN+ OUT CL RL 75 CL = 0pF POUT = 60dBmV @ MAX GAIN VCC VIN RTI 0.1 F VIN- 82.5 VIN+ 0.1 F 39.2 TOKO 617DB-A0070 1:1 GAIN - dB 0.1 F OUT- OUT+ GND 0.1 F OUT RL 75 28 25 CL = 50pF CL = 20pF CL = 10pF 22 19 1 10 FREQUENCY - MHz 100 TPC 1. Basic Test Circuit TPC 4. AC Response for Various Cap Loads 1.5 -30 f = 10MHz PD = 1 OUTPUT NOISE - dBmV in 160kHz 1.0 -34 GAIN ERROR - dB 0.5 f = 10MHz -38 0.0 f = 5MHz f = 42MHz -42 -0.5 -46 -1.0 f = 65MHz -1.5 -50 0 8 16 24 32 40 48 GAIN CONTROL - Decimal 56 64 72 0 8 16 24 32 40 48 GAIN CONTROL - Decimal 56 64 72 TPC 2. Gain Error vs. Gain Control TPC 5. Output Referred Noise vs. Gain Control 40 30 20 10 0 23D -10 -20 -30 -40 0.1 46D 71D 0 PD = 0 VIN = 116mV p-p -20 FEEDTHROUGH - dB MAX GAIN -40 GAIN - dB -60 00D -80 MIN GAIN -100 1 10 FREQUENCY - MHz 100 1k 0.1 1 10 FREQUENCY - MHz 100 1k TPC 3. AC Response TPC 6. Input Signal Feedthrough vs. Frequency REV. 0 -5- AD8323 -60 85 RTI = 82.5 -65 DISTORTION - dBc 80 POUT = 62dBmV @ MAX GAIN PD = 0 75 IMPEDANCE - -70 POUT = 61dBmV @ MAX GAIN POUT = 60dBmV @ MAX GAIN PD = 1 70 -75 65 -80 POUT = 58dBmV @ MAX GAIN -85 5 15 25 35 45 55 FUNDAMENTAL FREQUENCY - MHz 65 60 55 1 10 FREQUENCY - MHz 100 TPC 7. Second Order Harmonic Distortion vs. Frequency for Various Output Levels TPC 10. Input Impedance vs. Frequency -45 80 POUT = 62dBmV @ MAX GAIN 75 POUT = 61dBmV @ MAX GAIN 70 IMPEDANCE - -50 DISTORTION - dBc PD = 1 PD = 0 65 -55 -60 POUT = 60dBmV @ MAX GAIN 60 55 POUT = 58dBmV @ MAX GAIN -65 5 15 25 35 45 55 FUNDAMENTAL FREQUENCY - MHz 65 50 1 10 FREQUENCY - MHz 100 TPC 8. Third Order Harmonic Distortion vs. Frequency for Various Output Levels TPC 11. Output Impedance vs. Frequency 60 50 40 30 POUT - dBmV +ICC - mA 140 POUT = 60dBmV @ MAX GAIN 130 120 110 100 90 80 70 60 50 PD = 1 20 10 0 -10 -20 -30 -40 41.0 41.2 41.4 41.6 41.8 42.0 42.2 42.4 FREQUENCY - MHz 42.6 42.8 43.0 40 30 20 -50 -25 PD = 0 0 25 50 TEMPERATURE - C 75 100 TPC 9. Two-Tone Intermodulation Distortion TPC 12. Supply Current vs. Temperature -6- REV. 0 AD8323 APPLICATIONS General Application The gain transfer function is as follows: AV = 27.5 dB - (0.7526 dB x (71 - CODE)) for 0 CODE 71 where AV is the gain in dB and CODE is the decimal equivalent of the 8-bit word. Valid gain codes are from 0 to 71. Figure 4 shows the gain characteristics of the AD8323 for all possible values in an 8-bit word. Note that maximum gain is achieved at Code 71. From Code 72 through 127 the 5.25 dB of attenuation from the vernier stage is being applied over every eight codes, resulting in the sawtooth characteristic at the top of the gain range. Because the eighth bit is a "don't care" bit, the characteristic for codes 0 through 127 repeats from Codes 128 through 255. 28 21 14 7 0 -7 -14 -21 -28 0 32 64 96 128 160 GAIN CODE - Decimal 192 224 256 The AD8323 is primarily intended for use as the upstream power amplifier (PA) in DOCSIS (Data Over Cable Service Interface Specifications) certified cable modems and CATV settop boxes. Upstream data is modulated in QPSK or QAM format, and done with DSP or a dedicated QPSK/QAM modulator. The amplifier receives its input signal from the QPSK/QAM modulator or from a DAC. In either case the signal must be low-pass filtered before being applied to the amplifier. Because the distance from the cable modem to the central office will vary with each subscriber, the AD8323 must be capable of varying its output power by applying gain or attenuation to ensure that all signals arriving at the central office are of the same amplitude. The upstream signal path contains components such as a transformer and diplexer that will result in some amount of power loss. Therefore, the amplifier must be capable of providing enough power into a 75 load to overcome these losses without sacrificing the integrity of the output signal. Operational Description The AD8323 is composed of four analog functions in the power-up or forward mode. The