1 description ltc 6430-20 50mhz to 350mhz differential adc driver, if/rf amplifier demonstration circuit 2076 a-a features the lt c ? 6430-20 differential adc driver/if amplifier. the LTC6430-20 has a power gain of 20.8 db and is part of the ltc6430-yy amplifier series. the dc2076a-a demo board supports the ltc6430- yy amplifier family. the dc2076a-a demo board is optimized for the frequency range from 50mhz to 350mhz and utilizes a minimum of passive external components to configure the amplifier for this application. the native LTC6430-20 l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. p erformance s ummary simplifie d schematic has 100 differential input and output impedances, so the demo circuit uses 2:1 balun transformers to convert the differential i/o impedances to 50 single-ended imped - ance. single ended sma i/o connectors allows simple evaluation with most rf test equipment. design files for this circuit board are available at http://www .linear.com/demo/dc2076a-a specifications are at t a = 25c, v cc = 5v figure 1. dc2076a-a simplified schematic symbol parameter conditions value/units power supply v cc operating supply range all v cc pins plus out 4.75v to 5.25v i cc current consumption total current 165ma ?? ?? LTC6430-20 4 1000pf 1000pf 1000pf 1000pf 1000pf dc2076aa f01 560nh rf choke rf choke 560nh v cc v cc r load 50 r source 50 1000pf 1 6 5 3 3 6 1 5 4 dc2076aaf demo manual dc2076a-a
2 q uic k start proce d ure demo circuit 2076 a-a can be set up to evaluate the per- formance of the LTC6430-20. refer to figure 2 for proper equipment connections and follow the procedure below: tw o -tone measurement: connect all test equipment as suggested in figure 2. 1. the power labels of vcc 4.75 v-5.25v and gnd di - rectly correspond to the power supply . typical current consumption of the LTC6430-20 is about 165 ma. 2. apply two independent signals f1 and f2 from signal generator 1 and signal generator 2 at 240 mhz and 241mhz, while setting the amplitude to C17dbm/tone at the demo board input (j1). 3. monitor the output tone level on the spectrum analyzer . adjust the signal generator levels such that the output power measures +2 dbm/tone at the amplifier output j2, after correcting for external cable losses and at - tenuations. 4. change the spectrum analyzers center frequency and observe the two im3 tones at 1 mhz below and above the input frequencies. the frequencies of im3_low and im3_high are 239 mhz and 242 mhz, respectively. the measurement levels should be approximately C96dbc; +50 dbm is typical oip3 performance for the dc2076 a-a demo board at 240mhz. the oip3 calculation is: oip3 = p out + imd3 2 where: p out is the lower output signal power of the fundamental products. ? imd 3 = p out C p im3 ; p im3 is the higher third-order intermodulation product. single-tone measurement: 5. continue with step 4 above, turn off one signal source to measure gain and harmonic distortions. dc2076aaf demo manual dc2076a-a
3 q uic k start proce d ure combiner mini-circuits adp-2-9 signal generator 1 signal generator 2 spectrum analyzer (hp8644a) (hp8644a) amplifier low-pass filter 6db attn. pad (optional) 3db attenuation pad 20db attenuation pad dc2076aaf f03 rohde & schwarz fsem30 v cc = 4.75v to 5.25v coaxial cable (mini-circuits, zhl-2 or equivalent) amplifier low-pass filter 6db attn. pad (optional) (mini-circuits, zhl-2 or equivalent) dc power supply gnd v+ figure 2. proper equipment setup for ip3 measurement dc2076aaf demo manual dc2076a-a
4 operation demo circuit 2076 a-a is a high linearity, fixed gain am- plifier. it is designed for ease of use. the LTC6430-20 is internally matched to 100 differential source and load impedances from 20 mhz to 1400 mhz. due to the unpopularity of 100 differential test equipment, trans - formers have been added to convert these impedances to single-ended 50. the frequency range of the circuit is limited by the balun transformers. hence, this demo board works best over the frequency range from 50mhz to 350 mhz. figure 3 shows the two port dc2076a-as s- parameters . the demo circuit s schematic shows a minimum of required passive support components. at the boards input and output