input amplifier (preamp) can be used single-ended or differentially. If the input is used in the differential configuration, it is imperative that the input signals are 180 degrees out of phase and of equal amplitudes. This will ensure the proper gain accuracy and harmonic performance. The preamp stage drives a vernier stage that provides the fine tune gain adjustment. The 0.7526 dB step resolution is implemented in this stage and provides a total of approximately 5.25 dB of attenuation. After the vernier stage, a DAC provides the bulk of the AD8323's attenuation (8 bits or 48 dB). The signals in the preamp and vernier gain blocks are differential to improve the PSRR and linearity. A differential current is fed from the DAC into the output stage, which amplifies these currents to the appropriate levels necessary to drive a 75 load. The output stage utilizes negative feedback to implement a differential 75 output impedance. This eliminates the need for external matching resistors needed in typical video (or video filter) termination requirements. SPI Programming and Gain Adjustment GAIN - dB Figure 4. Gain vs. Gain Code Input Bias, Impedance, and Termination Gain programming of the AD8323 is accomplished using a serial peripheral interface (SPI) and three digital control lines, DATEN, SDATA, and CLK. To change the gain, eight bits of data are streamed into the serial shift register through the SDATA port. The SDATA load sequence begins with a falling edge on the DATEN pin, thus activating the CLK line. Although the CLK line is now activated, no change in gain is yet observed at the output of the amplifier. With the CLK line activated, data on the SDATA line is clocked into the serial shift register Most Significant Bit (MSB) first, on the rising edge of each CLK pulse. Because only a 7-bit shift register is used, the MSB of the 8-bit word is a "don't care" bit and is shifted out of the register on the eighth clock pulse. A rising edge on the DATEN line latches the contents of the shift register into the attenuator core resulting in a well controlled change in the output signal level. The serial interface timing for the AD8323 is shown in Figures 2 and 3. The programmable gain range of the AD8323 is -26 dB to +27.5 dB and scales 0.7526 dB per least significant bit (LSB). Because the AD8323 was characterized with a TOKO transformer, the stated gain values already take into account the losses associated with the transformer. REV. 0 The VIN+ and VIN- inputs have a dc bias level of approximately VCC/2, therefore the input signal should be ac-coupled. The differential input impedance is approximately 1600 while the single-ended input impedance is 800 . If the AD8323 is being operated in a single-ended input configuration with a desired input impedance of 75 , the VIN+ and VIN- inputs should be terminated as shown in Figure 5. If an input impedance other than 75 is desired, the values of R1 and R2 in Figure 5 can be calculated using the following equations: ZIN = R1 800 R2 = ZIN R1 ZIN = 75 - R1 = 82.5 AD8323 + R2 = 39.2 Figure 5. Single-Ended Input Termination -7- AD8323 Output Bias, Impedance, and Termination The differential output pins VOUT+ and VOUT- are also biased to a dc level of approximately VCC/2. Therefore, the outputs should be ac-coupled before being applied to the load. This may be accomplished by connecting 0.1 F capacitors in series with the outputs as shown in the typical applications circuit of Figure 6. The differential output impedance of the AD8323 is internally maintained at 75 , regardless of whether the amplifier is in forward transmit mode or reverse power-down mode, eliminating the need for external back termination resistors. A 1:1 transformer (TOKO #617DB-A0070) is used to couple the amplifier's differential output to the coaxial cable while maintaining a proper impedance match. If the output signal is being evaluated on standard 50 test equipment, a 75 to 50 pad must be used to provide the test circuit with the correct impedance match. Power Supply Decoupling, Grounding, and Layout Considerations input and output traces should be kept as short and symmetrical as possible. In addition, the input and output traces should be kept far apart in order to minimize coupling (crosstalk) through the board. Following these guidelines will improve the overall performance of the AD8323 in all applications. Initial Power-Up When the 5 V supply is first applied to the VCC pins of the AD8323, the gain setting of the amplifier is indeterminate. Therefore, as power is first applied to the amplifier, the PD pin should be held low (Logic 0) thus preventing forward signal transmission. After power has been applied to the amplifier, the gain can be set to the desired level by following the procedure in the SPI Programming and Gain Adjustment section. The PD pin can then be brought from Logic 0 to 1, enabling forward signal transmission at the desired gain level. Asynchronous Power-Down Careful attention to printed circuit board layout details will prevent problems due to associated board parasitics. Proper RF design technique is mandatory. The 5 V supply power should be delivered to each of the VCC pins via a low impedance power bus to ensure that each pin is at the same potential. The power bus should be decoupled to ground with a 10 F tantalum capacitor located in close proximity to the AD8323. In addition to the 10 F capacitor, each VCC pin should be individually decoupled to ground with a 0.1 F ceramic chip capacitor located as close to the pin as possible. The pin labeled BYP (Pin 21) should also be decoupled with a 0.1 F capacitor. The PCB should have a lowimpedance ground plane covering all unused portions of the component side of the board, except in the area of the input and output traces (see Figure 11). It is important that all of the AD8323's ground pins are connected to the ground plane to ensure proper grounding of all internal nodes. The differential The asynchronous PD pin is used to place the AD8323 into "Between Burst" mode while maintaining a differential output impedance of 75 . Applying a Logic 0 to the PD pin activates the on-chip reverse amplifier, providing a 74% reduction in consumed power. The supply current is reduced from approximately 133 mA to approximately 35 mA. In this mode of operation, between burst noise is minimized and the amplifier can no longer transmit in the upstream direction. In addition to the PD pin, the AD8323 also incorporates an asynchronous SLEEP pin, which may be used to place the amplifier in a high output impedance state and further reduce the supply current to approximately 4 mA. Applying a Logic 0 to the SLEEP pin places the amplifier into SLEEP mode. Transitioning into or out of SLEEP mode will result in a transient voltage at the output of the amplifier. Therefore, use only the PD pin for DOCSIS compliant "Between Burst" operation. 5V 10 F 25V AD8323TSSOP DATEN SDATA CLK 0.1 F PD 0.1 F SLEEP 0.1 F DATEN SDATA CLK GND1 VCC PD SLEEP GND2 VCC1 VCC2 GND3 GND4 GND5 OUT- GND11 VCC6 VIN- VIN+ GND10 VCC5 GND9 BYP VCC4 VCC3 GND8 GND7 GND6 OUT+ 0.1 F 0.1 F VIN- ZIN = 150 165 0.1 F VIN+ 0.1 F 0.1 F 0.1 F 0.1 F 0.1 F 0.1 F TOKO 617DB-A0070 TO DIPLEXER ZIN = 75 Figure 6. Typical Applications Circuit -8- REV. 0 AD8323 Distortion, Adjacent Channel Power, and DOCSIS In order to deliver 58 dBmV of high fidelity output power required by DOCSIS, the PA should be able to deliver about 60 dBmV to 61 dBmV in order to make up for losses associated with the transformer and diplexer. It should be noted that the AD8323 was characterized with the TOKO 617DB-A0070 transformer. TPC 7 and TPC 8 show the AD8323 second and third harmonic distortion performance versus fundamental frequency for various output power levels. These figures are useful for determining the inband harmonic levels from 5 MHz to 65 MHz. Harmonics