are balun transformers. each of these, t1 and t2, transformers has a 1:2 impedance transformation ratio . the input and output dc blocking capacitors ( c5, c7, c10 and c12) are required because this device is internally dc-biased for optimal operation. the frequency appropriate rf chokes ( l2 and l3) and the de-coupling capacitors ( c2, c3, c15 and c16) provide the proper dc bias to the rf out nodes. a single 5 v supply is required for the v cc pins on the device. l1, l4, c6 and c13 are optional parts. they are for addi- tional matching components when further optimization to a lower or wider frequency range applications is required. a pair of stability networks have been added. they consist of a 62 pf capacitor ( c4 and c11) and 348 resistor (r1 and r5) in parallel at the LTC6430-20 input network to ensure low frequency stability. the t_diode pin ( turret e1) can be forward biased to ground with 1 ma of current. the measured voltage will be an indicator of the chip junction temperature (tj). there is an optional circuit at the upper section of the demo board. this extra circuit can be used to calibrate for the insertion loss of the demo boards input and output components. please note that a number of dnc pins are connected on the demo board. these connections are not necessary for normal operation, however, failure to float these pins may impair the operation of the device. table 2 shows the function of each input and output on the board. dc2076aaf demo manual dc2076a-a
5 operation table 1. dc2076a-a board i/o descriptions frequency (mhz) power gain |s21| output third- order intercept point ( 1 ) oip3 output third-order intermodula tion ( 1 ) oim3 second harmonic distor tion ( 2 ) hd2 third harmonic distor tion ( 2 ) hd3 output 1db compression point p 1db noise figure ( 4 ) nf 50 17.8 48.6 C93.2 C82.8 C95.1 23.4 4.5 100 19.2 48.5 C92.9 C82.3 C96.1 23.4 3.4 140 19.4 49.2 C94.4 C82.6 C96.5 23.1 3.2 200 19.2 49.6 C95.2 C81.3 C90.8 ( 3 ) 22.9 3.2 240 18.9 49.9 C95.7 C81.2 ( 3 ) C84.9 ( 3 ) 23.2 3.3 300 18.4 51.5 C98.9 C77.6 ( 3 ) C81.4 ( 3 ) 22.8 3.7 350 17.6 51.0 C97.9 C80.2 ( 3 ) C83.6 ( 3 ) 22.9 3.9 units db dbm dbc dbc dbc dbm db notes : all figures are referenced to j1 (input port) and j4 (output port). 1. tw o -tone t est conditions: output power level = +2dbm/tone, tone spacing = 1mhz 2. single-t one test conditions: output power level = +6dbm. 3. outside of input and output t ransformers working frequency range 4. small signal noise figure frequency (mhz) |s21| (db) |s11|, |s12|, |s22|, (db) dc2076aa f02 20 18 16 22 14 12 10 8 6 4 ?4 ?8 ?12 0 ?16 ?20 ?24 ?28 ?32 ?36 0 100 200 300 400 |s21| |s11| |s12| |s22| figure 3. demo board s-parameters table 2. dc2076a-a board i/o descriptions connector function j1 (in) single-ended input. impedance matched to 50. drive from a 50 network analyzer or signal source. j4 (out) single-ended output. impedance matched to 50. drives a 50 network analyzer or spectrum analyzer. e1 (t_diode) the measured voltage will be an indicator of the chip junction temperature. e2 (v cc ) positive supply voltage source. e3 (gnd) supply ground. dc2076aaf demo manual dc2076a-a
6 a dd itional information as with any rf device, minimizing ground inductance is critical. care should be taken during the board layout when using these exposed pad packages. a maximum of small- diameter vias should be placed underneath the exposed ground pad. this will ensure a good rf ground and low thermal impedance. maximizing the copper ground plane will also improve heat spreading and lower the inductance to ground. it is a good idea to cover the via holes with solder mask on the back side of the pcb to prevent solder from wicking away from the critical pcb to the exposed pad interface. the dc2076a-a is a wide bandwidth demo board, but it is not intended for operation down to dc. the lower frequency cutoff is limited by on-chip matching elements . table 3 shows the ltc643x- yy amplifier series and its associated demo boards. each demo board lists the typical working frequency range and the input and output imped - ance of the amplifiers. table 3. the ltc643x-yy amplifier family and corresponding application demo boards. demo board number frequency range (mhz) notes/ applications boards in/out impedance amplifier amplifiers impedance dc1774a-a 50 to 350 low frequency 50 ltc6430-15 differential 100 dc1774a-b 400 to 1000 mid frequency 50 ltc6430-15 differential 100 dc1774a-c 100 to 1200 wide frequency 50 ltc6431-15 single-ended 50 dc2032a 50 to 1000 cable infrastructure 75 ltc6430-15 differential 100 dc2077a 100 to 1200 wide frequency 50 ltc6431-20 single-ended 50 dc2153a 700 to 1700 high frequency 50 ltc6430-15 differential 100 dc2090a 50 to 1200 power doubler 50 dual ltc6430-15 differential 50 dc2076a-a 50 to 350 low frequency 50 LTC6430-20 differential 100 dc2076a-b 300 to 1000 mid frequency 50 LTC6430-20 differential 100 dc2076aaf demo manual dc2076a-a
7 a dd itional information setup signal sources and spectrum analyzer the LTC6430-20 is an amplifier with high linearity perfor- mance. t herefore, the o utput intermodulation products are very low. even using high dynamic range test equipment, third-order intercept ( ip3) measurements can drive test setups to their limits. consequently, accurate measure - ment of ip3 for a low distortion ic such as the LTC6430-20 requires certain precautions to be observed in the test setup as well as the testing procedure. setup signal sources figure 2 shows a proposed ip3 test setup. this setup has low phase noise, good reverse isolation, high dynamic range, sufficient harmonic filtering and wideband imped - ance matching. the setup is outlined below: a . high per formance signal generators 1 and 2 (hp8644 a) are used. these suggested generators have low har - monic distortion and very low phase noise. b. high linearity amplifiers are used to improve the reverse isolation. this prevents cross talk between the two signal generators and provides higher output power. c. a low pass filter is used to suppress the harmonic content from interfering with the test signal. note that second order inputs can mix with the fundamental frequency to form intermodulation ( im) products of their own. we suggest filtering the harmonics to C50 dbc or better. d. the signal combiner from mini- circuits ( adp-2-9) combines the two isolated input signals. this combiner has a typical isolation of 27 db. for improved vswr and isolation, the h-9 signal combiner from ma/com is an alternative which features >40 db isolation and a wider frequency range. passive devices ( e.g. combiners) with magnetic elements can contribute nonlinearity to the signal chain and should be used cautiously. e. the attenuator pads on all three ports of the signal combiner will further support isolation of the two input signal sources. they also reduce reflections and promote maximum power transfer with wideband impedance matching. setup the spectrum analyzer a. adjust the spectrum analyzer for maximum possible resolution of the intermodulation products amplitude in dbc. a narrower resolution bandwidth will take a longer time to sweep. b. optimize the dynamic range of the spectrum analyzer by adjusting the input attenuation. first increase the spectrum analyzer s input attenuation ( normally in steps of 5 db or 10 db). if the im product levels decrease when the input attenuation is increased, then the input power level is too high for the spectrum analyzer to make a valid measurement. most likely, the spectrum analyzers 1 st mixer was overloaded and producing its own im products. if the im reading holds constant with increased input attenuation, then a sufficient amount of attenuation was present. adding too much attenua - tion will bury the intended im signal in the noise floor . therefore, select just enough attenuation to achieve a stable and valid measurement. c. in order to achieve this valid measurement result, the test system must have lower total distortion than the duts intermodulation. for example, to measure a 50dbm oip3, the measured intermodulation products will be C96 dbc below an C17 dbm/tone input level and the test system must have intermodulation products approximately C102 dbc or better. for best results, the im products and noise floor should measure at least C106dbc before connecting the dut. dc2076aaf demo manual dc2076a-a