higher in frequency will be sharply attenuated by the low-pass filter function of the diplexer. Another measure of signal integrity is adjacent channel power or ACP. DOCSIS section 4.2.9.1.1 states, "Spurious emissions from a transmitted carrier may occur in an adjacent channel that could be occupied by a carrier of the same or different symbol rates." Figure 7 shows the measured ACP for a 16 QAM, 60 dBmV signal, taken at the output of the AD8323 evaluation board (see Figure 13 for evaluation board schematic). The transmit channel width and adjacent channel width in Figure 7 correspond to symbol rates of 160 KSYM/SEC. Table I shows the ACP results for the AD8323 for all conditions in DOCSIS Table 4-7 "Adjacent Channel Spurious Emissions." RBW 500 Hz RF ATT 40dB -10 VBW 5 kHz SWT 12s UNIT dBm -20 -30 -40 -50 -60 -70 CL1 -80 CENTER 10 MHz CL1 60 kHz CU1 F1 SPAN 600 kHz C0 C0 CU1 CH PWR ACP UP ACP LOW 5.44 dBm -52.99 dB -54.36 dB Comparing the computed noise power of -48 dBmV to the 8 dBmV signal yields -56 dBc, which meets the required level of -53 dBc set forth in DOCSIS Table 4-8. As the AD8323's gain is increased from this minimum value, the output signal increases at a faster rate than the noise, resulting in a signal to noise ratio that improves with gain. In transmit disable mode, the output noise spectral density computed over 160 KSYM/SECOND is 1.0 nV/Hz or -68 dBmV. Evaluation Board Features and Operation The AD8323 evaluation board (Part # AD8323-EVAL) and control software can be used to control the AD8323 upstream cable driver via the parallel port of a PC. A standard printer cable connected between the parallel port and the evaluation board is used to feed all the necessary data to the AD8323 by means of the Windows-based, Microsoft Visual Basic control software. This package provides a means of evaluating the amplifier by providing a convenient way to program the gain/ attenuation as well as offering easy control of the amplifiers' asynchronous PD and SLEEP pins. With this evaluation kit the AD8323 can be evaluated with either a single-ended or differential input configuration. The amplifier can also be evaluated with or without the PULSE diplexer in the output signal path. To remove the diplexer from the signal path, move the 0 chip resistor at JP5 so the output signal is directed away from the diplexer and toward the CABLE port of the evaluation board. Also, remove the 0 resistor at JP4. A schematic of the evaluation board is provided in Figure 13. Overshoot on PC Printer Ports The data lines on some PC parallel printer ports have excessive overshoot that may cause communications problems when presented to the CLK pin of the AD8323 (TP5 on the evaluation board). The evaluation board was designed to accommodate a series resistor and shunt capacitor (R1 and C15) to filter the CLK signal if required. Transformer and Diplexer Figure 7. Adjacent Channel Power Table I. ACP Performance for All DOCSIS Conditions (All Values in dBc) TRANSMIT ADJACENT CHANNEL SYMBOL RATE CHANNEL SYMBOL RATE 160 KSYM/SEC 320 KSYM/SEC 640 KSYM/SEC 1280 KSYM/SEC 2560 KSYM/SEC 160 KSYM/SEC -53.0 -53.8 -55.0 -56.6 -56.3 320 KSYM/SEC -52.7 -53.4 -53.8 -54.8 -55.4 640 KSYM/SEC -53.8 -52.9 -53.3 -53.6 -54.2 1280 KSYM/SEC -53.7 -53.4 -53.0 -53.3 -53.5 2560 KSYM/SEC -55.4 -54.0 -53.6 -53.1 -53.3 A 1:1 transformer is needed to couple the differential outputs of the AD8323 to the cable while maintaining a proper impedance match. The specified transformer is available from TOKO (Part # 617DB-A0070); however, MA/COM part # ETC-1-1T-15 can also be used. The evaluation board is equipped with the TOKO transformer, but is also designed to accept the MA/ COM transformer. The PULSE diplexer included on the evaluation board provides a high-order low-pass filter function, typically used in the upstream path. The ability of the PULSE diplexer to achieve DOCSIS compliance is neither expressed nor implied by Analog Devices Inc. Data on the diplexer should be obtained from PULSE. Differential Inputs Noise and DOCSIS At minimum gain, the AD8323's output noise spectral density is 10 nV/Hz measured at 10 MHz. DOCSIS Table 4-8, "Spurious Emissions in 5 MHz to 42 MHz," specifies the output noise for various symbol rates. The calculated noise power in dBmV for 160 KSYM/SECOND is: The AD8323-EVAL evaluation board is designed to accommodate a Mini-Circuits T1-6T-KK81 1:1 transformer for the purpose of converting a single-ended (ground-referenced) input signal to differential inputs. Figure 8 and the following paragraphs identify two options for providing differential input signals to the AD8323 evaluation board. 2 10 nV x 160 kHz + 60 = -48 dBmV 20 log Hz REV. 0 -9- AD8323 Single-Ended-to-Differential Input (Figure 8, Option 1) Installing the Visual Basic Control Software Install the Mini-Circuits T1-6T-KK81 1:1 transformer in the T1 location of the evaluation board. Place 0 chip resistors at locations JP1, JP2, and JP3 such that the signal coming in VIN+ is directed toward the transformer and the differential signal coming out of the transformer is directed toward TP13 and TP14. For 75 input impedance, install 39.2 resistors in R5 and R6 located on the back side of the evaluation board. In this configuration the input signal must be applied to the VIN+ port of the evaluation board from a single-ended 75 signal source. For input impedances other than 75 , the correct value for R5 and R6 can be computed using the following equation: To install the "CABDRIVE_23" evaluation board control software, close all Windows applications and then run "SETUP.EXE" located on Disk 1 of the AD8323 Evaluation Software. Follow the on-screen instructions and insert Disk 2 when prompted to do so. Enter the path of the directory into which the software will be installed and select the button in the upper left corner to complete the installation. Running the Software (R5 = R6 = R), Desired Impedance = 2 x (R 800) Differential Input (Figure 8, Option 2) To invoke the control software, go to START -> PROGRAMS -> CABDRIVE_23, or select the AD8323.EXE icon from the directory containing the software. Controlling the Gain/Attenuation of the AD8323 If a differential signal source is available, it may be applied directly to both the VIN+ and VIN- input ports of the evaluation board. In this case, 0 chip resistors should be placed at locations R8, JP1, JP2, and JP3 such that the VIN+ and VIN- signals are directed toward TP13 and TP14. Referring to Figure 8, Option 2, a differential input impedance of 150 can be achieved by using a 165 resistor for R7. For input impedances other than 150 , the correct value for R7 can be computed using the following equation: Desired Impedance = R7 1600 The slide bar controls the AD8323's gain/attenuation, which is displayed in dB and in V/V. The gain scales at 0.7526 dB per LSB with the valid codes being from decimal 0 to 71. The gain code (i.e., position of the slide bar) is displayed in decimal, binary, and hexadecimal (see Figure 9). POWER-UP, POWER-DOWN AND SLEEP ( ) R6 DIFF IN T1 The "Power-Up" and "Power-Down" buttons select the mode of operation of the AD8323 by controlling the logic level on the asynchronous PD pin. The "Power-Up" button applies a Logic 1 to the PD pin putting the AD8323 in forward transmit mode. The "Power-Down" button applies a Logic 0 to the PD pin selecting reverse mode, where the forward signal transmission is disabled while a back termination of 75 is maintained. Checking the "Enable SLEEP Mode" box applies a Logic 0 to the asynchronous SLEEP pin, putting the AD8323 into SLEEP mode. Memory Section AD8323 R5 OPTION 1 DIFFERENTIAL INPUT TERMINATION VIN+ R7 VIN- The "MEMORY" section of the software provides a convenient way to alternate between two gain settings. The "X->M1" button stores the current value of the gain slide bar into memory while the "RM1" button recalls the stored value, returning the gain slide bar to that level. The "X->M2" and "RM2" buttons work in the same manner. AD8323 OPTION 2 DIFFERENTIAL INPUT TERMINATION Figure 8. Differential Input Termination Options -10- REV. 0 AD8323 EVALUATION BOARD FEATURES AND OPERATION Figure 9. Screen Display of Windows-Based Control Software REV. 0 -11- AD8323 Figure 10. Evaluation Board--Assembly (Component Side) Figure 11. Evaluation Board Layout (Component Side) -12- REV. 0 AD8323 Figure 12. Evaluation Board--Solder Side REV. 0 -13- AD8323 VCC TP14 YEL 2 R8 0 TP15 J1 C13 0.1 F 1 RED TP20 C8 0.1 F + C18 10 F 25V C1 0.1 F R5 82.5 NC = 5 4 R7 DNI 1:1 6 T1 DNI 1 C12 0.1 F 1 JP3 B 3 A 2 TP13 YEL 2 VIN- S2 AGND;3,4,5 R9 DNI BLK DATEN SDATA CLK 3 A B JP1 1 3 J2 1 AGND C3 0.1 F C4 0.1 F C2 0.1 F PD SLEEP C7 0.1 F C6 0.1 F C5 0.1 F VIN+ S3 AGND;3,4,5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 GND11 DATEN 27 VCC6 SDATA 26 VIN- CLK 25 VIN+ GND1 24 GND10 VCC 23 VCC5 PD U1 22 GND9 SLEEP 21 GND2 BYP 20 VCC4 VCC1 19 VCC2 VCC3 18 GND3 GND8 17 GND4 GND7 16 GND5 GND6 15 OUT- OUT+ JP2 1 B A 3 2 AD8323TSSOP TP3 WHT DATEN TP4 R2 WHT 0 WHT PD TP12 DNI C11 0.1 F TP11 DNI C14 DNI TP2 TP5 WHT CLK ETCC1-1T 3 2 1 C10 0.1 F T2A DNI 4 5 R1 WHT 0 C15 DNI TP17 R11 WHT 0 C16 DNI TP19 R12 WHT 0 C17 DNI TP18 WHT SPARE TP7 DNI TP16 WHT SLEEP SDATA TP6 TP9 DNI R6 39.2 WHT TOKO-B4F NC = 2 4 Figure 13. Evaluation Board Schematic 1:1 5 1 1:1 3 T2B 3 A 18 1 G1 A 17 G2 16 3 G3 A-B 15 G4 5 14 B G5 13 G6 12 G7 11 9 PULSEB5008 G8 OUT = 2,4,6,7,8 G9 10 U2 TP22 DNI JP4 JP5 2B1 TP10 DNI R3 0 CABLE S1 AGND;3,4,5 TP21 DNI HPP S4 AGND;3,4,5 R4 DNI -14- TP1 TP8 DNI AMP-552742 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 REV. 0 AD8323 EVALUATION BOARD BILL OF MATERIALS AD8323 Evaluation Board Rev. C SINGLE-ENDED INVERTING INPUT - Revised - June 22, 2000 Qty. 1 12 6 1 1 2 10 1 1 3 4 1 2 1 1 1 1 4 4 2 2 2 3 Description 10 F 16 V. `C' size tantalum chip capacitor 0.1 F 50 V. 1206 size ceramic chip capacitor 0 1/8 W. 1206 size chip resistor 39.2 1% 1/8 W. 1206 size chip resistor 82.5 1% 1/8 W. 1206 size chip resistor Yellow Test Point [INPUTS] (Bisco TP104-01-04) White Test Point [DATA] (Bisco TP104-01-09) Red Test Point [VCC] (Bisco TP104-01-02) Black Test Point [A.GND] (Bisco TP104-01-00) 0 0805 size chip resistors 75 right-angle BNC Telegartner # J01003A1949 Centronics type 36 pin Right-Angle Connector 5-way Metal Binding Post (E F Johnson # 111-2223-001) 1:1 Transformer TOKO # 617DB - A0070 Diplexer PULSE* AD8323 (TSSOP) UPSTREAM Cable Driver AD8323 REV. C Evaluation PC board #4 - 40 x 1/4 inch STAINLESS panhead machine screw #4 - 40 x 3/4 inch long aluminum round stand-off # 2 - 56 x 3/8 inch STAINLESS panhead machine screw # 2 steel flat washer # 2 steel internal tooth lockwasher # 2 STAINLESS STEEL hex. machine nut Vendor ADS# 4-7-6 ADS# 4-5-18 ADS# 3-18- 88 ADS# 3-18-113 ADS# 3-18-189 ADS# 12-18-32 ADS# 12-18-42 ADS# 12-18-43 ADS# 12-18-44 ADS# 3-27-22 ADS# 12-6-28 ADS# 12-3-50 ADS# 12-7-7 TOKO PULSE ADI# AD8323XRU DCS ADS# 30-1-1 ADS# 30-16-3 ADS# 30-1-17 ADS# 30-6-6 ADS# 30-5-2 ADS# 30-7-6 Ref Desc. C18 C1-8, 10-13 R1-3, 8, 11, 12 R6 R5 TP13, 14 TP1-6, 16-19 TP15 TP20 JP1-3 VIN+, VIN-, HPP, CABLE P1 VCC, GND T2 B U2 U1 Evaluation PC Board (p1 hardware) (p1 hardware) (p1 hardware) (p1 hardware) DO NOT INSTALL C14-C17, R4, R7, R9, T1, T2A, TP7-TP12, TP21, TP22. *PULSE Diplexer part #'s B5008 (42 MHz), CX6002 (42 MHz), B5009 (65 MHz). REV. 0 -15- AD8323 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 28-Lead TSSOP (RU-28) 0.386 (9.80) 0.378 (9.60) 28 15 0.177 (4.50) 0.169 (4.30) 0.256 (6.50) 0.246 (6.25) 1 14 PIN 1 0.006 (0.15) 0.002 (0.05) 0.0433 (1.10) MAX SEATING PLANE 0.0256 (0.65) 0.0118 (0.30) BSC 0.0075 (0.19) 0.0079 (0.20) 0.0035 (0.090) 8 0 0.028 (0.70) 0.020 (0.50) -16- REV. 0 PRINTED IN U.S.A. C02045-2.5-7/00 (Rev. 0) |
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