8 p arts l ist item qty reference part description manufacturer/ part number dc2076a-1 required circuit components 1 2 c1, c14 cap., x7r, 1000pf, 50v, 5%, 0402 avx , 04025c102 jat 2a 2 6 c2, c5, c7, c10, c12, c15 cap., x7r, 1000pf, 50v, 5%, 0603 avx , 06035c102 jat 2a 3 2 c3, c16 cap., x5r, 0.1f, 10v, 10%, 0603 avx , 0603zd104 kat 2a 4 2 c4, c11 cap., npo, 62pf, 25v, 5%, 0402 avx , 04023a620 jat 2a 5 0 c6, c13 cap., opt , 0603 opt 6 0 c17, c22 opt cap., npo, 62pf, 25v, 5%, 0402 7 0 c18, c19, c23, c24 opt cap., x7r, 1000pf, 50v, 5%, 0603 8 0 c20, c21 opt cap., x7r, 1000pf, 50v, 5%, 0402 9 3 e1-e3 testpoint, turret, .093" mill-max, 2501-2-00-80-00-00-07-0 10 2 j1, j4 conn., sma 50 edge-launch e.f.johnson, 142-0701-851 11 0 j2, j3, j5, j6 opt conn., sma 50 edge-launch 12 2 l1, l4 res., chip, 0, 0603 vishay, crcw06030000z0ed 13 2 l2, l3 inductor, chip, 560nh, 5%, 0603ls-1608 coilcraft, 0603ls-561xjlb 14 2 r1, r5 res., chip, 348 , 1%, 0402 vishay, crcw0402348rfked 15 0 r6, r7 opt res., chip, 348 , 1%, 0402 16 2 r2, r4 res., chip, 0, 0603 vishay, crcw06030000z0ed 17 0 r3 res., chip, opt , 0402 18 0 t3, t4, opt rf transformer, case style cd542 mini-circuits, adtl2-18+ 19 1 u1 balanced amplifier ltc6430aiuf-20, qfn24uf-4x4 linear tech., ltc6430aiuf-20 dc2076a1-a required circuit components 1 1 dc2076a general bom 2 2 c8, c9 cap., x7r, 1000pf, 50v, 5%, 0402 av x , 04025c102 jat 2a 3 2 t1, t2 rf transformer, case style cd542 mini-circuits, adt2-1t+ dc2076aaf demo manual dc2076a-a
9 information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. s chematic diagram 5 5 4 4 3 3 2 2 1 1 d d c c b b a a ???????????????????????????????????? ????????????????????????????? ???????????????????????????????? ??????????? ?? ????? ???????????? ?????????? ???? ?? ???????? ?????? ?? ???????? ? ?????????? ?????? ???????????? ??? ? ? ??? ??? ???????????????? ?????????????????????????????????????????????? ????? ? ? ?????????????? ?????????????? ?????????????? ?????????????? ??????????? ??? ??? ??? ??? ???????????????? ??????????? ???? ???????? ??? ??? ??????? ?????????? ? ???????? ?? ???????????????? ??????????? ???? ???????? ??? ??? ??????? ?????????? ? ???????? ?? ???????????????? ??????????? ???? ???????? ??? ??? ??????? ?????????? ? ???????? ?? ???? ????? ?????? ???? ????? ?? ?????? ????????? ???????? ???????? technology ?????????????????? ?????????????????? ???????????????????? ??????????????????? ?????????????????????????????????????? ??????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ?????????????????????????????????????????????????? ???????????????????????????????????????????????? ????????????????????????????????????????????????????? ??????????????????????????????????????????? ??????????????????????????????????????????????????? ???????????????????????????????????????????????????? ????????? ?????????????????????????????????????????????? ???????????? ?????????????? ? ???????????????????????? ?? rf/if amp/adc driver ?? ??????? ??? ?????????????? ?????????????????? ???? ????? ?????? ???? ????? ?? ?????? ????????? ???????? ???????? technology ?????????????????? ?????????????????? ???????????????????? ??????????????????? ?????????????????????????????????????? ??????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ?????????????????????????????????????????????????? ???????????????????????????????????????????????? ????????????????????????????????????????????????????? ??????????????????????????????????????????? ??????????????????????????????????????????????????? ???????????????????????????????????????????????????? ????????? ?????????????????????????????????????????????? ???????????? ?????????????? ? ???????????????????????? ?? rf/if amp/adc driver ?? ??????? ??? ?????????????? ?????????????????? ???? ????? ?????? ???? ????? ?? ?????? ????????? ???????? ???????? technology ?????????????????? ?????????????????? ???????????????????? ??????????????????? ?????????????????????????????????????? ??????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ?????????????????????????????????????????????????? ???????????????????????????????????????????????? ????????????????????????????????????????????????????? ??????????????????????????????????????????? ??????????????????????????????????????????????????? ???????????????????????????????????????????????????? ????????? ?????????????????????????????????????????????? ???????????? ?????????????? ? ???????????????????????? ?? rf/if amp/adc driver ?? ??????? ??? ?????????????? ?????????????????? ?? ???????????????? ?? ???????????????? ? ? ? ? ? ??? ??? ?? ?? ?? ????? ???? ?? ????? ???? ?? ???? ?? ???? ?? ? ???? ?? ? ???? ?? ?????? ???? ?? ?????? ???? ?? ???????????????? ?? ???????????????? ? ? ? ? ? ?? ? ?? ? ?? ??? ?? ??? ??? ??? ?? ??? ?? ??? ?? ??? ?? ??? ??? ????? ???? ??? ????? ???? ?? ??? ?? ??? ?? ?? ???????? ???????? ? ? ? ? ???????? ???????? ? ? ? ? ? ?? ???? ?? ???? ?? ??? ?? ??? ?? ? ?? ? ??? ??? ??? ?????? ???? ??? ?????? ???? ?? ??? ?? ??? ??? ?????? ??? ?????? ?? ??? ?? ??? ?? ?????? ???? ?? ?????? ???? ???????? ???????? ? ? ? ? ?? ?????? ?? ?????? ?? ?????? ?? ?????? ?? ? ???? ?? ? ???? ??? ??? ??? ??? ??? ?????? ???? ??? ?????? ???? ?? ?? ??? ???? ??? ???? ?? ?????????? ?? ?????????? ??? ? ??? ?? ??? ? ??? ?? ??? ? ??? ? ??? ? ??? ?? ??? ?? ??? ?? ??? ?? ??? ?? ??? ?? ???? ?? ??????? ?? ??? ? ??? ? ??? ? ??? ?? ??? ?? ??? ?? ???? ?? ??? ? ??? ?? ??? ?? ??? ??? ?? ?????? ?? ?????? ?? ?? ?? ????? ?? ????? ?? ??? ?? ??? ??? ??? ?? ????? ?? ????? ??? ?????? ??? ?????? ?? ??????? ?? ??????? ??? ???? ??? ???? ?? ?? ?? ??? ?? ??? ??? ???? ??? ???? ??? ??? ??? ?????? ??? ?????? ?? ?? ?? ???? ?? ???? ?? ??? ?? ??? ??? ?????? ???? ??? ?????? ???? ?? ??????? ?? ??????? ???????? ???????? ? ? ? ? ? ??? ?????? ???? ??? ?????? ???? ?? ?????? ???? ?? ?????? ???? ?? ?????? ?? ?????? ??? ?????? ???? ??? ?????? ???? ??? ?????? ???? ??? ?????? ???? ??? ?????? ???? ??? ?????? ???? dc2076aaf demo manual dc2076a-a
10 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com ? linear technology corporation 2014 lt 1114 ? printed in usa demonstration board important notice linear technology corporation ( lt c ) provides the enclosed product(s) under the following as is conditions: this demonstration board ( demo board) kit being sold or provided by linear technology is intended for use for engineering development or evaluation purposes only and is not provided by lt c for commercial use. as such, the demo board herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. as a prototype, this product does not fall within the scope of the european union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. if this evaluation kit does not meet the specifications recited in the demo board manual the kit may be returned within 30 days from the date of delivery for a full refund. the foregoing warranty is the exclusive warranty made by the seller to buyer and is in lieu of all other warranties, expressed, implied, or statutory, including any warranty of merchantability or fitness for any particular purpose. except to the extent of this indemnity, neither p arty shall be liable to the other for any indirect, special, incidental, or consequential damages. the user assumes all responsibility and liability for proper and safe handling of the goods. further, the user releases lt c from all claims arising from the handling or use of the goods. due to the open construction of the product, it is the users responsibility to take any and all appropriate precautions with regard to electrostatic discharge. also be aware that the products herein may not be regulatory compliant or agency certified (fcc, ul, ce, etc.). no license is granted under any patent right or other intellectual property whatsoever. lt c assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. lt c currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. please read the demo board manual prior to handling the product . persons handling this product must have electronics training and observe good laboratory practice standards. common sense is encouraged. this notice contains important safety information about temperatures and voltages. for further safety concerns, please contact a lt c applica- tion engineer. mailing address: linear technology 1630 mccarthy blvd. milpitas, ca 95035 copyright ? 2004, linear technology corporation dc2076aaf demo manual dc2076a-a
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